MSD Manual

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Pet Owner Version

Glaucoma in Horses


Kirk N. Gelatt

, VMD, DACVO, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida

Reviewed/Revised Apr 2019 | Modified Oct 2022

The glaucomas represent a group of diseases characterized by increased pressure within the eye. The high pressure eventually destroys the retina and optic disk (the spot where the optic nerve enters the eye). In horses, glaucomas may be underdiagnosed because testing of the pressure within the eye has not always been a part of ordinary equine examinations. Among horses, glaucoma appears most frequently in older animals, in the Appaloosa breed, or together with anterior uveitis or equine recurrent uveitis Equine Recurrent Uveitis (Periodic Ophthalmia, Moon Blindness) The uvea (or the uveal tract) is the colored inside lining of the eye consisting of the iris, the ciliary body, and the choroid. The iris is the colored ring around the black pupil. The ciliary... read more .

The early signs of glaucoma (slightly dilated pupils, mild redness of the eyes, or slight enlargement of the eyeball) are subtle and often go unnoticed by owners.

Once the pressure within the eye is significantly increased, signs include:

  • a dilated, unmoving or slow-moving pupil

  • redness in the white of the eyes

  • swelling and discoloration of the cornea

  • a firm eye globe

Prolonged increases of pressure within the eye can result in enlargement of the eyeball, displacement of the lens, and the appearance of lines within the cornea. Pain usually shows itself as behavioral changes and occasional pain around the eye.

There are various instruments a veterinarian can use to evaluate and manage glaucoma. The choice of medical or surgical (including laser) treatment or, most frequently, a combination of both, depends on the type of glaucoma present. Most glaucomas require longterm management.

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