Mechanical Model of Vitreoretinal Traction Illuminates Structural, Functional Risks

A posterior vitreous detachment (PVD) is often an innocuous age-related finding that occurs as the vitreous gel naturally shrinks and pulls away from the retina. However, if the detaching vitreous manages to pull on the retina itself, the traction between the vitreous and the retina could lead to a macular hole, if occurring at the macula, or a rhegmatogenous retinal detachment (RRD), if occurring elsewhere on the retina. Research published in Biomechanics and Modeling in Mechanobiology proposes a mechanical model for vitreous detachment and vitreoretinal traction.

The model, which is based on, and correlates with, clinical knowledge, offers insights into PVD shape and the associated risk of vitreoretinal traction. The model examines several possibilities of how vitreous liquefaction and the weakening of the adhesion of the vitreous and retina can potentially progress throughout the normal aging process. The researchers also take into account the variable adhesion strengths present between the vitreous cortex and retina throughout the vitreous chamber. The model reproduces the evolution of both standard PVDs and anomalous, or incomplete, PVDs, to determine how the course of a PVD can potentially affect vitreoretinal and vitreomacular traction.

When modeling a complete PVD, the researchers found that maximum traction on the retina always corresponds to the attachment boundary of the cortex wall and that higher maximum adhesion strength results in a larger angle between the vitreous and retinal wall. Because maximum adhesion is more likely to lead to traction, it may be worth it for clinicians to monitor vitreoretinal angles as a PVD progresses to gauge the potential for vitreoretinal traction.

When modeling an anomalous PVD, where vitreous liquefaction occurs without the vitreous simultaneously detaching from the retina, researchers found that the macula was subject to the most traction, which offers a potential explanation for the occurrence of macular holes. The model also offers potential parameters including the curvature of the vitreous and the dynamic stress generated by eye movement.

While the researchers explain that the model makes several assumptions and lacks important quantifiable data, the model does offer a potentially accurate link between the vitreoretinal angles observed in both normal and anomalous PVDs and the degree of resulting vitreoretinal traction. This may potentially offer an effective clinical monitoring tool for vitreoretinal traction sequelae. 

Reference      

Di Michele F, Tatone A, Romano MR, Repetto R. A mechanical model of posterior vitreous detachment and generation of vitreoretinal tractions. Biomechanics and Modeling in Mechanobiology. 2020;19(6):2627-2641. DOI: 10.1007/s10237-020-01360-1.