What is the most common cause of glaucoma in cats and horses?

• A. Primary
• B. Secondary
• C. Congenital
• D. Traumatic

Answer: (B)

Glaucoma in cats and horses is most often a consequence of another eye disease rather than an inherent angle abnormality. Inflammation is a frequent culprit: anterior uveitis causes immune and cellular debris, protein, and pigment to accumulate in the anterior chamber and clog the trabecular meshwork, raising outflow resistance. Chronic uveitis can also lead to synechiae, where the iris adheres to the cornea or lens and narrows or closes the iridocorneal angle, trapping fluid and driving pressure up. Equine recurrent uveitis is particularly common in horses and frequently progresses to secondary glaucoma, while feline anterior uveitis from infectious or inflammatory processes similarly predisposes cats to secondary glaucomatous disease. Primary glaucoma—driven by inherent developmental abnormalities of the drainage angle—is comparatively rare in these species. Trauma and congenital factors can cause secondary glaucoma too, but the prevailing pattern in cats and horses is glaucoma secondary to uveitis or other inflammatory or intraocular diseases.