NCLE Advanced Certification Exam Questions With Correct Answers

The answer is D. The posterior optical zone will directly affect the lens to cornea relationship of a rigid gas permeable lens. If the posterior optical zone is steepened, it will increase the sagittal depth. If it is flattened, it will decrease the sagittal depth. Changing the power, which is accomplished by changing the anterior optical zone, will not affect the sagittal depth of the lens, nor will changing its edge design. - Answer 1. The sagittal depth of a rigid gas permeable contact lens can be altered without changing the diameter by: A. Changing the power B. Changing the edge design C. Changing the radius of curvature of the anterior optical zone D. Changing the radius of curvature of the posterior optical zone The answer is A. A lens is truncated by removing a segment of the lower edge of a contact lens. This creates a straight edge that interacts with the lower lid and aids in lens positioning. Of the lens designs listed in the question, the only one that requires precise positioning of its optical portions is a translating bifocal lens. - Answer 2. A truncation is used on a rigid gas permeable contact lens to help enhance the performance of which type of design? A. Bifocal B. Aphakic C. Bitoric D. Keratoconus The answer is B. A lenticular or myoflange design will decrease the mass of an aphakic lens as well as increase the edge profile, which allows it to interact more with the upper lid and aid in positioning of the lens. - Answer 3. The mass of an aphakic rigid gas permeable contact lens can be reduced by making the lens design: A. Spherical B. Lenticular C. Tricurve D. Aspheric The answer is B. Increasing the optical zone diameter and increasing the overall lens diameter will both tighten and steepen the relationship of the lens to the cornea. Decreasing the optic zone diameter will serve to flatten and loosen the lens to cornea relationship. Using a prism-ballasted lens design will not affect the lens to cornea relationship as it relates to sagittal depth. - Answer 4. In order to tighten the fit of a rigid gas permeable lens you can: I. Increase the optical zone diameter 2. Decrease the optical zone diameter 3. Increase the overall lens diameter 4. Use a prism ballasted lens design A. 3 only B. 1&3 C. 2 only D. 2&3 The answer is D. A hyperflange will decrease edge thickness as well as lens awareness . Aspheric peripheral curves change the posterior design of the lens but do not reduce edge thickness. A higher Dk material will not change the overall lens edge thickness. A myoflange will actually add thickness to the lens edge and is used for high plus lenses not high minus lenses. - Answer 5. A high minus rigid gas permeable lens will be thin centrally with relatively thick edges. To reduce the edge thickness, and increase overall comfort, use: A. Aspheric peripheral curves B. A myoflange C. A higher Dk material D. A hyperflange The answer is C. One would rarely polish or attempt to manipulate the central posterior surface of a rigid lens. Applying polishing pressure to the mid-peripheral and the peripheral anterior surface would add plus power. Applying polishing pressure to the central anterior surface would add minus power. - Answer 6. To add minus power to a rigid contact lens with a rotating modifying spindle, one would: A. Polish the posterior surface of the rigid lens B. Polish the mid peripheral anterior surface C. Polish the central anterior surface D. Polish the peripheral anterior surface The answer is A. The keratometer readings indicate the need for a spherical back surface, which would rule out the use of a bitoric lens. A soft spherical lens would not correct the moderate amount of refractive astigmatism that is present, nor would the spherical rigid gas permeable lens. A front surface toric RGP would best meet this patient's needs since it has a spherical back surface, but has a toric front surface which would correct the residual astigmatism. - Answer 7. Which lens design would provide the best visual acuity for a patient with the following information? K's 42.00@ 180/ 42.50@90 Rx -6.75 +1.75 cx 90 A. Front surface toric rigid gas permeable B. Spherical rigid gas permeable C. Soft sphere D. Bitoric rigid gas permeable The answer is A. The wetting angle of a rigid gas permeable material describes how a fluid spreads over the surface. It is important to remember, however, that wetting angle is a description of the material outside of the patient's natural ocular environment. Within minutes of insertion, a rigid lens is encapsulated in the natural tear mucin and the wetting angle of the material is no longer important. - Answer 8. Which of the following describes the angle that the edge of a bead of water makes with the surface of a plastic? A. Wetting angle B. Surface angle C. Bead angle D. Reflection angle The answer is B. The back surface of a rigid lens will usually correct only the astigmatism that is found on the surface of the cornea. Therefore, when there is significantly more astigmatism in the refraction than on the surface of the cornea, residual astigmatism is anticipated. - Answer 9. If a patient has 1.50 D of refractive cylinder and keratometer readings of 44.00@ 180/ 44 .50 @ 90, a spherical rigid gas permeable lens will: A. Give the patient their best correctable vision B. Usually result in residual astigmatism C. Fit poorly D. Be uncomfortable The