Anamnesis: a three years-old female Colombian Paso Fino equine presented visual impairment related to an anesthetic intervention with two alpha-2-adrenergic agents (xylazine 0.8 mg/kg + detomidine 10 ug/kg). Clinical and laboratory findings: ophthalmologic exam resulted in positive threat test with evidence of impaired obstacle circumvention due to failure in perception of distances and details of objects, resulting in unsteady gait and mount inability. The eye fundus presented horizontal bands on the nontapetal area and mild peripapillary edema. Scotopic electroretinogram (ERG) was performed under white light evidencing a decrease in amplitude and increase in A and B wave latencies for both eyes, compared with the reference. Hyperreflective tapetal zones and retinal folds are also observed. Leptospira tests were negative (Patoc: 1.25, Icterohaemorrhagiae: 1.25, Grippotyphosa: negative, Pomona: negative, Canicola: 1.50, Hardjo: 1.25, Ballum: negative, Bratislava: 1.25). Therapeutic approach: dexamethasone (0.2 mg/kg IM, for three days) and a vitamin supplement were prescribed. Conclusion: administration of two alpha2- adrenergic agonists may cause retinal ischemia with later development of retinal degeneration in horses.