ObjectiveTo explore safe dosage of single intravitreal injection of ganciclovir (IVG) in healthy rabit eyes, and to explore retinal toxicity of different dosage of ganciclovir after continues intravitreal injection into the vitreous cavity of healthy albino rabbit eyes. MethodsTen healthy New Zealand albino rabbits were divided into 5 groups with 2 rabbits in each group. Each group was injected with 1 mg/0.025 ml, 2 mg/0.025 ml, 5 mg/0.025 ml, 10 mg/0.025 ml ganciclovir or 0.025 ml saline (control group). After 1 week of intervention, rabbits were examined by ultra-wide-angle fundus photography, optical coherence tomography (OCT) and full field electroretinogram (ERG). The maximum mixed response of rod and cone cells (Max-R) was measured under dark adaption conditions, cone response (Cone-R) and 30 Hz flicker response (30 Hz-R) were measured under light adaption conditions. Twenty-four healthy New Zealand albino rabbits were randomly divided into a low-dose experimental group, a low-dose control group, a high-dose experimental group, and a high-dose control group, with 6 rabbits in each group, with the right eye as the experimental eye. The rabbits in the high-dose experimental group were continuously injected with ganciclovir 2 mg/0.025 ml, once a week, for a total of 4 times. The rabbits in the low-dose experimental group were injected with 1 mg/0.025 ml ganciclovir, the induction period was 2 times/week, a total of 4 times; the maintenance period was 1 time/week, a total of 2 times. The rabbits in the high-dose control group and the low-dose control group were injected with 0.025 ml normal saline into the vitreous cavity respectively. Full-field ERG examination was performed 1 day before each injection and 1 week after the last injection. Max-R was measured under dark-adapted conditions, and Cone-R and 30 Hz-R were measured under light-adapted conditions. OCT was recorded before the first injection and one week after the last injection. One week after the last injection, the experimental rabbits in each group were sacrificed for hematoxylin-eosin staining, and the retinal structure was observed under a light microscope. The comparison of a-wave and b-wave amplitude of Max-R, Cone-R and 30 Hz-R amplitude at different time was performed by two independent sample nonparametric test. ResultsThere were no abnormal results of fundus photography, OCT and ERG after single intravitral injection of 1 mg or 2 mg ganciclovir. One week after single 5 mg IVG, fundus photography of rabbits showed vascular occlusion and preretinal hemorrhage and ERG showed slight decrease of amplitude of Max-R, Cone-R and 30 Hz-R. One week after single 10 mg IVG, retinal necrosis and exudative changes were also observed. OCT showed edema and unclear retinal structure in the necrotic area. ERG showed significant decrease of amplitude of Max-R, Cone-R and 30 Hz-R. After continuous IVG in high dose and low-dose experimental group, the amplitude of Max-R a wave (Z=－0.160, 0.000) and b wave (Z=－0.321, 0.000), Cone-R a wave (Z=－0.641,－0.641) and b wave (Z=－0.321, －0.160), and 30 Hz-R (Z=－0.321,－0.160) showed no difference compared to control group. No histologic evidences of retinal microstructure abnormalities were found in both groups. OCT and fundus photography before and after the intervention did not show any difference, either. ConclusionThere was no retinal toxicity of continuous 1 mg or 2 mg IVG recorded in albino rabbits.