Change in pupil diameter after phacoemulsification with intraocular lens implantation.

PURPOSE: To evaluate changes in scotopic pupil diameter before and after cataract surgery performed by phacoemulsification with intraocular lens implantation. METHODS: This prospective longitudinal observational study included patients who underwent cataract surgery. Scotopic pupil diameter was measured preoperatively and 30-40 days postoperatively using an automated keratometer after a standardized dark-adaptation period under controlled ambient illumination. Each eye was considered an independent unit of observation. Because some participants contributed both eyes, intraindividual correlation was accounted for using a linear mixed-effects model with random patient intercepts. Time of assessment (preoperative versus postoperative), age, sex, and eye laterality were included as fixed effects. RESULTS: A total of 354 eyes from 251 patients were analyzed. The mean patient age was 69.3±7.2 yr. Mean scotopic pupil diameter decreased from 5.3±0.9mm preoperatively to 4.8±0.8mm postoperatively, representing a mean reduction of 0.5mm (9.4%). In the linear mixed-effects model, cataract surgery was associated with a significant reduction in pupil diameter, with an adjusted mean difference of 0.45mm (95% confidence interval [95% CI], 0.39-0.51; p<0.001). Age (p=0.061), sex (p=0.920), and eye laterality (p=0.152) were not significantly associated with the magnitude of pupil diameter change. CONCLUSION: Phacoemulsification with intraocular lens implantation was associated with a significant reduction in scotopic pupil diameter, independent of age, sex, and eye laterality. This finding should be considered during preoperative planning, particularly when selecting intraocular lenses whose optical performance depends on postoperative pupil size.