The effect of pterygium on corneal astigmatism.

ABSTRACT

OBJECTIVE: To determine the effect of pterygium on corneal astigmatism. METHOD: Two hundred and forty three eyes of 173 patients with primary pterygium were included in the present study. The extension of pterygium was measured by slit lamp and corneal astigmatism was measured by corneal topography. Correlation of the data was discussed. RESULTS: The size of pterygium extended from 0.50 mm to 8.10 mm (2.11 +/- 1.10). The diopter of corneal astigmatism ranged from 0.10 diopter to 14.60 diopter (1.86 +/- 2.39). The axis of corneal astigmatism was found in vertical axis 156 eyes (64.2%), oblique axis 36 eyes (14.8%) and horizontal axis 51 eyes (21.0%). The degree of corneal astigmatism significantly correlated with the extension of pterygium on the cornea (R Square = 0.45, p < 0.001). When the extension of pterygium exceeded 2.25 mm, there was a chance of developing corneal astigmatism of 2 diopter or more (86.21% of sensitivity and 80% of specificity). CONCLUSION: The extension of pterygium is significantly correlated with the degree of corneal astigmatism in the positive direction, with the highest percentage of with-the-rule astigmatism. Pterygium exceeding 2.25 mm of length should be considered within the limits of surgery.