Development of Minipigs Surgical Model: Cauterization of the Choroid Following Scleral Dissection Mitigates Risk of Post-Operative Vitreous Hemorrhage Following Ocular Implantation of RPDS

Abstract

Purpose : To develop a surgical model in minipigs to qualitatively evaluate various surgical techniques for mitigating vitreous hemorrhage following Ranibizumab Port Delivery System (RPDS) implantation into the vitreous cavity.

Methods : Overall 43 male Yucatan minipigs at least 2 months of age and weighing 8-16 kg were randomly assigned to various surgical technique groups (N ranging from 1-5 per group). On Day 1 the RPDS Implant was surgically placed in the eye through the pars plana; surgical blade type, scleral incision length, scleral cauterization, choroidal cauterization, application of viscoelastic, and modulation of intraocular pressure (IOP) during surgery were evaluated. Animals were followed through Day 8 and impact of the surgical variables on mitigating vitreous hemorrhage as clinically determined was assessed.

Results : Wound configuration made by various blades and incisions, intra-operative IOP modulation, scleral cauterization, or application of viscoelastic had no effect on mitigating vitreous hemorrhage. Cauterization of the choroid obtained with either thermal cauterization or laser ablation after scleral dissection successfully mitigated vitreous hemorrhage at the time of RPDS surgery on Day 1 and through Day 8.

Conclusions : In this minipig ocular model that we developed, scleral dissection followed by choroidal cauterization was the most critical element in mitigating vitreous hemorrhage during and after placement of the RPDS implant into the vitreous cavity. This was independent of scleral dissection length, blade type, modulation of IOP, and viscoelastic usage. This finding indicates that the choroid at the pars plana is the main source of intraocular bleeding after RPDS Implant surgery, hence a prophylactic treatment to the choroid can prevent vitreous hemorrhage.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.