NCLE Prep Exam 3 of 4
Which of the following will NOT measure contact lens parameters? A. Keratometer B. Radiuscope C. Burton lamp D. Thickness gauge
A keratometer will measure the base curve of a lens with an attachment known as a con-ta-check; however, a radiuscope is most frequently used. A thickness gauge will measure the center thickness of a contact lens. A burton lamp evaluates the fluorescein pattern similar to a slit lamp.
One might utilize which of the following lens designs given the following information: K's 46.00 @ 75 / 48.50 @ 165 +2 distortion Rx -7.00 -3.50 x 165 Irregular retinoscopy reflexes A. Soper keratoconus design B. Myoflange design C. Front surface toric RGP design D. 1.00D flatter
A. Soper keratoconus design There is a high probability that this patient has keratoconus, typified by the steep keratometer readings, the high degree of cylinder and the irregular retinoscopy reflexes.
Which of the following preservatives has low incidence of ocular sensitivity with soft contact lenses? A. Sorbic acid B. Chlorbutanol C. Benzalkonium Chloride D. Thimerosal
A. Sorbic Acid Chlorbutanol and benzalkoniurn chloride are antimicrobial agents used in soft contact lens care products but has a high ocular sensitivity rate
The tolerance for the overall lens diamter according to the ANSI standards is: A. +/-0.005mm B. +/-0.05mm C. +/-0.01mm D. +/-0.1mm
B. According to the ANSI standards (Z80.2-1989), the tolerance for the overall diameter of a contat lens is +/-0.05mm. ANSI standards have been developed to maintain quality in the contact lens industry. It is important to have an understanding of the ANSI guidelines.
Enzymatic cleaning of soft lenses is important in: A. Preventing the development of GPC B. Preventing the lens from shrinking and tightening C. Maintaining the hydration of the lens D. All of the above
D. Enzymatic cleaning will remove protein from the surface of a soft lens which can contribute to the development of Giant Papillary Conjunctivitis (GPC). These deposits are also responsible for the soft lens becoming dehydrated and tightening on the patient's eye
Which of the following preservatives is a mercury based compound? A. Sorbic acid B. Thimerosal C. Benzalkonium chloride D. Polyquad
B. Thimerosal Thimerosal is an organic mercurial compound
Use of a Wratten #12 or Tiffen yellow filter is important in evaluating the fluorescein pattern of patients with RGP lenses because: A. Many patients are wearing lenses containing UV inhibitors that block fluorescein B. There will be too much fluorescence if a filter is not used C. 3 and 9 o'clock staining will not show up if the filter is not used D. The filter will help to identify patients with corneal warpage
A. B is incorrect because the cobalt blue filter on a slit lamp will block fluorescence from RGP lenses with LJV inhibitor in the lens. Choice D is incorrect as corneal warpage can be discerned with a retinoscope or keratometer or by failure or a patient to achieve a good end point during a refraction for glasses.
A rigid contact lens measures +15.00 BVP. The FVP will measure: A. A lesser dioptric reading B. A greater dioptric reading C. An identical dioptric reading D. An astigmatic reading
A. The power of a high plus lens will always measure a larger numerical value in back vertex power (BVP) when compared to the reading in front vertex power (FVP)
3 and 9 o'clock staining in RGP lens wearers can best be eliminated by: A. Reducing center thickness and teaching the patient to blink completely B. Adding a minus carrier to the lens C. Using preservative-free saline instead of RGP wetting/soaking solution D. Using a single cut rather than a multicurve lens design
A. Failure to resurface the peripheral cornea with tear film mucin is a major cause of 3 and 9 o'clock staining in RGP lens wearers. This often occurs because the edge of in excessively thick lens causes "lid gap" causing the lid to vault over the peripheral cornea, preventing it from spreading tear film mucin in this area. Incomplete blinking, sometimes exacerbated by a thick, uncomfortable lens edge promotes desiccation at 3 and 9 o'clock. The addition of a minus carrier will thicken the lens edge. Substitution of saline for RGP wetting and soaking solution will prevent proper in-eye wetting of an RGP lens and lead to reduced comfort. A single cut lens is rarely used since it does not contain a peripheral bevel which provides better alignment of the lens with patient's cornea
