Table 2.

Posterior corneal astigmatism in different groups of patients.

Groups	N (%)	Mean (D)	SD (D)	Aggregate astigmatism
SMV	7637 (97.55%)	0.34*	0.13	0.01 ± 0.37 @ 1.56
SMH	51 (0.65%)	0.10	0.09	0.03 ± 0.14 @ 179.65
SMO	141 (1.80%)	0.15	0.10	0.02 ± 0.18 @ 90.28
Low myopia	987 (12.60%)	0.32	0.13	0.01 ± 0.35 @ 183.65
Moderate myopia	4744 (60.60%)	0.33	0.13	0.01 ± 0.36 @ 0.84
High myopia	2098 (26.80%)	0.36†	0.14	0.01 ± 0.38 @ 3.19
MA < 0.50 D	2646 (33.80%)	0.29‡	0.11	0.01 ± 0.31 @ 0.62
0.50 D ≤ MA < 1.00 D	2991 (38.20%)	0.32	0.12	0.01 ± 0.34 @ 0.09
1.00 D ≤ MA < 2.00 D	1875 (23.95%)	0.40	0.14	0.01 ± 0.42 @ 0.45
2.00 D ≤ MA < 3.00 D	275 (3.51%)	0.51	0.14	0.06 ± 0.53 @ − 0.99
MA ≥ 3.00 D	42 (0.54%)	0.61	0.16	0.07 ± 0.64 @ 177.19

N number of eyes, D diopter, SD standard deviation, SMV steep meridian vertical, SMH steep meridian horizontal, SMO steep meridian oblique, MA manifest astigmatism.

*P < 0.0001 for comparison of SMV to SMH or SMO.

^†P < 0.0001 for comparison of high myopia to low myopia or moderate myopia.

^‡P < 0.0001 for comparison between any two of the MA groups, expect for comparison between the groups of 2.00 D ≤ MA < 3.00 D and MA ≥ 3.00 D.