Table 2: Proportion of different categories of astigmatism.

Types of refractive errors Distribution
Overall (N=1374)
(All percentages under this column calculated with N = 1374)
Gender Based Distribution Age based Distribution
Males (N =670)
(All percentages under this column calculated with N = 670)
Females (N = 704)
(All percentages under this column calculated with N = 704)
Age ≤ 40 (N =1284)
(All percentages under this column calculated with N = 1284)
Age >40 (N = 90)
(All percentages under this column calculated with N = 90)
N % N % N % N % N % N % N % N % N % N %
Astigmatism
(Cylinder ≥ 0.50 DC)
Low to moderate Astigmatism*
(≥ 0.50 DC and < 3.00 DC)
1078 78.5% 949 69.1% 534 79.7% 472 77.5% 544 77.3% 477 73.0% 1017 79.2% 897 69.9% 61 67.8% 52 57.8%
High Astigmatism*
(≥ 3.00 DC)
129 9.4% 62 10.2% 67 10.3% 120 9.3% 9 10.0%
WTR*
(+/- 30° on 90°; cylinder ≥ 0.50 DC)
784 57.1% 354 58.1% 430 65.8% 748 58.3% 36 40.0%
ATR*
(+/- 30° on 180°); cylinder ≥ 0.50 DC)
182 13.2% 117 19.2% 65 10.0% 168 13.1% 14 15.6%
OBL*
(120° to 150° and 30° to 60; cylinder ≥ 0.50 DC)
112 8.2% 63 10.3% 49 7.5% 101 7.9% 11 12.2%
Simple Myopic
[plano sphere (> −0.5 D to < +0.5 D) & Cyl (-ve) ≤ −0.5 DC]
112 8.2% 73 12.0% 39 6.0% 105 8.2% 7 7.8%
Simple Hyperopic
[plano sphere (> -0.5 D to < +0.5 D) & Cyl (+ve) ≥ 0.5 DC]
17 1.2% 12 2.0% 5 0.8% 12 0.9% 5 5.6%
Compound Myopic
(sph ≤ −0.5 D & cyl ≤ −0.50 DC)
895 65.1% 419 68.8% 476 72.9% 850 66.2% 45 50.0%
Compound Hyperopic
(sphere of ≥ +0.5 D &
cylinder of ≥ +0.50 DC)
29 2.1% 14 2.3% 15 2.3% 27 2.1% 2 2.2%
Mixed astigmatism^ 25 1.8% 16 2.6% 9 1.4% 23 1.8% 2 2.2%
No Astigmatism (Absolute cylinder ≤ 0.50 DC) 296 21.5% - - 136 20.3% - - 160 22.7% - - 267 20.8% - - 29 32.2% - -

WTR- With the rule ATR- Against the rule, OBL- Oblique, D- Diopter, DC- Diopter cylinder, *Absolute values, ^Astigmatism is mixed if sphere is positive (> 0.5 D) and cylinder value is negative (< -0.50 D) or vice versa and the cylinder > sphere, Cyl= cylinder, - Not applicable