Topical Dexamethasone Counters Intravitreal Ivermectin-Induced Ocular Toxicity in a Rabbit Model.

PURPOSE: Systemic use of Ivermectin has been reported to incite blindness in humans and veterinary patients. This study was designed to investigate the systemic and intravitreal effect of Ivermectin on ocular and retinal health and its attenuation with topical Dexamethasone.

METHODS: Systemic injection of Ivermectin@ 1.6 mg/kg S/C was administered, thrice a week for three weeks to New Zealand White rabbits ( N  = 4) with and without topical drops of Verapamil ( N  = 4). Pre and post-treatment ocular examination was conducted. At the end of three weeks the eyes were collected for histopathology.0.2 ml of Ivermectin solution (1.6 mg/ml) was injected intravitreally in one eye of the rabbit ( N  = 8), Half the rabbits received 0.1% dexamethasone drops thrice daily for 7 days, while the controls received PBS. Pre and post-treatment, detailed examination was conducted, which included the Schirmer Tear test, Fluorescein staining, Intraocular pressure, slit lamp biomicroscopy and fundus photography. The retina was harvested for histopathological and tunnel assay.

RESULTS: Systemic therapy with Ivermectin, with and without Verapamil did not incite any adverse response in the eye. Intravitreal Ivermectin evoked severe uveitis 4/4, cataract 3/4, corneal erosion 3/4 eyes and severe inflammatory response. Eyes that received dexamethasone were rescued from the adverse changes as demonstrated clinically, by histopathology and prevention of apoptosis.

CONCLUSIONS: Intravitreal Ivermectin incites severe inflammatory response. Topical dexamethasone counters the ocular toxicity incited by Ivermectin.