Deep Stromal Corneal Ulcers, Descemetocele, and Iris Prolapse
Most corneal ulcerations readily heal with appropriate antibiotic, antiproteinase (often topical serum), and mydriatic therapy. However, corneal ulcers detected late in the disease process, complicated by other ocular diseases, or given inadequate topical therapy can progress. These require surgical intervention using a conjunctival graft or, more recently, the commercially available porcine small-intestinal submucosa or experimental amniotic membranes. Deep corneal ulcers, descemetocele, and iris prolapse are seen with some frequency in dogs, cats, and horses. These conditions require immediate surgical support of the weakened cornea, because they can threaten or seriously compromise corneal integrity. Brachycephalic breeds and dogs with keratoconjunctivitis sicca are most vulnerable. 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. Secondary anterior uveitis with aqueous flare, miosis, ocular hypotony, and hypopyon is common.
Corneal ulcer depth must be accurately estimated using magnification, focal illumination using a slit-beam, and topical fluorescein. 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 (360°, 180°, bridge, or pedicle) that appears most appropriate.
For full-thickness corneal ulcers with iris prolapse, conjunctival grafts are also used, but the postoperative corneal opacity is usually larger and more dense. Postoperative therapy includes topical and systemic broad-spectrum antibiotics, systemic NSAIDs or corticosteroids, and mydriatics. Treatments are gradually tapered and administered for 4–8 wk. Postoperative complications include variable corneal scar and pigmentation, anterior and/or posterior synechiae, secondary cataract formation, and rarely bacterial endophthalmitis.