Glaucoma in Dogs and Cats

Last month’s article discussed a common ocular issue in dogs and cats – ulcers, or scratches, on the surface of the eye. Another condition that affects our pets’ eyes is glaucoma. Glaucoma is a disease in which the pressure inside of the eye, known as the intraocular pressure, is increased. This can happen quickly or gradually over time and can lead to blindness and pain, which can be extreme.

Glaucoma is divided into primary and secondary glaucoma. Primary glaucoma is considered inherited and often affects pure-bred dogs. It is rare in cats. Secondary glaucoma is caused by an underlying disease, either within the eye itself, or systemically from issues in other parts of the body. There can be many reasons for secondary glaucoma.

When a pet has glaucoma, it can occur acutely or develop slowly over weeks to months. Common signs can include blinking, holding the eye closed, redness in the sclera (the white part of the eye), discharge from the eye, or a blue tint associated with the cornea. Blindness is often a consequence, but it doesn’t always occur right away. If only one eye is affected, vision deficits might not be noticed immediately as the other eye is compensating. Glaucoma can also be painful and cause headaches, which often manifests as the pet acting lethargic or sleepy. The eye with glaucoma can also be noticeably bigger than the other eye, but that often occurs when the glaucoma has been occurring for a long time.

If glaucoma is suspected, your pet will typically receive a full physical exam as well as an ophthalmic exam. Diagnosis is often made via the use of tonometry. This will measure the intraocular pressure (IOP) to determine if the pressure within one or both eyes are elevated. If glaucoma is suspected, your veterinarian may advise on further diagnostics or even a referral to an ophthalmologist to try to determine the underlying cause and therefore the most effective treatment. Treatment is often initiated right away to try to save the pet’s vision and relieve the pressure and pain they are feeling.

Treatment is often divided into 4 categories: treatment of acute, severe elevation of pressure; medical management of chronic glaucoma; surgical therapy for eyes that still have vision (or potential to regain vision); and surgical therapy of chronic glaucoma in eyes that are blind. Sometimes, surgery and medical therapy must be combined when medical management alone is unsuccessful. Medical management typically involves eye drops, because systemic medications (oral or injection) will not reach the eye. There are various surgical techniques, most of which are performed by a veterinary ophthalmologist. If the pet’s glaucoma is unable to be controlled with medical management and the eye is no longer visual, enucleation (removal of the eye) is often considered to relieve the pain associated with glaucoma. Treatment also needs to consider the underlying cause, if one can be identified.

Prognosis varies, but the prognosis for primary glaucoma is unfortunately guarded. Most treatments can only stabilize, not cure, and the eyes eventually lose their vision. Sometimes treating the unaffected eye prophylactically can significantly delay or even prevent the onset of glaucoma in that eye. The prognosis for secondary glaucoma depends on the underlying cause and whether it can be effectively treated or managed. Glaucoma can develop and change quickly and can lead to permanent damage. If your dog or cat exhibits the symptoms mentioned above, the safest thing to do is to check with your veterinarian.