Glaucoma in Cats

Glaucoma in Cats

By: Dr. Jennifer Welser

Section: Veterinary Care In-depth

Veterinary care includes both diagnostic tests and subsequent treatment recommendations.

Diagnosis In-depth

  • A complete medical history and physical examination is often obtained by your veterinarian. Certain medical tests are needed to search for an underlying disease when the glaucoma is discovered to be secondary.

  • A complete ophthalmic examination is indicated to confirm the presence of glaucoma and to help determine if other eye diseases have led to the glaucoma. A comprehensive examination involves measurement of eye pressure (tonometry), staining of the cornea with fluorescein to detect ulcers, close scrutiny of the front of the eye for signs of inflammation or dislocation of the lens, and examination of the back of the eye to detect retinal damage.
    Your veterinarian may refer your cat to a veterinary ophthalmologist because a variety of specialized instruments may be needed to complete the evaluation, including a tonometer, a slit lamp biomicroscope, and an instrument to examine the retina.

    The eye examination may answer some of the following important questions. Answering these questions helps to determine the cause of the glaucoma and the prognosis:

  • What is the actual pressure within the eye?
  • Is the pupil dilated (completely open)?
  • Where is the lens?
  • How much inflammation is inside of the eye?
  • Are there any indications of a tumor or of trauma?
  • Do the retina and optic nerve appear healthy?
  • Is the cornea too cloudy to examine the interior of the eye?
  • Is there any evidence within the eye that a systemic disease may be present in the cat?

    Other tests may include:

  • Gonioscopy involves using a special lens placed on your pet's eye so that the drainage angle can be viewed. Gonioscopy can also be used to determine if a tumor is invading the drainage area. Depending on the temperament of your pet, this test is generally done with just topical anesthetic drops.

  • If the glaucoma is secondary to inflammation within the eye, then a complete laboratory work-up is often undertaken to determine a cause. Tests for FeLV, FIV, FIP and toxoplasmosis are submitted, as well as a complete blood count and biochemistry profile.

  • If a tumor is found within the eye, then a complete blood count, biochemistry profile and X-rays of the chest are performed to try and determine if the tumor has spread to other areas of the body.

    Treatment In-depth

    Treatment for glaucoma can be broken down into medical and surgical care. Depending on the cause of the glaucoma, different options are available.

    Medical Options

  • Acute glaucoma is uncommon in the cat. Glaucoma is much more likely to develop slowly in the cat. However, if acute glaucoma is encountered, then several medications are available to attempt rapid decrease of the pressure within the eye. These include injectable, oral and topical medications.

  • Topical products that are commonly used in cats to decrease the production of fluid in the eye include beta-blocking agents (especially timolol or levobunolol) and carbonic anhydrase inhibitors (especially dorzolamide). These two classes of drugs can also be used together (Trusopt = timolol and dorzolamide).

  • Other topical products that are used less often in cats include phospholine iodide, pilocarpine, and latanoprost. These products are irritating and may worsen inflammation within the eye.

  • Oral and topical anti-inflammatory drugs are used to treat any underlying uveitis in the eye: prednisone, triamcinolone, and dexamethasone (oral drugs) may be used when all infectious causes of uveitis have been ruled out. Topical steroids include prednisolone acetate, prednisolone phosphate, and dexamethasone. Oral nonsteroidal anti-inflammatory drugs, such as baby aspirin may be used if oral steroids cannot be given. Never give acetaminophen (Tylenol) to cats, as it is very toxic to them The topical nonsteroidal anti-inflammatory drugs are also avoided when glaucoma is present because they may aggravate the elevated pressure within the eye.

    Surgical Options

  • Laser or cryocycloablation – These procedures use a laser or freezing probe to kill the area in the eye that produces aqueous humor. These techniques are used mainly to treat primary glaucoma, which is very rare in the cat.

  • Gonioimplant or goniovalve insertion – This surgery involves placing a small tube in the eye to by-pass the abnormal drain in the eye, and to allow fluid to drain into the tissues around the eye. It is also used for treating primary glaucoma.

  • Enucleation - Enucleation is removal of the eye with permanent closure of the eyelids. This surgery is undertaken if the eye is blind or if a tumor is present inside of the eye.

  • Surgical therapy for lens luxation involves opening the eye and removing the dislocated lens manually, particularly if there is potential for vision and the eye is not terribly inflamed or infected.

     
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