Pterygium-induced corneal astigmatism

Background: Previous work has suggested an association between increasing s ize of pterygium and increasing degrees of induced corneal astigmatism. Objectives: To assess the quantitative relation between pterygium size and induced corneal astigmatism using a computerized corneal analysis system (T MS II) and slit-lamp beam evaluation of pterygium size, and to conclude whe ther corneal astigmatism is an early indication for surgical intervention. Methods: We evaluated 94 eves of 94 patients with unilateral primary pteryg ium of different sizes, using TMS II and slit-lamp beam measurements of the size of the pterygium (in millimeters) from the limbus to assess parameter s of pterygium size with induced corneal astigmatism Best corrected visual Snellen acuity was performed. Results: Primary pterygium induced with-the-rule astigmatism. Pterygium ext ending >16% of the corneal radius or 1.1 mm or less from the limbus produce d increasing degrees of induced astigmatism of more than 1.0 diopter. Signi ficant astigmatism was found in 16.16% of 24 eyes with pterygium of 0.2 up to 1.0 mm in size, in 45.45% of 22 eyes with pterygium of 1.1 up to 3.0 mm in size (P less than or equal to 0.0004), and in 100% of 3 eyes with pteryg ium of 5.1 up to 6.7 mm in size (P=0.0005), We found that visual acuity was decreased when topographic astigmatism was increased. Conclusions: When primary pterygium reaches more than 1.0 mm in size from t he limbus it induces with-the-rule significant astigmatism (greater than or equal to 1.0 diopter), This significant astigmatism tends to increase with the increasing size of the lesion, Topographic astigmatism tends to be imp roved by successful removal of the pterygium. These findings suggest that e arly surgical intervention in the pterygium may be indicated when the lesio n is more than 1.0 mm in size from the limbus.