Timed Exam Optoprep 1

You are working with an 80-year old patient who has wet macular degeneration. His visual acuity is measured at 8/200 in the right eye and 8/400 in the left eye through his habitual spectacle prescription. When performing a trial frame refraction, what spherical lenses do you start with for the right eye? +/- 10.00 D lenses +/- 2.00 D lenses +/- 2.50 D lenses +/- 1.25 D lenses +/- 5.00 D lenses

+/- 2.50 D lenses Correct Answer OD 8/200 = 20/500 Just noticeable difference is 5.00D; trial lenses would span the 5 D interval and be +/- 2.50 D.

What is the power of the tear lens created by a gas permeable contact lens with a base curve of 44.50D placed on a cornea with a spherical curvature of 43.75D? -1.25D -1.50D +1.50D +1.25D +0.75D -0.75D

+0.75D In order to find the power of the tear lens created by the back surface of a rigid gas permeable contact lens (base curve) and the anterior surface of the cornea (keratometry reading), the following equation may be used: Tear lens (TL) = base curve (BC) - keratometry (K) TL = 44.50 - 43.75 TL = +0.75 D When the base curve is steeper than the keratometry values, the tear lens will be of positive value.

You are measuring the keratometry values of your keratoconic patient using a manual keratometer. The drum readings do not go high enough to measure the corneal curvatures so you place a +2.25 trial lens to the keratometer to extend the range. Approximately how much do you need to add to the drum reading to obtain the true keratometry values? +12.00 +5.50 +16.00 +22.00 +8.00 +2.25

+16.00 When measuring the keratometry values utilizing a manual keratometer there are certain circumstances in which the reading may be out of the range of the drum values. In these cases, one will need to add a trial lens to keratometer in order to extend the ranges (lenses are added to the patient's side of the keratometer). Cases in which the curvature is steeper than the drum reading, plus trial lenses are required, and when the reading is flatter than the drum reading, minus trial lenses are necessary. In patients with steeper curvatures, typically a +1.25 trial lens is tried first. If a measurement can be found with this lens, one will need to add about 8-9D to the drum reading in order to obtain the true value. A +1.25 lens will extend the range from about 52D to 60 or 61D. If keratometry values are even steeper (in the 60-68D range), a +2.25 trial lens can be utilized to extend the drum range even more. In these cases, about 16D is added to the drum reading to reach the true keratometry value. This is the case in the above patient. If the curvature is flatter than can be measured with the manual keratometer, a minus lens can be added to extend the range in the opposite direction. Typically a -1.00 trial lens will encompass a keratometry reading from about 32-38D. If a -1.00 lens is added, one will need to subtract 6D from the drum reading.

You are comparing the measurements of the back vertex power and front vertex power of a high plus lens using the lensometer. The back vertex lens power reads +8.50 -1.25 x 170. When you flip the glasses around to measure the front vertex power, what do you expect the cylinder axis to read? 010 170 100 080

010 For higher-powered plus lenses, there is often a difference between the front and back vertex powers. This is due to the increased thickness of a plus lens. It is important to note that the cylinder axis for the front vertex power will be the mirror-image of the back vertex cylinder axis (therefore it is acceptable to refocus the lens by adjusting the cylinder wheel). For the example above, if the back vertex cylinder axis is 170, the mirror of this will be a cylinder axis of 010. This aforementioned fact is important because during the measurement of an add power of high plus lenses, one may not obtain an accurate reading of the add power because of this difference in vertex powers. Therefore, one must re-measure the distance power of the lens using the front vertex power and then measure the power through the near add. The difference between these two measurements will represent the most accurate add power.

One section of the scotopic portion of a light adaptation curve is depicted as a line with a corresponding slope of infinity. This slope signifies that the rods of the visual system are saturated. What percentage of rhodopsin molecules is bleached in order for rod saturation to occur? 10% 100% 30% 80% 50%

10% A light adaptation curve is generated by conducting an increment threshold procedure. An increment threshold procedure is carried out by presenting a test spot (stimulus) against a background of a given luminance. The luminance of the stimulus is increased until detected by the observer, allowing for threshold determination. Once a threshold is ascertained, the brightness of the background is increased and the threshold for the increment is again established. The scotopic portion of the light adaptation curve can be broken into four sections. The final division of the scotopic section is a straight vertical line, which has a slope of infinity, thereby signifying rod saturation. Rod saturation occurs when 10% of the rhodopsin molecules have become bleached. At this point, a key number of sodium channels are closed, rendering the rod cell incapable of further signaling any information regarding the stimulus.

When a chromophore absorbs a photon of light, which of the following changes occurs? 11-trans-retinal isomerizes to 11-cis-retinal 11-cis-retinal isomerizes to 11-trans-retinal all-cis-retinal isomerizes to 11-trans-retinal all-trans-retinal isomerizes to 11-cis-retinal 11-trans-retinal isomerizes to all-cis-retinal 11-cis-retinal isomerizes to all-trans-retinal

11-cis-retinal isomerizes to all-trans-retinal In the human visual cycle, light is converted into electrical signals in rod and cone photoreceptors in order for vision to occur. This process begins when opsins, which contain the 11-cis-retinal chromophore, absorb a photon of light. Once struck by a photon, 11-cis-retinal undergoes photoisomerization to the all-trans state (all-trans-retinal). This change leads to signal transduction cascades that eventually result in the closure of a cyclic GMP-gated cation channel and subsequent hyperpolarization of the photoreceptor cell. After this occurs, all-trans-retinal is reduced to all-trans-retinol. It then travels back to the retinal pigment epithelium (RPE) where it is esterfied and then converted to 11-cis-retinol. It is finally oxidized to 11-cis-retinal before traveling back to the photoreceptor outer segment and attaching to an opsin, forming a new, functional visual pigment that is ready for photoisomerization again.

You have a 56-year-old female patient who has an average intraocular pressure (IOP) of 32mmHg in her right eye and 28mmHg in her left eye. Considering her ocular and medical history, you decide to initiate glaucoma treatment with timolol b.i.d. OU. You are going to have her return in 1 month for an IOP check after starting the medication. Which of the following IOP measurements would you anticipate in each eye, assuming she responds to the timolol as expected (rounding to the nearest 1mmHg)? 24mmHg OD, 21mmHg OS 29mmHg OD, 25mmHg OS 19mmHg OD, 17mmHg OS 21mmHg OD, 18mmHg OS

24mmHg OD, 21mmHg OS The mean decrease in IOP with a topical beta-blocker is approximately 25% (this is greater than pilocarpine and topical carbonic anhydrase inhibitors). Timolol is typically prescribed twice per day (b.i.d.) as it has been shown that the IOP-lowering effect lasts for 12hours once instilled; however, timolol also works well as a once-daily therapy (q.a.m.) as the production of aqueous is naturally lower at night. With once a day instillation, the IOP reduction still ranges from about 17-28% with a single drop. Note: There is also limited proof that the 0.5% preparation provides any greater hypotensive effect than the 0.25% preparation.

In a developing toddler, resolution acuity (as determined by forced-choice looking) normally reaches adult levels by what age? 12 years old 1 year old 2 years old 8 years old 4 years old

4YO A one-month old infant possesses roughly 20/600 acuity as measured via the forced-choice preferential looking test. Normal 20/20 Snellen acuity is not generally reached until roughly 3-5 years of age due to retinal immaturity, particularly the cone receptors. On the other hand, visual evoked potentials (VEPs) have demonstrated that adult levels are actually reached by 6 to 8 months.

How many bones of the skull articulate to form the orbit? 5 bones 4 bones 8 bones 7 bones 6 bones 3 bones

7 bones The orbit is a pyramidal shaped area formed by bones of the skull in order to protect the eye. There are seven bones that articulate to form this cavity. - Frontal bone - Lacrimal bone - Ethmoid bone - Zygomatic bone - Maxillary bone - Palatine bone - Sphenoid bone

On average, what is the life cycle of photoreceptor discs? 9-13 days 20-25 days 2-5 days 15-20 days

9-13 days Photoreceptor disc production begins in the cell body. The rough endoplasmic reticulum produces proteins which are then packaged by the Golgi apparatus. This complex then moves up through the inner segment to the base of the outer segment. The discs become free-floating in rod cells. The discs move up slowly until they are shed and phagocytized by the retinal epithelial pigment cells. On average, rods shed about 10% of their discs per day. Rods tend to shed their discs during the day while cones get rid of their discs at night.

Which of the following lenses has a nominal power of +4.00 D? A meniscus lens with a front surface power of +5.00 D and an ocular surface power of -2.00 D A converging lens with a front surface power of +6.00 D and an ocular surface power of -3.00 D A plano-convex lens with a front surface power of +5.00 D A bi-convex lens with a front surface power of +2.00 D and an ocular surface power of +2.00 D

A bi-convex lens with a front surface power of +2.00 D and an ocular surface power of +2.00 D The nominal or approximate power of a lens can be determined by adding the powers of the front surface of the lens to the power of the back (ocular) surface. The only lens that fulfills the desired power of +4.00 D from the above combinations is a bi-convex lens with a front surface power of +2.00 D and a back surface power of +2.00 D.

Which of the following conditions would be categorized as causing amblyopia due to deprivation? A five-year old with an uncorrected prescription of OD: +7.00 D 20/400 OS: +0.50 20/20 A three-year with a constant right 30 prism diopter esotropia A child born with a large congenital cataract in one eye only A child born with a monocular 2 mm ptosis

A child born with a large congenital cataract in one eye only Form deprivation amblyopia results when a clear and focused retinal image is blocked to one eye during the critical period. This can occur by a complete congenital cataract in one eye, a large ptosis that covers most or all of the pupil or by some other element that occludes the eye. The lack of visual information to the retina causes the other eye (non-occluded eye) to become dominant and thusly have stronger and a greater number of synaptic connections to the brain. Amblyopia causes a disproportionate amount of cortical neurons to respond preferentially to the non-deprived eye. The occlusion must occur during the critical period, and the earlier the occlusion is detected and removed, the better the prognosis. A small ptosis (i.e. 2 mm) would not be expected to cause amblyopia because the pupil would not be occluded. An unequal prescription such as the one in the above question would cause anisometropic amblyopia in which one eye would receive a clear image while the other would receive a blurry image. The brain would favor the clear retinal image, resulting in a strong dominance of cortical neurons for the least ametropic eye. Strabismus results in the perception of two images that are not fusible by the brain, causing diplopia. In order to eliminate double vision, the eye will suppress an eye (usually the deviated eye). This suppression leads to amblyopia.

