Deep Stromal Corneal Ulcers, Descemetocele, and Iris Prolapse in Small Animals

Infected corneal ulcers are recognized by stromal loss, malacia, or stromal cellular infiltrate. Corneal cytological evaluation and aerobic bacterial and fungal corneal cultures with sensitivity should be performed to determine the underlying cause and guide appropriate medical treatment. In the interim, topical broad-spectrum antimicrobials, serum, mydriatics, and a systemic NSAID should be instituted. Referral to an ophthalmologist should be considered to determine whether surgical stabilization is required to preserve vision or the globe.

Most superficial corneal ulcerations readily heal with a topical broad-spectrum antimicrobial to prevent infection and a topical mydriatic with or without a systemic NSAID to address the reflex anterior uveitis. However, corneal ulcers detected late in the disease process, complicated by other ocular diseases, or given inadequate topical antimicrobial treatment can progress.

Brachycephalic breeds and dogs with keratoconjunctivitis sicca are particularly vulnerable to stromal loss from infectious keratitis. Ulcers with at least 50% stromal loss should be assessed by an ophthalmologist for surgical intervention using a conjunctival graft, the commercially available porcine small-intestinal submucosa, or experimental amniotic membranes.

Deep corneal ulcers, particularly descemetoceles as well as those that have ruptured with iris prolapse, require immediate surgical support of the fragile globe, because they can threaten or seriously compromise corneal integrity (see ulcerative keratitis image). These corneal defects often develop in the center of the cornea and can markedly impair vision.

Ulcerative keratitis with stromal loss, dog

Image

Courtesy of UC Davis Comparative Ophthalmology Service.

Important diagnostic aids are the Schirmer tear test to measure aqueous tear production and topical fluorescein to determine the extent of the corneal ulcer. Corneal culture and cytological evaluation can assist in choosing topical and systemic antimicrobials.

Reflex anterior uveitis, with associated clinical signs such as aqueous flare, miosis, ocular hypotony, fibrin, and hypopyon, is common and should be addressed with a topical mydriatic with or without a systemic NSAID.

Corneal ulcer depth must be accurately estimated using magnification, focal illumination using a slit lamp biomicroscope, and topical fluorescein. The Seidel test using fluorescein stain is particularly useful to check for active aqueous humor leakage if the cornea is ruptured. Central corneal ulcers are more vulnerable because they require more time for the healing response and vascularization. Adequate ulcer debridement is essential for successful adherence of a conjunctival graft. The corneal ulceration (stromal, descemetocele, or iris prolapse) is covered with the bulbar conjunctival graft that appears most appropriate (see deep corneal ulceration image).

Deep corneal ulceration, pedicle conjunctival graft, dog

Image

Courtesy of Dr. K. Gelatt.

Postoperative treatment after conjunctival graft placements includes topical broad-spectrum antimicrobials; mydriatics; systemic NSAIDs; and systemic antimicrobials if the globe has been ruptured. Treatments are gradually tapered and administered for 4–8 weeks. Postoperative complications include variable corneal scar and pigmentation, anterior or posterior synechiae, secondary cataract formation, and rarely bacterial endophthalmitis.

Regular recheck appointments are necessary to ensure proper healing is occurring. Intraocular pressure should be carefully monitored in breeds at risk for glaucoma, particularly when topical mydriatics are used.