Glaucoma: Problem, Diagnosis and Treatment

What is glaucoma?

Glaucoma is the medical term used to describe an increased pressure inside the eye(s). Normally, the pressure in a dogs or cats eye ranges between 10-25mmHg and when this range is exceeded, we are worried about complications which can lead to reduction of vision or blindness and pain.

Therefore, glaucoma requires urgent attention and investigation of the underlying problem. Although pets cannot describe the degree of pain or discomfort they experience, humans who suffer from glaucoma report headaches and migraine-type pain. In a normal eye, there is a balance between the fluid formed inside the eye (at the back chamber of the eye) and fluid drained away from the eye (at the front chamber of the eye), maintaining an equilibrium and the pressure of the eye at the normal range.

Glaucoma develops because of reduced flow (or drainage) of fluid from the eye, leading to increased pressure due to accumulation of excess fluid in the eye. Some of the conditions leading to glaucoma are outlined below:

• Lens luxation
• Hereditary glaucoma
• Trauma or injury to the eye
• Severe inflammation (uveitis)
• Increased systemic blood pressure
• Tumours inside the eye
• Complication of cataract surgery

Types of glaucoma

Glaucoma is classified as primary or secondary, depending on its aetiology.

• In primary glaucoma, dogs or cats are born with a predisposition to develop an abnormal draining area, limiting the outflow of fluid; this means that they are predisposed to developing glaucoma in both eyes.
• Secondary glaucoma is the consequence of trauma, severe inflammation, or tumours in the eye and, usually, this affects one eye.

Understanding the problem and establishing what condition your pet is suffering from is important to be able to give you an accurate prognosis about your pet’s vision.

Signs of glaucoma

If your dog is experiencing any of the following signs, please get in touch with your local vets who can initially examine your dog and then refer you to us if necessary:

• Cloudy or “blue” eyes.
• Red and painful eyes.
• Protrusion of the third eyelid (the membrane at the middle corner of the eye).
• Keeping their eyes shut.

Diagnosis of glaucoma

The initial diagnosis of glaucoma is based on measuring the pressure of the eye (intraocular pressure). This can be performed at most vet practices and is part of our routine assessment when your pet is presented for an assessment with one of our specialists. If the pressure of
the eye exceeds the normal range of 25mmHg, a suspicion of glaucoma is raised and further tests should be performed by a veterinary ophthalmologist to provide an accurate diagnosis.

Treatment of glaucoma

Glaucoma is a true emergency and requires urgent treatment to preserve vision in the affected eye. The initial treatment involves using a combination of eye drops to reduce the pressure inside the eye. If medical treatment with eye drops is successful, your pet will need to receive lifelong medication to maintain the pressure at a normal level and, when possible, preserve vision.

In cases where medical treatment is not sufficient, surgical options can be offered in the form of devices called shunts (a shunt is a tubing placed in the eye to actively transfer fluid away from the eye) or laser procedures (i.e., endocyclophotocoagulation).

Complications of glaucoma

The most common complication of glaucoma is loss of sight in one or both eyes. In addition to blindness, if the pressure is not controlled, glaucoma will lead to ongoing pain and discomfort.

After care

Once the optimal treatment has been titrated to your pet’s needs the aftercare focuses on using the recommended eye drops long term to keep the pressure of the eye at the desired level.