What is the most commonly encountered type of staphyloma? Total staphyloma Posterior staphyloma Intercalary staphyloma Anterior staphyloma

A posterior staphyloma is the most common type of staphyloma. This form of staphyloma tends to occur in individuals with very high degrees of myopia. Intercalary staphylomas occur usually secondary to inflammation and are located at the junction between the iris root and the ciliary body. Total staphylomas, also known as buphthalmos, are generally seen in conjunction with congenital glaucoma.

Which of the following laser treatments is thought to increase aqueous outflow by the clearing of trabecular meshwork debris through cell division and migration of macrophages induced by the laser, in addition to opening of untreated trabecular spaces by tightening of treated trabecular meshwork? Laser peripheral iridotomy Argon laser trabeculoplasty Laser peripheral iridoplasty Selective laser trabeculoplasty Trabecular cryotherapy

ALT Mechanism of action argon laser trabeculoplasty (ALT): - ALT involves the application of isolated laser burns to the trabecular meshwork in order to increase the outflow of aqueous, subsequently lowering intraocular pressure (IOP) - It is thought that increased outflow occurs as a result of the following: - Opening of adjacent untreated trabecular spaces by tightening of the treated trabecular meshwork - The clearing of trabecular meshwork debris by cell division and migration of macrophages induced by the laser treatment Mechanism of Action SLT: - Selectively targets pigmented trabecular meshwork cells, while sparing the non-pigmented (non-filtering) cells - The absorption of radiant energy by the melanin-containing cells leads to rupture of melanosomes and cellular destruction (photolysis) - The ruptured cells release metalloproteases and other proteolytic enzymes, triggering an inflammatory response mediated by macrophages and other phagocytic cells - Phagocytic action in and around the trabecular meshwork typically results in increased aqueous outflow and reduction in intraocular pressure

Regarding the bioavailability of a steroid, which formulation allows for the BEST corneal penetration through an intact epithelium with topical application? Phosphate Amide Acetate Alcohol

Acetate Steroids in acetate form will always result in the highest penetration into the anterior chamber, regardless of the condition of the corneal surface. Alcohols offer the second highest penetration, followed by phosphate derivatives. In the absence of an epithelium, phosphate penetration increases significantly. For this reason, several topical steroids are available in multiple formulations. Prednisolone is available in acetate and phosphate form. Dexamethasone can be prepared as an alcohol or as a phosphate. Amide is not an available form for topical steroids.

What is the MOST common etiology of viral conjunctivitis? Herpes simplex Adenovirus Your Answer Herpes zoster Enterovirus Molluscum contagiosum

Adenovirus By far, the most common cause of viral conjunctivitis is adenovirus, which accounts for approximately 65-90% of all viral conjunctival infections. Herpetic infections are typically the most serious and potentially sight-threatening viral infections; however, they are relatively uncommon.

Which of the following prescriptions, if left uncorrected during the critical period, will lead to meridional amblyopia, in which vertical lines will appear clearer and horizontal lines appear blurry? -0.25-5.00x046 -0.25-4.25x178 +0.25-4.00x137 +0.50-1.25x180 Pl-4.75x089

All of the above prescriptions are likely to lead to meridional amblyopia except for +0.50-1.25x180. This prescription is quite low and will not result in amblyopia if left uncorrected during the critical period. Meridional amblyopia is caused when lines of a certain orientation are in focus to a greater degree than lines of another orientation. For example, the above prescription of -0.25-4.25x178 will cause lines in the vertical meridian to be in focus (remember that the power is 90 degrees away from the axis), while lines that are horizontal will appear blurry. This person may have difficulty with optotypes containing horizontal components like the letter E. Meridional amblyopia can only result if the astigmatism is great enough and is present during the critical period.

The mother of a 6 year-old female reports that her daughter's right eye seems to turn out occasionally. A unilateral cover test performed at near reveals a tropia that is neutralized with 4 prism diopters base-in in upgaze, 10 prism diopters base-in in primary gaze, and 16 prism diopters base-in in downgaze. Which of the following patterns describes the ocular alignment of this patient? A-pattern exotropia V-pattern exotropia A-pattern esotropia V-pattern esotropia

An A-pattern exotropia is an incomitant ocular deviation in which there exists a significant difference in the magnitude of an exotropia when measured in up-gaze and down-gaze (typically greater than 10 prism diopters). The ocular deviation is less apparent in up-gaze and becomes more evident as the patient positions his or her eyes downward. It is for this reason that this type of deviation most commonly causes difficulty with reading. These patients will often adopt a chin-down compensatory head position in an attempt to attain fusion. A- and V-pattern ocular deviations occur as a result of abnormal relative contributions of the oblique and vertical rectus muscles, resulting in an imbalance of their horizontal components in up and down-gaze. For example, in the case of A-pattern deviations, there is either a primary superior oblique overaction, inferior oblique underaction with superior oblique overaction, or inferior rectus underaction, which causes the horizontal exo deviation to become larger in downgaze as compared to upgaze (or the eso deviation to become less apparent in downgaze).

The colon is divided into four regions. What is the order that undigested matter will pass through it prior to expulsion from the anus? Ascending colon, sigmoid colon, transverse colon, descending colon, rectum Ascending colon, transverse colon, descending colon, sigmoid colon, rectum Ascending colon, descending colon, transverse colon, sigmoid colon, rectum Ascending colon, transverse colon, sigmoid colon, descending colon, rectum

Ascending colon, transverse colon, descending colon, sigmoid colon, rectum The colon appears like an inverted U. Undigested matter will first pass through the ascending colon located on the right side of the abdominal cavity, pass through the transverse colon to the left side of the body, and travel down through the descending colon. Lastly the matter will pass through the s-shaped sigmoid colon into the rectum and out the anus.

Free radicals can cause severe damage to tissue. Which of the following electrolytes can function as an antioxidant in the aqueous? Chloride ions Sodium ions Albumin Ascorbate IgG

Ascorbate The aqueous humor contains many electrolytes including Na+, K+ , Cl-, HCO3-, glucose, lactate, amino acids, and ascorbate. Ascorbate is found in high concentrations in the aqueous (20x greater when compared to the concentration found in plasma). Ascorbate can serve as an antioxidant to eradicate free radicals reducing potential damage from ultraviolet light. Interesting note: the aqueous humor and tears of uncontrolled diabetics display higher levels of glucose than those of non-diabetics.

Most patients have a resting level of accommodation (also known as tonic accommodation) that is typically equivalent to which of the following values? 2.0 Diopters 0.0 Diopters 3.0 Diopters 1.0 Diopters

At rest, the eyes typically have some amount of residual or resting level of accommodation. This is also known as tonic accommodation; it is sometimes referred to as a lead of accommodation. The amount of tonic accommodation in a normal individual is typically between 0.50 and 1.50 diopters.

Which of the following landmarks of an electrocardiogram represents repolarization of the atria? P wave PR interval T wave S wave Q wave Atrial repolarization is obscured by the QRS complex

Atrial repolarization is obscured by the QRS complex An electrocardiogram machine processes electrical signals picked up through electrodes placed on the patient's skin. It then produces a graphical representation of the electrical activity of the patient's heart. The basic pattern of electrical activity is comprised of three waves: the P wave, QRS complex, and T wave. These landmarks are summarized below. - P wave: small upward deflection wave that represents atrial depolarization - Q wave: beginning of the QRS complex (depolarization of ventricles) that corresponds to the depolarization of the interventricular septum - S wave: the end of the QRS wave complex that represents the final depolarization of the ventricles at the base of the heart - T wave: signifies ventricular repolarization - PR interval: time between the first deflection of the P wave and first deflection of the QRS wave complex - There is no specific wave or landmark for the repolarization of the atria as it occurs during the same time at the main QRS complex and is obscured by this large wave

Which of the following preservatives, if used excessively, is MOST toxic to the cornea? Chlorobutanol Methylparaben Sodium perborate Benzalkonium chloride (BAK) Polyquaternium (polyquad)

BAK is frequently used in many topical antibacterial agents. With continual use, BAK can damage the lipid layer and lead to increased epithelial permeability. The corneal epithelium acts as a natural barrier against pathogens; when the epithelium becomes compromised, there is a greater risk of infection. Be careful when treating ocular infections with BAK as prolonged use can lead to corneal toxicity. All of the other options are also frequently used as preservatives in artificial tear preparations; however, BAK poses the greatest risk for corneal toxicity. Polyquad is a good preservative (especially for contact lens solutions) as it possesses a high molecular weight and will not soak into contact lenses. Chlorobutanol is used in some gas-permeable contact lens solutions. It is both antibacterial and antifungal but not very effective and tends to dissipate during long periods of storage. Chlorobutanol has a low risk of toxicity. Methylparaben is commonly found as a preservative in cosmetic and food preservatives. It has a very low risk of corneal toxicity. Sodium perborate undergoes several chemical reactions once in contact with the eye. It is converted from hydrogen peroxide to water and oxygen on the eye and thus has a very low change of cellular toxicity.

You ask your patient to place a red lens in front of their right eye and proceed to perform the red lens test. Your patient reports seeing two images, with the red image being perceived to the right of the white light. What direction should you place the prism over the right eye to neutralize the phoria? Base out Base down Base up Base in

BO The above scenario depicts an esophoria because the diplopia is uncrossed. Esophorias are neutralized with base out prisms. Remember, with tropias one must place the red lens over the fixating eye otherwise the chances are greater that the deviating eye will suppress the image.

You perform a blood pressure measurement on your 63-year-old female patient; the pressure reads 148/122mmHg. If her blood pressure levels persistently read at this level, she would be diagnosed as having which of the following stages of hypertension? Hypertensive crisis Stage 1 hypertension Elevated blood pressure Stage 2 hypertension Normal blood pressure

Blood pressure measurements that have a systolic reading above 180mmHg OR a diastolic reading higher than 120mmHg are indicative that the patient is experiencing a hypertensive crisis and must seek immediate emergency medical treatment. To meet this definition, you are not required to have blood pressure measurements on 2 different encounters. This is an exception to the classification guidelines.