Patient who are fit with lenses that will be worn overnight on a flexible or extended wear basis: A. Should be seen as early as possible in the morning for follow-up of overnight wear B. Should have their follow-up visits late in the day to evaluate their lenses and identify problems related to overnight wear. C. Should be scheduled for a follow-up visit 2 weeks after the initial fitting D. Will need minimal follow-up if they have worn daily wear lenses successfully
A. It is important to see patients who sleep in their lenses as soon as possible after awakening in order to detect corneal edema. The edema resolves as oxygen is transmitted through the lens in an open-eye environment and will probably be gone if the follow-up visits are scheduled later in the day. It is important to see all extended wear patients the morning after they sleep with their lenses for the first time to detect any adverse reactions, even if the patients have been long-term successful wearers of daily wear lenses
Carole's contact lenses are fit on flat K. Her refraction is: -5.00 +2.00 x 90 What is the power of her contact lenses? A. -3.00D B. -4.00D C. -5.00D D. -7.00D
A. -3.00 The first step is to convert the prescription to minus cylinder which results in -3.00 -2.00 x 180. The cylinder and axis are dropped which leaves -3.00 sphere. When the lens is fit on K, no compensation is needed for the resulting tear film so the lens power remains -3.00D
The tolerance for lens power under +/-10.00D is: A. 0.12D B. 0.25D C. 0.37D D. 0.50D
A. 0.12D According to the ANSI standards (Z80.2 - 1989), the tolerance for the power of a contact lens under +/-10.00D is +/-0.12D
Newly fitted extended wear patients should have their first recheck in: A. 24 hours B. 3 days C. 2 weeks D. 3 weeks
A. 24 hours All new extended wear patients should have their lenses checked within 24 hours of insertion
The FDA has recommended that extended wearing contact lenses be worn for a maximum of: A. 7 days B. 14 days. C. 30 days D. 45 days
A. 7 days While many extended wear materials have FDA approval for 30 days of continuous wear, a maximum of 7 days of continuous wear has been recommended.
Placing the concave side of a rigid gas permeable lens against the lens stop of the lensometer, will provide you with which of the following? A. Back vertex power B. Front vertex power C. Best vertex power D. Closest vertex power
A. Back vertex power By placing the back (posterior) surface of the rigid gas permeable lens against the lens stop, the reading that results will be in back vertex power
Prolonged periods of reading in contact lenses may lead to lens discomfort due to: A. Decreased blinking B. Corneal temperature changes C. Accommodative response D. Neovasularization
A. Decreased Blinking When a patient spends a great deal of time reading or any other activity in which they are intently staring at an object (watching tv, driving, etc.) they may experience some discomfort as their blink rate drops and new tears are not exchanged for old tears underneath the lens
An instrument that allows simultaneous verification of lens diameter, optic zone width and peripheral curve width is: A. Measuring magnifier B. Ophthalmometer C. Profile analyzer D. Radiuscope
A. Measuring magnifier An ophthalmometer, another name for the keratometer, cannot measure the listed parameters. The profile analyzer evaluates the peripheral curve blends and the radiuscope measures the base curve of the rigid contact lens. The measuring magnifier is the only instrument that will measure the parameters listed.
Which of the following materials would least likely require a weekly enzymatic cleaner? A. Polymethylmethacrylate B. Hydrophilic C. Hydroxyethyl Methacrylate D. Silicone acrylate
A. Polymethylmethacrylate All of the other lens materials are recommended to be cleaned weekly with an enzymatic cleaner.
Which of the following can NOT be used to measure the diameter of a rigid lens? A. Profile analyzer B. Measuring magnifier C. Diameter gauge D. Shadowgraph
A. Profile analyzer A measuring magnifier, diameter gauge and shadowgraph may all be used to determine the diameter of a rigid lens
Assessment of the quality of the peripheral curves (blends) of a rigid contact lens is achievable by the use of the: A. Profile analyzer B. Shadowgraph C. Profile analyzer D. Burton lamp
A. Profile analyzer All of the listed instruments show that a rigid contact lens has blends. However, the only instrument that can adequately assess the quality of the blends between the peripheral posterior curve (PPC), intermediate posterior curve (IPC) and the central posterior curve (CPC), is the profile analyzer.
