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Glaucoma in horses

Quick facts

  • Glaucoma is a rather rare but serious eye condition in the horse.
  • Glaucoma can lead to pain, blindness and even removal of the eye if left untreated.
  • Contact your veterinarian if you suspect your horse has glaucoma.

What is glaucoma? 

Glaucoma is a severe eye problem that occurs in less than one in 1,000 horses. It stems from poor fluid drainage that increases pressure in the eye. Usually this fluid drains from the eye at the same rate it’s produced.

If left untreated, glaucoma can result in pain and blindness. At the end stages, veterinarians often recommend removing the eye to relieve the pain.

What horses are prone to glaucoma?

Glaucoma usually occurs in horses that also have moon blindness. Swelling from moon blindness can block fluid drainage in the eye.

Signs of glaucoma

  • Cloudy blue cornea sometimes with white lines crossing it.

  • Redness in the white tissues around the cornea.

  • Signs of pain such as squinting and tearing.

  • Big pupils that don't shrink in bright light.

  • An enlarged eye.

  • Blindness.


Veterinarians diagnose glaucoma by completing an eye exam. They will often use local anesthetic blocks to help with the exam. The horse may need sedation depending on its temperament. The veterinarian will measure the pressure on the eye to diagnose glaucoma.


The goal of treatment is to lower the pressure in the eye. You should first try topical treatments such as eye drops or eye ointments. Be careful as some horses may not tolerate these.

  • Dorzolamine hydrochloride is a topical medication given three times daily. It reduces the amount of fluid produced in the eye.

  • Timolol is a topical medication given every 12 hours. It can mildly lower the pressure by reducing the amount of fluid produced. It’s often given with dorzolamine.

  • Systemic non-steroidal anti-inflammatories (such as banamine) and topical corticosteroid ointment can reduce swelling if moon blindness is present.


Grace Meyer, DVM, former student, College of Veterinary Medicine

Reviewed in 2018

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