Which of the following medications/supplements, if used in high doses, may produce crystalline retinopathy, whereby bilateral, fine, yellow deposits can be observed in the inner layers of the retina? Thioridazine Your Answer Chlorpromazine Chloroquine Hydroxychloroquine Canthaxanthin

Canthaxanthin Canthaxanthin is a carotenoid supplement that was previously used by individuals to enhance sun tanning. If it is used in high doses over a long period of time, tiny yellow, discrete, glistening deposits may present in a symmetric doughnut shape surrounding the macula. Chloroquine and hydroxychloroquine are systemic medications that also may produce retinal toxicity. The classic signs of retinopathy in these cases involves a "bulls-eye" macular lesion that presents as a central island of pigment, surrounded by a hypopigmented zone of RPE atrophy that is also encircled by another area of hyperpigmentation. Chlorpromazine and thioridazine belong to the phenothiazines class of medication and also may cause retinal toxicity in high daily dosages. Retinopathy is typically characterized by pigmentary granularity and clumping in the mid-periphery and posterior pole. In addition to pigmentary changes, chlorpromazine may also cause focal or diffuse atrophy of the RPE and choriocapillaris.

Due to its high level of toxicity, which of the following anti-infective medications should only be utilized as a last resort for treating ocular infections? Polytrim® Sulfacetamide Azithromycin Ciprofloxacin Chloramphenicol

Chloramphenicol should only be utilized in the presence of a severe infection that is not responsive to any other agent. Chloramphenicol is very lipid-soluble and easily crosses the blood-aqueous barrier; as such, it can cause bone marrow depression (which is reversible), aplastic anemia, gray baby syndrome (occurs if chloramphenicol is given within 2 weeks of birth), optic neuropathy, teratogenesis, and enterocolitis. Due to chloramphenicol's ability to cross the blood-brain barrier, it is useful in treating staphylococcal brain abscesses and certain types of meningitis.

Capillaries found in which 2 of the following structures of the eye are considered fenestrated vessels? (Select 2) Choroid Iris Retina Ciliary processes

Choroid and ciliary processes Fenestrated capillaries are present within two structures of the eye, the ciliary processes and the choroid. Contrastingly, the retina and iris contain non-fenestrated capillaries. If we examine this concept closely, it makes perfect sense. The choroid supplies the outer retina with nutrients, accounting for about 85% of total blood flow of the eye. In order for the choroid to supply the retina with these nutrients, the vessels must be able to allow the molecules to pass through. Additionally, in the ciliary processes, the fenestrated capillaries create oncotic pressure due to protein leakage through the vessels that allows for aqueous production through the process of ultrafiltration. Non-fenestrated capillaries of the retina and iris are essential for the formation of the blood-aqueous and blood-retinal barriers.

A woman who is colorblind mates with a man who is normal. What are the chances that their daughter will be a carrier? 75% 100% 0% 25% 50%

Color blindness is an X-linked recessive gene. As we know, it is the male that determines the sex of the child, either contributing an X or a Y. The female only contributes an X to her offspring. Therefore, if the female possesses an X-linked recessive gene (she manifests the phenotype, X'X'), she will pass it on to 100% of her sons; however, her daughters will all only be carriers but will not manifest the genetic defect (see image 1).

A colored filter is placed in front of an illuminated Tungsten light bulb, resulting in emergent light that appears red. Which of the following wavelengths is LEAST likely to be absorbed by the filter? 401 nm 648 nm 518 nm 471 nm 592 nm

Colored filters are used to block (absorb) some wavelengths while transmitting others, resulting in the perception of transmitted light that is a different color than the light that was incident upon the filter. A red filter that is placed in front of a white light source will strongly absorb the majority of the wavelengths, except for those in the red region (roughly 620 to 700 nm).

A 22-year old female patient presents with a unilateral scaly, itchy rash on the upper eyelid. Which of the following is the most likely cause? Seborrhoeic dermatitis Allergic conjunctivitis Contact dermatitis Acne

Contact dermatitis Contact dermatitis is most often associated with nail polish, perfume, or any substance that contacts the upper eyelid. Seborrhoeic dermatitis generally causes scaling, found mainly in the nasal labial folds and along the border of the scalp and is also associated with blepharitis. Acne rosacea can cause bumps but rarely involves the eyelid and is more frequently associated with meibomian gland disease. Allergic conjunctivitis involves the conjunctival surface but not the skin.

How is the temporal modulation transfer function expected to change in a person with early glaucoma not yet manifesting any defects on visual field testing? Decreased sensitivity to moderate and high temporal frequencies Decreased sensitivity to low temporal frequencies only Decreased sensitivity to moderate frequencies only Decreased sensitivity to low and moderate frequencies

Decreased sensitivity to moderate and high temporal frequencies Early glaucomatous damage can be difficult to detect because intraocular pressure and visual fields can be normal. Recent studies demonstrate that the magno cells may be damaged early on in glaucoma. The magno cells are a part of the "where" pathway and therefore display excellent temporal resolution. Due to this factor, there is evidence that clearly reveals a correlation between an altered temporal modulation transfer function and early glaucoma, with a marked decrease noted for the moderate and high temporal frequencies, even though the respective visual field is free of defects.

Which of the following systemic neuromuscular conditions preferentially spares the extraocular muscles? Myotonic dystrophy Duchenne muscular dystrophy Grave's disease Kearns-Sayre syndrome Myasthenia gravis

Duchenne muscular dystrophy Duchenne muscular dystrophy (DMD) affects most of the muscles of the human body due to an x-linked genetic mutation of the dystrophin gene. DMD is characterized by the progressive weakness and necrosis of striated muscle, with the exception of the extraocular muscles, which appear to be clinically unaffected. Although the etiology behind this exclusion is controversial, it is believed that the extraocular muscles have a better intrinsic ability to maintain calcium homeostasis as compared to other groups of striated muscle. Kearns-Sayre syndrome, Grave's ophthalmopathy, myasthenia gravis, and myotonic dystrophy (both types 1 and 2) are all conditions in which the extraocular muscles are either preferentially or exclusively involved.

In which of the following layers of the cornea are deposits observed in cases of whorl keratopathy? Bowman's Stroma Epithelium Descemet's Endothelium

Epithelium Patients with vortex keratopathy (also known as whorl keratopathy or corneal verticillata) present with whorl-like corneal epithelial deposits that occur as a result of the ingestion of certain systemic medications or as a manifestation of certain systemic diseases (such as Fabry's). These characteristic corneal changes begin as fine greyish or brownish opacities in the inferior corneal epithelial layer that arborize and create a whorl-like pattern that swirls outward from a point just below the pupil, sparing the limbus. Although deposits typically involve the visual axis, patients do not experience a decrease in visual acuity; however, some may report the presence of haloes around lights.

A patient with which of the following laboratory results would be considered diabetic? 2-hour postprandial glucose of 180 mg/dL Glycosylated hemoglobin of 6.7% Fasting blood glucose of 120 mg/dL

Glycosylated hemoglobin (HbA1c) reflects the percentage of free glucose bound to hemoglobin in red blood cells. Because the average lifespan of a red blood cell is approximately 3 months, this test is a good estimate of the average blood sugar of a patient over that period of time. Normal 5.7%, pre-diabetes 5.7-6.4%, diabetes >6.5% Two-hour postprandial glucose measures the serum level of glucose two hours after a meal. This is commonly measured in pregnant women to assist in the diagnosis of gestational diabetes. In healthy patients, blood glucose levels should normalize within two hours of eating (measured in mg/dL). Normal 70-141, Pre-diabetes 14-200, diabetes >200 Fasting blood glucose is the amount of glucose in the blood at the time of collection after the patient has refrained from eating or drinking anything but water for at least eight hours (measured in mg/dL). Normal <100, Pre-diabetes 100-125, diabetes >126

A patient presents with a cup-to-disc ratio of 0.65 with potential notching superiorly of the right eye. You wish to perform optical coherence tomography (OCT) imaging. Which of the following procedures should NOT be performed prior to obtaining OCT imaging on this patient? Evaluation of the fundus with a 90 D lens Biomicroscopy Refraction Goldmann applanation tonometry

Goldmann applanation tonometry In order to achieve maximal imaging results, it is recommended that the corneal surface remain as pristine as possible. A compromised corneal epithelium can lead to poor scan quality and therefore to potentially erroneous results. Should applanation tonometry need to be performed, it is best to complete this procedure after imaging has been completed.

Which of the following conditions may act as a protective factor against progression of diabetic retinopathy? Brown irides High myopia High cholesterol A high body mass index (BMI) Glaucoma

High myopia It has been seen in myopic patients, (particularly highly myopic subjects) that myopia may serve as a protective factor against the progression of retinopathy associated with diabetes. Axial elongation, posterior vitreous detachment, altered ocular blood flow and vitreous syneresis are all more commonly observed in patients with high myopia. Proliferation of diabetic retinopathy can be triggered by traction of the retina caused by incomplete detachment of the vitreous, which may lead to fibrovascular tissue formation. Myopic patients with a posterior vitreous detachment possess a decreased risk of traction and therefore a decreased risk of progression of diabetic retinopathy. Concurrent systemic conditions such as elevated cholesterol or hypertension may serve to exacerbate retinopathy, as can a high body mass index. To date, a link with iris color and diabetic retinopathy has not been established.

Which of the following drops is frequently used in the treatment of recurrent corneal erosions? Topical antihistamines such as emedastine difumarate Hyperosmotic drops Pilocarpine Topical steroids such as loteprednol

Hyperosmotic drops Recurrent corneal erosions can occur in the event of trauma (especially involving organic matter) to the anterior cornea, specifically the epithelial basement membrane. In the case of recurrent corneal erosion, once the injury heals the epithelial cells do not adhere properly to the basement membrane causing them to slough off in a recurrent fashion. It can take several weeks or months for the cornea to re-establish the proper connections between epithelial cell layers. Recovery can be accelerated with hyperosmotic drops which serve to draw out excess water, helping to further strengthen and establish adhesion between the basement membrane and the overlying epithelium. Pilocarpine, emedastine difumarate and loteprednol will not help to prevent further erosions.

Grave's disease can cause spontaneous diplopia. Which of the following extraocular muscles is the most commonly affected in a patient afflicted with Grave's disease? The medial rectus The inferior rectus The superior oblique The lateral rectus The inferior oblique

IR Grave's disease is an auto-immune condition caused by hyperthyroidism (overproduction of thyroid hormones). The eye muscles may become thicker and shorter due to an infiltration of lymphocytes, which limits the ability of the muscles to contract, eventually resulting in fibrosis of the muscle. Restriction of the extraocular muscle (EOM) causes a perceived palsy of the opposing EOM. The eye muscles most frequently affected are the inferior rectus, medial rectus, and the superior rectus, with the inferior rectus being by far the most commonly involved.

