Abstract
Background: In human medicine, Urrets-Zavalia syndrome (UZS) is a well-recognized, but uncommon postoperative complication characterized by a fixed dilated pupil, accompanied by iris atrophy and glaucoma. Although it was originally reported in 1963 after penetrating keratoplasty surgery for keratoconus, since then it has been associated with various ophthalmic procedures such as cataract surgery. The condition has not been previously published in veterinary literature.

Case description: Three client-owned diabetic dogs that developed UZS´s triad after cataract surgery are described. Despite uneventful phacoemulsification in the 6 eyes, 5 developed moderate to severe postoperative ocular hypertension (POH). Although the intraocular pressure spikes were initially controlled, fixed dilated pupils accompanied by iris atrophy and chronic ocular hypertension were seen in the 5 affected eyes. Aggressive medical and surgical management was able to maintain vision in 3 of those eyes. In one eye, the uncontrolled intraocular pressure led to blindness.

Conclusions: This is the first published description of Urrets-Zavalia syndrome in dogs, occurring after phacoemulsification. Despite no exact, demonstrable causative element could be determined, we believe that POH should be consider a triggering condition for this syndrome, as it directly affects the ocular blood flow autoregulation and intrinsic uveal tissue integrity. Until the contrary is proved, diabetes mellitus might be considered a risk factor for developing this syndrome after cataract surgery in dogs.

Key words: iris atrophy, mydriasis, ocular hypertension, phacoemulsification, postoperative complication