answer is C. Lenticular astigmatism usually exists when the amount of refractive cylinder is greater than the amount of corneal cylinder. It is assumed that the additional astigmatism originates in the crystalline lens. - Answer 10. If a patient has spherical K readings of 43.50 and an Rx of -4.00 +1.75 cx 90, the patient has: A. Corneal astigmatism B. Against the rule astigmatism C. Lenticular astigmatism D. Mixed astigmatism The answer is B. With regular astigmatism, even high degrees, a soft toric lens can work quite effectively. Presbyopic and aphakic patients can also be successfully fit with soft lenses. However, patients with irregular astigmatism will achieve their best visual acuity only with rigid gas permeable lenses since soft lenses will mold to the corneal contour and not mask the irregularity. - Answer 11. In which of the following situations is a rigid gas permeable lens always preferred over a soft lens? A. Regular astigmatism B. Irregular astigmatism C. Aphakia D. Presbyopia The answer is A. Decreasing the optical zone diameter while steepening the base curve of a rigid gas permeable lens will allow the lens to cornea relationship to remain the same, since decreasing the optical zone diameter loosens the lens to cornea relationship and steepen- ing the base curve tightens the relationship. Increasing the overall lens diameter also tightens the fit and will only exaggerate the change made to the lens to cornea relationship. Decreasing the center thickness or increasing the lens power will have no significant effect on the relationship of the lens to the cornea. - Answer 12. In order to steepen the base curve of a rigid gas permeable lens without changing the lens to cornea relationship, you would also need to: A. Decrease the optical zone diameter B. Decrease the center thickness C. Increase the overall lens diameter D. Increase the lens power The answer is B. Increasing the overall lens diameter or increasing the optical zone diameter will steepen the lens to cornea relationship. Conversely, decreasing the optical zone diameter, decreasing the overall lens diameter or flattening the base curve will loosen the relationship. If one change is made that tightens the relationship and another is made that loosens it, the changes will cancel each other out. - Answer 13. To steepen the lens to cornea relationship of a rigid gas permeable lens you could : A. Increase overall diameter and decrease optical zone diameter B. Increase overall diameter and increase optical zone diameter C. Increase optical zone diameter and decrease overall diameter D. Increase optical zone diameter and flatten base curve The answer is D. Modification of rigid gas permeable lenses is a valuable skill and can increase a practitioner's success at RGP fitting. Many in-office modifications can be utilized to improve the positioning of a lens, reduce discomfort for the patient and eliminate corneal staining. - Answer 14. Which is not an indication for modifying a rigid gas permeable lens? A. Corneal staining B. Poor lens position C. Discomfort D. Surface Wettability The answer is D. Many modifi~ations to rigid gas permeable lenses can be done in the office, saving time and improving service. Blending peripheral curves, adding minus power, adding plus power, polishing the edges, polishing the anterior and posterior surfaces, as well as reducing lens diameter are all examples of modifications that can be performed in the office. - Answer 15. Which of the following modifications can be made to a rigid gas permeable lens in the office? A. Blending B. Changing the power C. Polishing the edge D. Changing the base curve The answer is A. Lenses that position temporally or inferiorly are not typically indicated and should be avoided. Lenses that position superiorly are often lenses that have been designed with the apical alignment philosophy and have been fit flatter than the flattest keratometer reading in order to achieve this alignment. Lenses that are fit with apical clearance are fit steeper than the flattest corneal measurement and often will fit intrapalpebrally or centrally. - Answer 16. To achieve a lens to cornea relationship that exhibits apical clearance, the lens is designed steeper than the flattest corneal measurement. This lens will most often position: A. Centrally B. Temporally C. Superiorly D. Inferiorly The answer is C. The two visual systems utilized by rigid gas permeable bifocals are simultaneous and alternating. With simultaneous vision systems, both near and far images are received by the retina at the same time. Concentric and aspheric bifocal lens designs utilize simulta- neous vision principles. With alternating vision systems, the lens will move on the eye, delivering the focal length that is in front of the pupil as the lens translates . Segmented bifocal lens designs fall into this category. - Answer 17. Which of the following are visual systems used by rigid gas permeable bifocal lenses? A. Translating and hyperopic B. Simultaneous and instantaneous C. Simultaneous and alternating D. Truncated and prism ballasted The answer is D. Most translating or alternating rigid gas permeable bifocal lenses must be stabilized in order for the proper segment to align correctly with the pupil. Two methods of accomplishing this are by truncating and/ or prism ballasting the lens. In truncation, the bottom portion of the lens is removed, producing a straight edge that