If an RGP lens fails to provide acceptable visual acuity, the fitter should first: A. Flatten the lens to cornea relationship B. Have a sphero-cylindrical over refraction performed to see if the reduced acuity is due to residual astigmatism C. Refit the patient with a soft lens D. Use a lens with a higher Dk/L value
B. Refitting with a soft lens may be preferable in cases where residual astigmatism is responsible for the reduced visual acuity and a front toric lens rides too low, but a sphero-cylindrical over-refraction must be performed first. Refitting with a lens that has a higher Dk/L value is unrelated to the reduced visual acuity. Flattening the lens to cornea relationship may help if the reduced acuity is due to lens flexure, but should not be done as the fist step
Which of the following statements about the eye make-up is correct? A. Eyeliner should be applied to the inner margin of the eyelids behind the lashes B. Eyeliner and mascara should be replaced every 3 to 6 months to avoid contamination C. Mascara should be applied to the base of the lashes only D. Eye make-up should be applied before inserting contact lenses
B. Eye make-up preservatives will usually prevent or retard bacterial growth in these products for 3 to 6 months. After that, they may become contaminated and cause eye infections. Choice A is incorrect because eyeliner should be applied only outside the lash margin. Choice C is incorrect because mascara applied at the base of the lashes will clog the outlets of the meibomian glands. Choice D is incorrect because because if eye make-up is applied before contact lenses are inserted, the lenses may pick up particles of mascara and eyeliner. Eyeshadow may transfer to the fingers and then to the lenses during insertion. it is best to insert the lenses and then apply any eye make-up
Hydrogen peroxide care systems: A Should not be used to disinfect FDA Group IV lenses B. Is more effective against viruses and fungi than most chemical disinfection systems C. Does not required a red tip on its container, since it does not cause permanent damage if accidentally instilled into the eye D. Takes a minimum of two hours to be decomposed into water and oxygen
B. Most chemical systems are slow to kill viruses and fungi. Choice A is incorrect because hydrogen peroxide is safe to use with polymers in all four FDA groups. Choice C is incorrect because, although a hydrogen peroxide corneal bum usually heals without permanent damage, manufacturers have added a red tip to the containers because instillation of H202 in the eye will cause a red and painful corneal bum that can take several days to heal. Choice D is incorrect because two-step hydrogen peroxide systems such as Oxysept, Consept, and Mirasept can be neutralized in as little as 10 minutes
Given the following information: K's 42.50 @ 180 / 44.50 @ 90 Rx -3.50 -2.50 x 90 Select the lens power if the lens is ordered one half diopter steeper than K: A. -3.50D B. -4.00D C. -4.75D D. -6.00D
B. -4.00 The refraction is already in minus cylinder form, so there is no conversion needed. The cylinder/axis is dropped leaving the contact lens professional to deal with the -3.50D of the sphere power. Fitting the lens one half diopter steeper than flat K requires adding a half diopter of minus to the sphere which would result in a final lens power of -4.00D
According to the FDA, disposable contact lenses that are removed nightly should be discarded after: A. 1 week B. 2 weeks C. 1 month D. When they appear cloudy or hurt the patient
B. 2 weeks The FDA has approved the use of daily wear disposable contact lenses for 2 weeks of wear
Which of the following is a preservative found in soft contact lens solutions? A. Chlorbutanol B. Polyquad C. Benzalkonium chloride D. Benzyl alcohol
B. Bebzalkonium chloride All of the other preservatives listed are used in rigid lens solutions. They may build up in high concentration in the matrix of soft lens and cause corneal damage.
Which medication should not be used with soft contact lenses as it will turn the lens brown? A. Antacids B. Epinephrine C. Digitalis D. Insulin
B. Epinephrine Epinephrine, found in nasal sprays and medications used in the treatment of glaucoma, has been known to turn soft contact lens brown.
The instrumental used for magnification of the edge of a rigid contact lens is a: A. Keratometer B. Shadowgraph C. Profile analyzer D. V-groove gauge
B. Shadowgraph A keratometer measures the corneal curvature. A profile analyzer measures the peripheral curves (blends) and a v-groove gauge measures the diameter of a rigid contact lens.
Conventional daily wear soft contact lenses, properly cared for, should be replaced at least: A. Quarterly B. Yearly C. Every two years D. When they hurt
B. Yearly Durable soft contact lenses will need greater care than their disposable or frequent replacement counterparts. When properly cared for, they should be replaced yearly
Poor RGP insertion or recentering techniques may result in: A. 3 and 9 o'clock staining B. The lack of a fulcrum at 3 and 9 o'clock C. Arcuate stainging D. Coalesced SPK centrally
C. Since the edge of an RGP lens is curved, it will damage epithelial cells in an arcuate pattern if it is inserted or recentered incorrectly. Three and nine o'clock staining is related to peripheral desiccation and can be caused by lid gap, incomplete blinking and failure to resurface the area just outside the lens edge with tear film mucin with each blink. Lack of a fulcrum (bearing point) for an RGP lens is unrelated to lens insertion or recentering techniques. Choice D, coalesced SPK (superficial punctate keratitis) centrally, could be due to excessive apical bearing from a flat lens, central corneal clouding from a tight, steep lens or a lens that supplies insufficient oxygen to the cornea. It could also be caused by a foreign body that has been trapped centrally under the lens.
