PHOTORECEPTOR DECAY OVER TIME AND APOPTOSIS IN EXPERIMENTAL RETINAL-DETACHMENT

Background: Data are scarce on the actual rate and mode of outer nucle ar layer decay in retinal detachment (RD). We used an experimental rab bit model to assess the presence of apoptosis and rate of photorecepto r death following RD. This model included the creation of localized an d stable retinal blebs, while controlling for any decline of retinal e levation over time. Methods: RD was produced in New Zealand white rabb its by injecting 0.05 ml of 15% sodium hyaluronate (Healon GV) under t he neural retina using a microsurgical technique. Animals were killed at 1, 2, 4, 7, 13 and 29 days. Retinal tissue was processed for light and electron microscopy and for in situ end labeling of fragmented DNA using a modification of the TUNEL technique. Photoreceptor cell nucle i were counted in the RD areas of maximum retinal elevation of 28 eyes , and an additional I eyes were used for nick end labeling. Results: p ositive DNA nick end labeling, ultrastructural features and absence of necrotic cells indicated apoptotic photoreceptor cell death. Also, th ere was a rapid, almost linear elimination of photoreceptor nuclei ove r time. At 14 days only half of the number of nuclei were discernible, while approximately one tenth remained after 29 days. There was a sta tistically significant, but minimal decline in RD height over the 3 we eks of study. Conclusion: Following experimental RD in rabbits. apopto tic cell death is associated with an almost linear elimination of phot oreceptor cells over time. The use of highly viscous sodium hyaluronat e in separating the neural retina from the retinal pigment epithelium allows the RD to maintain a nearly constant height over a period of 4 weeks.