interacts ·with the lid and aligns the lens in its proper position. With prism ballasting, the bottom portion of the lens is made thicker than the top portion. Following the same principles as prism ballasting of a soft toric lens, the thicker portion of the lens will be forced from under the upper lid to an inferior position. - Answer 18. Which of the following are methods for stabilizing the rotation of rigid bifocal contact lenses? A. Back surface toric and front surface toric B. Edge roll and polish C. Alternating and translating D. Truncation and prism ballast The answer is D. Flattening the base curve of the lens and decreasing the overall diameter will each decrease the sagittal depth of the contact lens. By combining both factors, the impact will be magnified. Steepening the base curve and increasing the overall diameter will both increase the sagittal depth. - Answer 19. To decrease the sagittal depth of a rigid gas permeable contact lens you can: 1. Steepen the base curve 2. Flatten the base curve 3. Increasetheoveralldiameter 4. Decrease the overall diameter A. 1and4 B. 1and3 C. 2and3 D. 2and4 The answer is B. Dimple veil staining is not traditional staining but is rather a pooling of fluorescein in depressions or "dimples" on the surface of the cornea. These dimples are caused by air bubbles that become trapped behind a rigid lens in an area where the distance between the lens and cornea is too great. Dimples will be found centrally if the base curve is too steep and peripherally if the base curve or peripheral curves are too flat. - Answer 20. Dimple veil staining on the cornea is caused by: A. Poor polishing of peripheral curves B. Air bubbles trapped under a rigid lens C. Debris trapped under a rigid lens D. A cracked contact lens The answer is B. The parameters listed in C and D will flatten the lens to cornea relationship. While answer A does steepen the lens' relationship, it does not take into account the change in the power that is necessary when the base curve of the lens is altered. - Answer 21. The GP multifocal design that relies on the use of a variable rate of curvature across the lens surface to achieve a change in power is known as: A. Concentric B. Translating C. Aspheric D. Truncated The answer is B. "Dk/L" stands for the oxygen transmissibility of a specific lens when manufactured with a given center thickness. "Dk" stands for the oxygen permeability of the material, but the actual transmission of oxygen thr ough this material is also dependent on the thickness of the lens. While the concept of permeability is important to understand, the real impact is found in the transmissibility of the lens. Wetting angle relates to the ability of tears to spread on the plastic, specific gravity relates to the weight of the lens material and neither are related to corneal oxygenation. - Answer 22. To allow for proper corneal oxygenation when fitting rigid gas permeable lenses, which of the following material characteristics must be considered? A. Dk B. Dk/t C. Wetting angle D. Specific gravity The answer is C. To determine the parameters of a bitoric rigid lens, place the most plus (least minus) power on the flattest meridian (-2.00 Don the 42.00 D meridian) and the most minus (least plus) on the steepest meridian (-2.00 D plus an additional -5 .00 D, for a total of -7.00 Don the 45.25 D meridian). The -7.00 D must be vertexed, which results in -6.50 D. Since we are fitting the lens "on K", the final lens parameters are 42.00 / 45.25 -2.00/-6.50. - Answer 23. Given the following information: K's 42.00@180/45.25@90 Rx -2.00 -5.00 cx 180 Which of the following specifications, given in actual drum readings, would represent a bitoric lens fit "on K"? A. 42.00/45.25 -2.00 /-3.00 B. 42.00/45.25 -2.00 /-5.00 C. 42.00/45.25 -2.00 /-6.50 D. 42.00/45.25 -2.00 /-9.00 The answer is A. The only listed set of specifications that will give the patient a good visual result is answer A. In this case, the lens is fit 0.50 D flat in the horizontal meridian and is 0.50 D flat in the vertical meridian. To determine the lens power, work with the patient's refraction in minus cylinder and apply the principles of "SAM/FAP" (Steep Add Minus, Flat Add Plus) to the sphere power only. In this case, the flattest meridian was fit 0.50 D flatter, creating 0.50 D of minus power. To compensate for this, 0.50 D of plus must be added to the -1.00D of sphere power in the patient's Rx, resulting in -0.50D. The 3.000 of refractive cylinder is corrected by the 2.00 D of cylinder on the posterior surface of the lens. Back surface toric lenses will correct refractive cylinder that is 1 1/ 2 times the amount of cylinder on its back surface. While all back surface toric lenses do not need to be fit 0.50 D flatter than Kin both principal meridians, none of the other options listed will result in an appropriate lens prescription . - Answer 24. Given the following patient information: K's 41.25@180 / 43.25@90 Rx -1.00 -3.00 cx 180 The best parameters for a back surface toric rigid gas permeable lens would be: A. 40.75/42.75 -0.50 B. 40.75/43.25 -1.00 C. 41.25/43.25 -4.00 D. 41.25/44.25 -1.00 25. The answer is D. A front surface toric lens will show clear mires in all meridians which indicates a spherical posterior surface. Warped, bitoric and back surface toric lenses will all show unclear mires in the radiuscope indicating that the posterior surface is not spherical. In the lensometer, bitoric, back