Glaucoma in Cats

What Is Glaucoma in Cats?

Glaucoma is a condition where there is an increase in the fluid, called aqueous humor, inside the eye.

Aqueous Humor: Aqueous humor is the fluid that gives eyes their round shape and provides nutrients to the structures inside the eye. There is a balance between enough fluid to support the eye and too much fluid, which can create high pressure inside the eye and damage it due to lack of drainage.

Intraocular Pressure: Increased pressure inside the eye, called intraocular pressure (IOP), can cause irreversible blindness if not treated quickly. Glaucoma is caused by increased IOP due to lack of aqueous humor drainage.

Types of Glaucoma in Cats

There are two types of glaucoma in cats:

Primary Glaucoma

This is caused by an abnormal aqueous humor drainage ability due to an anatomical abnormality. It is a genetic predisposition that is generally seen in dogs and not commonly in cats.

Secondary Glaucoma

This is caused by a secondary disease that creates a physical barrier to aqueous humor drainage. This barrier may be created by white or red blood cells, cancer cells, an eye lens that is out of place (lens luxation), or an overgrowth of tissue covering the drainage angle due to a chronic eye inflammation called anterior uveitis.

Symptoms of Glaucoma in Cats

Cats that develop glaucoma may have

• Sudden blindness
• Red or cloudy eyes
• Excessive tearing or squinting
• Different-sized pupils
• One eye that looks bigger than the other or that bulges out

Glaucoma is painful, and your cat may act different than normal due to pain. This can look like

• Hiding or avoiding interaction or play
• Sudden aggression
• Sleeping more than normal

Since glaucoma is mainly secondary to other diseases, cats may have signs of illness in other parts of their body which may include:

• Change in appetite
• Weight loss
• Vomiting
• Diarrhea

Causes of Glaucoma in Cats

Secondary causes include:

• Chronic anterior uveitis, or inflammation in the front of the eye, caused by infectious diseases like:
  • Feline leukemia virus, also known as FeLV (viral)
  • Feline infectious peritonitis, also known as FIP (viral)
  • Feline immunodeficiency virus, also known as FIV (viral)
  • Toxoplasmosis (parasitic)
  • Cancers like lymphoma or ocular (eye) melanoma
• Lens luxation (dislocation)
• Eye trauma
• Fungal diseases
• Sepsis
• Unknown causes (idiopathic)

How Veterinarians Diagnose Glaucoma in Cats

Your veterinarian can easily diagnose cat glaucoma with an eye test called tonometry, which measures pressure inside the eye, or intraocular pressure (IOP). Normal IOP in cats is 15-25 mmHg. Any IOP above normal is considered glaucoma. Sustained elevations in IOP will cause blindness due to damage to the optic nerve and retina.

Treatment of Glaucoma in Cats

In emergency situations where the pressure inside the eye is very high and blindness may occur, your veterinarian may administer:

• Intravenous (IV) medication, called mannitol, to rapidly decrease eye pressure
• Topical treatment to reduce aqueous humor production. This is usually done using an eyedrop medication called dorzolamide, which is sometimes combined with timolol.

Once intraocular pressure is normalized, your veterinarian may conduct other tests to determine the underlying cause, including bloodwork and additional eye tests.

If no underlying cause for the glaucoma can be found with extensive testing, the intraocular pressure cannot be well controlled and the eye is blind, or the cause is eye cancer, then surgical removal of the eye, called an enucleation, is generally recommended.

Uncontrolled glaucoma is painful, and removing the eye provides significant pain relief for your cat. It is also curative for cases of primary eye cancer and can provide a diagnosis of the underlying cause for glaucoma in cats where one could not otherwise be found.

Cost of Treatment for Glaucoma in Cats

Treatment cost for glaucoma in cats depends on the underlying cause and whether it presents as an emergency that needs emergency treatment as described above.

Cats with glaucoma either need lifelong treatment of glaucoma to maintain eyesight and prevent pain, or they may need surgical removal of the eye, as well as treatment for the underlying cause.

Recovery and Management of Glaucoma in Cats

Due to various underlying medical conditions that can cause glaucoma in cats, the long-term prognosis is difficult to generalize.

In cases of infectious diseases or trauma, if the infection or injury can be cured, then the eye may recover.

In cases caused by cancer, if the cancer is only in the eye, surgery to remove the eye is curative. In cases where the cancer is metastatic (in other parts of the body) or with non-curable infections like FeLV or FIV, your veterinarian will prescribe daily medication.

Regardless of the cause, once blindness has occurred, it will not improve unless there is early intervention with either surgery or medication. Most cats will go on to live relatively normal lives especially in cases where only one eye is removed.