If a soft contact lens becomes adherent to the cornea, the patient should: A. Irrigate the eye profusely with warm water until the lens becomes loose B. Pinch the lens off the eye by placing the thumb and forefinger at 3 and 9 o'clock on the cornea and squeezing to break the suction C. Irritate the eye with saline or rewetting drops until the lens begins to move freely again D. Use a DMV suction cup to remove the lens
C. A lens adheres to the cornea if it is not wet enough or salty enough. Either way, irrigation with saline solution or rewetting drops formulated for soft lens wearers will restore the salt and water content of the lens and allow it to move freely again.
Thermal disinfection of soft lenses: A. Extends the life of the contacts since it kills microorganisms better than chemicals B. Can be done by boiling the lens case in a pot of water for one hour if a thermal disinfection unit is not available C. Is effective against acanthamoeba cyst and trophozoites D. Does not require prior to cleaning with a surfactant since it kills microorganisms so effectively
C. Choice A is incorrect because repeated bakes on deposits and shortens the life of the lens polymer. Choice B is incorrect because 10 minutes of boiling in a covered pot is sufficient to disinfect soft lenses when a thermal unit is not available. Longer boiling will shorten lens life. "D" is incorrect since surfactant cleaning is necessary to remove tear film deposit and cosmetic residues so they will not be "baked on" during thermal disinfection.
Which of the following statements is most accurate: A. Routine cosmetic daily wear patients should be seen at 3 month intervals for a contact lens evaluation B. Patients with a history of GPC should be refit with disposable soft lenses and followed on a bi-weekly basis for 6 months C. New soft lens fits should be seen one week, one month, three months and 6 months from the time their initial fit, then every 6 to 12 months D. Patients who are wearing RGP lenses after penetrating keratoplasty need fewer follow-up visits than keratoconus patients because their corneas are now spherical
C. Choice A would be correct only for patients who have already gone through the sequence of follow-up care recommended for new contact lens wearers as outlined in Choice C. Choice B involves an excessive number of follow-up visits which can be inconvenient for the patient and impractical for the practitioner. If the GPC is so severe that the patient must return every two weeks, they are not yet ready to be refit with contact lenses. Choice D is incorrect because it is rare that a penetrating keratoplasty results in a spherical cornea and post-graft patients tend to be more difficult to fit with contact lenses. One must also watch the graft/host junction closely for problems
When can Johnny, a 12 year old new soft lens wearer, comfortably be sent home with new lenses? A. When the mom has worn for years B. When he can remove the lenses by himself C. When he can insert and remove the lenses by himself D. When he promises to remove the lenses daily
C. New lens wearers should never be allowed to leave the contact lens professional's office until they can demonstrate successful lens insertion and removal
The bas curve of a rigid lens was ordered 7.84mm and was received measuring 7.94mm. This lens is __________ than ordered. A. 0.50D steeper B. 1.00D steeper C. 0.50D flatter D. 1.00D flatter
C. 0.50D flatter Every 0.50mm if radius equals approximately 0.25D. The lens ordered was 43.00D, but was received as a 42.50D
If an adapted contact lens wearer complains of a sudden onset of discomfort, the technician should suspect: A. A change in corneal curvature B. Giant Papillary Conjunctivitis C. A damaged contact lens D. Tight lens syndrome
C. A damaged contact lens A change in the corneal curvature, GPC and tight lens syndome would all cause a more gradual decrease in lens comfort
Which of the following may cause a soft lens to need to be replaced more often? A. Chemical disinfection B. Enzymatic cleaning C. Heat disinfection D. Nightly cleaning
C. Heat disinfection Heat disinfection will coagulate surface deposits onto the lens often causing it to need more frequent replacement
Which type of lens would best satisfy this patient's visual needs given the following information: K's 43.00 @ 160 / 44.00 @ 75 3+ distortion Rx -2.00 +1.00 x 75 A. Spherical soft lens B. Soft toric lens C. Soft bifocal lens D. Spherical RGP lens
D. The 3+ distortion is most probably due to irregular astigmatism and is best corrected with a rigid lens option.
Which of the following statements concerning lens movement is not correct: A. A tight lens may cause blanching of the limbal vessel B. A tight lens may cause scleral indentation C. A loose lens may cause blurred vision immediately following the blink D. A loose lens will be considerably more comfortable than a tight lens
D. A patient will have much greater awareness of a loose lens and may experience a constant foreign body sensation when wearing a lens that moves excessively. A "tight" lens on the other hand may not cause immediate symptoms but may cause burning, stinging and foggy vision due to corneal edema several hours after insertion
The purpose of a combination wetting / soaking RGP solution is to: A. Maintain lens surface wettability B. Disinifect the lens C. Cushion the lens during insertion D. All of the above
D. All combination wetting/soaking solutions meet FDA criteria for lens disinfection in a 4 hour soak time. The "wetting agents" in these solutions help to cushion the lens on insertion and help tears to spread evenly across lens surface.
