Morphological changes of the sensory retina following the occlusion of ciliary arteries in rabbits

The whole retina, except for the medullary fiber zone in a rabbit eye, is supplied by choroidal circulation. Therefore, the histopathological changes of the sensory retina due to choroidal circulatory disturbance in rabbits may be comparable to that of the human sensory retina in the case of ophthalmic artery occlusion. This study was carried out to evaluate the histopathological changes of the ischemic retina secondary to the occlusion of choroidal circulation. The experimental occlusion of all posterior ciliary arteries and anterior ciliary arteries in the horizontal rectus muscle of rabbit eyes was performed and the subsequent histopathological changes of the sensory retina were observed by transmission electron microscopy. The morphological changes of the sensory retina following the occlusion of the ciliary arterial system are as follows: severe loss of the inner and outer segments of the photoreceptor, mild to moderate degeneration of the ganglion cells, and excellent preservation of the Muller's cell fibers and the extension of the cytoplasmic villous processes to the cytoplasmic vacuolar spaces of other degenerated cells. These findings indicate that the Muller's fibers in the ischemic condition of retina might contribute to the formation of gliosis or scarring of a damaged retina.

Effect of a modified rectus tuck on anterior ciliary artery perfusion

Strabismus surgery results in the permanent interruption of anterior ciliary blood flow, predisposing the eye to anterior segment ischemia (ASI). A primate model was used to assess the effectiveness of a new muscle-scleral tuck for preserving anterior ciliary artery circulation. The model consisted of removing 3 rectus muscles from both eyes of 2 rhesus monkeys, then performing a tuck on the inferior rectus (IR) right eye while leaving the left IR as a control. Four weeks later, a modified tuck was performed on the virgin left IR. Fluorescein iris angiograms of both eyes were obtained, and preoperative angiograms at 5-15 sec. showed normal 360 degrees perfusion. Postoperative follow-up angiograms showed segmental superior temporal filling defects and preservation of perfusion in the distribution of the IR. Comparison of fellow eyes tucked vs control IR showed no difference in the filling pattern in both monkeys. Comparison of the same eye before and after tuck also showed essentially the same filling pattern in all 4 eyes with preservation of inferior circulation. Our conclusion is that the modified tuck preserves the anterior ciliary blood flow and may be useful as a muscle-strengthening procedure in patients predisposed to developing ASI.