Feline Glaucoma: Symptoms and Treatment

Feline glaucoma, a serious and potentially blinding condition, is characterized by a gradual or sudden increase in intraocular pressure (IOP). Normal IOP in cats ranges from 15 to 25 mmHg. When this pressure elevates, it damages the optic nerve, leading to vision loss and ultimately blindness if left untreated. Understanding the symptoms and available treatments is crucial for ensuring the best possible outcome for your affected cat.

Symptoms of Feline Glaucoma:

The symptoms of glaucoma in cats vary depending on the severity and the speed of onset. Acute glaucoma, characterized by a sudden and dramatic increase in IOP, presents a more urgent and noticeable clinical picture. Cats experiencing an acute episode may exhibit significant pain. This pain can manifest in several ways, including:

Eyelid spasms (blepharospasm): The cat may involuntarily squeeze its eyelids shut due to discomfort.

Excessive tearing (epiphora): Increased tear production is a common response to pain and irritation within the eye.

Vocalization: Severe pain can cause a cat to vocalize, often with meows or yowls indicating distress.

Lethargy and Anorexia: The intense pain associated with acute glaucoma can lead to a significant decrease in activity level and appetite.

These symptoms can progress rapidly. If left untreated, irreversible blindness can occur within 24 to 48 hours of the initial acute episode. Beyond the pain indicators, other noticeable signs of acute glaucoma include:

Corneal edema: The cornea, the clear front part of the eye, may become cloudy or swollen due to the increased intraocular pressure.

Shallow scleral congestion: The sclera, the white part of the eye, may appear red and congested. This is due to the increased blood flow in response to the eye’s distress.

Enlarged pupils: The pupils might appear larger than normal.

Buphthalmos: In severe cases, the eye itself may enlarge, becoming visibly bigger than the other eye.

Chronic glaucoma, on the other hand, develops more gradually. The pain associated with chronic glaucoma is often less severe and may be subtle or intermittent. However, it’s crucial to note that even though the signs may be less dramatic, the underlying damage to the optic nerve continues to progress. Cats with chronic glaucoma might exhibit some or all of the symptoms seen in acute cases, but to a lesser degree. These cats may display subtle changes in behavior, such as squinting or rubbing their eyes, and may not show the overt signs of pain displayed in the acute cases. This insidious nature makes early detection and intervention particularly critical. Regular veterinary checkups are therefore essential, especially in older cats or those with predisposing conditions.

Causes of Feline Glaucoma:

Glaucoma arises from an imbalance between the production and drainage of aqueous humor, the fluid that fills the eye. When the outflow of aqueous humor is impaired, the pressure within the eye builds up, leading to damage of the optic nerve. This impaired drainage can stem from various factors:

Primary Glaucoma: This type of glaucoma is often linked to developmental abnormalities in the eye’s drainage system. Developmental anomalies of the iridocorneal angle are a common cause, resulting in a narrowing or blockage of the outflow pathways. This is often associated with a congenital defect in the trabecular meshwork, a tissue structure responsible for draining the aqueous humor.

Secondary Glaucoma: This form of glaucoma develops as a consequence of other underlying eye diseases. Conditions such as uveitis (inflammation of the uvea), lens luxation (dislocation of the lens), tumors, and trauma can all obstruct aqueous humor outflow, leading to increased IOP and secondary glaucoma.

Treatment of Feline Glaucoma:

The goal of glaucoma treatment is to lower the intraocular pressure (IOP) and prevent further damage to the optic nerve. Treatment strategies vary depending on the severity of the condition and the cat’s overall health. Veterinary ophthalmologists employ several methods, including:

Medical Management: This often involves the use of medications to reduce IOP. These may include topical eye drops, such as prostaglandin analogs, beta-blockers, and carbonic anhydrase inhibitors. These medications work through different mechanisms to either decrease the production of aqueous humor or increase its outflow. In acute cases, intravenous osmotic diuretics might be administered to rapidly lower IOP.

Surgical Intervention: When medical management fails to adequately control IOP or in cases of severe glaucoma, surgery may be necessary. Several surgical procedures are available, aiming to improve the outflow of aqueous humor. These can include laser trabeculoplasty, filtering surgeries, or cyclodestructive procedures.

Enucleation: In some cases, particularly when the eye is severely damaged, blind, and painful despite all other treatment efforts, enucleation (surgical removal of the eye) may be the most humane option. This procedure often involves replacing the removed eye with a silicone implant to maintain the shape of the eye socket. This prevents the development of a sunken appearance and minimizes further complications.

The prognosis for feline glaucoma varies greatly depending on several factors, including the severity of the disease, the speed of diagnosis and initiation of treatment, and the cat’s overall health. Early detection and consistent treatment are essential for maximizing the chances of preserving vision and minimizing pain and suffering. Regular veterinary checkups, particularly for older cats, are crucial for early identification and management of this potentially blinding condition. Owners should immediately seek veterinary attention if they notice any of the symptoms discussed above. Early intervention can significantly improve the outcome for your feline companion.