Chapter 8: Preliminary examination

early treatment diabetic retinopathy study (ETDRS) chart

-The ETDRS chart was developed in 1982 and then revised in 2000 by the National Eye Institute for use in the Early Treatment Diabetic Retinopathy Study. -It differs from the Snellen chart in that there is an equal number of letters per row, the rows and letters are equally spaced on a log scale, and the individual rows are balanced for letter recognition difficulty. -The ETDRS chart has become the preferred or required chart used in most clinical trials

iris

-The iris is normally clear to inspection. The color depends on the amount of pigment in the stroma and the posterior layer of the iris. A heavily pigmented iris appears brown, whereas a lightly pigmented iris appears blue. -The iris is normally well supported by the underlying lens. Tremulousness of the iris usually means the presence of a dislocated lens.

lid margins

-The lid margins should be observed for any redness, scaling, or discharge, indicative of blepharitis. -The position of the lid margin should be noted, it should be tight against the globe and not sag outward (ectropion) or inward (entropion). -The punctum on the medial aspect of the lower eyelid should not be visible without depressing the lower eyelid. -More common affections on the lid margins: styes, chalazions, and growths

brightness acuity tester (BAT)

-The patient looks into the machine or at some Snellen letters arranged on a wall chart. -The examiner then turns on lights that shine directly into the patient's eyes. -The lights have been calibrated to imitate the brightness of headlights coming toward the patient at night, both high and low beams. -With the lights on, the patient is instructed to read the letters on the chart. The acuity is measured after glare testing is recorded. -With high beam light, this usually falls off considerably if lens opacities are present.

tear production

-The presence of tearing in the absence of any other signs of inflammation should be noted. -Distension and chronic inflammation of the lacrimal sac may cause a small, smooth elevation in the lacrimal fossa. -Pressure inward on this area causes the contents of the lacrimal sac to be expressed by way of the puncta on the conjunctiva. -It should be noted whether the contents are tears, mucus, or purulent material.

pupil shape

-The pupil is normally round and regular. -Irregularities in the shape of the pupil may result from congenital abnormalities, inflammation of the iris, trauma to the eye, and surgical intervention.

pupil - equality of size

-The pupils should be equal in size and react equally to direct light stimulation, consensual light stimulation, and near objects. -In the light of an ordinary room, the diameter of the normal adult pupil is between 3 and 5 mm.

pupil size

-The size of the pupil varies with age, the color of the iris, and refractive error. -The pupil tends to be largest in blue-eyed young children who are myopic. -Conversely, the pupil tends to be smaller in infants and older adults. -Dim light dilates the pupil and bright light constricts it.

tears

-The tears are normally carried from lateral to nasal sides along the lid margin. -When they reach the opening of the lower lid (punctum), they drain into the nasolacrimal duct and finally into the nose. -Blinking spreads the tear film over the eye but also moves the tears toward the punctum with each blink. -Tears contain albumin, globulin fractions, and an antibacterial enzyme called lysozyme. -Tear production may decrease 30% or more in a person older than 50 years.

drug-induced dilation

Iatrogenic or self-contamination may occur with a variety of dilating drops, such as cyclopentolate hydrochloride (Cyclogyl), tropicamide (Mydriacyl), homatropine, scopolamine, and atropine. The pupil is fixed and dilated, and unlike third nerve palsy, does not respond to constricting drops.

drug-induced constriction

Iatrogenic or self-induced pupillary constriction may be caused by a variety of drugs, including pilocarpine, carbachol, and echothiopate iodide

transillumination

If a light is brought to bear on the iris at close range against the sclera, the light may seem to glow in a patchy way in areas where there has been marked pigment loss -This can occur with some forms of glaucoma (pigmentary), after iritis, or with albinism

relative afferent pupillary defect (RAPD)

If initial ocular examination appears normal, testing for a RAPD is a way to implicate or rule out optic nerve disease. -In the case of an RAPD: When one shines a light in the good eye, both pupils constrict. When one shines the light in the other eye, an optic nerve that is injured will transmit light but to a lesser and slower degree. As a result, when the light is moved from the good eye to the bad eye, the central nervous system interprets this as a decrease of light being presented. The central nervous system's response is to dilate both pupils to let more light in.

spontaneous venous pulsation (SVP)

If present, suggests that there is no papilledema because this disappears early.

light perception (LP)

If the patient cannot distinguish the projection but is able to just detect the light, the visual acuity is recorded as light perception. If the patient is unable to detect light at all, the vision is recorded as absent light perception.

light projection (L Proj)

If the patient cannot even detect hand movements, the room is darkened, a test light shone into the eye from the four quadrants, and the patient is asked to point in the direction of the light. If the patient can accurately point to the light, vision is recorded as light projection.

hand movement (HM)

If the patient perceives hand movements, the vision is recorded as HM, or hand movements.

