PurposeTo compare clinical and morphological differences in idiopathic macular holes (IMHs) between stage 3 and stage 4.MethodsIn this retrospective cross-sectional observational study, patients with stage 3 and stage 4 IMHs based on Gass's classification in 1988 were enrolled. Horizontally and vertically, optical coherence tomography (OCT)-based parameters including minimum linear diameter (MLD), basal diameter (BD), and macular hole height (H) were measured; fluid cuff (FC), diameter hole index (DHI), macular hole index (MHI), traction hole index (THI), and hole form factor (HFF) were calculated. Afterwards, stage 3 IMHs smaller than 400m were excluded according to Gass's classification in 1995. Clinical features, such as age, duration of symptoms, and baseline best-corrected visual acuity (BCVA), and OCT parameters were compared respectively between two stages based on both classifications.ResultsGiven classification of 1988, stage 3 IMHs had significantly shorter duration of symptoms (P=0.020) and smaller horizontal BD (P=0.041). Horizontally and vertically, MLD (P=0.001, 0.004 respectively), DHI (P=0.032, 0.021 respectively), and HFF (P=0.032, 0.017 respectively) were significantly smaller and THI (P=0.011, 0.020 respectively) was significantly larger in stage 3 holes. Clinical features like age and baseline BCVA showed no significant differences. When staged by classification of 1995, IMHs of the two stages shared similar features.ConclusionsStage 3 IMHs, instead of owning shorter duration of symptoms and smaller diameters, share similar clinical and morphological features with stage 4 IMHs according to Gass's classification in 1995, which excludes IMHs smaller than 400m from stage 3 compared to his 1988 version.