Materials and Methods: Axial length, anterior chamber depth, corneal curvature of flat and steep meridian (K1, K2), corneal astigmatism amount (K2-K1), astigmatism type (with the rule, against the rule, oblique) values of phakic right eye from 275 patients were examined from the coherence interferometer in this descriptive study. Age was divided into 5 groups (?40, 41-50, 51-60, 61-70, >70). Comparisons were performed between different age groups and the causative groups of the differences were found.

Results: Mean corneal astigmatism was 1.00±0.74 diopters (D) and 60.8% (n=167) of the cases were lower than 1 D, 39.2% (n=108) of the cases were higher than 1 D. According to astigmatism type, 40.0% (n=110) was with the rule, 36.4% (n=100) was against the rule, 23.6% (n=65) was oblique. There was a statistically significant difference between age groups according to astigmatism type (p<0.001). This difference resulted from comparisons between age groups of ?40 and 61-70 (p=0.01); and between age groups of ?40 and >70 (p<0.001). Against the rule astigmatism increased with age.

Conclusions: High frequency of with the rule astigmatism in young age groups and high frequency of against the rule astigmatism in elderly groups seems to be important for the choice of clear corneal incision site (superior/temporal), astigmatic correction surgeries and preference of toric intraocular lenses. Keywords : Astigmatism, biometry, cataract surgery, with the rule, against the rule