Glaucoma in Cats: Symptoms, Diagnosis, and How To Help Your Cat

Glaucoma in cats is a painful eye condition caused by increased pressure inside the eye. Without prompt veterinary treatment, it can permanently damage the optic nerve and lead to irreversible vision loss or blindness. 

While primary glaucoma is rare in cats, secondary glaucoma—often caused by another eye disease, such as uveitis—is more common. Recognizing the early signs and getting your cat evaluated as soon as possible can help preserve vision, relieve pain, and improve long-term outcomes. 

What Is Glaucoma in Cats?

Glaucoma in cats occurs when there’s increased pressure inside a feline’s eye. When the pressure builds up inside your cat’s eye, it causes pain and migraine-like headaches. 

If the pressure builds up too high inside the eye, it can lead to blindness. 

There’s always fluid inside the eye. This clear fluid helps maintain the shape of the eye, deliver nutrients to the structures inside the eye, and remove any wastes within the eye itself. Because the fluid is clear, it also refracts light, aiding in normal vision. 

When there’s a problem with the fluid balance inside the eye, that’s what leads to increased pressure and glaucoma. 

Types of Glaucoma in Cats 

Let’s look at the two types of glaucoma in cats: 

1. 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. 

2. 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

Common symptoms of glaucoma in cats include: 

• 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 

• Hiding or avoiding interaction or play 

• Sudden aggression 

• Sleeping more than normal 

Since glaucoma in cats 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

Common causes of glaucoma in cats include: 

• Chronic anterior uveitis, 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

Glaucoma in cats is treated with medicated eye drops when it’s caught in the early phases.  

Medications like dorzolamide 2% ophthalmic suspension and timolol 0.5% ophthalmic suspension are often prescribed. 

Sometimes oral pain medications will be prescribed as well, especially while waiting on the topical eye drops to kick in. Your doctor may recommend an oral anti-inflammatory med, like Onsior, or a daily, long-term pain medication, like gabapentin. 

If the pressure inside the eye gets too high and vision is lost, a surgery called an enucleation may be recommended. In this surgery, the veterinarian will remove the eye to restore comfort. 

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 incurable infections like FeLV or FIV, your veterinarian will prescribe daily medication, like gabapentin or prednisolone, to help keep your cat comfortable. 

Regardless of the cause, once blindness has occurred, it won’t improve unless there’s 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. 

Prevention of Glaucoma in Cats

The best way to prevent glaucoma in cats is to address all eye issues with a veterinarian right away. As many of the underlying eye conditions that lead to glaucoma are treatable, managing them sooner before they lead to glaucoma is the best way to minimize your cat’s risk. 

Certain purebred cat breeds are genetically more prone to inherited glaucoma, like Siamese and Burmese cats.  

If your cat is diagnosed with primary glaucoma that they inherited, it’s recommended that you don’t breed them.