Understanding Glaucoma in Pets
The “aqueous humor” does not describe a funny guy on the swim team, but is actually a clear liquid that helps the eye maintain its shape. The aqueous humor also provides nourishment to the tissues in the eye. When this fluid is unable to drain away properly and the eye continues to produce more of it, the pressure within the eye increases causing a condition known as “glaucoma.” Last week I discussed keratoconjunctivitis (KCS) so this week I decided to remain on the eye and discuss this fairly common condition that also affects the eye.
When the pressure in the eye goes up the pet will most likely experience pain and in certain cases the pain could be extreme. One would think that when the pet is experiencing pain it would be easy to know that but many times it is not. The pet can’t reliably let us know what they are feeling other than the fact that there may be a reduced desire to play, to eat, the pet might become less active, sometimes squinting, and the eye may show some redness. If swelling or bulging is visible, the disease most likely has progressed quite far and immediate attention will be required to prevent blindness.
If glaucoma is inherited, it is considered “primary” and if the glaucoma is caused by something else it is labeled as “secondary.” Breeds susceptible to primary glaucoma are Akitas, Labrador Retrievers, Elkhounds, Siberian Huskies, Chow Chows, Shar Peis, and Cocker Spaniels. This disease may occur in cats but is extremely rare. Causes for secondary glaucoma on the other hand could include chronic retinal detachment, inflammation of the inner layers of the eye, and some have even suspected a tightly worn collar can cause the blood pressure to increase, in time leading to glaucoma, especially if the breed already has a predisposition.
It is extremely important to get the proper early diagnosis for this condition. A veterinary ophthalmologist may use a few different procedures to determine whether or not the dog has glaucoma. Once diagnosis is made then the veterinarian will usually decide on whether medications or surgery is the best approach for treatment. There are a few different kinds of medications used to treat glaucoma in pets; these classes are divided into the following:
- Miotics – Shrinks the pupil allowing fluid to flow out through the canal. Some available drugs: Pilocarpine, Humorsol.
- B-blocker – Reduces aqueous humor production.Some available drugs: Timolol maleate, metipranolol.
- Carbonic Anhydrase Inhibitor – Reduces aqueous humor production. Some available drugs: Dorzolamide, Daranide, Neptazane, Diamox
- Osmotic diuretic- Dehydrates the humor. Some available drugs: Mannitol , glycerine or glycerol.
- Prostaglandin analog- Improves fluid flow from the eye. For example: Xalatan (latanoprost).
- Cholinesterase inhibitor- Delays onset of glaucoma in unaffected eye. For example: Demecarium bromide.
The most important aspect of eye care in a pet is to be aware and alert of the signs and symptoms so that they may be treated early. In many cases the only way to get a definitive diagnosis is to visit the veterinarian. Having a good relationship with the veterinarian is vital at maintaining the health of your pet. Having a veterinarian detect the early signs of this potentially blinding condition may save your pet’s vision.
As always, if you have any medication related questions a 1800PetMeds pharmacist is available and will be happy to answer those for you.