The Effect of LASIK on Post–Op Physical Pupil Size

Abstract

Abstract: : Purpose: To determine whether physical pupil size is affected by LASIK. Methods: From a retrospective randomized study of 120 eyes of 60 patients, physical pupil size was calculated using the formula physical pupil diameter (PP, in mm) = measured pupil diameter (in mm)*(1–B) where B = anterior chamber depth (in meters)* central K (in Diopters)/1.3375. The measured pupil under dark conditions (Zywave, Bausch&Lomb), mean central K (Keratron Scout Optikon, Rome, Italy) and processed over central 3–mm region using OSUCTT software (Mahmoud AM, et al. IOVS 2000;41:ARVO Abstract 3599) and anterior chamber depth (Orbscan, Bausch&Lomb) were collected pre– and six–months post–LASIK. Subjects were divided into two groups by different surgeon. Group A eyes were treated in pairs by a Technolas 217A (Bausch&Lomb) and LADARVision 4000 (Autonomous) for each eye and Group B eyes the Technolas 217A and the Star S3 (VISX). Analysis of variance (SAS) was used to compare the mean difference in physical pupil size between the two groups post–LASIK. Results: The mean difference in physical pupil diameter at 6 months post– versus pre–LASIK for all subjects was 0.19±0.50mm and ANOVA confirmed that the difference was signficantly non–zero (P>.01). ANOVA analysis of the mean difference in postop PP for each group was 0.32±0.47 for Group A that was significanly non–zero (P>.01) and 0.054±0.50 for Group B that was not significantly non–zero (P=.41). Conclusions: The calculated mean physical pupil diameter significantly increased following LASIK across all eyes. The measured increased effect was observed in Group A (P>.01) however not in Group B (P=.41).

Keywords: refractive surgery: LASIK • pupil