Page 84 - The Indian Digital Edition September-October 2020

TABLE 1 TABLE 2
PRISMATIC EFFECT AT THE NVP PRISMATIC EFFECT AT THE NVP DUE TO EACH +1.00 D OF
DUE TO PLUS SPHERICAL POWER. CYLINDER POWER.
N.B. FOR MINUS POWERS REVERSE N.B. FOR MINUS CYLINDER POWERS REVERSE THE BASE
THE BASE DIRECTION. DIRECTION
Sphere Prismatic effect in Δ Sphere Power Prismatic effect in Δ
Power Vertical Horizontal R EYE L EYE Vertical Base UP Horizontal Base UP

+0.25 0.2 base UP 0.05 base OUT 180 180 0.80 base UP 0
+0.50 0.4 0.1 5 175 0.81 base Up 0.07 base OUT
+0.75 0.6 0.15 10 170 081 0.14
+1.00 0.8 0.2 15 165 0.80 0.21
+1.50 1.2 0.3 20 160 0.77 0.28
+2.00 1.6 0.4 25 155 0.73 0.34
+2.50 2.0 0.5 30 150 0.69 0.40
+3.00 2.4 0.6 35 145 0.63 0.44
+3.50 2.8 0.7 40 140 0.57 0.48
+4.00 3.2 0.8 45 135 0.50 0.50
+4.50 3.6 0.9 50 130 0.43 0.51
+5.00 4.0 1.0 55 125 0.36 0.51
+5.50 4.4 1.1 60 120 0.29 0.50
+6.00 4.8 1.2 65 115 0.22 0.47
+6.50 5.2 1.3 70 110 0.16 0.43
+7.00 5.6 1.4 75 105 0.10 0.39
+7.50 6.0 1.5 80 100 0.06 0.33
+8.00 6.4 1.6 85 95 0.02 0.27
+8.50 6.8 1.7 90 90 0 0.20
+9.00 7.2 1.8 95 85 0 0.13
+9.50 7.6 1.9 100 80 0 0.06
+10.00 8.0 2.0 105 75 0 0.01 base IN
+10.50 8.4 2.1 110 70 0.03 base UP 0.08
+11.00 8.8 2.2 115 65 0.07 0.14
0.25 intervals can be found by simple 120 60 0.11 0.20
addition: 125 55 0.17 0.24
130 50 0.23 0.28
e.g., +2.75 = +2.50 and +0.25
for +2.50: prism due to sphere = 135 45 0.30 0.30
2.0Δ base UP and 0.50Δ base OUT 140 40 0.37 0.31
for +0.25: prism due to sphere = 145 35 0.44 0.31
0.2Δ base UP and 0.05Δ base OUT 150 30 0.51 0.30
so for +2.75 D sphere prism at NVP = 155 25 0.58 0.27
2.2Δ base UP and 0.55Δ base OUT 160 20 0.64 0.23
For other cylinders, multiply the 165 15 0.70 0.19
values given in Table 3 by the new 170 10 0.74 0.13
cylinder power. 175 5 0.78 0.07
Note that the Jump is always base
down (unless its value is zero!).

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