When not to dilate before asking the eye doctor

1) The depth of the anterior chamber is very important. If the depth is shallow because of a narrow angle, there is a risk of precipitating angle-closure glaucoma. Do not dilate. 2) Before cataract extraction with implantation of an iris-supported intraocular lens. Do not dilate. The dilation of the iris in these patients could result in a dislocated intraocular lens. 3) If the patient is undergoing neurologic observation and pupillary signs are being followed, dilation may alter the diagnosis and confuse the attending physician. Do not dilate until the neurologist or neurosurgeon thinks it is safe to do so.

pupil shape - corneal laceration

A corneal laceration with prolapse of the iris may result in the drawing up of a segment of the iris to the site of laceration (adherent leukoma)

retinometer

A microaperture is illuminated by a halogen bulb through a red filter and imaged by an optical system into the patient's pupil. The optical system consists of two lenses between which optical grids with variable spacing can be positioned in the parallel beam that passes through them. The resulting diffraction forms a circular test pattern with equally spaced red and black lines on the retina. Because the beam in the pupillary plane is very narrow, a tiny "window" in the opacity of the lens is enough to allow the light to pass through for a successful examination.

Proptosis is a sign of: A) thyroid disease B) adult glaucoma C) ptosis D) hypertension E) all of the above

A) thyroid disease Protrusion of the eyes is usually measured with the exophthalmometer. When it occurs in one eye, it frequently indicates a retrobulbar mass, a hemangioma being most common. But when it occurs in both eyes, it means thyroid disease until proved otherwise. Deposits of fat, hyaluronic acid-like material, and inflammatory cells cause the typical bulging of the eyes.

Wirt stereo test

Animals in three lines are shown to young school-aged children or even to preschoolers. If all three lines of animals are correctly selected, the patient has stereopsis of approximately 100 seconds of arc.

Depth perception requires: A) good vision in each eye B) overlapping visual fields C) normal alignment of the eyes D) all of the above E) none of the above

D) All of the above Most authorities believe that depth perception cannot be acquired. If there is a congenital strabismus and the eyes are straightened at age 3 years, that child will not have depth perception. Having poor depth perception may not be of practical importance because there are so many monocular clues to judge distance. Pilots need it in the rare instances that they have to make a visual landing. Athletes, like baseball or tennis players, are also handicapped without depth perception.

pupil w/ 3rd nerve palsy

Dilation of a pupil to 5-6 mm can result from paralysis of the third cranial nerve. -If the lesion is a result of a third nerve palsy, the size of the pupil in the affected eye remains unchanged when the light is directed into the fellow eye.

external examination

Documentation of abnormal external features will aid the ophthalmologists in the recording of these abnormalities, as well as alerting him or her to the problems that are incidental to the main complaint of the patient. This exercise helps instill an awareness of and interest in unusual eye problems, whether they are abnormal or pathologic. The ophthalmic assistant should begin the external examination of the eye by systematically noting the symmetry of the orbits, the eyelashes, the lid margins, the conjunctiva, the lacrimal apparatus, the sclera, the cornea, the iris, the anterior chamber, the pupil, and the lens.

pupil size- during sleep

During sleep, the pupil is constricted. This is such a constant finding that it serves as an aid in differentiating true from simulated sleep.

pupil w/ cycloplegic drug

Failure of a large, dilated pupil to constrict to light is most commonly caused by a cycloplegic drug such as atropine. Such a pupil is 7-8 mm in diameter, spherical, and immobile when light is shone into the eye.

True or false: In visual acuity recordings, 6/12 is equal to 20/60 vision.

False. 6/6 vision in meters is equivalent to 20/20 vision. 6/12 vision in meters is equivalent to 20/40 vision. In Canada and the United States, visual acuity charts are designated in feet, whereas in Europe the metric system is used.

True or false: In occlusion nystagmus, the vision is improved when one eye is occluded.

