Understanding the mechanism of retinal displacement following rhegmatogenous retinal detachment repair: A computer simulation model

Purpose Retinal displacement is common following rhegmatogenous retinal detachment (RRD) repair. A computer simulation was developed to assess forces applied by a gas tamponade of various sizes in the setting of pneumatic retinopexy (PnR) versus pars plana vitrectomy (PPV). Design Computer simulation model. Methods The contact angle and pressure between the tamponade and the retina were calculated using interfacial tension and the densities of gas and vitreous. A simulation determined the dynamics of fluid motion in the subretinal space and calculated deformations of the retina. Results Bulk flow of fluid away from the tamponade in a direction along gravity stretched the retina and caused displacement in the simulations. Extent of displacement is attributable to the subretinal fluid layer thickness, and area of contact and contact pressure applied by the tamponade. Larger gas tamponades have greater contact pressure applied to the retina. Reducing gas bubble size from 93% to 6.25% with PPV versus PnR, there was a 79% reduction in the mean contact pressure (1.4 mmHg-0.29 mmHg), and a 93% reduction in the surface area of contact (11 cm(2)-0.8 cm(2)). Therefore, the contact force applied to the entire retina decreases by 97% from 83 mN (PPV) to 2.9 mN (PnR). The model resembling PnR had more than three times less displacement compared to PPV. Conclusions This model provides a framework to study retinal displacement. Our findings suggest that proportional to their size, gas tamponades stretched the retina by displacing subretinal fluid following RRD repair.