Thursday, November 10, 2016

Primer on Glaucoma

Written and reviewed by John A. Bukowski, DVM, MPH, PhD
and Susan E. Aiello, DVM, ELS

Glaucoma in dogs is a condition where pressure builds up in the eyeball, thereby damaging the structures of the eye and leading to the dog's blindness. 

The eyeball of a dog is filled with fluid that nourishes the eye, cushions it, and helps it keep its shape. Some of this fluid is thick, like jelly, while some is thin, like water. The fluid is constantly moving because new fluid is added all the time while older fluid is removed.

Any problem that either blocks the outflow of fluid or increases the inflow results in pressure building up in the eyeball, a condition known as glaucoma.

 Over time, the increased pressure can seriously damage the structures of the eye, especially the delicate retina, and optic nerve, resulting in blindness.

Fluid drains out of the eye in the area between the lens and the cornea. Glaucoma can develop if this area is damaged from trauma (eg, car accident), a bacterial or viral infection, a tumor, parasites, etc. Genetic problems with the fluid outflow are seen in certain breeds of dogs (eg, American Cocker Spaniel, Basset Hound, Siberian Husky, Samoyed, and Shar Pei), which increases their risk of glaucoma.

In early glaucoma, signs include redness in the whites of the eyes, a slightly enlarged pupil, and an eyeball that is a little larger or harder than normal. In more advanced glaucoma, signs include an obviously enlarged eyeball, a noticeably enlarged pupil, and a cloudy cornea.

Glaucoma can also be very painful, so your dog may squint, paw at its face, or stop eating. Signs of illness often develop gradually but can occur quite suddenly if the fluid drainage from the eye is blocked abruptly.

If you notice signs of glaucoma, you should take your dog to your veterinarian as soon as possible. 

Signs that occur suddenly should be treated as an emergency. 

Your vet will anesthetize the eye with local anesthetic eye drops and then measure the pressure in the eye with an instrument called a tonometer. (If your dog is a member of a high-risk breed, your vet may recommend periodic tonometry so that if glaucoma does develop, it can be caught early).

Treatment is aimed at managing pain, decreasing the pressure in the eyeball, and preventing blindness (when possible). 

Eye drops can be prescribed to ease painful spasms and to enlarge the fluid drainage area. In some cases, oral medication can also be used to lower pressure in the eye by decreasing fluid production. Surgery may be needed to open up the drainage area or to place artificial drains that can help draw fluid off the eye. In such cases, your veterinarian may refer you to a specialist or veterinary teaching hospital.

In cases of long-term or advanced disease, in which blindness has already developed, surgery to remove the painful eye may be recommended.


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