False. Occlusion nystagmus is a congenital condition in which nystagmus and esotropia may be induced by covering one and decreasing vision. The decrease in light sensation is enough to cause the other eye to oscillate. Such children, when given routine vision tests, score poorly because the examiner fails to look for this condition. In these children, the eye that should be occluded can be fogged with a +10.00 diopter lens to allow proper vision in the other eye.

triple line test (measurement of amplitude of accommodation)

In this test, two small vertical lines as found on the Lebensohn chart, are brought toward the patient. -The near point is reached when the patient sees three lines instead of two.

Worth four-dot test

One white disc, one red disc, and two green discs are presented to the patient, who is wearing spectacles with a red-free green lens before one eye and a green-free red lens before the other eye, thus allowing both the patient's eyes to see the white disc. -If all 4 discs seen, both eyes are functioning. -If 3 discs are seen, eye behind green lens is seeing while eye behind red lens is suppressed. -If 2 discs are seen, eye behind red lens is seeing while eye behind green lens is suppressed. -If 5 discs are seen, then another problem is indicated (the eyes are not fusing and muscular imbalance is suspected).

tropicamide (Mydriacyl)

Onset of maximum cycloplegia: 20-40 min Duration of activity: 4-6 h Comment: A good drug for office use with an effect similar to Cyclogyl.

homatropine hydrobromide

Onset of maximum cycloplegia: 30-60 min Duration of activity: 3 days Comment: Requires half hour to an hour to take effect and lasts 3 days; not used routinely

scopolamine hydrobromide

Onset of maximum cycloplegia: 30-60 min Duration of activity: 4-7 days Comment: Used in atropine-allergic patients

cyclopentolate hydrochloride (Cyclogyl)

Onset of maximum cycloplegia: 30-60 min Duration of activity: 6-24 h Comment: Active in 30-60 min; two sets of drops given 5 minutes apart; a good rapid-acting cycloplegic drop for office use

atropine sulfate

Onset of maximum cycloplegia: 45-120 min Duration of activity: 7-14 days, especially in a blue-eyed child Comment: Not used routinely except for the assessment of accommodative strabismus in children

superior oblique

Primary action: down and in Fourth nerve innervation

inferior rectus

Primary action: down and out Third nerve innervation

superior rectus

Primary action: down and out Third nerve innervation

medial rectus

Primary action: in Third nerve innervation

lateral rectus

Primary action: out Sixth nerve innervation

inferior oblique

Primary action: up and out Third nerve innervation

pupil size- psychic influences

Psychic influences such as surprise, fear, and pain markedly dilate the pupil.

pupil shape - severe iritis

In severe iritis, the iris may be bound down to the lens by adhesions (posterior synechiae) and irregular changes may occur in the shape of the pupil

iritis

Slit-lamp examination shows keratitic precipitates and cells in the anterior chamber and a prominent ciliary flush. The intraocular inflammation stimulates pupillary constriction.

proximity method (measurement of amplitude of accommodation)

Small print is held at a comfortable arm's length and gradually brought closer. The distance at which the patient reports blurring of the letters is measured in centimeters and reported in diopters. -To convert the centimeters into diopters, divide the measurement into 100. If the patient is too presbyopic to comfortably hold reading material, an auxiliary lens may be added but then subtracted from the total findings.

lens

The entire lens is normally not visible without the aid of a slit-lamp microscope. -An advanced cataract may be seen with the naked eye because it causes a gray, opaque appearance in the pupillary aperture.

disc margins

The margins of the disc are sharp and distinct, except for the margins of the upper and lower poles, which may be slightly fuzzy

sclera

The normal sclera is visible behind the conjunctiva as a white, opaque fibrous structure. Blue discoloration of the sclera may be normal in a very young child because of the sclera's thinness and the underlying prominence of the dark choroid. Blue discoloration in an adult invariably indicates a pathologic condition: tumor, thinness of the sclera with a protrusion of the underlying uvea (staphyloma), or a nevus. In older adults, the sclera may appear yellowish because of the presence of fat and other degenerative substances.

pupil

The ophthalmic assistant can test pupillary function with no special instrument except a small light.

