EVALUATION OF RAT MODEL OF CHRONIC GLAUCOMA BY LIGATING EPISCLERAL VEINS

Objective To develop and evaluate the rat model of chronic glaucoma by episcleral veins ligation (EVL). Methods Experimental glaucoma was induced unilaterally in 28 male Sprague-Dawley rats by ligating two episcleral veins. Intraocular pressure (IOP) in rats was measured by a Goldmann applanation tonometer under 3% pentobarbital sodium anesthesia. The optic nerve head and retinal vasculature were assessed by repeated fundus examinations. The amount of optic nerve axons was assessed by Image-Pro Plus image analysis system in a masked fashion. Results IOP without EVL was (19.21±1.23)mmHg, whereas the EVL eyes gained about 1.8-fold higher IOP (33.96±2.73)mmHg] after EVL immediately (P<0.001). The elevated IOP gradually decreased over time. However, the differences were kept significant up to 8 weeks after EVL. The IOP was reduced to similar levels as contralateral eyes at 12 and 16 weeks after EVL. The glaucomatous optic nerve excavation appeared in EVL eyes at 8 weeks after EVL, and the optic nerve excavation enlarged gradually with the increasing post-operation time. The amount of optic nerve axons also significantly decreased in EVL eyes at 8 weeks after EVL, and the amount of axons decreased gradually with the increasing post-operation time. Conclusion Increase of IOP caused by EVL represents a useful and efficient model of experimental glaucoma in rats.