Apoptosis Of Retinal Photoreceptor Induced By Transpupillary Thermotherapy In Pigmented Rabbits

Objective: To observe the histological changes and apoptosis of retinal lesions by TTT. Methods: Fourteen pigmented rabbits were divided into seven groups(control g- roup,50mw,70mw,90mw,110mw,130mw,150mw group)by different power of TTT randomly,while duration and beam spot diameter of TTT were fixed at 60s a- nd 1.2mm respectively.Two rabbits in each group were sacrificed at 24,48 hours after photocoagulation. Light microscopy examination was performed for the histological changes. Apoptotic cells were identified by TDT-mediated biotin-dUTP nick- end labeling (TUNEL) technique and flow cytometry(FCM)Results:The burns: retinal colour were not remarkably changed in 50-70mw gr- oup,it was subthreshold photocoagulation.With TTT power increasing ,the burns col- or became intense gradually,the burns diameter became large. Light microscopy exa- mination: Compared with control group,the retinal tissue was not obviously changed in 50-70mw group .But in 90-130mw group,the integra retinal became thicker, swel- ling and degeneration were observed in photoreceptor layer,condensed nuclei and cy- toplasmic vacuolation were seen in the inner nuclear layer.The difference of histolog- ical changes between 24h and 48h was not obvious in above groups. Swelling and de- generation were observed in every layer of retina,the inner and outer segments of ph- otoreceptor lost in 150mw\24h group.Obvious necrosis and cell loss were observed in 150mw\48h group.TUNEL examination: Compared with controll groups ,the apopto- sis index of photoreceptor in each group was significantly increased,apoptosis gradu- ally involved the inner nuclear layer and ganglion cell layer.The apoptosis index of photoreceptor between 24 hours and 48 hours was significantly different within same power group, Except 70mw group.Flow cytometry(FCM) examination: The peak ofapoptotic cell was seen in every group of 24 hours after photocoagulation. Conclusion: Under subthreshold photocoagulation (50-70mw),retinal tissue of rabbits was not obviouse changed but apoptosis index of photoreceptor was signifi- cantly increased . With increasing power, swelling,degeneration even necrosis we- re observed in retinal tissue , apoptosis gradually involved the inner nuclear layer and ganglion cell layer.