Abstract： Objective To evaluate the safety repeated intravitreal injection of bevacizumab (Avastin) with different dosage in rabbitst eyes.Methods Fourteen chinchilla rabbits were randomly divided into 3 groups,including both eyes of 2 rabbits in the control group,the right eyes of the other 12 rabbits in the experimental group,and the left eyes of the 12 rabbits in the experimental control group.The eyes in the experimental group underwent intravitreal injection of bevacizumab with the dosage of 2.5 mg/0.1 ml and 5.0 mg/0.2 ml of bevacizumab;the eyes in the experimental control group underwent intravitreal injection of normal saline with the same dosage as in the experimental group.Injections were performed every two weeks and lasted six weeks.Clinical observation and retinal function tests were performed before and two days after every injection.The eyes were sacrificed 1 week and 4 weeks after last intravitreal injection respectively.Electron and optical microscope and TUNEL were performed.Results After intravitreal injection,no obvious anterior chamber flare,abnormal change of the ocular fundus,or vitreous opacity and hemorrhage was observed in all of the eyes.No change was found by indirect ophthalmoscope,B-ultrasonic inspection,ultrasound biomicroscopy and optical coherence tomography.The number of anterior chamber flare before and after the injection with the dosage of 2.5 and 5.0 mg,the difference among the 3 groups didn't differ much from each other (P>0.05).Amplitude and pattern of ERG responses and flash VEP were similar between the control and experimental groups (P>0.05).Some inflammatory cells were found in the some bevacizumab-injected eyes 1 week after injection,and vanished 3 weeks later.The histological configuration of the retina didn't change in both experimental control and the control group.Electron microscopy showed that plasma cells were presented and vacuole-like change was observed in part of the photoreceptor cells in 5.0 mg experimental group 1 week after injections.Cellular apoptosis was observed in the photoreceptor cell layer.The number of apoptotic cells was more in 5.0 mg experimental group than that in the control and experimental control group 1 week after injections (P<0.01).Conclusion Multiintravitreal injection with 5.0 mg bevacizumab may have mild toxicity to the retina in the rabbits.