Abstract
Abstract: :
Purpose: To examine and compare best-corrected visual acuity (BCVA) and contrast sensitivity (CS) in patients who had monofocal and multifocal intraocular lenses (IOLs) under different levels of illumination. Methods: Retrospective review of 34 consecutive non-randomised patients who had uneventful phacoemulsification cataract extraction, 11of whom had monofocal and 23 multifocal IOLs. Patients were recruited and examined after a minimum postoperative period of 6 weeks and 4 patients were excluded because of ambloypia, posterior capsular opacification (PCO) or ocular co-morbidity. Binocular distance and near BCVA and CS were tested using logMAR and Pelli-Robson charts respectively. The charts were externally illuminated with 20, 200, 400 and 1600 lux and BCVA and CS were compared in each group as the illumination was increased and between the two groups at different illumination levels. Mann-Whitney and Wilcoxon signed ranks tests were used for comparison. Results: Thirty patients were included, 10 of them had monofocal (33%) and 20 multifocal (67%) IOLs. In the monofocal group, distance and near BCVA significantly increased as illumination was increased from 20-200lux (p=0.008, 0.005) and from 200-400lux (p=0.048, 0.046). Also, in the multifocal group, distance and near visual acuity significantly improved by increasing illumination from 20-200lux (p<0.005) whereas only distance acuity significantly improved as illumination was increased from 400 to 1600lux (p=0.005). In both groups, CS significantly improved as illumination was increased from 20-200lux (p=0.008,0.002). No significant difference in BCVA or CS was found between the two groups at any of the 4 levels of illumination. Conclusions: Depending on the implant type, distance and near BCVA and CS can be variably improved in patients with monofocal and multifocal IOLs by increasing illumination. Also, BCVA and CS are comparable for the two implants under different levels of illumination. Both findings will help in perioperative counselling of patients.
Keywords: visual acuity • contrast sensitivity • brightness and lightness