Under Pressure: Glaucoma

Written by University of Florida veterinary student, Michelle Haramboure

Glaucoma occurs when there is an impairment of fluid drainage from the eye, causing an increase in ocular pressure. In a normal eye, fluid production and drainage occur at the same rate. Overall, the incidence of glaucoma in horses is low, but when it does occur, it is painful and should be managed by a veterinarian.

In horses, glaucoma is often secondary to Equine Recurrent Uveitis (ERU): an autoimmune disease which causes inflammation within the eye. The inflammatory proteins block drainage channels leading to an increase in intraocular pressure. This increase in pressure causes stress to the retina and optic nerve, which may lead to blindness.

Signs that your horse may have glaucoma include:

• Increased tearing

• Dilated pupils

• Redness of the sclera, the white part of the eye

• Blue hue, cloudiness of the eye

• Bulging of the eye

• Blindness

• Pain near the eye

If you are concerned that your horse is developing glaucoma, you should call your veterinarian and have your horse seen as soon as possible. The goal is to catch the development of glaucoma early and to decrease pain as much as possible.

How is Glaucoma diagnosed? First, we will fully examine your horse to ensure systemic wellness, and check reflexes associated with vision. The mainstay of diagnosing glaucoma is obtaining an intraocular pressure (IOP) with a tonometer. A normal range in a horse is between 20 and 30 mmHg, above this range, there is concern for glaucoma. We may also recommend other tests such as a fluorescein eye stain to ensure there are no concurrent corneal ulcers.

Your horse has glaucoma, what now? Depending on the severity of glaucoma, we may recommend beginning medical management or, in severe cases, removal of the eye. You will be sent home with topical eye drops for your horse to be administered 2 to 3 times daily. It is important to note that medical management slows the process of vision loss but will not eliminate the disease. In cases that do not respond well to medical management or in which medicating is challenging, removal of the eye is a viable option. Our priority in managing glaucoma is to decrease your horse’s pain. Though the loss of an eye may seem scary at first, it eliminates the source of pain and horses can lead a normal life afterward.

Although equine glaucoma is not very common, it is an important disease to keep in mind, especially for horses that experience equine recurrent uveitis. If you find yourself facing a glaucoma diagnosis in your horse, we hope this information takes some of the pressure off!