Standing superficial keratectomy provides long-term control of epithelial and stromal equine immune-mediated keratitis

Objective: To describe the demographics and treatment outcomes of horses definitively diagnosed with epithelial or stromal immune-mediated keratitis (IMMK) by use of in vivo confocal microscopy (IVCM) and/or histopathology. Methods: Medical records of horses presented to the Cornell University Equine Hospital definitively diagnosed with epithelial or stromal IMMK with IVCM and/or histopathology between 2020 and 2024 were reviewed. Patient signalment, affected eye(s), diagnostics, treatments, and outcomes were assessed. Results: 22 horses met the inclusion criteria. The mean age was 16.9 years (SD, ± 7.3 years). There were significantly more geldings (n = 16) than mares (6). Nineteen horses were unilaterally affected (11 right eyes and 8 left eyes) and 3 bilaterally affected. Twenty horses underwent IVCM, of which 8 had histopathology following superficial keratectomy with agreement in diagnosis. Two horses had corneal histopathology without IVCM. All horses were initially managed medically. Seven horses subsequently underwent episcleral cyclosporine implantation, of which 2 were controlled at last follow-up (median, 532 days). Standing superficial keratectomy was performed in 10 horses, with IMMK controlled in 9 of 10 horses at last follow-up (median, 692 days). Recurrence was documented in 1 horse 12 months after keratectomy. Conclusions: IVCM allowed for a rapid noninvasive diagnosis of equine IMMK that correlated with histopathology. Standing superficial keratectomy was an effective diagnostic and therapeutic option for equine IMMK. Clinical Relevance: Standing superficial keratectomy was an effective diagnostic and treatment for equine IMMK that provided long-term control of disease and minimized the need for long-term daily medications.