Optic neuritis in dogs: 96 cases (1983-2016).

Abstract

OBJECTIVE: To characterize ocular and neurologic findings, causes, and treatment outcomes of dogs with optic neuritis. PROCEDURE: Medical records from dogs with a diagnosis of optic neuritis at North Carolina State University, College of Veterinary Medicine, Veterinary Hospital between 1983 and 2016 were reviewed. RESULTS: Ninety-six cases (20 unilateral, 76 bilateral), comprised of 38 males and 58 females with a mean age of 6.1 ± 3.0 years (range 0.5-13), were identified. Seventy-four cases were presented for vision loss, and 42 had other concurrent neurologic abnormalities. Funduscopic findings included optic nerve head elevation (n = 92), peripapillary retinal edema or separation (n = 37), retinal hemorrhage or dilation of retinal vasculature (n = 23), and multiple inflammatory foci in the peripapillary region (n = 13). Retrobulbar optic neuritis was diagnosed in four cases. The final diagnoses included the following: multifocal meningoencephalitis of unknown etiology (MUE, n = 35), isolated optic neuritis (I-ON, n = 42), neoplasia (n = 10), microbial infection (n = 6), orbital inflammation (n = 2), and suspected ivermectin toxicosis (n = 1). Dogs with I-ON were more commonly male, and medium-to-large breed, when compared to dogs with MUE. Follow-up was available in 72 cases, 50 of which remained blind, 10 had partial visual improvement, and 12 were assessed as having normal vision in the affected eye(s). CONCLUSION: Optic neuritis was most commonly associated with multifocal MUE or was isolated as the sole neurologic finding, with a similar incidence between the two groups. Findings suggest that a clinical syndrome of isolated optic neuritis, distinct from multifocal MUE, occurs in dogs.