Prediction of Mean Corneal Power Change After Pterygium Excision

Abstract

The aim of this study was to predict the mean corneal power change preoperatively for simultaneous pterygium excision and cataract extraction. This study was performed in 2 stages. First, 66 eyes undergoing pterygium excision were recruited, and the subjects were divided into 2 groups based on a pterygium length of 2.0 mm (group 1: <2.0 mm, group 2: ≥2.0 mm). Keratometric values (K) were measured before, 1 month after, and 3 months after surgery. Multiple regression analyses were used to predict the postoperative mean K using preoperative K and morphological factors that significantly affect corneal power change. In the second stage, the regression equation was applied to 50 eyes (23 with pterygium <2.0 mm and 27 with pterygium ≥2.0 mm) in several clinics. Prediction accuracy was graded based on the difference between the calculated mean K and the postoperative mean K. In group 1, the mean Ks did not change significantly after the surgery, and therefore, the predicted mean K was not statistically different from the preoperative mean K. In group 2, the horizontal and mean Ks steepened significantly, and the regression analysis predicted the mean K within the range of 0.5 diopter difference in 22 of 31 eyes, showing a better approximation compared with the preoperative mean K (P < 0.001). The prediction accuracy was verified similarly in other clinics, and the regression analysis was useful for pterygium exceeding a length of 2.0 mm. Pterygium exceeding a length of 2.0 mm induced a significant corneal power change after surgery. The mean K predicted from the regression analysis could be used as an approximation for a simultaneous pterygium and cataract surgery.