Vytautas Al Pakalnis

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.

Modulation of the blood-aqueous barrier by Gram positive and Gram negative bacterial cell wall components in the rat and rabbit

Acute anterior uveitis in man is related to Gram negative bacterial infection occurring at sites distant to the eye. This could involve intraocular localization of inflammatory bacterial cell wall constituents. Modulation of the blood-aqueous barrier in rabbit and rat, by muramyl dipeptide (the monomer of peptidoglycan) and lipopolysaccharide (and its monomer lipid A) was studied. The rabbit eye was found to be highly susceptible to MDP and LPS, although without cellular infiltration. In contrast the rat eye was demonstrated to be totally refractory to MDP. The response to LPS in the rat was modest, required high dosages and ocular changes were slow to occur, but cellular infiltration was readily apparent. Since MDP is found in Gram positive (as well as Gram negative) bacterial cell walls it is hypothesized that Gram positive bacteria might also play a role in causing uveitis in man.

Topical Fluorescein Application Can Induce Iritis and Glaucoma

Various side effects have been reported after intravenous use of fluorescein. However, the adverse reactions to topical administration of this chemical have not been well documented. We report a case of unusual reaction to fluorescein when used topically on an intact cornea for the measurement of intraocular pressure. The patient manifested photophobia, conjunctival injection, iritis and elevated intraocular pressure, which necessitated medical management. These symptoms and signs occurred on each of four separate occasions when fluorescein was used topically, but disappeared upon discontinuing the use of this chemical agent. We believe that our patient exhibited an unusual hypersensitivity response to topical application of fluorescein akin to Posner-Schlossman syndrome.