CORRELATION BETWEEN PTERYGIUM SIZE AND INDUCED CORNEAL ASTIGMATISM

Purpose. Before invasion of the visual axis, pterygia typically induce with-the-rule astigmatism, which can be visually significant. In this study, we attempted to assess the quantitative relation between ptery gium size and induced corneal astigmatism using corneal topography and digital imaging. Methods. Thirty-three eyes of 25 patients with prima ry pterygia were evaluated using corneal topography (TMS), slit-lamp p hotography, and digital imaging to correlate parameters of pterygium s ize with induced corneal astigmatism at the 3- and 6-mm optical zones. Results. Pterygia induce asymmetric with-the-rule astigmatism. Lesion s extending >45% of the corneal radius or within 3.2 mm of the visual axis produce increasing degrees of induced astigmatism. Conclusion. On ce pterygia reach a critical size, they induce visually significant ce ntral with-the-rule astigmatic changes that may not be apparent by sub jective refraction. This finding helps to identify those patients who may benefit from surgical intervention.