Idiopathic Unilateral Transient Miosis in Dogs

Idiopathic unilateral transient miosis, in the absence of other ocular or systemic disease, occurs predominantly in young dogs and is seen across various breeds and eye colors. Australian Shepherds, Miniature Australian Shepherds, the merle phenotype, blue eyes, and females were disproportionately represented in this cohort. Episodes were most commonly observed after sleep, typically lasted around 30 min, and recurred in more than half of affected dogs. To the authors' knowledge, this is the first report of idiopathic unilateral transient miosis in dogs.