The Prediction of Changes in Mean Corneal Refractive Power by Pterygium Size after Pterygium Surgery

ABSTRACT

PURPOSE: To assess the changes in mean corneal refractive power (DeltaK) following pterygium surgery and to predict DeltaK in cases of combined cataract and pterygium surgery. METHODS: Thirty-seven eyes of unilateral pterygium patients who underwent pterygium surgery were analyzed retrospectively with at least more than 1 month of follow-up. Preoperative and postoperative 1 month corneal refractive power was measured using auto-keratometer (RK-F1, Canon, Tokyo, Japan). Pterygium horizontal extension, width, and area were measured and correlation with DeltaK before and after surgery analyzed. We also compared DeltaK of the contralateral normal eye. RESULTS: The mean corneal refractive (Km) power measured before and 1 month after surgery was 43.30 +/- 1.66 D and 44.07 +/- 1.42 D, respectively. The Km significantly increased at 4 weeks after surgery (p < 0.001). However, postoperative Km was not significantly different when compared with the contralateral normal eye (43.86 +/- 1.34 D; p = 0.59). All parameters of pterygium size including horizontal extension, width, and area were positively correlated with the mean DeltaK. Among parameters, horizontal extension was best correlated with mean DeltaK (p < 0.001). The mean DeltaK with horizontal extension was predicted using linear regression (2.5 mm to 1 D, 4.0 mm to 1.8 D). CONCLUSIONS: We recommend contralateral corneal refractive power or prediction of corneal refractive power using linear regression with pterygium horizontal extension for determining intraocular lens power in cases of combined cataract and pterygium surgery.