Visual outcome and ocular survival following iris prolapse in the horse: a review of 32 cases.

The research explores the outcomes of 32 horses that were treated for iris prolapse, a condition where the iris projects out through a defect in the cornea, over an 8 year period at the University of Florida. It highlights the various associated conditions and treatments involved, and evaluates the success rate in preserving vision in affected horses.

Study Details and Findings

• Medical records of 32 horses treated for iris prolapse (IP) were analyzed over an 8 year period. Causes of IP were divided into perforated corneal ulcers (47%), ruptured stromal abscesses (6%), and full thickness corneal lacerations (47%).
• Every horse initially exhibited IP along with severe iridocyclitis, an inflammation of the iris and ciliary body. Cornea-related complications such as keratomalacia, a condition resulting in softening of the cornea, were found in 8 cases with corneal ulcers, one with a stromal abscess and another with a corneal laceration.
• Hyphema, or blood in the front part of the eye, was present in 7 cases with corneal lacerations.
• The treatment approach for 30 horses included both medical and surgical therapy while 2 were only treated with topical antibiotics.
• The surgical repair for perforations had a success rate of almost 88%, with 21 out of 24 being closed successfully and then 13 out of these were further treated with a conjunctival graft, a transplantation of tissue from the conjunctiva.
• The combined therapy was able to save vision in 6 horses (40%) with perforating corneal disease and 5 horses (33%) with perforating corneal lacerations.
• Out of the horses that remained blind post operation, more than half developed phthisis bulbi, a shrunken or atrophied eyeball.
• Enucleations, or the removal of the eye leaving the eye muscles and remaining orbital contents intact, were performed in specific extreme cases involving conditions such as endophthalmitis or keratomalacia.

Treatment Outcomes and Observations

• Horses with ulcerative keratitis for less than 15 days or with corneal lacerations less than 15 mm in length showed good visual outcomes. Conditions such as keratomalacia, hyphema, corneal lacerations longer than 15 mm and lacerations extending to, along, or beyond the limbus had a negative impact on visual outcomes.
• Iridectomy, a surgical procedure to remove part of the iris, did not seem to negatively affect anterior uveitis, inflammation of the front part of the uvea, or the visual outcome.
• Ocular survival rate after combined therapy was found to be 80% for horses with corneal lacerations and 67% for horses with ulcerative keratitis.