Keratoconjunctivitis sicca with associated secondary uveitis elicited in rats after systemic xylazine/ketamine anesthesia

The systemic administration of an anesthetic dosage of a combination of xylazine and ketamine hydrochloride produced an acute exposure keratopathy which progressed into a syndrome resembling keratoconjunctivitis sicca. Within a few minutes corneal changes occurred that were characterized by viscous mucus, loss of corneal luster and dryness. Other acute but transient changes included development of cataracts, mydriasis and proptosis. Progressive changes were observed in the cornea within 4 days which lasted at least 8 weeks in some cases, and included punctate epithelial keratopathy progressing to devitalized or keratinized epithelial plaques. Polymorphonuclear cell infiltration of the corneal stroma associated with plaques occurred. Epithelial denudation and neovascularization of the cornea, dilation and engorgement of iridial blood vessels, as well as flare in the anterior chamber were also seen. The ocular lesions induced by xylazine/ketamine should be considered carefully when designing or interpreting research on the anterior segment. Ketamine hydrochloride with sodium pentobarbital produced excellent anesthesia without any significant ocular side-effects and may be preferred in many instances.