palpebral conjunctiva

The palpebral conjunctiva of the lower eyelid is seen by depressing the lower lid while the patient looks toward the ceiling. The palpebral conjunctiva lining the upper eyelid can be seen only by everting the upper lid. Eversion of the upper eyelid is carried out by grasping the lashes of the lid between the thumb and the index finger and turning the eyelid over a cotton-tipped applicator or other blunt instrument. It is important that the patient is asked to look downward to relax the levator muscle. With eversion of the upper eyelid, the tarsal conjunctiva is visible and the meibomian glands running vertically from the lid margins are easily seen. *The conjunctiva should be inspected for follicles, discharge, color, and growths such as pterygium and pinguecula.

fly test

The patient is provided with polaroid lenses and asked to touch the wings of a fly. If the patient has depth perception, the wings will appear to stand out before the picture. The patient will have gross stereopsis of approximately 3600 seconds of arc.

acute glaucoma

The patient may complain of pain and/or nausea and vomiting. The eye is red , vision diminished, intraocular pressure elevated, and pupil is middilated and poorly reactive.

Use of pinhole

The pinhole disc, if placed before the eye, eliminates peripheral rays of light, improves contrast, and generally improves vision to almost within normal limits. The pinhole disc thus serves to differentiate visual loss caused by refractive errors from poor vision resulting from disease of the eye.

pupil of eye w/ acute narrow-angle glaucoma

The pupil may also be dilated and fixed to direct light stimulation and consensual light stimulation after an episode of acute narrow-angle glaucoma. However, this pupil is characteristically oval.

pupil of eye with retina problem

The pupil may also be large, immobile, and unresponsive to the direct application of light because of severe afflictions of the retina and optic nerve that results in blindness. -If the pupillary dilation is a result of disease of the retina or optic nerve, the consensual light reflex produced by shining light into the sound eye will produce a constriction of the pupil in the affected eye.

tear film

The tear film that covers the surface of the eye is composed of the following three layers: 1) A superficial oily layer derived from the meibomian glands and the sebaceous gland of Zeiss. It prevents evaporation of the underlying tear layer. 2) The tear film, which is the middle layer, is secreted by the lacrimal gland and the accessory glands of Krause and Wolfring. 3) The deepest layer is the mucoid layer and is secreted by the goblet cells of the conjunctiva.

pupil shape - eye trauma

Trauma may cause tears of the iris in the form of a wedge-shaped defect, either at the pupillary margin or at its base.

True or false: Shining a light in the eye not being examined is a valid way of doing a pinhole assessment of vision.

True. A pinhole disc before the pupil improves vision to normal limits if the loss of vision is a result of a refractive error. The pinhole test separates refractive visual error from pathologic visual loss. With disease, a pinhole over the pupil makes vision worse. Shining a light in the other eye causes both pupils to constrict and is a simple way of achieving the pinhole test.

commonly used abbreviations

VA = visual acuity OD = oculus dexter (right eye) OS = oculus sinister (left eye) VOD = vision right eye VOS = vision left eye OU = oculi uterque (both eyes) RE = right eye LE = left eye EOM = extraocular muscles NPC = near point of convergence NPA = near point of accommodation Rx = prescription for eyeglasses or drugs Δ = prism diopter D = diopter T = tension

glare testing

Visual acuity may degrade considerably in the presence of bright light. A number of glare test devices are available on the market (true visual acuity [TVA], brightness acuity tester [BAT], Eye Con) Vision with opacities in the ocular media, cornea, lens, posterior capsule, and vitreous, when under the effect of bright light, degrades considerably and provides a true visual acuity in ambient lighting.

visual fields

Visual field testing is important in a thorough workup of a patient to screen any possible interference in the nerve pathways from the eye to the brain.

aphakia

absence of a lens -The iris loses its support, flattens, and deepens the anterior chamber; may become tremulous

variation of Schirmer's test

accomplished by placing an anesthetic drop into the conjunctival sac before the Schirmer paper -eliminates reflex tearing caused by the paper itself

convergence

act by which the eyes are turned toward each other to view an object in the midline plane situated close at hand -It is measured by having the patient look at a small target such as a pin, letter, or toy -The near point of convergence (NPC) is the point at which fusion can no longer be maintained and one eye deviates outward

fluorescein

an ocular stain used to show defects and abrasions in the corneal epithelium -pooling of fluorescein on small corneal defects is best seen by means of ultraviolet or cobalt blue light for illumination -danger with solution form is contamination with Pseudomonas aeruginosa

interferometer

apparatus similar to the PAM Instead of a Snellen chart that is imaged on the retina through breaks in the cataract, the interferometer shines red laser light or white achromatic light directly through the opaque portion of the cataract. *If the patient can name the orientation of several grids with very thin stripes, it is assumed that the retina can resolve images at that visual level and should approximate good postoperative acuity.

