Retrospective Assessment of Carbonic Anhydrase Inhibitors in Topical or Episcleral Implant Form for the Treatment of Equine Glaucoma

Objective To assess whether topical carbonic anhydrase inhibitors (CAIs) with or without episcleral brinzolamide implants control intraocular pressure (IOP) in horses with glaucoma. Animals Studied 12 client‐owned horses diagnosed with glaucoma. Procedures Medical records of horses treated with topical CAIs for ≥ 14 days, with a subset receiving episcleral brinzolamide implants, were reviewed. Diagnosis, signalment, concurrent ocular disease, medications, IOP, visual status, and additional procedures were recorded. Treatment failure was defined as horses with IOP > 30 mmHg resulting in phthisis bulbi or requiring a procedure or enucleation. Results Secondary glaucoma was diagnosed in 8/12 (67%) eyes and primary glaucoma in 4/12 (33%) eyes. IOP was < 30 mmHg in 7/12 (58%) eyes after treatment with topical CAIs for a median of 28 days. Episcleral brinzolamide implants were placed in 7/12 eyes after a median of 58 days of medical therapy. Treatment failure occurred in 3/7 horses (43%) receiving brinzolamide implants at a median of 189 days and in 4/5 medical therapy‐only horses (80%) at a median of 51 days. While 6/12 eyes (50%) were visual at last follow‐up (median of 161 days), enucleation was the final outcome in 10/12 (83%) eyes. Conclusions Topical CAIs appear to result in temporary IOP control in a subset of horses, though some horses may be refractory. Episcleral brinzolamide implants may extend IOP control in horses with glaucoma, but prognosis for vision remains guarded and further optimization is needed.