Glaucoma is a disease of the eye where there is an increase in the pressure within the eye, this is called the intraocular pressure. This disease can be quite painful and will often result in blindness.
An increase in intraocular pressure is caused by the globe of the eye being unable to drain. Inside the eye is the ciliary body, this structure not only contains the ligaments that hold the lens in place and helps it focus it also produces aqueous humor. Aqueous humor is a fluid that provides nutrition to the eye, helps the eye maintain its shape due and provides the intraocular pressure of the eye. Aqueous humor is located in the anterior chamber of the eye which is the front most chamber between the cornea and the iris. This fluid is being constantly produced by the ciliary body, in order to maintain homeostasis in the eye it must drain at a commensurate rate. The area where drainage occurs is called the iridocorneal angle. When the eye’s drainage of aqueous humor does not keep up with its production, intraocular pressure is increased and glaucoma is the result. An increase in intraocular pressure is problematic because it causes nerve damage and changes to the retina and optic nerve.
Glaucoma can be broken down into primary and secondary glaucoma. Primary glaucoma is an inherited malformation with the iridocorneal angle. This inherited malformation seems to be more common in certain breeds such as Beagles, Basset Hounds, BostonTerriers, Cocker Spaniels and Labrador Retrievers to name a few. Secondary glaucoma is an acquired disease that results from a physical obstruction of the iridocorneal angle. The iridocorneal angle can become blocked with things like red blood cells, cellular debris, inflammatory cells or white blood cells . Adhesions of the iris to the lens or the cornea.
Glaucoma can be acute (sudden onset) or chronic (persisting for several days or longer). Acute glaucoma is defined as an elevation in intraocular pressure in a 12 – 24 hour period. Under the right circumstances vision may be restored if acute glaucoma is treated right away. Chronic glaucoma has been present for days or longer. Even with medical management and a resulting decrease in intraocular pressure there is usually a permanent loss of vision.
Signs of glaucoma include The most common signs noted by owners are:
- Eye pain or pain in the surroundings areas.
- Watery discharge from the eye.
- Loss of appetite
- Physical swelling and bulging of the eyeball.
- The white of the eye (sclera) looks red and engorged.
- The cornea or clear part of the eye may become cloudy or bluish in color.
In a case of acute glaucoma these signs will come on very quickly, with chronic glaucoma the opposite is true and may have been present for some time without the pet showing any signs at all.
Diagnosis of glaucoma is initially based on a history of the above symptoms as well as a complete eye examination. A measurement of the eye’s intraocular pressure is typically performed at the time of the ocular exam if glaucoma is suspected. This test is performed with an instrument called a tonometer, it is non-invasive and typically well tolerated by patients. In some cases referral to a veterinary ophthalmologist may be considered.
Unfortunately there is no cure for glaucoma, but there are both medical and surgical treatment options. There are several different topical medications that work in different ways that can be used to control glaucoma. In the case that these medications don’t work surgery may be the next step.