toric and front surface toric lenses will all display sphero-cylindrical readings. Only the warped lens will show a spherical lensometer reading. - Answer 25. When verifying the posterior curves of a rigid gas permeable not all of the mires are clear in all meridians. This can occur in all but a: A. Warped lens B. Bitoric lens C. Back surface toric lens D. Front surface toric lens The answer is D. VLK, or Vascularized Limbal Keratitis, is a condition associated with rigid gas permeable lenses, predominantly those lenses that are designed with low edge lifts and large diameters. In its most advanced stage, a heaping of the corneal epithelium in the area of irritation becomes evident. This area becomes vascularized from the conjunctiva to the limbus leading to the elevated mass in the area. Staining on the cornea and conjunctiva accompany patient symptoms which may include reduced wearing time, redness, photophobia and in some instances, pain. - Answer 26. Heaping of epithelium, vascularization, and staining of the conjunctiva and cornea are characteristic of... A. Corneal warpage B. Gian papillary C. Vascularized limbal keratitis D. Dendritic keratitis The answer is D. When adding a spherical over-refraction to a bitoric lens, it must be added to both meridians Example: -1.00 / -4.50 -1.00 / -1.00 -2.00 / -5.50 - Answer 27. Lens specifications in actual drum readings: 43.50/45.50 -1.00/-4.50 9.2 Over-refraction: -1.00 sphere What is the new lens power? A. plano/-3.50 B. -1.00/-5.50 C. -2.00/-4.50 D. -2.00/-5.50 The answer is D. Decreasing the height of the bifocal segment is the only option that will drop the seg and alleviate the visual confusion caused by the segment bisecting the pupil. All of the other options will move the bifocal segment further up into the line of vision. - Answer 28. A translating bifocal wearer complains of blur at distance. Upon slit lamp exam, you notice that the bifocal segment bisects the pupil. In order to improve this situation, you should: A. Increase the seg height B. Decrease truncation C. Decrease prism ballast D. Decrease seg height The answer is B. Dimple veil staining may occur when there is either a steeper or flatter than recommended lens to cornea relationship. Air bubbles become trapped in the excessive space and create dimples on the corneal surface. Antibiotics will not affect dimple veil staining, nor will lenticulating the edges. Re-evaluating the lens to cornea relationship will identify the problem and allow the fitter to change the base curve and/ or peripheral curves to eliminate the dimples. - Answer 29. Dimple veil staining is resolved by: 1. Antibiotics 2. Steepening the lens to cornea relationship 3. Flattening the lens to cornea relationship 4. Lenticulation A. 1 and 2 are correct B. 2 and 3 are correct C. 1, 2 and 4 are correct D. None of the above will resolve dimple veil staining The answer is B. The Rose K, McGuire and Soper lenses are all designs specifically created for the keratoconus eye, with steeper, smaller optical zone diameters and customized peripheral curve systems to improve the fit on the unique corneal topography of a keratoconic eye. - Answer 30. Rose K, McGuire and Soper are all different types of which lens design? A. Post-refractive surgery B. Keratoconus C. Torie D. Aspheric The term-28answer is A. An uncut rigid gas permeable lens has both the posterior and anterior surface cut and polished. It does not have a peripheral curve system, or a final diameter. The subsequent steps in lens fabrication would be to reduce the lens to within a 1/ 10 of a millimeter of its projected finished diameter, apply the posterior peripheral curves, bevel the front edge and round and taper the edges. - Answer 31. An uncut rigid gas permeable contact lens will have the following: A. Both sides surfaced B. One side surfaced C. Semi-finished blank D. One side molded The answer is C. VascularizedUmbal Keratitis (VLK)is believed to be caused mainly by large diameter rigid gas permeable lenses with low edge lifts. These lenses chafe the epithelium in the limbal area in the three and nine o' dock areas, The tear film in the area may also be altered by this traumatic mechanical effect and has a synergistic effect in causing the vasogenic response known as VLK. - Answer 32. Vascularized Limbal Keratitis is usually caused by: A. Dry eye syndrome B. Allergic reaction to solutions C. Mechanical irritation D. Excessive exposure to ultraviolet radiation The answer is A. When comparing wetting angles, the greater the angle, the less hydrophilic is the lens material. A drop of fluid that creates a 90 degree angle between the drop and the surface is considered an indication of a hydrophobic surface. When there is an angle of 0, the material is considered completely wet. The smallest wetting angle represents the most wettable surface, which is most desirable in RGP materials. - Answer 33. When comparing wetting angles, which of the following would be the most desirable? A. 10 B. 20 C. 30 D. 60 The answer is B. A drop of fluid that creates an angle of 90 degrees or greater is considered an indication of a hydrophobic or non-wetting surface. A drop of fluid that creates an angle of 0 to 90 degrees indicates a more wettable material with the lowest values representing the most wettable surfaces. A drop of fluid that creates an angle of O indicates that the material is totally hydrophilic. - Answer 34. The