Analysis of the pterygium size inducing marked refractive astigmatism.

PURPOSE Astigmatic changes induced by the pterygium and their relation to its size and morphology were analysed to establish the critical size for surgery before significant astigmatism occurs. MATERIALS AND METHODS We evaluated the refraction in 148 eyes of 108 adult patients with primary pterygia. We grouped the astigmatic values according to the keratometric results correlating with the maximal length, width and the approximate total area of the pterigium encroaching on the corneal surface. RESULTS Pterygia with length or width > or = 3.00 mm were related to significantly higher astigmatism than other groups (p<0.01). The effect of the pterygium morphology on corneal astigmatism was not significant. CONCLUSIONS Pterygia exceeding 3.00 mm of length or width should be considered within the limits of surgery.