Quantification of Peripheral Blur in Ultra-Widefield Fundus Imaging Following Diffractive Multifocal Intraocular Lens Implantation

Background/Objectives: Diffractive multifocal intraocular lenses (IOLs) are widely used following cataract surgery, but their impact on peripheral retinal image quality in ultra-widefield (UWF) fundus imaging has not been objectively characterized. This study aimed to quantify peripheral image sharpness in UWF fundus photographs and assess wavelength-specific differences between diffractive multifocal and enhanced monofocal IOLs. Methods: In this retrospective cohort study, 65 eyes from 51 patients implanted with enhanced monofocal (Tecnis Eyhance; n = 32) or diffractive multifocal IOLs (Tecnis Synergy, n = 19; Clareon PanOptix, n = 14) were analyzed. Non-mydriatic UWF fundus photographs (Optos; ~200°) were acquired within 1 month postoperatively. Red (R), green (G), and composite channel images were analyzed using three sharpness metrics—Laplacian variance, Brenner gradient, and Tenengrad gradient—within a predefined peripheral annular region (1.5–3.0 times the fovea–optic disc distance). Generalized estimating equations (GEE) with age as a covariate were applied as the primary analysis to account for inter-eye correlation and age differences between groups. Results: Brenner and Tenengrad gradient scores were significantly lower in the multifocal group in the R channel (p = 0.037 and p = 0.041, respectively), but not in the G or composite channels. The Laplacian metric revealed no significant intergroup differences in any channel. Subgroup analysis revealed no significant difference between hybrid multifocal and quadrifocal subtypes (p > 0.05). Group-level mean heatmaps confirmed a spatially distributed reduction in gradient magnitude across the annular zone in multifocal eyes. Conclusions: Diffractive multifocal IOL implantation was associated with a localized reduction in peripheral R channel sharpness, hypothesized to reflect transverse chromatic aberration. Composite channel quality remained comparable between groups, suggesting limited impact on routine clinical imaging. These findings may inform IOL selection and interpretation of peripheral retinal findings in multifocal IOL patients.