greater the ability of a rigid gas permeable lens to wet, the ____ the wetting angle? A. Higher B. Lower C. Deeper D. Rounder The answer is C. Oxygen transmissibility is useful clinically as an indication of oxygen delivery. This is because it represents the amount of oxygen moving through a specific lens with a given thickness instead of simply the oxygen moving through a plastic of unknown thickness, since the oxygen delivery will vary according to the thickness of the lens. - Answer 35. Dk/t is: A. Oxygen Permeability B. Lens Thickness C. Oxygen Transmissibility D. Specific Gravity The answer is A. Imagine a contact lens as a portion of a sphere. Assuming that the diameter of a lens is kept constant, if the base curve of a lens is steepened, the distance from the lens periphery to the imaginary center of the sphere will be shorter. (See diagram) The base curve of a lens is expressed by the length of its radius. The shorter the radius, the steeper the curve, conversely the longer radius, the flatter the base curve. Therefore, when the posterior radius of curvature is decreased, the base curve of the rigid gas permeable lens is made steeper. Diameter is constant in each lens, 14mm. The shorter the radius the steeper the lens. - Answer 36. When the base curve of a rigid gas permeable lens is said to be made steeper, it means that the posterior radius of curvature is: A. Decreased B. Divided C. Increased D. Elongated The answer is B. Decreasing edge thickness will allow the lid to re-wet the affected area in the corneal periphery. A base curve cannot be steepened nor can the diameter of a lens be increased, either in the lab or in the office and a new lens would have to be ordered if these changes were required. A diameter gauge is a measuring instrument, not a modification tool. - Answer 37. What in-office modification can be performed to alleviate three and nine o'clock staining? A. Steepen the base curve with a conical tool B. Decrease edge thickness with a conical tool C. Flatten the base curve with a conical tool D. Increase the diameter with a diameter gauge The answer is D. When a rigid gas permeable lens flexes on the eye, the patient will notice a number of phenomena. The most obvious is the fluctuation in vision that occurs during the blink. Continuous flexing of the lens on the eye may also result in a lens that warps over time and can lead to decreased comfort. - Answer 38. Higher Dk materials and high minus prescriptions present a greater chance for the contact lens to flex excessively on the eye. This may result in which of the following situations? A. Variable acuity B. Discomfort C. Warped central posterior curve D. All of the above The answer is C. Lens flexure usually occurs when the center of the lens is not thick enough to counteract the force of the lids on a blink. This may occur when there is a great deal of corneal cylinder and the lid forces the lens to flex over a highly astigmatic surface. It may also occur when the lens is inherently thin in the center such as in a high minus lens. Increas- ing the center thickness of the lens will reduce the impact of the lids and will keep the lens from flexing on the eye. Historically, decreasing the Dk of the material will also reduce the ability of the lens material to flex and choosing a lens with a lower Dk is an advantage when attempting to control lens flexure. The closer the lens is to the surface of the cornea, the less it will flex, so fitting the lens in an alignment fitting philosophy will be to the fitter's advantage. - Answer 39. What situation will most likely result in lens flexure? A. High plus Rx, low dk B. High plus Rx, high dk C. High minus Rx, high dk D. High minus Rx, low dk The answer is C. Due to the irregular surface that often results from this vascular growth, the patient's best chance of optimum vision will come with a rigid gas permeable lens. A smaller diameter lens will also have less chance of irritating the pterygium than a larger diameter lens. - Answer 40. When fitting a patient with a pterygium that impinges on the cornea by 2 mm at the 9 o'clock area, which of the following designs should be ? A. Soft contact lens B. 9.8 mm diameter RGP lens C. 8.8 mm diameter RGP lens D. Prism ballasted soft lens The answer is A. Just as the thickness of a rigid gas permeable lens will affect its transmissbility, the thickness of a soft lens will have the same effect. A thicker lens of the same material or thicker parts of a lens (i.e. prism) will be less permeable to oxygen. - Answer 41. When fitting an alternating design RGP multifocal lens, the primary function of a truncation is to: A. Center the lens better B. Make the lens more comfortable C. Allow the lens to translate more efficiently D. Lower the bifocal segment The answer is B. An inverted or flat fitting lens will often display edge lift or stand off. - Answer 42. The thickness of a soft contact lens will affect the: A. Oxygen transmissibility of the lens B. Power C. Opaque Tint D. Patients visual acuity The answer is A. Three point touch refers to the relationship of the soft lens to the cornea. The lens should make contact centrally with the corneal apex, vault the limbus, and have its edges rest on the sclera. Ultra-thin soft lenses, due to their flexure, may drape the cornea completely. A soft lens should never be fit with apical clearance, as this will result in fluctuating vision and seal off in the periphery, resulting