C. A hyperope wearing glasses will have the highest demand. A hyperope will have increased accommodative demand to overcome the prescription. When comparing, plus specs vs contact lenses, plus power spectacles require more convergence.

B. An increase in lens diameter will allow for better lid attachment. Flattening the base curve, decreasing center thickness to reduce weight, or changing to minus carrier design can help with lid attachment.

A. This pattern is classic for WTR astigmatism. The opposite pattern of clearance and touch indicates ATR. General clearance or touch is more characteristic of a spherical cornea. You would expect an inferior spot of lens touch.

B. First, calculate the BC of the DxCL → 337.5/7.67 = 44.00 D. The equation for lacrimal lake is LL = BC – K. In the 180 meridian, 44.00 – 44.50 = -0.50 D. In the 90 meridian, 44.00 – 43.00 = +1.00 D. Therefore, LL = +1.00 -1.50 x 090.

C. -1.00 x 090. The equation of note is RA = SRcyl – Kcyl. We know that SRcyl = -0.50 x 180. Using the K values, we determine the corneal cyl is -1.50 x 180. Solving for RA = (-0.50 x 180( – (-1.50 x 180) = +1.00 x 180 or -1.00 x 090

C. A back surface toric is appropriate as the information supports the “123” rule. The “1” is the residual astigmatism. The “2” is double the RA and represents corneal astigmatism. The “3” is double that of the corneal astigmatism and represents the vertex refraction (be sure to adjust the refraction before deciding which lens.

D. Using the LARS rule, the answer is -1.00 -1.00 x 085. The mark has rotated clockwise, or Left, so will need to add the 10 degrees to an axis. Most forget that we adjust the axis of the original subjective refraction rather than the diagnostic lens. Therefore, 85 is the new axis.

C. The minimum amount of clearance is 50 microns. In practice, it is best to aim for 100-150 but 50 microns will still allow for corneal clearance even with blinks.

B. Using an optic cross, be sure to have -4.25 at the 180 and -6.00 at the 090. Vertexing results in -4.00 in the 180 and -5.50 at the 90. The final prescription is -4.00 -1.50 x 180.

D. Increased oxygen transmission via silicone as the water content decreases. Increasing water content leads to lower ratio of Silicone to water. Therefore, more water in the lens means less oxygen from tears through the silicone.

C. This lens belongs to Group 3. Group 1 is defined as low water content and on-ionin. Group 2 is high water content and non-ionic. Group 3 is defined by low water content and ionic. Group 4 is ionic with high water content. Group 5 describes all silicone hydrogel lenses.

A. Warpage occurs on AND off the eye. Flexure only occurs ON the eye. Higher Dk lenses have more chance of flexure.

C. Feq = +14.00 DS. To calculate, recall the equation Feq = F1 + F2 – cF1F2. As there is no separation in the equation, we simply calculate F1 + F2.

D. The expected mag power is -60.00 DS. The equation of Mag Power = – Foc/Fobj. Solving this out, Mag = – (X)/+12.00 = 5 = 5×12 = – 60 DS. As this is a Galilean telescope, recall that the ocular lens will be minus.

B. 20/50. The equation of note is test distance / M unit = 20 ft / size of Snellen letter. It is also an important number to recall as it represents average news print letter size and is a standard in low vision.

C. 5x. Recall the equation Effective magnification = F/4 = 20/4. Standard distance is 25 cm as the standard presbyopic and emmetropic patient needs a +4.00 add for magnification.

A. +6.00. Recall Kestenbaum’s Rule when determining initial ADD power. In this case, BCVA is 20/120. Therefore starting ADD is 120/20 = +6.00 D.

C. It would be appropriate to begin a prism trial with 10 BI in each eye. Recall the equation, ADD + 2 = prism in EACH eye.

D. 20/500 is considered Profound low vision. Recall the following pairs: Normal = 20/12 -20/25, Near-Normal = 20/30 to 20/60, Moderate = 20/70 – 20/160, Severe = 20/200 – 20/400, Profound = 20/500 – 20/1000, Near Blindness > 20/2000. Blindness is no perception of light or motion.

B/D: THe legal definition for blindness is the inability to read any letters on the 20/100 line in the better seeing eye and/or a visual field less than or equal to 20 degrees. If there is a central scotoma, subtract scotoma from overall diameter.