Section 1 Keratometry and Rx Interpretation

Question 1

Determine Spherical equivalent:  
-1.00 +1.00 x090
-2.00 -1.00 x180
\+1.00+1.00 x090
-5.50+2.00 x090
\+1.00-1.00x 180

Answer 1

-0.50
-2.50
+1.50
-4.50
+0.50

Question 2

Determine Base Curve:

43. 00/41.00@090 fit on K
44. 00/44.00@090 fit on K
45. 00/44.00@090 fit 1/2 D steeper
46. 00/41.00@090 fit 1/2 D flatter

Answer 2

41. 00
42. 00
43. 50
44. 50

Question 3

Convert D to mm:

41. 00
42. 00
43. 50
44. 50

Answer 3

337. 5/41.00= 8.23mm
338. 04
339. 94
340. 33

Question 4

To determine the diameter for an Intrapalpebral fit:

Answer 4

Diameter = Vertical lid aperature (VLD)-0.2mm

Iris visable between open lids up and down

Question 5

To determine the diameter for an Upper lid attachment (corneal alignment)

Answer 5

Diameter = Visable Iris Diameter - 2.3mm

(whole size of iris) side to side.

Question 6

What is the vertex distance adjustment formula?

Answer 6

Fc= Fs/1-dFs

Question 7

WITH the Rule:

Answer 7

Horizontal 180 is flatter (lower#) Minus cylinder in 180 deg

Question 8

AGAINST the Rule:

Answer 8

Vertical 90 flatter, Minus cylinder in 90 deg

Question 9

Determine base curve:
K 42.75/44.25@090
Lens diameter = 9.2mm (use chart)

Answer 9

Flat K = 42.75
Delta K = 44.25-42.75=1.50D
1.50D @ 9.2mm =0.25 Steeper
BC= 42.75 + 0.25 = 43.00D

Question 10

Determine Power:
K 42.75/44.25@090
-6.00+1.00 x090
BC = 43.00
Diam=9.2mm

Answer 10

-5.00-1.00x180
-5.00 @ 12mm = -4.75 corrected for vertex
Adjust for tear lens: BC is steeper than Flat K, plus tear film, compensate for this Add Minus Power SAM Flat K 42.75 BC 43.00 Tear comp = 0.25
Adjusted power-5.00

Question 11

Rx +3.00+1.00x090
Contact Diameter 8.7mm
K 43.00/44.50 @090
Calculate final parameters for order

Answer 11

BC 43.50D
Diam 8.7mm
+3.50D

Question 12

Calculate Residual Astigmatism:
+2.00-2.50x090
45.50/44.00@090

Answer 12

Delta K = 1.50 (Corneal)
Refracted 2.50
Residual 1.00
Correct with Front toric

Question 13

Calculate Residual Astigmatism:

0. 00-2.00x180
1. 50/42.00@090

Answer 13

Delta K 2.50
Refract 2.00
Residual 0.50
Correct with Back Toric

Question 14

With a Back toric what are you correcting:

Answer 14

Corneal Astigmatism of 2.50D or higher

Question 15

With a Front toric what are you correcting:

Answer 15

Residual Astigmatism of 0.75 or higher

Question 16

For a Bitoric lens what are you correcting:

Answer 16

Corneal astig of 2.50D AND Residual astig of 0.75 or more.

Question 17

To properly adjust the eyepiece, turn the knob all the way _______. Slowly turn the knob ______ until proper focus is achieved.

Answer 17

counterclockwise

clockwise

Question 18

The test balls are generally in the range of 44.00 D, 42.50 and 40.75. The central ball, equivalent to a ___ corneal refracting power, is the one generally used for basic calibration tests.

Answer 18

42.50 D

Question 19

Remember that if the cornea is _____, it will be _____ to get the plus and minus signs, (both principal meridians) in focus at one time. For greater accuracy, focus the plus or horizontal mires sharply then ____ for the minus or vertical readings.

Answer 19

astigmatic
impossible
refocus