in a tight fit. - Answer 43. Soft lens fitting should result in: A. Three point touch B. Apical clearance C. Upper lid attachment D. None of the above The answer is D. The general rule of thumb in choosing a soft lens diameter is that it should be at least 2.0 mm larger than the HVID. If the HVID is 11.0mm, the smallest soft lens diameter should be 13.0 mm. - Answer 44. If the HVID (Horizontal Visible Iris Diameter) is 11.0mm, the minimum diameter soft lens you should choose is: A. 14.5 mm B. 14.3 mm C. 14.0 mm D. 13.0 mm The answer is B. The overall lens diameter and the curve of the posterior portion of the lens determine the sagittal depth of any contact lens, soft or rigid. The larger the diameter and/ or the steeper the base curve, the greater the sagittal depth. Conversely, the smaller the diam- eter and/ or the flatter the base curve, the smaller the sagittal depth. - Answer 45. The sagittal depth of a soft lens is determined by: A. Diameter and power B. Base curve and diameter C. Diameter and water content D. Base curve and thickness The answer is C. Decreasing the lens diameter and flattening the base curve will only serve to loosen this already flat lens. Increasing the center thickness may also loosen the lens fit, as it de- creases capillary attraction and results in greater lens movement. - Answer 46. A soft lens displays inferior edge lift on the eye. What can be done to remedy this situation? A. Decrease lens diameter B. Flatten base curve C. Steepen base curve D. Increase center thickness The answer is C. Tint is the only characteristic listed that does not influence the fit of a soft contact lens. Changes in diameter, water content or sagittal depth will affect the soft lens fit. - Answer 47. Which characteristic of a soft lens does not affect the fit? A. Diameter B. Sagittal depth C. Tint D. Water content The answer is B. The most reliable method of assessing the fit of a soft lens is to put your thumb on the lower lid, have the patient look up slightly and push the lens up. If the lens moves freely without much force and then moves gently back into place, it is considered a good fit. Asking the patient how the lens feels should not be a criterion for final evaluation, as patients will usually choose lenses that are initially tight. Fluorescein evaluation will not provide information about the fit of a soft lens and may be absorbed by the lens, causing discoloration. - Answer 48. The most effective method of assessing the fit of a soft contact lens is: A. Asking the patient how it feels B. Push up test C. Fluorescein evaluation D. Slit lamp observation with optic section The answer is B. The larger the diameter, the greater the sagittal depth if the base curve is kept the same. The 14.5 diameters have a greater sagittal depth than their 14.0 counterparts. The steeper the base curve, the greater the sagittal depth. That would mean that the 8.4 would result in a greater sagittal depth than the 8.8 indicating that the 8.4/14.5 lens would have the greatest sagittal depth. - Answer 49. If all of the following soft lenses are made with the same design and material, which should have the greatest sagittal depth? A. 8.4/14.0 B. 8.4/14.5 C. 8.8/14.0 D. 8.8/14.5 50. The answer is C. When considering sagittal depth, if the base curves of the lenses are the same, the smaller the diameter, the shorter the depth. This indicates that the 14.0 diameters are looser than the 14.5 diameters. If the lens diameters are equal, the flatter the base curve, the looser the lens. Therefore, the 8.8 would be flatter than the 8.4 and confirms that the 8.8 base curve with the 14.0 diameter would most loosely fit of the choices given. - Answer 50. Which of the following soft lenses would you expect to fit the loosest on the eye if the lens material and design are all the same? A. 8.4/14.0 B. 8.4/14.5 C. 8.8/14.0 D. 8.8/14.5 Tr is A. The patient's Rx needs to first be transposed to minus cylinder form: -2.00 -1.00 ex 80 When evaluating the rotation of a soft toric lens, the placement of the axis markings on the lens will allow the contact lens professional to determine how much and in what direction to compensate for axis rotation. If the lens rotates to the fitter's left the amount of rotation is added to the axis of the patient's spectacle Rx. If the lens rotates to the fitter's right, the amount of rotation is subtracted from the axis of the patient's spectacle Rx. In the example given, the lens rotated 15 degrees to the right, which means 15 degrees is subtracted from the patient's cylinder axis: 80 -15 =65 - Answer 51. Given the following information: Diagnostic Lens -2.00 -1.00 cx 90 Patient's Rx -3.00 +1.00 cx 170 The diagnostic lens rotates 15 degrees to the right. What soft toric lens power would you order for this patient? A. -2.00 -1.00 cx 65 B. -2.00 -1.00 cx 75 C. -2.00 -1.00 cx 105 D. -2.00 -1.00 cx 155 The answer is B. HVID stands for Horizontal Visible Iris Diameter and is determined by measuring the iris horizontally at its widest part. An average HVID is 11.5 mm. - Answer 52. Initial selection of a soft lens diameter is decided by measuring the HVID. What does this stand for? A. Highest Visible Initial Diameter B. Horizontal Visible Iris Diameter C. Hydrogel Viewing Interstromal Device D. Horizontal VerticalIris Diameter The answer is A. Cast molding of a soft contact lens results in very consistent lens parameters which allows manufacturers to