The use of which 3 of the following medications/supplements has been associated with the development of idiopathic intracranial hypertension (pseudotumor cerebri)? (Select 3) Cupric acid Naladixic acid Vitamin B12 Tetracyclines Oral contraceptives Penicillins

Idiopathic intracranial hypertension (also known as pseudotumor cerebri) is defined as the presence of elevated intracranial pressure in the absence of an intracranial space-occupying lesion, or enlargement of the ventricles due to hydrocephalus. Eye care professionals are often the first to identify this condition due to the development of visual symptoms resulting from papilledema. Several risk factors for this condition have been identified, with the majority of patients falling into a category of overweight women of childbearing age. Other associations include the use of several medications, most notably tetracyclines, naladixic acid, and oral contraceptives. Steroids, vitamin A, isotretinoin (Accutane®), growth hormones, sulfa drugs, tamoxifen, thyroid replacement therapy, and phenytoin have also been shown to have a correlation with this condition.

Which TWO of the following are TRUE in regards to frame adjustments on a patient's face? (Select 2) If the right lens is too high, bend the right temple up If the right lens is too close to the face, bring the right temple in If the right lens is too low, bend the left temple down Your Answer If the right lens is too far from the face, bring the left temple out

If the right lens is too high, bend the right temple up If the right lens is too close to the face, bring the right temple in If the temple spread of a pair of spectacles is uneven, or one side of the patient's head is somewhat wider than the other, it is possible that one lens will be closer to the face than the other. For example, if the right lens is too far from the patient's face, this could be due to the fact that either the right temple is not spread far enough, making that side fit too tightly, or that the left temple is too loose. The opposite is true if the right lens were to be sitting too close to the face. A simple rule of thumb for frame adjustment is: -If the right lens is in -> move the right temple in (or left temple out) -If the left lens is in -> move the left temple in (or right temple out) -If the right lens is out -> move the right temple out (or left temple in) -If the left lens is out -> move the left temple out (or right temple in) If the frame is not straight on the face, it could be because of incomplete standard alignment, or because one ear of the patient is positioned slightly higher than the other. The solution is the same regardless of the cause of the misalignment: -If the right lens is up -> bend the right temple up (or left temple down) -If the left lens is up -> bend the left temple up (or right temple down) -If the right lens is down -> bend the right temple down (or left temple up) -If the left lens is down -> bend the left temple down (or right temple up)

A patient who has a high spatial frequency cut-off of 40 cycles per degree will have what predicted Snellen acuity? 20/20 20/15 20/30 20/40

In order to convert from cycles per degree to Snellen acuity, simply divide 600 by the cycles per degree; this will solve for the denominator of the Snellen acuity. For the above example 600/40 = 15. Therefore, the predicted Snellen acuity would be 20/15.

An object in air is located 40 cm to the left of a +4.25 D spherical CR39 plastic surface (n=1.498). In order to solve for the distance of the resultant image from the apex of the surface, which of the following must be calculated FIRST? The image vergence at the refracting surface The object location from the refracting surface The radius of curvature The object vergence at the refracting surface The index of the surrounding medium

In order to solve for the distance of the image from the refracting surface, the object vergence must be calculated. In the above problem, this is solved as follows: L=n/l where L= the object vergence, n=the index of the medium containing the object, and l=the distance of the light rays from the object to the refracting surface in meters. L= 1.0/-0.4= -2.5. The paraxial relationship deems that the vergence of light rays forming an image is the combination of incident vergence and the power of the refracting surface. One can now determine that the vergence of the incident light on a +4.25D plastic surface is -2.50. Adding the two values together yields the power of the image vergence L'=L+P where L= the object vergence and P= the power of the refracting surface, which in this case is -2.50 +4.25 = +1.75 D. Because the light rays forming the image are converging, the image is real. The location of the image is calculated using the formula L'=n'/l' where L= the image vergence, n'= the index of the medium in which the light rays form an image, and l'= the distance between the refracting surface and the image. We have already determined that L'= +1.75 D and n'= 1.498. Solving for l', +1.75=1.498/l', l'= 0.856 or 85.6 cm to the right of the refracting surface. Support Blog · FAQ · Authors · Student Representatives · References · Terms & Conditions · NBEO®

A red blood cell is placed into a solution of 100% distilled water. What will happen to the red blood cell? It will remain unchanged Crenation It will shrink It will swell

It will swell The cell will swell because the replacement surrounding solution (distilled water) is hypotonic to the cell. Because the cell contains a higher concentration of solutes, water will diffuse into the cell in an attempt to equalize the solute concentration. If a red blood cell is placed into a solution that contains a higher concentration of solutes than the cell (that is, the solution is hypertonic to the cell) water will rush out of the cell due to osmosis and the cell will shrink and become crenated. If both the cell and the surrounding medium contain equal concentrations of solute then the two are said to be isotonic, and water will not leave or enter the cell.

Which of the following conditions is NOT known to be a potential complication of uveitis? Band keratopathy Phthisis Glaucoma Retinal detachment Cataract Cystoid macular edema Keratoconus

KCN Chronic uveitis is associated with a high incidence of vision-threatening conditions such as cataracts, glaucoma, retinal detachment, cystoid macular edema, band keratopathy, and phthisis bulbi, some of which are irreversible. Keratoconus is a non-inflammatory eye disease and is not related to uveitis.

Which of the following conditions is NOT known to be a potential complication of uveitis? Phthisis Cystoid macular edema Cataract Keratoconus Band keratopathy Retinal detachment Glaucoma

KCN Chronic uveitis is associated with a high incidence of vision-threatening conditions such as cataracts, glaucoma, retinal detachment, cystoid macular edema, band keratopathy, and phthisis bulbi, some of which are irreversible. Keratoconus is a non-inflammatory eye disease and is not related to uveitis.

A finding in which keratic precipitates present in a triangular pattern with base-down presentation in the inferior portion of the cornea is known as which of the following? Stocker's line Hudson-Stahli line Krukenberg's spindle Arlt's triangle

Keratic precipitates are collections of white cells (leukocytes) deposited on the corneal endothelium which occur as a result of inflammation of the iris or ciliary body (anterior uveitis). They often collect in a triangular pattern with base-down presentation in the inferior portion of the endothelial surface (Arlt's triangle); however, they may also be distributed diffusely over the entire corneal endothelium, or concentrated in one area only. Krukenberg's spindle represents the vertical collection of pigment granules on the corneal endothelium and is observed in patients with pigment dispersion syndrome. A Hudson-Stahli line is a horizontal line of iron deposition often found in the inferior 1/3 of the cornea; it is commonly seen in patients over the age of 50. Stocker's line is a vertical line of iron deposition found at the leading edge of a pterygium. Note: Don't confuse Arlt's triangle with Arlt's line, which is a band of scarring that can present on the superior palpebral conjunctiva in patients with chlamydia trachomatis.

Which of the following is normally present in the corneal stroma? Hemoglobin Myelinated nerves Keratocytes Blood vessels

Keratocytes The central cornea is generally devoid of blood vessels. To maintain clear vision and decrease light scatter it is important that the visual axis remain avascular. Because the central portion of the cornea is avascular, one should not expect to find hemoglobin since it is found within blood vessels. The cornea does contain many nerve endings, however the nerves are not myelinated when they extend to the central cornea because myelination would cause light scatter and decreased vision. Keratocytes are located in the central cornea to maintain and uphold collagen which is the main component of the stroma.

Which 3 signs are typically associated with pigment dispersion glaucoma? (Select 3) Narrow angles Krukenberg spindle Shallow anterior chambers Heavily pigmented trabecular meshwork Peripheral/mid peripheral transillumination defects Cataracts

Krukenberg spindles, heavily pigmented TM, peripheral/mid peripheral transillumination defects The anterior chamber in patients with pigment dispersion glaucoma is usually very deep with wide open angles. The reason for deep anterior chambers is the presence of a backward bowing of the peripheral iris (this leads to an increase in lens/iris contact). Patients with pigment dispersion glaucoma tend to be male and myopic.

The surface ectodermal cleft that becomes buried between the frontonasal process and the upper maxillary process of the first branchial arch becomes which of the following? The interpalpebral fissure Meibomian glands Lining of the nasolacrimal system Lacrimal gland

Lining of the nasolacrimal system Note in the attached figure that the surface ectoderm buried in the crease between the frontonasal process and the upper edge of the maxillary process of the first branchial arch becomes the epithelial lining of the nasolacrimal drainage system.

Which 2 of the following alterations to the cornea commonly occur after several years of contact lens wear? (Select 2) The cornea becomes less sensitive to touch The cornea epithelium thins The cornea becomes more sensitive to touch The corneal epithelium thickens

Long-term extended wear of contact lenses has been shown to lead to thinning of the corneal epithelium. Additionally, the corneal nerves exhibit a decrease in sensitivity over time.

A 52-year old male is seen at your office complaining of red, irritated, and burning eyes. He has been using over-the-counter redness reliever drops every half an hour for two days but he feels as if his eyes have gotten worse. He initially started using the drops because his eyes were mildly itchy. Biomicroscopy reveals bilateral corneal superficial punctate keratitis (SPK) and 2+ injection of the conjunctiva. Based upon the above information, which of the following is the BEST diagnosis for his current condition? Vernal keratoconjunctivitis (VKC) Medicamentosa Chrysiasis Dry eye syndrome

Medicamentosa Medicamentosa refers to the situation in which a patient reacts to medication or the preservatives contained within an ophthalmic preparation. Symptoms include pain, foreign body sensation, burning, and photophobia, depending on the severity. Ocular signs include conjunctival injection, SPK, chemosis, and ulceration, and scarring in very severe cases. Treatment includes discontinuation of the offending agent and management of the inflammation with preservative-free ocular lubricants and topical steroids if necessary. Dry eye syndrome may have been a factor initially, but because this patient states that his eyes got worse when he started using the drops, one can presume that this is attributable to his extreme overuse of over-the-counter ophthalmic drops. Gold salts are used to manage rheumatoid arthritis, primarily when other treatment options have failed. Chrysiasis occurs secondary to the deposition of gold in the skin, lens, and cornea, causing a gray discoloration of the skin and brown/gold deposits in the deep stroma of the cornea. VKC is a condition of the young and presents with an increased frequency in males. This type of allergy typically develops before age 14 and lasts for 4-10 years before the child outgrows it; it occurs predominantly in the spring and summer. The condition progressively gets better, with the first episode being the worst. Usually VKC is seen in patients who are prone to atopy; they typically suffer from eczema, asthma, or hay fever as well as itchy eyes and photophobia. The condition basically presents as a very severe type of allergic conjunctivitis. Signs include cobblestone papillae of the upper lid, lid swelling, and ropy discharge that is worse in the morning. Corneal defects (usually superiorly) known as keratitis of Togby may also be present. Occasionally, patients will develop a shield ulcer and Tranta's dots which are calcified eosinophils seen circumlimbally (they appear as chalky concretions) which may lead to the feeling of an associated foreign body sensation. Treatment includes mast cell stabilizers (these should be started several weeks prior to re-occurring episodes), pulse steroid therapy, cool compresses, and sunglasses to help alleviate ensuing photophobia.

