Longitudinal changes in objective scatter index and associated clinical factors in phakic eyes

We aimed to characterize longitudinal changes in the objective scatter index (OSI) in phakic eyes and identify baseline demographic, clinical, and ocular factors associated with changes in optical quality over time. This retrospective longitudinal observational study included 1,228 phakic eyes from 691 patients with at least two serial OSI measurements obtained using a double-pass optical quality analysis system. All available preoperative measurements were included for eyes that subsequently underwent cataract surgery. Longitudinal OSI changes were evaluated using linear mixed-effects models accounting for repeated measurements within eyes and correlation between fellow eyes. Baseline factors associated with monthly OSI change were assessed through interactions with follow-up time. Sensitivity analyses were performed across alternative follow-up durations, analytic populations, and random-effects structures. In total, 3,111 serial OSI measurements were analyzed. Individual eyes demonstrated substantial variability in longitudinal OSI trajectories, while the unadjusted population-level trend showed an average increase of 0.034 OSI units per month. Variability in estimates based on the first and final measurements decreased with longer follow-up durations. In the multivariable longitudinal model, older age, diabetes mellitus, and worse baseline best-corrected visual acuity were associated with faster increases in OSI, whereas greater baseline lens thickness was associated with slower OSI progression. The direction of the estimated associations were generally maintained across sensitivity analyses, although the strengths and statistical significances of individual associations varied under alternative model specifications. Serial OSI measurements provide an objective method for assessing longitudinal deterioration in optical quality in phakic eyes. Older age, diabetes mellitus, worse baseline visual acuity, and thinner baseline lenses were associated with faster increases in OSI. Serial OSI assessment may serve as an objective adjunct to the longitudinal assessment of optical quality in phakic eyes.