Deep Stromal Corneal Ulcers, Descemetocele, and Iris Prolapse in Animals
Most superficial corneal ulcerations readily heal with a topical, broad-spectrum antibiotic to prevent infection and a topical mydriatic and/or 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 therapy, 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 or 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, ideally require immediate surgical support of the fragile globe, because they can threaten or seriously compromise corneal integrity. These corneal defects often develop in the center of the cornea and can markedly impair vision.
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 cytology can assist in choosing topical and systemic antibiotics. Reflex anterior uveitis with aqueous flare, miosis, ocular hypotony, fibrin, and/or hypopyon is common and should be addressed with a topical mydriatic and/or systemic NSAID.
Corneal ulcer depth must be accurately estimated using magnification, focal illumination using a slit-beam, 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.
Postoperative therapy after conjunctival graft placements includes topical, broad-spectrum antibiotics, mydriatics, systemic NSAIDs, and systemic antibiotics if the globe was ruptured. Treatments are gradually tapered and administered for 4–8 weeks. Postoperative complications include variable corneal scar and pigmentation, anterior and/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.