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 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 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 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.
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.
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.