Study of Retinochoroidal Circulation with Fluorescein Angiography after Whole Eye Transplantation in Rodents

PURPOSE Approximately 39 million people worldwide are blind. Whole eye transplantation (WET) could potentially provide a viable optical system to people worldwide with irreversible vision loss. As a first step toward realizing this goal, we have developed an orthotopic model for whole eye transplantation in the rat. Given that viability of the retina is crucial to functional visual return, we evaluated the structural integrity of the retinochoroidal circulation after transplantation using fluorescein angiography (FA), which is the gold standard to evaluate retinal circulation.

METHODS Brown Norway rats underwent syngeneic whole eye transplantation (n=4). At post-operative week 1, transplanted animals had ocular exams under anesthesia and wide-field FA and fundus photographs of both eyes were obtained to evaluate retinochoroidal blood flow. Ocular examinations were performed by an ophthalmologist with retina specialization to evaluate the anterior and posterior segments of the eye. We used a stereo microscope that has florescence imaging capability to capture fundus and fluorescein angiography images. The objective lens of the microscope is used in conjunction with a 78D Volk lens, which allows for wide-field imaging. The right eyes of 3 unoperated naïve Brown Norway rats (n=3) served as controls.

RESULTS FA revealed that retinochoroidal circulation was restored in all transplanted eyes exhibiting normal choroidal background, arterial and venous filling, and no leakage from the vascular tree. These results were comparable to normal naïve eyes. In two of the transplants, retinal arteries were narrowed in fundus examination, fundus images and fluorescein angiography, while in the other two transplants retinal vasculature seemed similar to the control eyes. There appeared to be decreased retinal perfusion in the animals with narrowed retinal arteries as compared to controls.

CONCLUSION FA results have confirmed that retinochoroidal circulation can be established after WET in a rat model. Although 2 out of 4 rats exhibited some vascular attenuation in comparison to naïve rats, all rats exhibited a normal vascular filling pattern and the absence of vessel leakage which indicates that the structural integrity of blood-retinal barriers can be maintained after WET. The etiology of vascular attenuation and presumed decrease in retinal perfusion will be investigated in future studies.