Canine glaucoma

Canine glaucoma refers to a group of diseases in dogs that affect the optic nerve and involve a loss of retinal ganglion cells in a characteristic pattern. Raised intraocular pressure is a significant risk factor for developing glaucoma (above 22 mmHg or 2.9 kPa). Untreated glaucoma in dogs leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.

The group of multifactorial diseases which cause glaucoma in dogs can be divided roughly into three main categories: congenital, primary or secondary. In dogs, most forms of primary glaucoma are the result of a collapsed filtration angle, or closed angle glaucoma.

Glaucoma often goes unnoticed in dogs until it is in a more severe state. There are rarely any symptoms in the early stages of the disease so regular eye checks by qualified veterinary professionals are important. Dogs will sometimes rub the eye if it is painful. An eye affected with glaucoma may be red, swollen, sore, or become clouded in appearance.

Veterinarians employ three general methods: (1) tonometry, (2) gonioscopy, and (3) ophthalmoscopy. Tonometry measures the intraocular pressure with an instrument. Normal intraocular pressure in dogs can range between 12 and 25 mm Hg and the two eyes should be similar in pressure. Gonioscopy is a diagnostic procedure to examine the angle of the anterior chamber. Direct and indirect ophthalmoscopy is necessary to evaluate the retina and particularly the optic nerve.

Treatment for dog glaucoma has several options, with surgery often being the most effective for long term management.

Laser surgery is often performed to selectively destroy the tissue, ciliary body, in an effort to reduce aqueous fluid production. Laser surgery can also be combined with placement of a shunt.

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