MACULAR POSTERIOR VITREOUS DETACHMENT: Mechanical Insights From Volume-Rendered Swept Source Optical Coherence Tomography.

PURPOSE: To characterize the structural features and mechanical failure patterns of macular posterior vitreous detachment using volume-rendered swept source optical coherence tomography and to analyze the forces governing cortical tearing versus vitreomacular separation.

METHODS

In this retrospective study, eyes with developing or recent macular posterior vitreous detachment were imaged with swept source optical coherence tomography optimized for vitreous visualization by defocusing into the vitreous cavity. Volumetric data sets 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 after tearing.

CONCLUSION

Volume-rendered swept source optical coherence tomography demonstrates that macular posterior vitreous detachment 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.