Upon slit-lamp examination of your 81 year-old male patient, you observe the presence of an age-related cataract in which there is significant liquefaction such that the nucleus of the crystalline lens begins to sink inferiorly. This type of cataract is known as which of the following? Morgagnian cataract Hypermature cataract Mature cataract Immature cataract

Morgagnian cataract Correct Answer When classifying the maturity of an age-related cataract, there are several factors to consider, including the cloudiness of the lens, the appearance of the capsule, and the location of the lens nucleus. Immature cataracts are those in which the lens is partially opaque. A mature cataract will present with a completely opaque crystalline lens. Hypermature cataracts also have a completely opaque appearance to the lens, in addition to showing wrinkling and shrinking of the anterior capsule due to leakage of water out of the lens. Morgagnian cataracts are hypermature cataracts in which there is significant liquefaction such that the nucleus of the crystalline lens begins to sink inferiorly.

Disruption of sympathetic innervation to which of the following structures is responsible for the ptosis seen in Horner's syndrome? Muller's muscle Orbicularis oculi Levator palpebrae superioris Frontalis muscle

Muller's Horner's syndrome results from a disruption of the sympathetic innervation to the eye due to a lesion or mass located either post-ganglionically or pre-ganglionically. The classic triad of signs seen in a patient suffering from Horner's syndrome is miosis, a small ptosis and anhidrosis (lack of sweat) on one side of the head or body depending of the location of the lesion. Be sure to test for miosis in dim illumination as it is more evident under this lighting condition. Muller's muscle is under sympathetic innervation and is responsible for 2-4 mm of eyelid elevation. The frontalis muscle is controlled by cranial nerve VII and is only active in extreme upward gaze. The levator palpebra superioris in under control of cranial nerve III and is the primary muscle used to open the eye. Orbicularis oculi is innervated by cranial nerve VII and is responsible for eyelid closure.

Which of the following electrodiagnostic tests provides a 40-50 degree topographic map of the central retina function for the cone system? Multifocal electroretinogram (mfERG) Visual evoked potential (VEP) Electro-oculogram (EOG) Full-field electroretinogram (ffERG) Pattern electroretinogram (pERG)

Multifocal electroretinogram (mfERG) mfERG- this test provides a topographic map of the central retina function for the cone system with a diameter of 40-50 degrees. The signals are detected with a corneal electrode on a dilated eye. The mfERG waveforms mainly represent photoreceptor and bipolar cell responses. Amplitude and time of the positive response (P1) are most commonly used for analysis. ffERG- this is a mass retinal response elicited by stimulating dilated eyes with flashes of light from a Ganzfeld stimulator. It is routinely recorded with corneal electrodes. It allows for evaluation of the cone and rod systems and can delineate photoreceptor and bipolar cell contributions. The responses are evaluated based on the morphology and other measurable parameters of waveform components. pERG- this is primarily used for evaluation of ganglion cells in the central retina. A corneal electrode is used to record the response to checkerboard-pattern stimuli of an undilated eye. VEP- this is an electrophysiological signal recorded at the occipital lobe in response to a checkerboard pattern (for pattern VEP) or flash stimulation (for flash VEP) presented in the central visual field of an undilated patient. EOG- this evaluates RPE function under dark and light phases. Responses decrease with dark adaptation and then increase with light adaptation. Reduced Arden ratio (the light peak/dark trough ratio) indicates RPE dysfunction.

The gray line of the eyelid margin represents the junction between the anterior and posterior lamellae of the lid and is an extension of which of the following muscles? Muscle of Riolan Levator palpebrae superioris Muller's muscle Horner's muscle

Muscle of Riolan The eyelid margin can be divided into the anterior lamella (ciliary portion) and posterior lamella (tarsal portion). These lamellae are separated from each other along what is known as the "gray line", which represents the terminal extension of the muscle of Riolan within the eyelid. This muscle is present along the entire length of the eyelid margin, located between the tarsal plate and the eyelash follicles, and arises from the orbicularis oculi muscle. It is thought that the muscle of Riolan aids in maintaining proper apposition of the eyelid to the globe, as well as helping to express the contents of glands during blinking.

Which of the following genus of organisms is responsible for tuberculosis and leprosy? Salmonella Borrelia Mycobacterium Klebsiella

Mycobacterium Mycobacterium is an aerobic, Gram-positive (although this is somewhat debatable) genus that includes several pathogenic species. Mycobacteria are extremely difficult to treat due to the nature of their cell walls which are truly neither Gram-negative nor Gram-positive (although they are classified as Gram-positive because they are acid-fast). M. tuberculosis is responsible for causing tuberculosis. M. leprae is the culprit that causes Hansen's disease (also termed Leprosy). A species of Borrelia can cause Lyme disease. Salmonella has been known to cause food poisoning. Contraction of Klebsiella can lead to the development of pneumonia.

Which of the following statements BEST reflects the correlation between myopia and contact lens wear? Myopes who wear contact lenses tend to develop signs of presbyopia later than those who do not Myopes must converge more when looking through contact lenses than with glasses Myopes accommodate less when looking through contact lenses than with glasses Myopes who wear contact lenses often complain of decreased peripheral vision when wearing their contact lenses than with their glasses

Myopes who wear contact lenses often develop symptoms of presbyopia earlier than those who wear glasses. This is attributable to the fact that myopes have to accommodate to a greater degree while wearing contact lenses. Myopes must also converge more when looking through contact lenses. With glasses on, a myope views through a small amount of base-in prism while converging, this is not present with contact lenses.

Hutchinson's sign associated with herpes zoster is an indication of reactivation of which of the following cranial nerves? Lacrimal branch of the trigeminal nerve Facial nerve Nasociliary branch of the trigeminal nerve Frontal branch of the trigeminal nerve

Nasociliary branch of the trigeminal nerve A vesicular eruption on the tip of the nose in patients with herpes zoster indicates the reactivation of herpes involving the nasocilary branch of the ophthalmic division of the trigeminal nerve. This sign may provide an early predictive factor of impending eye involvement (herpes zoster ophthalmicus).

Which 2 of the following statements are TRUE in regards to gas-permeable contact lens designs? (Select 2) Flexure of a gas-permeable contact lens will result in an increase in over-refraction cylinder in the opposite meridian of the corneal toricity Polishing or adding power to a front surface toric contact lens is an easy, in-office modification Toric peripheral curves result in an oval optic zone and spherical peripheral curves result in a circular optic zone Optics of bitoric contact lenses are usually not as crisp as those of the base curve toric design SPE bitoric contact lenses act optically like a spherical lens

Optics of bitoric contact lenses are usually not as crisp as those of the base curve toric design SPE bitoric contact lenses act optically like a spherical lens The following statements are true in regards to gas-permeable contact lenses: SPE bitoric contact lenses act optically like a spherical lens - When prescribed, SPE bitoric lenses will not have any effect on the over-refraction cylinder, and lens rotation on the eye will not alter vision or the refractive error measured; therefore, they are typically used in patients with high amounts of corneal cylinder and low amounts of residual astigmatism (when a spherical diagnostic lens is placed on the eye) Optics of bitoric contact lenses are usually not as crisp as those of the base curve toric design - In cases where a CPE bitoric lens is considered, it is important to first rule out the possibility of a base curve toric lens - These lenses tend to be cheaper, have better optics, and in-office modification and polishing are possible Polishing or adding power to a base curve toric contact lens is an easy, in-office modification due to the spherical front surface of the lens Toric peripheral curves result in a circular optic zone, and spherical peripheral curves result in an oval optic zone - With spherical peripheral curves, the meridian with the flatter base curve will have the larger optic zone diameter - Toric peripheral curves typically allow for better lens stabilization Flexure of a gas-permeable contact lens will result in an increase in over-refraction cylinder in the same meridian of the corneal toricity - If a gas-permeable lens flexes or warps on an against-the-rule cornea there will be an increase in against-the-rule cylinder in the over-refraction - On a with-the-rule cornea, lens flexure will lead to an increase in with-the-rule cylinder, which may be beneficial in cases where a decrease in against-the-rule cylinder is desired

Degenerative retinoschisis occurs from the separation of which two layers of the retina? Inner nuclear layer and ganglion cell layer RPE and photoreceptor layer Nerve fiber layer and the ganglion cell layer External limiting membrane and outer nuclear layer Outer plexiform layer and inner nuclear layer

Outer plexiform layer and inner nuclear layer Degenerative retinoschisis occurs when there is a split within the neurosensory retina. This separation commonly takes place between the outer plexiform layer and the inner nuclear layer. Patients are usually asymptomatic and the condition tends to be bilateral, and is typically located in the inferior temporal quadrant of the retina. Visual field testing may show an absolute scotoma corresponding to the area of the retinoschisis. Retinoschisis is different from a retinal detachment, which is the separation of the neurosensory retina from the RPE. This separation usually takes place between the RPE and photoreceptor layer. Optical coherence tomography (OCT) can assist in differentiating retinoschisis from a retinal detachment. The OCT scan of a retinal detachment would show a separation of the full thickness neurosensory retina from the RPE. On the other hand, a scan of retinoschisis would show a split within the neurosensory retina. This split most commonly occurs between the outer plexiform layer and the inner nuclear layer.