produce the vast quantities of lenses needed to satisfy the disposable lens market. Lathe cutting is a more costly and labor-intensive method of manufacturing soft lenses and is used for conventional lenses. Spin casting causes the posterior surface of the lens to change as the power increases and results in an aspheric design and a less predictable fit. - Answer 53. The manufacturing process most often used for disposable contact lenses is: A. Cast molding B. Lathe cut C. Spin cast D. Wax molding 54. The answer is B. Soft toric lenses are generally made with cylinders of 0.75 D and greater. While not all patients with only 0.75 D of cylinder will require a soft toric lens, this should be a starting point for discussion and evaluation of the need for a soft toric lens to provide the best visi_onfor the patient. - Answer 54. What is the least amount of cylinder a patient should have before soft toric lenses are discussed? A. 0.25 D B. 0.75 D C. 1.25 D D. 2.00 D The answer is A. Discharge, itching and lens displacement in a long time soft lens wearer are classic symptoms of GPC (Giant Papillary Conjunctivitis). Everting the upper lid and looking for enlarged papillae and injection will help the practitioner make the positive diagnosis. - Answer 55. When a longterm soft lens wearer complains of discharge, itching, and an occasional pulling up of the lens by the upper lid, the practitioner should: A. Evert the upper lid and check for GPC B. Remove the lens and check for follicles C. Raise the upper lid and check for SLK D. Pull the lower lid down and check for jelly bumps The answer is C. Soft toric lens manufacturers generally begin with cylinder powers at 0.75 D. Cylinder power requirements less than that are usually not corrected with a toric lens design. While custom soft toric lenses can correct 4.00 D and more of refractive cylinder, the standard range is usually Jess than 3.00 D. - Answer 56. What is the average cylinder power range of standard toric soft lenses? A. 0.25 to 1.50 D B. 0.25 to 2.50 D C. 0.75 to 2.50 D D. 0.75 to 4.00 D The answer is A. The FDA Classifications for soft lens materials are grouped by the water content of the material (low water versus high water) and the electrical charge on their surface (ionic versus non-ionic). Contact lens materials that carry an electrostatic charge are ionic and lens materials that do not carry an electrostatic charge are classified as non-ionic. The neutrally charged lens materials (i.e. non-ionic) are less likely to attract the positively charged proteins and lipids in the tear film. Soft Jens materials that are classified as low water, non-ionic are considered the most deposit resistant materials. - Answer 57. Which of the following soft lens material groups is considered the most resistant to deposit formation? A. Low water, non-ionic B. High water, non-ionic C. Low water, ionic D. High water, ionic The answer is D. The lens material group that is considered the least resistant to deposit formation is the high water, ionic (negatively charged lens surface) lens material. It is also the lens material that is most reactive to solutions and their preservatives. - Answer 58. Which of the following soft lens material groups is considered the least resistant to deposit formation? A. Low water, non-ionic B. High water, non-ionic C. Low water, ionic D. High water, ionic The answer is D. Daily disposable lenses or single use lenses are approved to be worn for only one day and then thrown away. They have not been approved to be used with solutions, nor should they need to be, as they must be discarded after one use. - Answer 59. The approved protocol for single use lenses is: A. Clean and disinfect daily B. Clean and disinfect weekly C. Clean and disinfect bi-weekly D. Discard upon lens removal The answer is A. The FDA has approved the use of extended wear disposable lenses for no longer than 1 week (6 nights/7 days). Disposable lenses that are worn on a daily wear basis should be replaced after two weeks of daily wear. - Answer 60. What is the FDA recommended replacement schedule for disposable lenses that are worn on an extended wear basis? A. 1 week B. 3 months C. 2 weeks D. 1 month The answer is A. The tonicity of the water in which soft contact lenses are exposed will greatly affect their behavior. For instance, in cases where the soft lens is exposed to a hypotonic solution (i.e. freshwater lakes) the lens diameter will increase and the lens will fit tighter on the eye. In cases where the soft lens is exposed to a hypertonic solution (i.e. salt water}, the lens will fit looser on the eye. - Answer 61. Most soft lenses today have a handling tint. The amount of light absorbed by these lenses is: A. 20-30% B. 10-20% C. Less than 10% D. 30-40% The answer is A. When a soft lens becomes too tight at the edge, it will squeeze down in the periphery and cause limbal compression. Removing the soft lens will often show an indentation ring caused by the edge of the lens. While edema and neovascularization may result from longterm wear of a tight soft lens, they are not the condition that was described. In- creased IOP (intraocular pressure} occurs inside the anterior chamber and is not affected by a tight soft lens. - Answer 62. A soft lens is too tight and causes pressure on the sclera at the periphery of the lens edge. This is known as: A. Limbal compression B. Neovascularization C. Edema D. Increased IOP The answer