Anatomical and Functional Outcomes of Macular Hole Surgery According to Internal Limiting Membrane Flap Size

Purpose: We evaluated the effect of internal limiting membrane (ILM) flap size on anatomical and functional outcomes of macular hole surgery, to determine the optimal flap size according to hole size.Methods: This retrospective study included 145 patients (147 eyes) with idiopathic full-thickness macular holes who underwent pars plana vitrectomy with ILM flap covering, followed for ≥6 months between January 2015 and August 2025 at a single center. Macular holes were classified as medium (250–400 μm) or large (400–800 μm) by minimum linear diameter. Patients were categorized by flap size into a standard group (≤1.5 disc diameters [DD]) and an extended group (>1.5–3 DD). Postoperative best-corrected visual acuity (BCVA), closure rate, foveal contour (U-, V-, or W-type), restoration of the external limiting membrane and ellipsoid zone, and complications were compared at 1 and 6 months.Results: In medium holes, both groups achieved 100% closure and comparable visual improvement, with no significant between- group differences. In large holes, the extended flap group showed greater BCVA improvement (ΔBCVA at 6 months, 0.49 vs. 0.12), higher closure rate (94.0% vs. 86.8%), more U-shaped foveal contours (48.0% vs. 13.2%), and higher external limiting membrane restoration (56.0% vs. 15.8%) than the standard group (p < 0.05). Multivariable analysis identified extended flap as an independent predictor of closure (adjusted OR, 6.77; 95% CI, 1.49–30.79; p = 0.013) and external limiting membrane restoration (adjusted OR, 10.42; 95% CI, 2.77–39.15; p = 0.001).Conclusions: In large macular holes, an extended ILM flap of approximately 1.5–3 DD improved anatomical stability and visual recovery, representing an effective surgical strategy. In medium holes, the standard flap achieved comparable outcomes, suggesting flap size modification may not be necessary for optimal results.