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Learn About Glaucoma

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.

Turtle sitting in a person's hand

Background

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 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 diseases, such as dislocation of the lens, trauma, inflammation, or tumors.

Prognosis

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, preventative medications will be prescribed and you should monitor it closely for signs of vision loss, pain, or a cloudy appearance.

Treatment

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 that uses a diode laser to impair the ciliary body’s ability to produce the aqueous fluid. This procedure has the advantage 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

  • Intraocular Prosthesis is 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

  • An Intraocular Prosthesis is used to relieve discomfort in an eye that is irreversibly blind. Glaucoma is the most common condition which is treated in this way. The surgery involves an incision in the eye though which the inner contents of the eye (lens, retina, iris, ciliary body) are removed. A prosthetic ball is then implanted into the eye to maintain it’s shape. Once healing is complete, the eye looks nearly normal. The eye blinks and moves in coordination with the other eye. It is important to recognize that the outer layers of the eye are still living tissue and, thus, subject to injury or infection although this is rarely a problem.

An alternative to a prosthesis is enucleation (removing the entire eye).

Enucleation

  • Enucleation is the surgical removal of the eye with the closure of the eyelids.

  • You will be given information about these options as they apply to your pet’s condition.

  • Enucleation means the removal of the entire eye. The eyelids are then stitched closed. This gives the appearance that the animal is “winking”. There is some discomfort for several days which is controlled with pain medication. Once the stitches are removed in 2 weeks and then the hair grows back, the appearance is not objectionable. This procedure is indicated in situations where the removal of a tumor is necessary or where the outer portion of the eye is not healthy enough to support a prosthesis. As this procedure is reserved for those eyes which are blind and (usually) painful, removal of the eye causes no additional handicap and is used to make the animal more comfortable.

In some cases, both eyes are affected and vision may be permanently lost.

Rabbit jumping in grass and covering its eyes

Can Blind Pets Lead Happy Lives?

The answer is an unequivocal “YES!”

Fortunately most eye diseases can be successfully treated with medication or surgery. However, in some unlucky pets, vision is irreversibly lost in both eyes. Progressive retinal atrophy (PRA) and Glaucoma are two common causes of permanent bilateral blindness. Veterinarian ophthalmologists are often asked whether a blind dog or cat can lead a happy life.

Living Happily, Blindly

While there are certainly some things that they may be unable to do safely, most of the activities that are important to our pets are still possible. A blind dog or cat will behave remarkably normally in their own home. Animals that lose vision gradually appear to adjust better than those that lose vision rapidly. With a bit of patience and TLC, we have found that almost every pet can make this adjustment. They will remember where their food and water are and rarely bump into things in the home. Try not to rearrange the furniture and you will be amazed at how well your pet will remember the floor plan — even going up and down stairs. They will still play with toys, but may prefer a ball with a bell or a squeak toy. They will enjoy interacting with their human family in most all of the same ways as they did before they lost vision. A blind pet can continue in every way in their primary role as a loving companion.

It is important to recognize that, while vision is important to dogs and cats, they have many other senses that help them adjust to the loss of this one. Their senses of hearing and smell are much more sensitive than ours — dogs would think our normal senses a handicap! Loss of vision does not represent the same hardship for our pets as it would for us. For us, blindness would mean an inability to read and drive a car as well as a definite loss of independence. Our pets are already (happily) dependent on us. Unlike animals in the wild, pets typically do not need to hunt for their meals nor escape predators.

A blind pet does have some special needs, including a protected environment. This is particularly important because they behave so normally that you may forget that they are handicapped. Hazards for a blind pet include swimming pools, traffic and balconies. A blind dog should always be kept on a leash when outside of a fenced yard; you may find a harness works better than a collar for guiding your pet on walks outdoors. Cats who are blind really need to become indoor-only pets: no matter what they may tell you. There are tools available to help you keep your pet safe while still allowing some freedom. For example, there is an alarm you can attach to your pets collar to alert you if they fall in the swimming pool.

Visually Impaired Pets

Online Resources

If you have a pet that has lost vision, you may appreciate some of these websites related to this subject. Veterinary Vision does not specifically recommend any of the products mentioned on these pages.

Books Related to Vision-Impaired Pets

There are also two very useful books by Caroline Levin, RN: “Living With Blind Dogs: A Resource Book and Training Guide for the Owners of Blind and Low-Vision Dogs” and “Blind Dogs Stories: Tales of Triumph, Humor, and Heroism.” They are available from Lantern Publications. Many of her tips are excellent, but she is not a veterinarian, so be sure to verify any medical information you read in the books with your pet’s ophthalmologist.

Cathy Symons offers advice for enriching the lives of blind dogs in her book, “Blind Devotion” available through her website.