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Dog: Glaucoma

General information

Other common/scientific names: increased pressure in the eye

The fluid that fills the eye is called aqueous humour. This fluid allows the eye to maintain its shape and creates the pressure inside the eye or the intraocular pressure (IOP). Aqueous humour is produced by a structure in the eye called the ciliary body. It flows through the eye and is drained from the eye through a drainage system called the iridocorneal angle. The IOP is kept at a constant, normal pressure by fluid being created while equal amounts are drained from the eye.

Glaucoma occurs when the intraocular pressure is increased. This is usually a result of the fluid not being able to escape through the drainage system. Continued high IOP causes damage to the eye and will result in blindness. Because of this, glaucoma is a veterinary emergency.

Abb. GGT96Z0B
Abb. GGT96Z0B: Schematic illustration of the eye, side view, showing the position of the iridocorneal angle, the anterior chamber and the posterior chamber.

Causes

The causes of glaucoma can be either congenital (present at birth), primary or secondary to another condition. While congenital glaucoma is rare in dogs, signs can be seen in puppies 3-6 months of age.

Primary causes of glaucoma are hereditary and seen most commonly in these breeds: Cocker Spaniel, Basset Hound, Chow Chow, Shar-Pei and Boston Terrier. Primary glaucoma results when the drainage system is abnormally formed.

Secondary glaucoma is caused by another eye condition such as chronic inflammation of the eye or uveitis, a luxated (slipped) lens, tumors or trauma. In these cases, the drainage system is formed normally but is being blocked or plugged.

Cardinal symptom

Painful eye

Symptoms

Glaucoma is very painful and human patients with glaucoma complain of severe headaches or migraines. A dog exhibits ocular pain by rubbing his eyes with his paw, against furniture or carpet. Other signs of pain include squinting, excessive blinking and tearing. In addition to pain, acute cases of glaucoma will show a dilated pupil, cloudiness to the cornea, redness and increased size of the blood vessels in the white portion of the eye. Dogs with chronic glaucoma usually have an enlarged, blind eye due to the damaging high pressure. Dogs with glaucoma are frequently lethargic and anorexic.

Diagnosis

Diagnosis of glaucoma is made by a complete eye examination and measurement of the intraocular pressure of the eye with an instrument called a tonometer.

Treatment

Glaucoma is an emergency and a dog with a severe case of glaucoma will need to be hospitalized. Medications are administered to reduce the pressure in the eye and provide pain relief. Oral, intravenous and topical (applied to the eye) medications may be used. Medications which constrict the pupil aid to reduce pressure by increasing the drainage of fluid from the eye. Other medications are effective in reducing pressure by decreasing the production of aqueous humour. In secondary glaucoma, medications to treat the underlying disease will be necessary.

Surgical treatment of glaucoma is indicated when medical therapy no longer controls the intraocular pressure. If eye is still visual, laser or cryosurgery can be performed by a veterinary ophthalmologist to reduce the production of aqueous humour. Another surgical technique involves using implants and tubing to help move fluid out of the eye.

Permanent treatment of glaucoma is recommended for blind and/or painful eyes. An intraocular prosthesis can be inserted. In this procedure, the internal contents of the eye are removed and replaced with a silicone ball. Another technique involves enucleation or complete removal of the eye. While this may seem like a horrid surgery by human standards, this procedure is actually a very humane and simple way to restore a pain free life to your dog. And lastly, the ciliary body can be completely destroyed by injecting an irritating medication into the eye. There are pros and cons to these permanent treatments of glaucoma which should be discussed with your veterinarian.

If your dog has been diagnosed with glaucoma, it is important to administer all medications as recommended by your veterinarian. Frequent recheck examinations will be needed.

Prognosis

Glaucoma can be difficult to treat in dogs. Many dogs will need to be on life-long medications which can be both frustrating and expensive. While glaucoma usually begins in one eye, it can affect both eyes and lead to complete blindness. However, if acute glaucoma is diagnosed and treated promptly, vision can be saved.

Tips

If your dogs shows any signs of glaucoma, call your veterinarian immediately!

Update version: 4/24/2014, © Copyright by www.enpevet.de
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