Section: Clinical Methods & Interventions

Cat Third Eyelid Showing Sick

Cats have a specialized third eyelid, known technically as the nictitating membrane, that normally remains tucked away in the inner corner of the eye. When this membrane becomes visible and covers part of the eye, it is often a sign that something is wrong. This article explains why a cat's third eyelid may show when they are sick, what conditions are associated with it, and how to respond as a responsible pet owner.

Quick Q&A: Common Questions

Question: Why is my cat's third eyelid showing?

Answer: A visible third eyelid in cats can indicate underlying illness, pain, or neurological issues. Common causes include eye infections, dehydration, weight loss, or systemic conditions like fever or gastrointestinal upset. It warrants a veterinary examination to determine the root cause and appropriate treatment.

Understanding the Third Eyelid in Cats

The nictitating membrane is a thin, pale pink or whitish tissue located at the inner corner of each eye. In healthy cats, it remains mostly hidden, only briefly sweeping across the eye to moisten the cornea and remove debris. When the membrane remains elevated and partially covers the eye, this is called prolapse of the third eyelid or visible nictitans.

This membrane contains a small gland that produces about 30 to 50 percent of the tear film. It also has lymphoid tissue that helps fight surface infections. A visible third eyelid is not a disease itself but rather a clinical sign that something is affecting the cat's overall health or local eye function.

Common Causes of a Visible Third Eyelid

Systemic Illness

When a cat is unwell due to systemic disease, the third eyelids may become prominent bilaterally (in both eyes). This can occur with:

  • Fever from viral or bacterial infections
  • Significant dehydration or electrolyte imbalance
  • Gastrointestinal upset causing nausea or pain
  • Metabolic disorders such as kidney disease or liver dysfunction
  • Severe parasitism causing weight loss and lethargy

In these cases, the third eyelid elevation is thought to result from reduced retraction due to weakness or altered sympathetic nerve tone. The eyes may also appear sunken if the cat has lost orbital fat.

Haws Syndrome

Haws syndrome is a specific, generally benign condition seen in cats, particularly young adults. It involves bilateral, pronounced elevation of both third eyelids without other obvious eye abnormalities. The exact cause is unclear, but it often follows gastrointestinal upset, diarrhea, or parasitic infection. Most cats recover spontaneously within two to six weeks without specific treatment.

Eye Pain and Local Conditions

Unilateral (one eye) third eyelid protrusion suggests a problem confined to that eye or its surrounding structures. Possible causes include:

  • Corneal ulcers or scratches from trauma
  • Foreign bodies such as plant material or dust
  • Conjunctivitis from infections or allergies
  • Glaucoma causing increased intraocular pressure
  • Uveitis or inflammation inside the eye
  • Orbital swelling or abscess behind the eye

Cats with eye pain often squint, have discharge, or paw at the affected eye. The third eyelid acts as a protective shield in these situations.

Neurological Causes

Disruption of the nerves that control eye position can cause third eyelid protrusion. Conditions include Horner syndrome, which involves a drooping eyelid, small pupil, and visible third eyelid on one side. This can result from ear infections, neck trauma, or nerve damage. More rarely, brainstem lesions may affect both eyes.

Weight Loss and Decreased Orbital Fat

Significant weight loss causes loss of fat behind the eyes, allowing the eyeball to sink backward slightly (enophthalmos). This makes the third eyelid appear more prominent even in an otherwise healthy cat. Older cats with chronic illness or poor nutrition may show this sign.

When to Seek Veterinary Care

A visible third eyelid that persists for more than a few hours, especially when accompanied by other signs such as lethargy, decreased appetite, vomiting, diarrhea, or eye discharge, requires veterinary attention. If your cat is squinting, has a cloudy eye, or appears painful around the face, see a veterinarian promptly.

For a cat that seems otherwise well but has a mildly prominent third eyelid, monitor closely for 24 hours. If the condition does not improve or worsens, schedule a veterinary visit.

Home Care and Observation

While waiting for a veterinary appointment, you can help your cat by:

  • Keeping the eyes clean with a soft, damp cloth (wipe from inner to outer corner)
  • Preventing your cat from scratching or rubbing the eyes (a soft Elizabethan collar may help)
  • Ensuring fresh water and palatable food are available to encourage hydration and nutrition
  • Reducing stress with a quiet, comfortable environment
  • Not applying any human eye drops or ointments, as these can be harmful

If your cat has concurrent gastrointestinal signs, offer a bland diet such as boiled chicken and rice, and consult your veterinarian about supportive care.

What to Expect at the Veterinary Clinic

The veterinarian will perform a thorough physical examination, including careful evaluation of both eyes. Key diagnostic steps may include:

  • Fluorescein stain to detect corneal ulcers or scratches
  • Schirmer tear test to measure tear production
  • Tonometry to measure intraocular pressure
  • Examination with an ophthalmoscope to view internal structures
  • Neurological assessment if Horner syndrome or nerve damage is suspected

Based on findings, your veterinarian may recommend bloodwork, fecal testing, or imaging such as X-rays or ultrasound. Treatment depends entirely on the underlying cause and may include antibiotics, anti-inflammatory medications, eye lubricants, or surgery in rare cases.

Prevention Tips

While not all causes are preventable, these measures can help reduce risk:

  • Maintain regular veterinary checkups and vaccinations
  • Provide a balanced diet to support healthy weight and immune function
  • Keep your cat indoors or supervise outdoor access to reduce trauma and infections
  • Practice good parasite control for fleas, ticks, and intestinal worms
  • Observe your cat daily for any changes in behavior, appetite, or appearance

Prompt attention to early signs of illness can prevent progression and improve outcomes.

Prognosis and Recovery

The outlook for a cat with a visible third eyelid depends on the underlying cause. Cats with Haws syndrome or mild systemic illness typically recover fully with supportive care. Conditions like corneal ulcers or infections respond well to appropriate treatment. Even neurological causes like Horner syndrome often resolve over weeks if the underlying trigger is addressed.

Persistent or severe cases may require specialist referral to a veterinary ophthalmologist. With timely diagnosis and proper management, most cats regain normal eye appearance and function.

Always trust your instincts as a pet owner. If something seems off with your cat's eyes or overall health, a veterinary consultation is the safest course of action. Your cat depends on you to recognize subtle signs and seek help when needed.