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A new retinal reattachment surgical procedure is based on a stent that is deployed to press the retina back in place. An eye-stent finite element model studied the strain induced by the stent on retina. Finite element model simulations were performed for several stent geometric configurations (number of loops, wire diameter, and intraocular pressure). The finite element model was validated against experiment. Parametric studies demonstrated that stents could be successfully designed so that the maximum strain would be below permanent damage strain threshold of 2%.

The retina is a light-sensitive tissue layer that lines the inside of the eye and relays visual information directly to the brain via the optic nerve. Retinal detachment occurs when the retina is lifted or pulled from its physiological location. This condition can result in partial or total vision loss. Retinal detachmentis a leading cause of permanent vision loss.

The motivation for the herein presented research stems from a new retinal reattachment procedure, which consists of carefully pressing the detached retina tissue into place via a shape memory alloy (SMA) and self-expanding stent. The initial study described in this article focused on modeling the mechanical interaction among stent and neighboring human eyeball tissues: retina, choroid and sclera. The study was performed via finite element analysis (FEA). The tissues were modeled with either hyperelastic or linear elastic material models in order to predict strain distributions on retina and the rest of the eye tissues due to stent placement. The FEA model included the following eyeball tissue: retina, choroid, sclera, cornea, zonular fibres, lens, and ciliary muscle. The simulations, shown for a sample stent configuration, have shown that the strain distribution developed due to stent placement was below levels which would induce permanent retina damage at the stent location. The simulations have shown that, by assuming that the retina was subjected to physiological internal ocular pressure (16.5 mmHg) in parallel to stent pressure (2200 Pa), the retinal strain reached a maximum of 2.67% , which was below a permanent damage strain threshold of 3.3%.

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