Glaucoma in cats is a condition in which the pressure inside the eye reaches abnormal levels. This increase in pressure damages the optic nerve and retina of affected cats, creating a multitude of problems.

Feline glaucoma is a progressive disease that develops quickly and has permanent effects. 

But before that, let’s talk about what glaucoma in cats is. We’ll talk about everything you need to know about this eye issue, from the signs right up to how it’s prevented.

What Is Glaucoma in Cats?

To get a good grasp on what glaucoma is and how it works, it's crucial to understand a few terms.

• Aqueous Humor. The aqueous humor is the fluid inside the eyeball that maintains eye pressure. 

• Ciliary Body. The ciliary body is responsible for producing the aqueous humor and aids the lens in focusing on objects. 

• Intraocular Pressure. IOP is the pressure of the fluid inside the eye. 

• Iridocorneal Angle. Otherwise known as the drainage angle, the iridocorneal angle is the primary passageway for the outflow of the aqueous humor. 

Normally, a cat’s eyes constantly produce and drain fluid at a stable rate. This continuous process supplies the eyes with nutrients and maintains the pressure within the eye. When this process gets obstructed, then IOP increases.

What are the Types of Glaucoma in Cats?

Feline glaucoma is generally categorized into two types: primary and secondary glaucoma. 

Primary Glaucoma

This type of glaucoma is considered rare, which often happens due to inherited factors and structural abnormalities of the eye’s structure, particularly the drainage system. 

Some cat breeds develop narrowly formed drainage angles, which slow down the outflow of the aqueous humor. Because of this slow drainage, the pressure accumulates and builds up over time. Cat breeds that carry an increased risk of glaucoma include:

• Persians

• Burmese

• Siamese

Secondary Glaucoma

Secondary glaucoma in cats is a more common type, as it happens because of another underlying health or eye condition. This type often occurs later in life and can progress rapidly depending on the cause. Common factors include:

• Uveitis. Uveitis is the painful inflammation of the middle layer of the eye. This results in swelling and protein buildup, which can result in the obstruction of the eye’s drainage angle.

• Lens Dislocation. The lens, which is held together by zonules, can shift forward or backward, causing problems with the outflow of fluid. 

• Intraocular Tumors. Tumors can block or compress the structures that are involved in the drainage of the aqueous humor. 

• Eye Injuries and Intraocular Bleeding. Injuries to the eye, such as blunt trauma, scratches, or penetration, result in intraocular bleeding, which can negatively impact the drainage system.

• Advanced Cataracts. When the lens becomes clouded from advanced cataracts, this can block the normal flow of fluid within the eye, causing increased intraocular pressure.

What are the Symptoms of Glaucoma in Cats?

Glaucoma in cats often develops silently, with subtle signs that can be easily missed. These include:

• Redness in the Eye. One of the earliest indicators of increased pressure in the eyes is the presence of a red color. The redness can come from the dilation of the blood vessels.

• Frequent Squinting or Blinking. Affected cats may squint or blink more frequently because of the constant discomfort they feel. Some may keep their eyes partially closed.

• Excessive Tearing or Watery Eyes. Another sign is tearing or watery eyes. An increase in tearing can happen as the eye enlarges and tries to flush out the fluid.

• Cloudy or Bluish Cornea. Swelling in the cornea, as caused by fluid buildup, can make the eyes look cloudy or hazy.

• Enlarged Eyeball. In advanced cases, the eyeballs may look enlarged. This occurs due to persistent pressure. 

• Vision Loss or Disorientation. If your cat starts bumping into objects, hesitates to enter unfamiliar spaces, or has trouble navigating, it might be losing its vision.

• Unequal Pupil Size. One pupil may look larger than the other if the affected eye has increased pressure. 

• Behavioral Changes. Cats may appear irritated and withdrawn, while some may tend to hide or have a reduced appetite. 

Is Glaucoma Painful for Cats?

Glaucoma can be very painful for cats, especially as eye pressure increases. In advanced stages, the pain can progress to other areas around the eyes, causing headaches and nausea. While they might feel pain, cats are known to hide their feelings.