is B. The keratometer, normally used for measuring the central curve of the cornea, can help to determine if a soft lens is too tight. If the mires clear after the blink and then blur, the lens is too steep or tight. If the mires are clear and then blur after the blink, the lens is too flat or loose. The mires of a well fitting soft lens will remain clear at all times. - Answer 63. Which measuring device could help determine if a soft lens is too steep? A. Profile analyzer B. Keratometer C. Ophthalmoscope D. Radiuscope The answer is A. An average Dk for soft lens materials that contain less than 55% water are in the 8 to 16 range. For soft lens materials that have a greater water content, the average Dk for the material is 20 to 38. - Answer 64. What is the approximate clinical measurement of oxygen permeability through a 38 % water content hydrogel lens? A. 9 +/- B. 20 +/- C. 38 +/- D. 55 +/- The answer is B. Extended wear soft contact lenses are available in a wide range of water contents. Increasing water content is only one method of increasing the oxygen transmission of the lens. Another means of increasing oxygen is making the lens thinner. - Answer 65. Extended wear soft contact lenses come in what water contents? A 38% to 55% B. 24% to 79% C. 55% and above D. 71% to 79% The answer is D. When evaluating the alignment of a diagnostic soft toric lens, the calculations for the new lens are always made in respect to the patient's spectacle prescription, not the diagnostic lens. If the lens rotates to the observer's left, add the amount of rotation to the patient's spectacle axis. If it rotates to the right, subtract the amount of rotation from the axis of the spectacle axis. - Answer 66. Given the following information: Rx -3.50 -1.50 ex 170 Diagnostic lens 8.8 -3.50 -1.50 cx 180 Upon initial evaluation, the lens rotates 10 degrees to the observer's left. The lens or- dered should be: A. 8.8 -3.50 -1.50 cx 10 B. 8.8 -3.50 -1.50 cx 160 C. 8.8 -3.50 -1.50 cx 170 D. 8.8 -3.50 -1.50 cx 180 The answer is A. The ordered lens should always orient at the same place as the diagnostic lens. If it does not, the cylinder axis of the lens will not align correctly with the patient's cylinder axis. - Answer 67. Referring to the question above, when the patient's new lens is received, where would you expect the new lens to orient? A. 10 degrees to the observer's left B. 10 degrees to the observer's right C. The six o'clock position D. At 90 degrees The answer is B. "SEAL" is typically found in soft lens wearers and stands for Superior Epithelial Arcuate Lesion. "SEAL" is characterized by an epithelial lesion of 1 to 3 mm. The lesion is generally 1 mm from the superior limbus, is arcuate in shape and parallel to the limbus. It is generally considered to be the result of a soft lens that does not flex enough to conform to both the flat sclera and steeper cornea. The upper lid rubs the lens into the superior cornea, causing the epithelium to split. Discontinuing lens wear until the condition resolves and then refitting with a softer, thinner lens material will usually solve the problem. - Answer 68. "SEAL" is a condition, which is characterized by: A. A lesion in the inferior cornea B. A lesion in the superior cornea C. Edema in the corneal endothelium D. Loss of central vision The answer is A. A spin cast soft lens is created with a constant anterior (outside) curve. It is the posterior curve that changes as the power of the lens changes. - Answer 69. Where is the power curve on a spin cast soft lens? A. Posterior surface B. Anterior surface C. Astigmatic surface D. On the edge The answer is C. Tensile strength refers to a material's ability to return to its original shape after it has been manipulated by outside forces. This is an important property in soft hydrogel lenses. The index of refraction refers to the ability of light to pass through a material. Crosslinking agents are the part of the lens material whose main purpose is to hold the polymer chains together. An elastomer is a co-polymer with many repeating polymer units. - Answer 70. The major concern in using silicone as a contact lens material is it's? A. Hydrophilic nature B. Optics C. Hydrophobic nature D. Oxygen transmission The answer is B. Microcysts are tiny pockets of cellular debris that move through the epithelium until they appear on the surface of the cornea and are blinked away into the tear film. While they themselves do not cause pain or irritation, they are a sign that the cornea is not receiving adequate oxygen. Contact lens wearers who display microcysts should be instructed to remove their contact lenses and leave them off until the situation is resolved, which may take several weeks to months. Before resuming lens wear, the patient's situation should be evaluated and steps should be taken to increase the amount of oxygen being delivered to the cornea. This might inv9lve reducing wearing time or increasing lens Dk. Microcysts are most common in extended wear patients and these patients should be refit for daily wear only. - Answer 71. When 50 or more epithelial microcysts are noted during the slit lamp exam, the patient should be told to: A. Continue lens wear but switch to heat disinfection B. Discontinue lens wear until they go away, usually in three months C. Reduce lens wear until they go away, usually in three days D. Switch to high water content lenses and remove weekly The answer is D.