What is glaucoma?
Glaucoma is a condition associated with elevated pressure within the eye. The fluid, which fills the eye is constantly being produced, circulates around the lens, and exits the eye through the iridocorneal angle. The balance between fluid production and outflow results in normal intraocular pressure. Elevation in intraocular pressure occurs as a result of poor fluid outflow. As pressure is raised above normal levels for even a short period of time the retina can become damaged, which often leads to blindness.
What causes glaucoma?
Glaucoma most commonly occurs as a primary inherited disease in many breeds of dogs particularly the Cocker spaniel, Basset hound and Chow Chow. Inadequate fluid outflow may also occur from secondary causes such as dislocation of the lens, trauma, inflammation, or tumors. In these cases, treatment will be directed at the primary disorder.
How do I recognize that my pet has glaucoma?
With acute onset of glaucoma, your pet will be uncomfortable around the eye and the head. You may notice squinting, a redness of the eye, tearing, and a cloudiness of the eye. If the second eye is involved, sudden blindness is often noted. Some animals will try to hide, or sleep a lot. People with glaucoma describe a severe headache. Chronic cases show more subtle signs and the eye might be enlarged. In chronic cases vision is usually permanently lost in the affected eye.
What is the prognosis for vision?
The prognosis for vision in an eye with glaucoma depends on the degree and duration of elevated pressure. Irreversible damage to the retina and optic nerve may occur within a day or two if the pressure is markedly elevated. If only one eye is involved, your pet may compensate for his loss of vision until permanent damage has occurred in the involved eye. Since primary glaucoma will often ultimately affect both eyes, evaluation of the "normal" eye is very important. Gonioscopy is an examination of the iridocorneal angle that will assist in this evaluation.
How is glaucoma diagnosed?
Tonometry is used to measure the intraocular pressure. Normal pressure will range from about 10mmHg to about 25mmHg. Gonioscopy is used to evaluate the drainage angle. This can help determine which type of glaucoma (primary or secondary) your pet has and if the fellow eye should be treated as well.
How is glaucoma treated?
Treatment for glaucoma depends on whether permanent vision loss has occurred. In early cases, medications may be given to lower the pressure immediately. However, rarely is medication alone successful in the long-term. In most cases, surgery offers the best opportunity to restore and maintain vision. Laser cyclophotocoagulation is a relatively new technique which uses a diode laser to burn small areas in the tissue in the eye (ciliary body) which produces fluid so that less fluid is produced. This procedure has the advantages of being relatively quick with minimal post-operative discomfort. Results are variable though and occasionally, more than one procedure may be required. A shunt can be placed to drain the fluid from the eye. Some cases require a combination of medical and surgical management and all cases require close clinical supervision. You should watch for signs of loss of vision, pain, or a cloudy appearance to the eye.
How is glaucoma treated if vision is lost?
If it is determined that vision 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 Chemical ablation.
- Enucleation: surgical removal of the eye with closure of the eyelids.
You will be given more 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.