cilioretinal arteries

arising from the ciliary circulation are seen in about 20% of patients and account for the blood supply to the macular region

lissamine green

can be used as an alternative to rose bengal; less irritating

Miller-Nadler glare tester

commonly used to test for visual discrimination during bright daylight conditions -It consists of a tabletop viewing screen and a slide projector with 17 slides of varying sizes of land, dot, sea, and rings. -With each progressive slide, the background is made progressively darker, decreasing contrast. -The projector screen acts as a glare around the edge of the slide and shines into the patient's eyes. *The ability or inability to detect breaks in rings of smaller size and lower contrast correlates with loss of functional vision outdoors in bright sunlight.

anisicoria

condition in which the two pupils are unequal in size -may be harmless but it is never physiologic

lamina cribosa

connective tissue layer through which the fibers of the optic nerve pass

blepharospasm

continual squeezing of the eyelids together -occurs as a result of inflammatory diseases of the anterior segment, Parkinson's disease, and stress

coloboma

defect in the iris; indicates the absence of some portion of the iris, may be the result of previous surgery or a congenital abnormality

heterochromia

difference in the color between the two irides -may be indicative of a congenital abnormality, iris tumor, retained intraocular foreign body, or old iritis

hypotropia

downward deviation of the eye

kinetic vision

moving vision; cannot be measured, but it is known that acceleration reduces acuity.

unilateral constriction of the pupil

occurs with iritis, interruption of the sympathetic pathways of the eye, and irritative lesions of the cornea

Argyll Robertson pupil

one of the classic signs of late syphilis -small, irregularly shaped, and nonreactive to either direct or consensual light stimulation but reactive to near stimulation

exotropia

outward turning of the eye

rose bengal

red dye that has affinity for degenerated epithelium -stains in areas in which the epithelium has been sloughed off -intact, nonviable epithelial cells of the conjunctiva or cornea stain brightly with rose bengal -helpful in diagnosing keratoconjunctivitis sicca or other conditions associated with dryness of the conjunctiva

caruncle

seen as a fleshy mound of tissue at the inner canthus

macular photostress test

sensitive test for detecting macular dysfunction such as cystoid macular edema, central serous retinopathy, and senile macular degeneration -Normal recovery to bright light is 0-30 seconds but it becomes prolonged to more than 1 minute in patients with maculopathies.

Hardy-Rand-Rittler plates

series of pseudoisochromatic plates for yellow-blue color blindness as well as red-green color deficiency -The background is neutral gray on which a series of colored circles, crosses, and triangles are superimposed. -These geometric designs are present in higher and lower saturations of color to detect the degree of color vision defiency

Colormaster

sophisticated, completely automatic and programmable computerized form of presenting colored sequences of constant hue, saturation, and brightness to an individual

Schirmer's test

standardized filter paper is inserted in the unanesthetized lower fornix of each eye -with the eyes gently closed, these strips become moistened by the tears -some strips have a methylene blue bar that indicates the amount of tear flow -normally, the lacrimal gland, under the irritation of filter paper, should produce sufficient tears to wet at least 10 mm of filter paper in 5 minutes -any tear production less than 10 mm indicates dryness of the eye and that the condition of xerosis may be present

red reflex

the red glow filling the person's pupil which is caused by the reflection of your ophthalmoscope light off the inner retina.

biopter test

this instrument has the fundamentals of a home stereoscopic viewer in which slightly different images are presented to each eye The sensation of depth is appreciated by the slightly disparate images.

Adie's syndrome

tonic pupil -The pupil responds to light stimulation very slowly. Responds better to near stimulation than light. -Diagnosed by instilling a low dose (0.125%) of pilocarpine, which can result in the constriction of the tonic pupil caused by cholinergic denervation hypersensitivity, whereas a normal pupil will not constrict with such a low dose. -The condition is thought to be related to aberrant innervation of the iris by axons that normally stimulate the ciliary body. -Absent knee jerks are usually associated.

hypertropia

upward deviation of the eye

cobalt blue filters

used for fluorescein studies of the fundus as well as examination of the cornea with fluorescein strip papers.

