Methodological Approach to Improve Surgical Outcomes of a Pig Subretinal Implantation Model

Purpose: To improve outcomes for subretinal implantation surgery in pigs. Methods: Analysis of variables affecting the success of subretinal implantation surgery was performed on videos of 37 surgeries. Ex vivo experiments were conducted to measure intraocular pressure (IOP) and test various prototyped implanters for effective-ness at maintaining IOP. Results: A video analysis revealed a prolonged sclerotomy open time owing to a combi-nation of uncontrolled bleeding and excessive fluid outflow often resulting in retinal prolapse. Precauterization of the choroid before full-thickness sclerotomy (n = 10) resulted in a reduced incidence of uncontrolled bleeding from 39.1% (9/23) versus 0% (0/10) (P = 0.005) and improved implantation success from 73% to 90%. An ex vivo analysis of the IOP revealed a mean decrease in the IOP from 30.2 ± 3.0 mmHg to 5.0 ± 2.1 mm Hg after a fully penetrating sclerotomy. To address this situation, we produced a series of plugs that integrated with a custom implant insertion device to seal the sclerotomy during implantation. The use of the plugs was cumbersome, however, and so we opted instead to increase the width of the inserter tip to fill the open sclerotomy. This improved device restored and maintained IOP during implantation (27.1 ± 1.9 mm Hg). Combined with precauterization the improved inserter resulted in 100% successful implantation (n = 4). Conclusions: For subretinal implantation in pigs, a modified procedure to precauter-ize the choroid before sclerotomy combined with an instrument that better fills the scleral opening decreases bleeding, hypotony, and open sclerotomy time, improving the success rate. Translational Relevance: Better management of IOP and bleeding from a sclerotomy will improve implant-based therapies.