Blessed to have glaucoma treatments for pets

(MCT) — Glaucoma in dogs and cats results from a variety of abnormal conditions of their eyes which cause a rise in the pressure of the fluids within the globe.

Normal intraocular pressure, or IOP, the pressure of fluids inside the eye, is controlled by a delicate balance between fluid production and fluid removal. Specifically this fluid is aqueous humor, produced in the posterior chamber of the eye (behind the iris) by the ciliary body. The iris is the portion of the eye that provides "eye color" and which opens and closes to make the pupil larger or smaller. Aqueous humor flows between the iris and the lens to the anterior chamber (in front of the iris) where it exits the eye via the trabeculae in the drainage angle, a hidden part of the eye just beyond the cornea, the clear portion of the front of the eye. The iris also plays a part in removal of aqueous humor.

Pressure measurement is generally performed using a tonometer in a procedure called tonometry. There are three types in common use, the Tonopen, the TonoVet (manufactured by a competing company) and the Schiotz. Tonopen and TonoVet are fairly automated devices that are considered to give easy, accurate readings. Some longtime users of the Tonopen are switching to the TonoVet, while some doctors don't care for it at all.

Like many things in practice, it's a personal preference. The Schiotz tonometer is a mechanical device that gives a reading, which is then converted to intraocular pressure. IOP is usually read in millimeters of mercury by both devices. Normal is considered to be between 10 and 20 for the Tonopen and TonoVet, and 15 and 30 (some veterinary ophthalmologists use 25 as the upper limit) for the Schiotz.

When pressure begins to increase, the eye responds with redness, "steamy" or cloudy cornea, dilated and unresponsive pupil, blindness, bulging of the eyeball. These are the outwardly visible changes and not necessarily all of them are present in every eye. Ophthalmoscopic examination by your pet's doctor can reveal additional changes inside the eye.

Time is of the essence in diagnosis and treatment of glaucoma. In short order the high pressure inside the eye will damage the retina, leading to permanent blindness. Indeed, approximately half of the patients in whom glaucoma is diagnosed have already lost vision in one eye.

The good news is that vision may be spared for a time in the other half of affected eyes and unaffected eyes (on the other side) can be treated prophylactically, perhaps permanently saving vision in that eye.