Application of a New Subretinal Injection Device in the Dog

Abstract

Abstract: : Purpose: To evaluate a new subretinal injection device (SID) for application in dogs. Methods: Young, adult normal dogs of various ages were used. The pupils were pharmacologically dilated, and the animals were anesthetized. Proper positioning of the globe was ensured by retrobulbar injection of saline and a scleral stay suture. In one group the temporal sclera was surgically exposed, cauterized, and the globe penetrated through the sclera with a 25G needle 6mm from the limbus. The needle was then removed. A 30G Knolle anterior chamber irrigating cannula was inserted through the same site and brought into tangential apposition with the retinal surface for the subsequent 150 µl subretinal injection of saline or India ink. The fundus was visualized through a Machemer vitrectomy lens. The cannula was withdrawn and the conjunctiva over the sclerotomy site closed in standard fashion. In the second group the SID was used to penetrate the conjunctiva and the sclera 6mm from the limbus. Once the tip of the SID was close to the retinal surface, the 39G capillary fiber was extended and brought into apposition with the retina for the subsequent subretinal injection. No closure of the conjunctiva was required. Postoperative management was identical in the two groups. The animals were monitored for 1 week after surgery. The eyes were then harvested for routine histological analysis. Results: Both approaches provided access to the subretinal space. The SID was easier to use and required less manipulation, which resulted in milder postoperative ocular inflammation. The SID created a much smaller retinotomy with less leakage. The eyes are now being processed for histologic evaluation to compare procedure–associated damage to the eyes. Conclusions: The SID is a new instrument that is useful for subretinal injections as used in gene therapy or cell transplantation in experimental studies in the dog model.  

Keywords: retina • injection • gene transfer/gene therapy