Which of the following statements is correct? A. If patients touch the tip of a solution container to their skin or eyelashes, they should wash the tip with soap and water B. If a soft contact lens dries out, it should be immersed in warm water until it softens C. Disinfecting solutions should be "topped off" nightly and changed weekly D. Solution containers should always be capped after use to prevent contamination
D. Keeping solution containers capped when not in use prevents microorganisms and dirt from settling on the tips or working their way into the container. Choice A is incorrect because further contamination might occur if the patient attempts to wash the tip of a container. If the tip has become contaminated, the solution should be discarded. Choice B is incorrect because water contains many microorganisms, including the dreaded acanthamoeba. And, since water is hypotonic, it will cause a soft lens to become adherent to the cornea upon insertion. Choice C is incorrect because there is a marked decrease in the efficacy or re-used chemical solutions. For patients using hydrogen peroxide care systems, no disinfection at all occurs from re-used solutions since the hydrogen peroxide is decomposed into water and oxygen by the catalytic disc or neutralizer
Which of the following is not considered a normal adaptive response to soft lenses? A. Awareness of the lenses in the eye B. Awareness of bright sunlight C. Slight itching sensation D. Lenses feeling "hot" in the late afternoon
D. Lenses feeling "hot" in the late afternoon may be an indication that the lens may be too tight. All of the other choices are normal adaptive responses that should improve over time
When verifying a rigid lens on a radiuscope, you notice tat the mires are not in focus in all principle meridians. This might indicate a: 1) Warped Lens 2) Back toric lens 3) Bi-toric lens 4) Front toric lens A. 1 only B. 1 and 3 C. 2 and 4 D. 1, 2, and 3
D. 1, 2 and 3 A front toric lens will show a spherical posterior curve on the radiuscope and a sphero-cylindrical Rx on the lensometer
A technician can perform a preliminary evaluation of soft contact lens movement by: A. Observing the movement of the lens edge in relation to the position of a conjunctival vessel B. Having the patient look up and blink C. Observing movement and lens lag in upward and lateral gaze with a penlight D. All of the above
D. Al of the above All of these techniques can be used to evaluate soft lens movement without the use of a slit lamp
Which of the following hobbies and activities should be discussed with patients? A. Long periods of computer work? B. Long periods of reading? C. Long periods of driving? D. All of the above
D. All of the above Patients who spend a lot of time on attention-intensive tasks such as computers, reading or driving tend to have a reduced blink reflex. This may result in drying of the lens, discomfort and fluctuating visual acuity.
Circumcorneal injection in a soft lens wearer may be a sign of: A. Tight lens syndome B. Solution sensitivity C. Keratitis D. All of the above
D. All of the above Tight lenses, sensitivities to solutions and keratitis may all result in circumcorneal injection in soft lens wearers
If fluorescein evaluation reveals apical staining, it could be due to: A. A lens that is too flat and loose B. A lens that is too steep and tight C. Corneal Edema D. All of the above
D. All of the above Apical staining can occur because the lens is too flat and loose; too steep and tight; or in the case of corneal edema
Which of the following is a non-approved wetting solution that is quite safe for the patient to use? A. Saliva B. Toothpaste C. Dish soap D. None of the above
D. None Patients should never be allowed to use any solution that has not been approved for that specific use
All of the following will enable the practitioner to verify the overall rigid gas permeable lens diameter except: A. Slot gauge B. Shadowgraph C. Measuring magnifer D. Radiuscope
D. Radiuscope The slot gauge, shadowgraph and measuring magnifier will all enable the practitioner to verify the overall lens diameter of rigid gas permeable lens. The radiuscope is an instrument that will measure the base curve of a rigid lens.
A warped lens will show ________ base curve(s) on the radiuscope and a ________ power on the lensometer. A. One / sphero-cylindrical B. Two / sphero-cylindrical C. One / sphero-cylindrical D. Two / spherical
D. Two / spherical Verification should show the following: Lens type - Radiuscope - Lensometer Spherical - One base curve - Spherical Rx Warped - two base curves - spherical rx Front toric - one base curves - sphero-cylindrical rx Back toric - two base curves - sphero-cylindrical rx Bi-toric - two base curves - sphero-cylindrical rx