Which 3 of the following characteristics of retinal photoreceptor cells are TRUE? (Select 3) Photoreceptors depolarize in response to a light stimulus Photoreceptors release less neurotransmitter in response to light Photoreceptors produce graded potentials Photoreceptors hyperpolarize in response to a light stimulus Photoreceptors release more neurotransmitter in response to light Photoreceptors produce action potentials

Photoreceptors release less neurotransmitter in response to light Correct Answer Photoreceptors produce graded potentials Correct Answer Photoreceptors hyperpolarize in response to a light stimulus Correct Answer Photoreceptors of the retina have many characteristics that are unlike most other neurological cells in the human body. For example, photoreceptors produce graded potentials in which the signal varies in intensity; this is in contrast to action potentials, which display an all-or-none response. Additionally, photoreceptors hyperpolarize in response to light. Therefore, bright light will lead to a greater degree of hyperpolarization, whereas dim light produces less hyperpolarization. When hyperpolarization of a photoreceptor occurs, the cell releases less of its neurotransmitter (glutamate). Therefore, photoreceptors release a greater amount of glutamate while in darkness.

Which of the following topical pharmaceutical agents stimulate accommodation? Pilocarpine Ketorolac Tropicamide Tetracaine Dexamethasone Phenylephrine

Pilo Accommodation can be stimulated by the installation of topical pilocarpine drops into the eye. Pilocarpine is a muscarinic agonist that, when applied, binds to muscarinic receptors, leading to contraction of the ciliary muscle. Accommodation by this process is known as involuntary accommodation, which is typically greater in amplitude than voluntary accommodation. In addition to being pharmacologically stimulated, accommodation can also be pharmacologically blocked (known as cycloplegia). Muscarinic antagonists such as tropicamide cause paralysis of the ciliary muscle by competitively binding and blocking muscarinic receptors, preventing acetylcholine (or other muscarinic agonists) from stimulating accommodation.

A 29-year old male is referred to your office for treatment of keratitis caused by Herpes simplex virus (HSV). Biomicroscopy reveals a large central dendritic ulcer. Which of the following medications should NOT be used alone in your initial treatment plan? Ganciclovir (Zirgan®) ophthalmic gel Preservative-free artificial tears Trifluridine (Viroptic®) eye drops Prednisolone (Pred-Forte®) 1% eye drops Vidarabine ointment

Prednisolone (Pred-Forte®) 1% eye drops Pred-Forte® or any steroid drop should NEVER be used alone on an infected eye regardless of the offending pathogen. Steroids serve to suppress the immune system's response, resulting in a decreased inflammatory reaction. Because of the diminished response due to steroid use, the body's ability to fight the cause of the infection decreases, resulting in a heightened infection. HSV is commonly treated with steroid drops, particularly when there is stromal involvement; however, the drops are used in conjunction with an anti-viral agent. Artificial tears are frequently used to keep the eye flushed and clean, thereby speeding up the healing period. The use of artificial tears in the absence of any other medication will not worsen the infection, nor will it serve greatly in its treatment. Vidarabine and ganciclovir are both anti-viral medications that are helpful in the treatment of HSV. Ganciclovir has a slight advantage over vidarabine in that it has proven to demonstrate less corneal toxicity.

A protanope has a neutral point of 492 nm. Light with a wavelength of 502 nm will MOST likely be perceived as what color by this individual? Blue Yellow Green Red

Protanopes lack the photopigment erythrolabe and possess a neutral point of 492 nm. Wavelengths above the neutral point are perceived as various hues of yellow, and those below the neutral point are seen as blue that increases in saturation towards the shorter wavelengths.

Which of the following tissue cells are insulin-independent? Skeletal muscle cells Red blood cells Adipose cells Heart muscle cells Cells that line the walls of blood vessels

RBC Insulin is a hormone secreted by the beta cells of the pancreas in response to elevated blood glucose. The target sites for insulin are the liver, adipose tissue, and muscle cells where the hormone stimulates anabolic pathways. In muscle cells, there is an increase in the uptake of glucose. In the liver, glucokinase and glycogen synthase are activated; this results in an increase in the uptake of glucose and an increase in the synthesis of glycogen respectively. The enzyme acetyl-CoA carboxylase is also activated, causing a rise in fatty acid synthesis. Conversely, glycogen phosphorylase is inhibited, producing a decrease in the breakdown of glycogen. Lipoprotein lipase enzymes are activated in adipose tissue triggering an increase in the synthesis of triglycerides. Red blood cells, brain cells, lens fiber cells, and kidney cells do not require insulin for proper functioning and therefore do not possess insulin receptors. Glucose entry into these cells is not regulated by insulin but rather the concentration difference of glucose levels on the inside versus the outside of the cell. Muscle cells and adipose cells require insulin receptors which mediate the transportation of glucose into the cells. Insulin-independent cells are therefore more susceptible to damage in diabetes cases as the glucose intake into these tissues is not as regulated as those that possess insulin receptors.

What is the normal core temperature of the human body? 98.6 degrees Celsius 90.2 degrees Celsius 37 degrees Celsius 30 degrees Celsius

Remember the body is a delicate system whose enzymes, hormones, and proteins function optimally within a certain temperature and pH range. The core temperature of a healthy person's body is 37 degrees Celsius or 98.6 degrees Fahrenheit. If the core temperature drops below 35 degrees Celsius, the breathing and heart rates slow and consciousness may be lost.

Your patient wishes to be fit with a soft contact lens. Subjective refraction reveals OD: -1.50 -1.25 x 090. You place a -1.50 -1.25 x 100 diagnostic contact lens on her right eye. After 20 minutes the lens has settled and you notice that it is rotated 10 degrees to your right and is stable. What final contact lens should be ordered? -1.50 -1.25 x 070 -1.50 -1.25 x 110 -1.50 -1.25 x 080 -1.50 -1.25 x 100 -1.50 -1.25 x 090

Remember the rule of LARS (Left Add Right Subtract). When a toric lens is rotated to the Right you need to Subtract the degree of rotation from the SUBJECTIVE refraction axis, NOT the diagnostic contact lens axis!! When the lens is rotated to the Left you need to Add the degree of rotation to the SUBJECTIVE refraction axis. A very important thing to note is that lens rotation is measured from the DOCTOR'S right or left NOT the patient's. For the above problem the lens is rotated right by 10 degrees therefore the new contact lens will have a calculated axis of 090-010=080 or 80 degrees.

Which slit-lamp biomicroscopy illumination technique utilizes reflected light from the iris or fundus to detect fine endothelial or epithelial changes of the cornea? Direct illumination Scleral scatter Indirect illumination Specular reflection Retroillumination

Retro The use of retroillumination with a slit-lamp biomicroscope is helpful in better visualizing fine corneal epithelial and endothelial changes, such as keratic precipitates, epithelial cysts, and small blood vessels. The technique involves utilizing the reflected light from the iris or fundus (through a dilated pupil) to illuminate the cornea. Specular reflection is a mirror-like reflection of light from the cornea that occurs when the angle of incidence of the beam of light equals the angle of reflection. This technique is helpful in viewing abnormalities of the endothelium such as guttata. Scleral scatter involves moving the slit beam of light laterally so that it is incident on the limbus, but with the microscope focused centrally. This creates total internal reflection within the cornea and aides in the visualization of stromal lesions, subtle stromal haze, or infiltration of cellular or lipid components. Direct illumination is used to detect gross abnormalities of the cornea by directing a slit-beam of light to illuminate the area of interest. Indirect illumination involves viewing an area of the cornea to either side of the direct slit-beam of light. This is helpful in detecting more subtle abnormalities that can be washed out by excessive light levels.

Which of the following extraocular muscles is considered the antagonist pairing to the right lateral rectus? Left lateral rectus Right medial rectus Right superior oblique Left superior oblique Left medial rectus

Right MR Agonist-antagonist extraocular muscle pairs are those muscles of the same eye that move the eye in opposite directions. The agonist muscle is the primary muscle that contracts to move the eye in a given direction. The antagonist is the muscle of the ipsilateral eye that acts to move the eye in the opposite direction when contracted. Therefore, in this question, the agonist is the right lateral rectus, which moves the eye to the right, and the antagonist is the right medial rectus, which will move the eye to the left if contracted.

Which of the following retinal conditions is the MOST common complication associated with the presence of an optic disc pit? Optic disc edema Choroidal neovascular membrane Primary open angle glaucoma Central serous retinopathy Serous macular detachment Optic disc coloboma

Serous Macular Detachment An optic pit is a round- or oval-shaped pit that is typically observed at the temporal aspect of the optic disc but can also present centrally in some cases. The optic nerve itself is typically larger than normal, and the pit can be of variable size. Visual acuity remains normal in these patients, as long as there are no associated complications. About 45% of patients with a non-central optic disc pit will develop a serous macular detachment during their lifetime (average age is 30 years). The subretinal fluid that leads to the detachment of the outer retinal layers is thought to be derived from the vitreous. There may be associated subretinal deposits present surrounding the macula in these cases, and the appearance may initially be mistaken for central serous retinopathy (CSR). Therefore, it is important to examine the optic disc carefully in patients that present with signs and symptoms of suspected CSR or other causes of macular edema.

Which of the following autoimmune systemic disease is characterized by inflammation and destruction of the salivary and lacrimal glands? Systemic lupus erythematosus Wegener granulomatosis Systemic sclerosis Polyarteritis nodosa Sjogren's syndrome

Sjogren's syndrome Sjogren's syndrome is an autoimmune disease that causes inflammation and destruction of both the lacrimal and salivary glands. It may be manifested in isolation (primary) or in association with other diseases (secondary) including rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, chronic active hepatitis, myasthenia gravis, and primary biliary cirrhosis. Sjogren's syndrome primarily affects adult women. Signs of Sjogren's syndrome include enlargement of the salivary glands with diminished salivary flow rate and a dry, fissured tongue. Occasionally, the lacrimal glands may also become enlarged, and patients will exhibit decreased tear production and quick tear break-up times, leading to ocular dryness and grittiness. In addition to dryness of the mouth and eyes, patients also typically experience dry nasal passages and decreased vaginal secretions. Tests that aid in confirmation of a diagnosis of Sjogren's syndrome include serum autoantibodies, Schirmer's tear testing and biopsy of the minor salivary glands.