accommodation

mechanism by which the eye internally adjusts to changes in the proximity of an object before the eye to maintain a clear image on the retina -affected by alterations in the radius of curvature and thickness of the eye's lens; adds power to the eye as an optical instrument

bilateral constriction of pupils (miosis)

most commonly caused by glaucoma medication, such as pilocarpine

instillation of eyedrops and ointment

-All drops, with the exception of topical anesthetics are placed into the inferior cul-de-sac with the patient looking up. -Topical anesthetic drops, such as those used when intraocular tension is being measured, are placed in the eye when the patient is looking down with the solution directed at the 12:00 position of the sclera near the limbus. -When ointments are required, a small amount is instilled into the lower cul-de-sac as the patient looks up.

eyelashes

-Cilia, or eyelashes, are hairs on the margins of the lids. -They are located in two rows, totaling about 100-150 on the upper lid and half that number on the lower lid. -The bases of these cilia are surrounded by sebaceous glands (glands of Zeiss); infection = stye -Average life span: 3-5 months, after which it falls out and a new one grows in its place. -If eyelashes are cut short, regrowth is rapid and lashes may appear normal in a few weeks -Some glaucoma medications (ex. latanoprost, travoprost, and bimatoprost) cause eyelashes to become darker and longer.

trauma

-Damage to the iris sphincter may result from a blunt or penetrating injury. -Iris transillumination defects may be visible with the ophthalmoscope or slit lamp and the pupil may have an irregular shape

color vision

-Defects in color vision may be congenital or acquired. -Congenital color defects occur in about 8-10% of males and in only 0.4% of females. -This defect is transmitted through the female and appears predominantly in the male. -Acquired color blindness may occur after diseases of the optic nerve or central retina.

pupillary reflexes

-For assessment of the direct light reflex, the patient should be seated in a dimly illuminated room, with the light evenly distributed throughout the room -The normal direct light response causes constriction of the pupil on that side. -For assessment of the consensual light reflex, light is directed into one eye while the second eye is observed. An intact consensual response to light causes constriction of the pupil of the unilluminated eye. -During the swinging flashlight test, if the amount of light information transmitted from one eye is less than that carried by the fellow eye, immediate dilation of the pupil, instead of the normal initial constriction, may be noted when the light is swung from the good eye to the defective eye.

counting fingers (CF)

-If it is impossible for the patient to distinguish the large letter, the examiner holds his or her fingers before the patient's eye in good light and the vision is recorded as the farthest distance at which the fingers can be counted.

third nerve palsy

-If the pupil is fixed, the cause may be third nerve palsy. -This condition may be associated with ptosis and a motility disturbance, characterized by the eye being deviated out and down. -The pupil responds to constricting drops, such as pilocarpine. -This is a neurosurgical emergency, and the possibility of an intracranial mass lesion must be ruled out.

symmetry of orbits

-In proptosis (exophthalmos), in which one eye protrudes, the upper lid is often retracted and there is exposed sclera above and below the cornea. -Another method of determining the presence of proptosis is to stand behind the patient, draw the upper lids upward and note which eye bulges outward more. -The degree of proptosis is measured with an exophthalmometer.

6th nerve innervation

-Lateral rectus

blinking

-Most people blink 15 times per minute -The duration of a blink is approximately 0.3-0.4 second -The average period between blinks is about 2.8 seconds in men and 4 seconds in women.

near vision testing

-Near vision charts are designed to be read 14-16 inches. -In patients with accommodative loss, as in patients with early presbyopia, a corrective lens is required to record the near vision. -The near vision is recorded as the smallest type that can be comfortably read at the distance at which the card is held. *Near vision in children does not always correspond to the vision taken in the distance. Children can usually read despite significant refractive errors because they can hold reading material close to their eyes and thereby obtain magnification by the powerful range of accommodation.

4th nerve innervation

-Superior oblique

3rd nerve innervation

-Superior rectus -Medial rectus -Inferior rectus -Inferior oblique

vision assessment

-Vision should be assessed both with and without glasses on a standardized chart, and each eye should be tested independently. -Visual acuity (VA) is determined by the smallest object that can be clearly seen and distinguished at a distance. -The results of vision testing are expressed as a fraction. The numerator denotes the distance the patient is from the chart of letters and the denominator denotes the distance from the chart at which a normal person can see the chart letters. -Generally, in the Western Hemisphere, visual acuity is measured in feet. In Europe, the metric system is used. -A quiet area should be selected for testing visual acuity. The chart should be fastened at eye level on a light, uncluttered wall that has no windows nearby to avoid glare. -In assessing vision, the examiner places an occluder over one of the patient's eyes without exerting any pressure on the eye.

