Glaucoma is a condition associated with elevated pressure within the eye. The aqueous fluid which fills the eye is constantly being produced by the ciliary body. It circulates around the lens and exits the eye through the iridocorneal angle (see drawing). When fluid is produced and drained from the eye in equal amounts, this results in a stable, healthy intraocular pressure of 10-30 mm Hg. Impaired drainage of fluid from the eye results in an abnormally elevated pressure or glaucoma. This in turn damages the retina and optic nerve, resulting in loss of vision and pain.
Glaucoma occurs as a primary or inherited disease of the iridocorneal drainage angle in many breeds of dogs, including the Cocker spaniel, Basset hound and Chow. The dog version of primary glaucoma (closed angle) is unfortunately worse than the form seen in their human counterparts (open angle). Inadequate fluid outflow may also occur secondarily to other ocular disease, such as dislocation of the lens, trauma, inflammation, or tumors.
For even more information, here is a brochure on glaucoma provided by the American College of Veterinary Ophthalmologists.
The prognosis for vision in an eye with glaucoma depends on the degree and duration of elevated pressure. Irreversible blindness from damage to the retina and optic nerve may occur within a day or two if the pressure is dramatically elevated. If only one eye is involved, your pet may compensate for his loss of vision using the other eye. This is great except that it makes it very easy to miss the problem until permanent damage has occurred. Since glaucoma will often ultimately affect both eyes, evaluation and treatment of the “normal” eye is very important. Gonioscopy is an examination of the iridocorneal angle that may be recommended to assess whether an eye is at high risk of developing glaucoma. If the “good” eye is considered at risk based this exam or a breed related risk, a preventative medications will be prescribed and you should monitor it closely for signs of vision loss, pain, or a cloudy appearance.
Treatment for glaucoma depends on whether permanent vision loss has already occurred. In acute cases of glaucoma, medications may be given in the hospital on an emergency basis to lower the pressure, which may even restore vision that had been recently lost. However, rarely are medications alone successful in the long-term since glaucoma is a chronic and inevitably progressive condition.
Laser treatment (cyclophotocoagulation) is a technique which uses a diode laser to impair the ciliary body’s ability to produce the aqueous fluid. This procedure has the advantages that it is relatively quick and causes minimal post-operative discomfort. However, outcomes are variable, its effect on pressure is less than immediate, and more than one procedure may be required. Some cases require a combination of medical and surgical management and all cases require a great deal of owner commitment and close clinical supervision.
When the eye pressure is greatly elevated, people and pets develop a dull headache-like pain, which is not always obvious. If it is determined that vision has been lost and cannot be restored, treatment is directed at relieving discomfort and achieving optimal appearance. Options for management of pain include.
Intraocular prosthesis: a surgical procedure where the contents of the globe are replaced with a sphere which retains the shape and general appearance of the eye.
Ciliary body ablation: techniques used to decrease intraocular fluid production; these include laser cyclophotocoagulation and a drug injection procedure
Enucleation: surgical removal of the eye with closure of the eyelids.
You will be given information about these options as they apply to your pet’s condition.
In some cases, both eyes are affected and vision may be permanently lost.
Can Blind Pets Lead Healthy Lives? Absolutely YES!
Glaucoma is a challenging disease – successful management requires close cooperation between you and your pet’s ophthalmologist. Please feel free to ask questions at any time during treatment.