The following gas-permeable contact lenses provide your patient with an alignment fitting relationship and a plano DS over-refraction OU: OD: 43.25 D base curve / -2.87 D power OS: 42.87 D base curve / -2.00 D power If the patient inserts the above lenses into the wrong eyes (right lens inserted into left eye and left lens inserted into right eye), what over-refraction would you predict? OD = -1.25 D and OS = +1.25 D OD = -1.25 D and OS = -1.25 D OD = +1.25 D and OS = -1.25 D OD = +0.50 D and OS = -0.50 D OD = -0.50 D and OS = +0.50 D

Solution by inspection of data Before lens switch: OD: 43.25 / -2.87 gave alignment fit and plano DS OR OS: 42.87 / -2.00 gave alignment fit and plano DS OR Lenses switched: OR changes by OD: new lens (42.87) flatter by 0.37D (SAM-FAP) +0.37 DS new lens (-2.00) more plus power by 0.87D -0.87 DS Resultant OR = -0.50 DS OS: new lens (43.25) steeper by 0.37D (SAM-FAP) -0.37 DS new lens (-2.87) more minus power by 0.87D +0.87 DS (P)OR = +0.50 DS SAM-FAP (Steep Add Minus, Flat Add Plus)

The optic foramen is a small hole found in which of the following bones of the orbit? Lacrimal bone Palatine bone Ethmoid bone Sphenoid bone Zygomatic bone

Sphenoid The optic foramen is a small hole that is found within the lesser wing of the sphenoid bone at the apex of the orbit. This foramen allows for the passage of the optic nerve (cranial nerve II) and the ophthalmic artery. Remember that the superior orbital fissure is an opening that is created between the greater and lesser wings of the sphenoid bone and is located lateral to the optic foramen. Here, the four cranial nerves (CN III to CN VI) controlling movements of the eye and eyelid pass through. Additionally, the inferior orbital fissure is another opening at the apex of the orbit that is formed between the maxillary, zygomatic, and greater wing of the sphenoid bone; the inferior orbital fissure allows for the transmission of the maxillary branch of cranial nerve V.

Superior limbic keratoconjunctivitis (SLK) is commonly associated with which of the following system conditions? Rheumatoid arthritis Hypertension Systemic lupus erythematosus Thyroid dysfunction Diabetes mellitus

Superior limbic keratoconjunctivitis (SLK) is believed to occur as a result of mechanical trauma during blinking from abnormal forces between tight upper lids and/or loose, redundant conjunctiva. This is likely precipitated by a deficiency of the tear film, which results in decreased ability of the upper eyelid to move freely over the conjunctiva. This leads to increased movement of the bulbar conjunctiva and subsequent disruption of normal epithelial development and damage of both the bulbar and tarsal conjunctiva from continued mechanical trauma. This theory is supported by the fact that there is increased lid apposition in patients with thyroid dysfunction-induced exophthalmos (who are known to have an increased risk of SLK), as well as a noticed decrease in SLK symptoms with increased ocular lubrication. SLK most commonly affects middle-aged females, many of whom tend to have associated thyroid dysfunction.

The hip joint is an example of which type of joint? Cartilaginous joint Hinge-like joint Synovial joint Fibrous joint

Synovial joints Joints are points of contact or near contact between bones. Synovial joints are the most common type. This joint type separates bones via a cavity, and the involved ends of the bones are covered with a layer of cartilage that helps to cushion the joint. Cells that line the capsules also secrete fluid called synovial fluid into the cavity of the joint. Ball-and-socket joints allow for a full range of movement. Hinge-like joints, like the knee and elbow, allow for movement in one plane. Cartilaginous joints are found between the vertebrae and some of the ribs. In this joint type, the space between the bones is filled with cartilage, which allows for little if any movement. Fibrous joints do not exhibit cavities. This joint type serves to unite bones and is found on the skull bones of a newborn baby.

During gestation, when does the secondary vitreous begin to develop? The 9th week of gestation The 20th week of gestation The 30th week of gestation The 1st week of gestation

The 9th week of gestation The primary vitreous develops at around the third week of gestation. It is formed by mesoderm. The secondary vitreous begins to develop during the ninth embryonic week and later becomes the mature vitreous. The secondary vitreous stems from primary vitreal cells and retinal glial cells and therefore originates from neuroectoderm. The secondary vitreous expands to fill the globe while compacting the primary vitreous in the center of the globe.

Travelling on an airplane can cause the ears to make a "popping" sound. This noise is attributable to an equalizing of air pressure between the middle ear and the atmosphere. Which of the following structures serves to aid in this equalizing process? The cochlea The vestibular apparatus The Eustachian tube The utricle

The Eustachian tube The Eustachian tube runs from the middle ear to the pharynx. When pressure builds inside the ear, the tube helps to circumvent the excess pressure by allowing for equalization of air between the middle ear and the atmosphere. Rapid change in altitude can result in ear "popping" due to this equalization process. The cochlea contains the organ of Corti, which is vital for hearing. The utricle is part of the vestibular apparatus and plays an important role in balance and spatial orientation.

The vasculature of the choroid is regulated by which system? Lymphatic system Parasympathetic nervous system Sympathetic nervous system Pulmonary system

The choroidal vasculature is controlled by the sympathetic nervous system, specifically the superior cervical ganglion. Stimulation of the sympathetic nervous system leads to constriction of the choroidal blood vessels. The vasculature of the retina is not under autonomic control. Retinal vessels maintain an even flow rate by reacting to local alterations in carbon dioxide and oxygen levels.

The internal limiting membrane of the retina is replaced by a thin layer of astrocytes at the optic disc. What is the name of this membrane at the optic disc? Bowman's membrane The lamellar disc membrane The lamina cribrosa The inner limiting membrane of Elschnig

The inner membrane of Elschnig The internal limiting membrane does not extend over the optic disc, instead there is a thin layer of astrocytes that continue over the disc and are collectively known as the inner limiting membrane of Elschnig. Bowman's membrane or layer is found in the cornea below the epithelial layer. The lamellar disc membrane does not truly exist, this answer choice is meant to be a distractor. The lamina cribrosa is composed of collagen bundles, in a mesh-like formation, which cover the posterior scleral foramen to allow for the optic nerve fiber layer axons to exit the eye.

Which structure of the eye is isolated from the immune system and as such can be classified as antigenic? The retina The lens The optic nerve The cornea The iris

The lens The only structure of the eye that is isolated from the immune system is the lens. This is due to the fact that the lens is completely avascular and derives all of its nutritional needs from the aqueous humor. Because the lens is contained within a capsule, the body is never exposed to its protein contents and therefore if the proteins do become exposed, such as in a hypermature cataract or a dropped nucleus during cataract surgery, the body surmounts an immune reaction because it will not recognize the proteins.

In order for the visual system to detect a stimulus as flickering which of the following must hold true? The modulation depth should be very low The temporal frequency should be greater than the critical flicker fusion frequency The modulation depth should be moderate The temporal frequency should be very high

The modulation depth should be moderate If a stimulus is to be perceived as flickering, the modulation depth (the amplitude of the luminance change) should not be too low or the stimulus will appear steady. Also, if the temporal frequency of the stimulus is too rapid, the visual system will register a steady light rather than rapid flickering. The critical flicker fusion frequency denotes the temporal frequency above which the stimulus will be perceived as a continual light without flicker.

A patient with an AC/A ratio of 9/1 is prescribed a reading add of -1.00 D. Which of the following clinical results would be expected? The amplitude of accommodation would increase by roughly 1.00 D The near phoria would be expected to become more esophoric or less exophoric The monocular estimation method retinoscopy values would decrease in positive power or would increase in minus power The negative relative accommodation would be expected to decrease by roughly 1.00 D

The near phoria would be expected to become more esophoric or less exophoric A patient who has an AC/A ratio of 9/1 and is prescribed an add of -1.00 D would be expected to have the following clinical findings: the amplitude of accommodation would decrease by roughly 1.00 D, the near phoria would become more esophoric or less exophoric by 9.00 prism diopters, the monocular estimation method retinoscopy value would increase in plus power, the negative relative accommodation findings would increase by about 1.00 D, and the positive relative accommodation values would decrease by approximately 1.00 D.

Cover testing of your patient through their best correction reveals 6 prism diopters of esophoria at distance. While performing Von Graefe testing at distance, with 6 base-up prism in front of the left eye and 14 base-in prism over the right eye, the patient reports only seeing one target. When each eye is covered individually, the patient reports seeing the target, but with both eyes together does not report seeing two targets. What is the MOST likely explanation for the patient's lack of diplopia? The patient's refractive error is affecting the results of the test The patient is suppressing an eye Your Answer The biasing prism in the phoropter has neutralized the patient's heterophoria The phoropter is not aligned properly

The patient is suppressing an eye The most likely explanation for the patient's lack of diplopia on Von Graefe testing is suppression of an eye. One can infer both that the phoropter is aligned properly and the patient's prescription is not a factor, since the patient can see an image with each eye individually but does not report diplopia with both eyes together. One can also deduce that the prism in the phoropter has not neutralized the patient's phoria, given that the cover test revealed 6 prism diopters of esophoria and, all else being equal, the horizontal biasing prism in the phoropter is more likely to neutralize 14 prism diopters of exophoria.

While fitting a patient with a gas-permeable lens, you notice that there is a lot of fluorescein pooling under the lens and decide to change the base curve from 45.00 D to 44.25 D. Based on these new parameters, how should you adjust the prescription? The prescription should be increased by +0.75 D The prescription should be decreased by -1.25 D The prescription should be increased by +1.25 D More information is required to answer this question The prescription should be decreased by -0.75 D

The prescription should be increased by +0.75 D A good rule of thumb to follow is that of SAM FAP (Steep Add Minus, Flat Add Plus). When altering a base curve, one must also adjust the prescription due to changes in the tear film. Flattening the base curve of a lens induces a minus tear film; therefore, to offset this power change one must add plus power to the prescription. On the other hand, steepening of the base curve induces a plus tear film and therefore must be compensated for by adding minus to the prescription.

While performing Goldmann applanation tonometry, the mires are lined up properly horizontally; however, the lower semi-circle is much larger and almost complete, while the upper one is small. If no adjustment is made, how will this alignment affect the reading of the intraocular pressure (IOP)? It is not possible to determine how the reading will be affected The reading will be falsely low The reading will not be affected The reading will be falsely high

The reading will be falsely high If the mires are not equal in size during Goldmann applanation tonometry, the resultant IOP reading will be falsely elevated.

The right lung possesses how many lobes? One Two Four Three

The right lung is tri-lobed and the left lung has two lobes. A good way to remember this fact is that the word right has more letters than the word left; therefore, the right lung should have more lobes than the left.

A person who is completely dark-adapted and is shown scotopic stimuli will report that light of which wavelength will appear the brightest? 650 nm 507 nm 555 nm 610 nm

The scotopic system is meditated by rods and contains the photopigment rhodopsin, whose peak absorbency is 507 nm. The scotopic system cannot discern colors and is very sensitive to dim illumination; the scotopic system also possesses poor spatial resolution, good spatial summation, good temporal summation, poor temporal resolution, and poor contrast sensitivity. The photopic system, on the other hand, possesses three photopigments - erythrolabe, cyanolabe, and chlorolabe. This system has phenomenal color discrimination as well as spatial and temporal resolution. Cones display poor temporal and spatial summation. The photopic system displays a peak spectral sensitivity to wavelengths that are 555 nm.