Horner's syndrome

-constricted pupil (miosis) -mild ptosis of the upper lid -retraction of the lower lid *Adrenergic innervation to the iris dilator muscle is diminished.

central retinal vein

-found lateral to the central retinal artery -larger and dark red

direct ophthalmoscope

-one of the most popular for all practitioners -greater magnification (x 15) -easier to use with small/undilated pupils -mechanically easier to use -contains a number of spherical lenses

optic disc

-oval structure that represents the site of entrance of the optic nerve; color and shape are noted -usually light pink and may have a central yellowish white depression called the physiologic cup, created by separation of the nerve fibers

indirect ophthalmoscope

-permits binocular vision with depth perception (stereoscopic vision) -permits a wider field of view of a given area -the image is inverted -may be used in the operating room without contamination and permits indentation of the sclera and a better view of the periphery of the fundus -more intense illumination and frees the hands for operative manipulation

macula

-small avascular area that appears darker red than the surrounding fundus -center is a glistening oval reflex (fovea) -at its center is the foveola, which has a high density of cones

tips on ophthalmoscopy

1) If the examiner has any significant astigmatic error, he or she should wear corrective lenses. 2) A smaller light spot should be used for astigmatic eyes to minimize distortion from toric corneas. 3) The cornea and anterior structures of the eye should be examined from a distance of 1 foot through the sight aperture of the ophthalmoscope. The examiner then moves to within 1 inch of the eye to observe the retina. 4) The patient should be asked to gaze on all quadrants to observe the peripheral retina. Each arteriole is followed out to the periphery. 5) To avoid coming too close to the patient's eye, the examiner may put his/her middle finger against the patient's cheek.

universal method of using any lensmeter

1) Place the lens to be measured in the lensmeter on the table, convex side toward you, with the lens surface firmly against the instrument and with no tilt. Tilting a lens will introduce an error that may result in an inaccurate axis and cylinder power. 2) Center the target, then set the power to zero. Move the power wheel from zero to a point well beyond the focus of the target and then back toward zero to the point where the first target meridian or dots come into focus. Take the reading. This is the spherical power. 3) Continue rotating the power wheel in the same direction (do not reverse direction) to bring the second meridian into focus. The algebraic difference is the cylindric power. The sign of the cylinder is opposite that of the sphere. Note the axis of the second meridian. 4) Make this check. If the target line or smeared dots is nearly horizontal, it will be near zero or 180 degrees. If they are nearly vertical, the reading will be near 90 degrees.

visual acuity testing for children

1) Whenever there is doubt about the child's motivation, intelligence, or attention, the E game should be used because it is unnecessary for the child to make a judgment concerning a visual symbol. 2) A false idea of visual acuity will be obtained if an isolated letter is presented to the patient rather than a line of letters. 3) There can be differences in recognition of letters in the same line. 4) Vision should always be tested with and without the patient's glasses so that a comparison between the two can be made. 5) In children, visual acuity testing should not be prolonged and fatiguing. 6) The child who cannot comprehend the organization of the E game should receive practice at home. 7) In all visual acuity measurements, the assistant should note any consistent pattern in the letters missed by the patient. 8) If both eyes are tested together, it is usually found that one eye reinforces the other. 9) A false visual acuity test will be obtained if the patient closes an eye or squints. 10) The patient should be observed during testing to prevent peeking around the occluder.

A 10 year-old boy has 14.00 diopters of accommodation. A 45 year-old man has ____________ of accommodation left.

3.50 diopters The decline in accommodation is most striking between ages 30 and 40 when it drops from 8.00 to 4.50 diopters. It is caused by atrophy of ciliary muscle and loss of elasticity of the lens of the eye. Unfortunately there is no way to halt the process, thus it is inevitable that everyone eventually needs reading glasses, except near-sighted people, who merely take their glasses off.

pupil size - irritation of the cornea/conjunctiva

Any irritation of the cornea or conjunctiva such as an abrasion results in constriction of the pupil.

The following tests are suitable for color vision testing: A) The Worth four-dot test B) The Ishihara test plates C) The fly test D) All of the above E) None of the above

B) The Ishihara test plates Ishihara test plates are those most commonly used for the detection of color deficiency. Other devices such as the Nagel anomaloscope are superior in detection of possible defects and in quantifying them. The Ishihara plates, however, are inexpensive to purchase so they can be used by every industrial or school nurse. They are simple to use, no expertise is required, and the results are reproducible. It is basically a color vision screener and not an analyzer.

