AIM:To investigate the natural course and adverse event of branch retinal vein occlusion(BRVO)rat model induced by laser photochemical method.

METHODS: Thirty SD(Sprague Dawley)rats were administrated Bangladesh via tail vein. Then 532nm laser(80mW, 100μm and 100ms)was performed on retinal vein secondary bifurcation of bitamporal optic disk for 50 spots. Electroretinogram(ERG), fundus fluorescein angiography(FFA), optical coherence tomography(OCT)and fundus(fluorescein)photograph were applied on 1, 3, 5, 7, 10, 14 and 21d after BRVO model constructed. Two rats were sacrificed, respectively, on 1, 5 and 21d after photocoagulation to carry on HE(Hematoxylin-Eosin stain)and VEGF-α(vascular endothelial growth factor-α)immumohistochemical staining.

RESULTS: There were three rats died, three rats with severe retinal detachment for excessive bleeding, one rat with retinal sunken, and one rat with cataract. FFA and fundus(fluorescein)photograph showed that the successful BRVO rat model was 73%(22/30). It was found that the near-end photocoagulation vein became coarse, far-end became diminution on 1d and the photocoagulation vein total recanalization was on 3-7d. ERG showed the amplification of b wave(dark-adaptation 3.0 response)decreased to 0.694±0.042 of control eyes and on 5-7d decreased to rock bottom about 0.487±0.064 of control eyes. Then it increased all the time to 0.708±0.0465 of control eyes on 21d. OCT and HE staining found that retinal ganglion cells and outer nuclear layer became edema on 1d in vivo and in vitro. It was observed that the thickness of retina on photocoagulation vein(0μm or 250μm)decreased from 5d and there were 3-4 layer cells in ONL on 21d. The expression of VEGF-α at injured site were significantly more than control eyes on 1d and there were no significant difference on 5d; But the expression of VEGF-α were slightly less than control eyes on 21d.

CONCLUSION: Photochemical method was a feasible method to establish BRVO rat model. The evolution and development of the BRVO model could partly mimic human BRVO phenomenon. At the same time, it should be improved to increase the successful model rate.