DEBRIDEMENT OF THE PIG RETINAL-PIGMENT EPITHELIUM IN-VIVO

Objective: To study the morphologic effects of surgical debridement of the retinal pigment epithelium (RPE) in an animal model. Methods: A p ars plana vitrectomy was performed in the domestic pig, and a neurosen sory retinal detachment was created by injecting the calcium-chelating agent edetic acid (commonly referred to as ethylenediaminetetraacetic acid or EDTA) into the subretinal space through a retinotomy. Twenty minutes later, the RPE was debrided by gently brushing Bruch's membran e with a soft-tip silicone catheter. Dissociated RPE was aspirated fro m the subretinal space, and the retina was reattached with a fluid-gas exchange. Results: Light microscopic analysis confirmed that Bruch's membrane was devoid of native RPE and the choriocapillaris was morphol ogically intact immediately after debridement. Photoreceptor outer seg ments were disrupted and foreshortened immediately after RPE debrideme nt. One to 4 weeks later, a layer of hypopigmented RPE covered most of the previously debrided areas of Bruch's membrane. The choriocapillar is was intact in areas of Bruch's membrane that were repopulated by hy popigmented RPE, and remained intact 12 weeks after debridement. Some regions of Bruch's membrane near the retinotomy remained devoid of RPE for more than 4 weeks after debridement. The choriocapillaris was atr ophic and there was extensive disruption of the outer retinal layers i n these areas. Conclusions: The RPE healed in most areas after surgica l debridement of the RPE in the experimental animal. Atrophy of the ch oriocapillaris was present in areas of poor RPE healing near the retin otomy.