Macular Posterior Vitreous Detachment: Mechanical Insights from Volume-Rendered Swept-Source OCT

PURPOSE: To characterize the structural features and mechanical failure patterns of macular posterior vitreous detachment (PVD) using volume-rendered swept-source optical coherence tomography (OCT) and to analyze the forces governing cortical tearing versus vitreomacular separation. METHODS: In this retrospective study, eyes with developing or recent macular PVD were imaged with swept-source OCT optimized for vitreous visualization by defocusing into the vitreous cavity. Volumetric datasets were processed and rendered three-dimensionally. Structural findings were analyzed descriptively and interpreted using vector-based mechanical modeling of cortical tensile forces and insertion geometry. RESULTS: Fifty-three eyes of 44 patients were imaged; 48 were evaluable. Circumferential tears of the posterior vitreous cortex were identified in 43 of 48 eyes (89.6%), including partial and complete tears. In a minority of eyes, detachment occurred without cortical rupture. The premacular bursa was preserved in partial tears and absent in complete tears. Measured insertion angles at the vitreomacular interface were shallow (<10°). Vector analysis demonstrated that at small insertion angles, the normal component of cortical tension is markedly attenuated (F⊥ = F sin θ), favoring cortical rupture at the insertion site over adhesive failure at the macula. Volume rendering demonstrated residual full-thickness cortical plaques adherent to the macular surface following tearing. CONCLUSIONS: Volume-rendered swept-source OCT demonstrates that macular PVD commonly involves circumferential cortical tearing. Mechanical analysis indicates that shallow insertion geometry favors cortical rupture as an initial failure mode, dissipating traction but leaving a residual cortical plaque that may contribute to subsequent epiretinal membrane formation.