In order for a corrective lens to focus an object that is located at optical infinity onto the retina of a myopic eye, which of the following must be coincident with the far point of the eye? The point on the lens where the index of refractive is greatest The primary focal point of the corrective lens The secondary focal point of the corrective lens The thickest portion of the lens

The secondary focal point of the corrective lens Corrective lenses for myopia (minus-powered lenses) diverge light rays so that the resultant image is focused onto the retinal surface rather than in front of it. In order for an object located infinitely from a myopic eye to be in focus on the retinal surface, the secondary focal point of the corrective lens must coincide with the far point of the eye. An image that is located at the far point of the eye will be imaged at the retinal plane.

In which of the following conditions are bandage contact lenses NOT typically utilized? Bullous keratopathy Eyelid entropion Filamentary keratitis Post-LASIK surgery Recurrent corneal erosion

There are several indications for the use of therapeutic bandage contact lenses; however, when deciding to place a contact lens on an already compromised cornea, the risks and benefits should be carefully considered. Bandage contact lenses may be used to promote corneal epithelial healing in cases where an epithelial defect persists (abrasion or recurrent corneal erosion), as the lens acts to protect the epithelium from the rubbing action of the eyelids, allowing the hemidesmosomes to create a strong attachment to the basement membrane. In addition to promoting corneal healing, bandage contact lenses are also commonly utilized for pain relief in certain conditions such as bullous keratopathy, Thygeson's superficial keratitis, filamentary keratitis, and trichiasis. The bandage contact lens relieves pain by protecting exposed corneal nerves from the shearing forces of the eyelids during blinking or via mechanical protection of the cornea from inwardly turned eyelashes. Bandage contact lenses are also used post-surgically in all cases of photorefractive keratoplasty (PRK) to allow healing of the corneal epithelium that has undergone the surgical procedure. Contact lenses are not typically applied after LASIK surgery unless there has been a serious complication.

A 7.76 mm base curve / -3.75 DS power diagnostic GP contact lens is applied to a patient's eye, and an over-refraction of -1.25 DS is obtained. What contact lens power should be prescribed to obtain a plano DS over-refraction if a 7.63 mm base curve is prescribed? -5.75 D -3.25 D -5.12 D -4.25 D -5.00 D

This is an application of the SAM-FAP rule (steepen add minus - flatten add plus). If the patient was to be prescribed a 7.76 mm (43.50 D) base curve, you would order a -5.00 D contact lens power (-3.75 D (+) -1.25 D = -5.00D). However, the base curve you are ordering, 7.63 mm (44.25 D), is 0.75 D steeper. Since you are steepening the base curve by 0.75 D, you need to compensate for the change in tear lens by the same amount. Steepen add minus (SAM-FAP) by 0.75 D in this case (-5.00 D (+) -0.75 D = -5.75 D).

In order to maintain an electrochemical potential across a membrane, what must occur? Two Na+ ions are pumped into the cell for every three K+ ions pumped out of the cell Two Na+ ions are pumped out of the cell for every three K+ ions pumped into the cell Three Na+ ions are pumped out of the cell for every two K+ ions pumped into the cell Three Na+ ions are pumped into the cell for every two K+ ions pumped out of the cell

Three Na+ ions are pumped out of the cell for every two K+ ions pumped into the cell Cells maintain an electrochemical gradient so they remain capable of normal regulatory functions. This gradient also allows for the ability of some cells to undergo action potentials. Ion pumps are used to sustain the voltage difference between the outside and inside of the cell. The pump hydrolyzes adenosine triphosphate (ATP) as the energy source used to power the active pumping of three sodium ions out of the cell for every two potassium ions pumped into the cell.

Horizontally polarized light is incident on a polarizer with an absorption axis that is rotated 25 degrees from the horizontal. Which of the following equations will solve for the percentage of light that will be transmitted? Tpol=cos2(25 degrees) Tpol=cos2/(25 degrees) Tpol=cos2/(65 degrees) Tpol=cos2(65 degrees)

Tpol=cos2(65 degrees) An ideal polarizing sheet is composed of dichroic material that will transmit 100% of light parallel to its transmission axis and will absorb 100% of incident light perpendicular to this axis. The transmittance of light that is oriented at a certain angle from the polarizing axis will follow Malus' law, which is Tpol=cos2 theta, where Tpol= the amount of transmitted light after it has passed through the polarizer, and theta= the angle between the incident light and the transmission axis. For the question above, the absorption axis is tilted 25 from the horizontal and its transmission axis is perpendicular to that, so the angle between the incident light and the transmission axis is 65 degrees or 90-25 degrees. Tpol=cos2(65 degrees)=0.178 or 18%. When answering these types of questions, ensure that the answer makes sense. In the above case, the absorption axis is close to the original orientation of the incident polarized light and therefore one should expect a low transmission percentage.

Hemoglobin is an example of which type of protein? Regulatory protein Transport protein Enzyme Contractile protein

Transport protein Proteins are created via polymers of amino acids which are linked together by peptide bonds. Proteins vary in their structure and function. Transport proteins are created to bind specific molecules and transfer them to their designated destinations. Hemoglobin is designed to carry oxygen. Contractile proteins (collagen, for example) are important in maintaining structural support. Regulatory proteins serve to manage physiological processes such as controlling blood sugar via insulin and glucagon. Enzymes are proteins that alter the rate of a reaction. An example of a biological enzyme is DNA helicase which serves to uncoil DNA.

Which of the following types of ultraviolet (UV) light is considered the LEAST damaging to the eye? UV-C UV-B UV-A All UV light is equally damaging to the ocular structures

UV-A is the longest of the three types of UV light, ranging between 315-380 nm. UV-A is considered the least damaging of the types of UV light and penetrates into the deeper layers of the skin. UV-A radiation is much more abundant than any of the other types of UV light that reaches the surface of the earth. UV-B light ranges between 280 and 315 nm, and over-exposure to this type of UV light can lead to sunburn. UV-B exposure has a higher correlation with skin cancer and cataract formation than UV-A. UV-C light ranges from 100 to 280 nm, and because it has a shorter wavelength, it is also very high-energy; therefore, prolonged exposure can lead to solar keratitis. The majority of UV-C light is absorbed by the ozone layer.

A patient is seen at your office reporting constant diplopia. The patient notes that the diplopia is still present when you cover her right eye. Based upon this information, what is the MOST likely etiology of her diplopia? Aneurysm Lateral rectus palsy Uncorrected refractive error Superior oblique palsy

Uncorrected refractive error Monocular diplopia is never caused by any type of cranial nerve dysfunction. The most common cause of monocular diplopia is an uncorrected refractive error. Other causes of monocular diplopia include corneal irregularities, lens irregularities, lens subluxation (very rare), or an improper glasses prescription. Whenever you are confronted with a recent onset of diplopia, the first thing you must determine is whether the diplopia is present monocularly or binocularly.

A 10-year old male is seen at your office complaining of itchy eyes and severe photophobia. He has a history of eczema and hay fever. Biomicroscopy reveals bilateral cobblestone papillae of the superior eyelids, ropy discharge, and mild superior corneal disruption that stains with sodium fluorescein. Given the above findings, what is your diagnosis? Vernal keratoconjunctivitis (VKC) Iritis Epidemic keratoconjunctivitis (EKC) Bacterial conjunctivitis

VKC is a condition of the young and presents with an increased frequency in males. This type of allergy typically develops before age 14 and lasts for 4-10 years before the child outgrows it; VKC occurs predominantly in the spring and summer. The condition progressively lessens in severity, with the first episode being the worst. Usually VKC is seen in patients who are prone to atopy; therefore they suffer from eczema, asthma, or hay fever. Patients typically suffer from itchy eyes and photophobia. The condition basically presents as a very severe type of allergic conjunctivitis. Signs include cobblestone papillae of the upper lid, lid swelling, and ropy discharge that is worse in the morning. Corneal defects (usually superiorly) known as keratitis of Togby may also be present. Occasionally, patients will develop a shield ulcer and Trantas' dots (calcified eosinophils seen circumlimbally that appear as chalky concretions), which may lead to the feeling of an associated foreign body sensation. Treatment includes mast cell stabilizers that should be started several weeks prior to re-occurring episodes, pulse steroid therapy, cool compresses, and sunglasses to help alleviate ensuing photophobia. EKC and bacterial conjunctivitis typically do not cause extreme itching and should not present with cobblestone papillae. The number one symptom associated with iritis is photophobia, and the patient should be neither complaining of itching nor have cobblestone papillae present on biomicroscopy.

In order to properly perform keratometry, what type of acuity are you utilizing? Recognition acuity Detection acuity Vernier acuity Stereoacuity

Vernier acuity

You are verifying a spectacle lens prescription that has returned from your lab. You ordered an Rx for the right eye of +1.00 -2.50 x 100. Which of the following values should be used for determining the ANSI standard for the sphere power? -3.50 -1.50 +1.00 +3.50 -2.50

When determining the error tolerance for the sphere power of spectacle lenses, one must first find the meridian of highest absolute power. The easiest way to find this number is to put the ordered prescription on an optical cross. In this case, the highest absolute power is -1.50.

While performing streak retinoscopy on a 6 year-old patient at a working distance of 50cm, you observe with-motion with no lenses in place. Which of the following refractive errors can you deduce that this patient is MOST likely to possess? Astigmatism You cannot conclude the type of refractive error based upon the above findings Myopia Hyperopia

You cannot conclude the type of refractive error based upon the above findings With motion can be observed in hyperopia, myopia and astigmatism; therefore, until the reflex is neutralized with retinoscopy and the working distance is accounted for, one cannot accurately deduce the type of refractive error without any lenses in place. For example, performing retinoscopy at a working distance of 50cm on a 1.00 D myope with no lenses in place will initially display with-motion of the reflex. Neutralization of the reflex will require the addition of +1.00 D (gross retinoscopy). To determine the net refractive error, the working distance must be subtracted from the gross retinoscopy findings. Because the working distance is 50cm, 2.00 D must be subtracted (reciprocal of the working distance) from the above gross findings of +1.00 D, yielding a net of -1.00 D.