Retinal surgery with flexible robots: Biomechanical advantages

Robotic innovation in vitreoretinal surgery aims at increasing the dexterity of clinicians and reducing the risk of retinal tear, intraocular lens damage, and ocular hypotony. Recently, research groups revisited the concept of snake-like instruments for vitreoretinal surgery as a means to increase the reachable intraocular workspace while minimising the risks arising from manipulating straight rigid instruments through a fulcrum point. Despite these efforts there has been no attempt to biomechanically explain their potential in reducing the inadvertently applied forces on the retina or the disruption of the gel-like vitreous of the eye. This paper presents a biomechanical model of the vitreous humour based on its physiological parameters, and studies the effect of rigid versus flexible tools in performing a similar surgical task in an intact vitreous humour. It is shown that the forces that a flexible tool applies on the retina are reduced by up to 30%, following reductions in vitreous gel displacement. Since retinal tears can be formed by minuscule accidentally applied traction forces, our results constitute a first understanding of the safety benefits that flexible robots may introduce in retinal surgery.