An Experimental Study On Micropulse Diode Laser Lesions And Restoration In Rabbit Retina

Objective:To study the histopathological changes of retinal lesions and restoration and to observe the effects on apoptosis of retinal cells induced by micropulse diode laser and argon green laser in rabbits. Content and methods: 1) Set up the model of the damage of rabbit retina for laser photocoagulate under the therapic parameter of diabetic macular edema(DME). 2) The histopathological alterations of retinal lesions and restoration were observed and compared with fundus photography? Fluorescein angiography ? light microscope and transmission electron microscope after laser photocoagulation. 3) To assess the apo- ptosis by terminal deoxynucleotidy transferase mediated biotin -dUTP nick end labeling(TUNEL).To analyze mechanism of retinal lesions after laser photocoagulation. Results: 1) The laser spots of micropulse subthreshold retinal lesions and leakage of fluorescein were undetectable in 24h and 4 week after photocoagulation.Theâ… degree spots of argon laser and threshold diode laser were detectable. The leakage of fluorescein were observe in 24h and 4week after photocoagulation. 2) Observed by light microscope: The lesions were slightly at subthreshold spots of micropulse diode laser and spots of argon laser observed by the H.E dyeing and those were completely recovery in 4 week after photocoagulation. The inner retinal lesions and reduction of outer nuclear layer cells were observed at threshold spots of diode laser. The layer of photoreceptor cells was more thinner in 4week after photocoagulation. 3) Observed by transmission electron microscope: The outer membranous discs were arranged disorder lightly at micropulse spots.No obvious changes were seen in outer nuclear layer.The outer membranous discs were arranged disorder and rare at argon spots. The hydroncus of retinal nodal cells was seen. The heterochromatin became multy in outer nuclear layer. Hyperplasia of pigment and collagen were seen in 4week. While threshold retinal lesions were obvious. It showed reduction of outer nuclear layer cells. Condensed nuclei and cytoplasmic vacuolization were seen in the inner or outer nuclear layer. The layer of photoreceptor cells was more thinner and fibrous tissue was more thicker in 4 week. 4) Observed by TUNEL: The results of TUNEL examination indicated that several positive cells were sporadic found in outer nuclear layer at micropulse spots and were none in inner nuclear layer. Many apoptosis cells were found in outer nuclear layer and the apoptosis gradually involved the inner nuclear layer at argon spots.The massive positive cells were found in inner nuclear layer?outer nuclear layer and retinal nodal cells at threshold spots. 5) Rate of apoptosis cells of photoreceptor at spots of every laser is higher than normal retinal.There is statistical difference in comparison (P<0.05). Rate of apoptosis cells of photoreceptor at spots of micropulse diode laser is lower than argon laser. There is statistical difference in comparison(P<0.05). Conclusion: 1) From observation of retinal lesions and restoration,under the therapic parameter of DME the retinal lesions produced by micropulse diode laser were slightly than produced by argon laser. The micropulse diode laser technique did not injury the inner structure of retina. 2) Apoptosis is an important mechanism of lesions produced by laser photocoagulation.There were apoptosis cells of photoreceptor at spots of micropulse diode laser.