Posterior segment approach for subretinal transplantation or injection in the canine model

A posterior segment approach for cell transplantation or injection into the subretinal space of the dog has been developed. Controlled penetration to the subretinal space was achieved using a 29-gauge injection cannula, eithe r blunted or with a 30 degrees sharpened bevel, and partially ensheathed wi th moveable plastic tubing. Depending on the injection volume used, the ret ina detached, and the fluid was reabsorbed within 1-3 weeks, although for s maller volumes the retina reattached within a matter of days. The optimal i njection volume used was between 100 and 150 mul, or two injections of 55 m ul each. By ophthalmoscopy following the surgery, it was possible to serial ly monitor the injection site and retinal bleb through fundus photography. Light microscopy demonstrates the distribution of stable, viable RPE cells in the subretinal space up to 6 months. The transplantation technique devel oped for the dog is atraumatic and free from any major surgical or clinical complications. It can be readily used to deliver cells or fluids to locali zed regions of the subretinal space.