Table 3

Comparison of topographic patterns, in relation to astigmatism and quantitative indices

Topographic patternRefractive astigmatism (D) Mean (SD)Keratometric astigmatism (D) Mean (SD)Topographic astigmatism
(simk)
Mean (SD)
SRI
Mean (SD)
SAI
Mean (SD)
I Non-astigmatic1.67 (0.76)1.17 (0.99)1.61 (0.85)0.82 (0.39)0.60 (0.27)
II Regular astigmatism4.20 (2.98)5.08 (3.21)5.93 (3.92)1.63 (1.26)0.97 (0.61)
 Oval2.17 (1.22)2.96 (3)2.70 (1.97)1.61 (1.32)1.06 (0.49)
 PSBT4.09 (1.81)7 (2.57)8.18 (4.63)1.82 (1.04)1.01 (0.54)
 PABT4.41 (3.50)5.45 (2.76)6.22 (3.28)2.07 (1.48)1.20 (0.76)
 OSBT4.81 (2.99)4.63 (3.70)6.82 (5.79)1.08 (0.59)0.73 (0.59)
 OABT4.62 (2.79)5.65 (3.17)5.72 (2.88)1.49 (1.24)0.90 (0.38)
III Irregular astigmatism3.37 (2.38)4.03 (2.87)3.98 (2.47)2.06 (1.67)1.44 (0.88)
 Prolate irregular (PI)4.61 (2.49)5.37 (3.14)5.20 (2.49)1.78 (1.25)1.09 (0.57)
 Oblate irregular (OI)5.46 (1.51)6.47 (2.07)5.70 (2.64)2.50 (2.21)1.22 (0.98)
 Mixed4.22 (2.92)5.56 (3.66)4.83 (2.73)1.96 (1.82)1.19 (0.77)
 Steep/flat (SF)2.39 (1.62)2.87 (1.39)3.43 (1.87)1.96 (1.79)1.70 (0.99)
 Localised steep (LS)2.50 (1.77)3.02 (2.14)3.34 (2.57)2.10 (1.57)1.68 (0.82)
 Triple3.78 (2.95)2.91 (0.61)2.70 (1.54)1.11 (0.38)0.94 (0.47)
 Horseshoe2.08 (1.61)2.20 (0.82)2.26 (1.25)0.97 (0.54)0.97 (0.42)
 Unclassified3.37 (2.35)4.58 (3.91)4.23 (2.43)3.19 (1.92)1.78 (1.12)