When neutralizing lenses, the displacement of the target by the prism is always recorded in terms of the ___________ of the prism.

Base If the lens has a prism, the center of the lens does not coincide with the center of the target. The displacement measured in circles of expanding radii is a measure of the power of the prism and is recorded as base in, out, up, or down. The distance between each circle represents 1.00 prism diopter. With the new automatic devices, prism power is digitally recorded and results are instant.

Defects in color vision are present predominantly in __________.

Boys Congenital color defects, red-green being the most common, are transmitted by the female and appear predominantly in the male. In fact, 8-10% of males are color deficient. Total color blindness is another matter; it is rare and very disabling and causes blindness and nystagmus in children

anterior chamber depth

By shining a small penlight from the side, one can make an estimation of the depth of the anterior chamber. If the anterior chamber is shallow, it should be so recorded because the patient may be prone to narrow angle glaucoma.

contrast sensitivity

Contrast sensitivity charts or machines are used. The contrast sensitivity chart presents a pattern of stripes of varying contrast, size, and orientation. The patient is asked to describe the orientation of the stripes. If the patient answers correctly several times, it is assumed that he or she is able to see these objects at that particular size and contrast.

potential acuity meter (PAM)

It is often difficult to see behind a dense cataract, or even an early cataract, to give a good estimate of the potential visual acuity of any particular eye. The Guyton-Minkowski potential acuity meter (PAM) is a small apparatus that attaches to a slit lamp. The patient looks into a small aperture in the machine and sees the Snellen acuity chart. The examiner can control the position of the acuity meter, shine it through the pupil, and direct it through particular sections of the patient's crystalline lens. *This has important prognostic significance for determining what the visual acuity will be following cataract surgery. It lets the physician know that the retina and media are intact and gives an estimate of potential visual acuity.

Ishihara test plates

The Ishihara book consists of a series of pseudoisochromatic plates that determine total color blindness and red-green blindness. -These plates are viewed by the observer under good illumination. -They consist of dotted numbers of one color against a background of another color. *If color vision is normal, the dots stand out and the patient can read the appropriate number, whereas a color-blind person viewing the same plate would interpret the dots as forming a completely different number.

effect of age on accommodation

The ability of the eye to make these changes in focusing adjustments is greatest in childhood, when the crystalline lens is softest and most malleable. The range of accommodation declines rather precipitously with age as the lens becomes harder.

bulbar conjunctiva

The bulbar conjunctiva is readily visible.

cornea

first and most powerful lens of the eye's optical system -radius of curvature: 7.8 mm -refractive index: 1.376 -power: 48.8 diopters -posterior surface: 25.8 diopters -total power: 43.00 diopters; 70% of total refractive power -The reaction of the cornea to disease is unique. Being avascular, it cannot easily fend off infection. The surface layer of the cornea, the epithelium, is easily disrupted but it fully regenerates when injured. -The normal cornea should be smooth, shiny, and free of irregularities. -The cornea is normally free of blood vessels. The presence of blood vessels indicates a pathologic condition and disease. -Corneal sensation should be tested with a small wisp of cotton directly applied to the cornea.

muddiness of the iris

general loss of clarity of the pattern of the iris -caused by inflammatory exudates in the anterior chamber or on its surface

depth perception

highest quality of binocular vision because it provides the individual with judgment concerning depth, based on the coordinate use of the two eyes together -A prerequisite for depth perception is good vision in each eye, overlapping visual fields, and normal alignment of the eyes in all positions of gaze -4 main tests: fly test, Wirt stereo test, Worth four-dot test, and biopter test

arcus senilis

in older adults, a white ring present near the corneal periphery; caused by deposition of cholesterol and lipids in the peripheral cornea, a common aging process

lensmeter

instrument designed to measure the prescription of an optical lens -Lenses are made up of either spheres or cylinders or a combination of both. -By using a target area on the lensmeter, one can determine the exact prescription of any lens

TearScope

instrument for analyzing the tear film in vivo -assesses dry eye symptoms and in contact lens work when one wants to know whether the tear film is stable or punctal plugs are required -held in hands or attached to slit lamp -measures the break-up time of tears and tear film with fluorescein stained tears

esotropia

inward turning of the eye