Quarterly Newsletter

2014-May_IVG Newsletter-Ophtho-PainMgt

The IVG Hospitals Quarterly Veterinary Newsletter features articles of interest to the veterinary medical community, written by veterinarians and veterinary specialists at our four locations.

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DIAGNOSIS Glaucoma presents as a red, painful, or cloudy eye. Dry eye, corneal ulceration, glaucoma and conjunctivitis appear similarly. I recommend a complete eye exam for any pet presented for a red, painful eye. This includes menace response, pupillary light response, Schirmer tear test, fluorescein stain and tonometry. If you find that a pet has one condition, complete the eye exam! Just because a dog has dry eye does not mean that she does not have glaucoma. The only way to diagnose glaucoma is to measure intraocular pressure; either a Tonopen, TonoVet or a Schiotz tonometer is completely adequate for this purpose. The key to using any of these is experience and comfort with the instrument. I would encourage you to acquire one of these and to use it on a regular basis, on client animals as well as your own pets. Normal intraocular pressure is published as 10-25 mmHg. However this can vary with operator or tonometer differences. At my practice, a normal intraocular pressure range is more like 8-18 mmHg with either the TonoPen or the TonoVet. As you become comfortable with using your tonometer you will also find what is a normal intraocular pressure range in your hands. Once you diagnose glaucoma, you will need to answer two questions in order to plan a course of treatment. The first is whether the glaucoma is acute or chronic, and the second is whether the glaucoma is primary or secondary. ACUTE OR CHRONIC Once you have concluded that a pet has glaucoma, it is important to determine whether the glaucoma is acute or chronic. Most chronic cases will be irreparably blind; eyes with acute glaucoma will be temporarily blind due to the effects of the increased intraocular pressure (IOP) on the optic nerve, and in some cases vision can return once IOP is normalized. Owner history may be helpful, but keep in mind that owners may understate the duration of the disease due to a lack of initial observation, or guilt at not seeking prompt veterinary attention. Probably the most useful factor in determining chronicity is the size of the eye. Chronic glaucoma is the ONLY cause of enlargement of the globe (buphthalmos). In almost all cases, an enlarged globe is irreparably blind. There are a few exceptions to this rule – young animals, Cairn Terriers, Shar Peis, Australian Cattle Dogs and Chow Chows. The reason for this in puppies and kittens is thought to be the elasticity of the sclera. In the above-mentioned breeds, I do not know the reason why patients may retain vision in an enlarged eye, it is just a clinical observation of mine. However, if an adult animal of another breed has an enlarged globe, it is very likely that the eye is irreparably blind. Diagnosis and Treatment of Glaucoma Glaucoma is among the most frustrating ocular conditions for both veterinarians and owners. In this article I hope to give some practical guidelines for diagnosis, treatment, and possibly the most important aspect of managing cases of glaucoma – owner counseling! Although glaucoma occurs in our feline patients it is much more common in dogs than cats, so the main focus here is canine glaucoma. Ruth Marrion, DVM, PhD. DACVO practices at Bulger Veterinary Hospital in North Andover, MA Ruth Marrion, DVM, PhD, DACVO | 1 |

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