Cat's Third Eyelid Showing: Causes & What It Means

Quick Answer
  • A briefly visible third eyelid can be normal when a cat is very sleepy, but it should usually retract once your cat is fully awake.
  • If the third eyelid stays up, it can point to eye pain, conjunctivitis, corneal ulcer, uveitis, dehydration, weight loss, or a whole-body illness.
  • One eye affected is more concerning for a local eye problem like injury, ulcer, foreign material, or inflammation.
  • Both eyes affected can happen with systemic illness or Haws syndrome, a condition sometimes linked with gastrointestinal upset in otherwise bright cats.
  • Do not use human eye drops unless your vet specifically tells you to. Some products can worsen ulcers or delay diagnosis.
Estimated cost: $90–$350

Common Causes of Cat's Third Eyelid Showing

Cats have a third eyelid, also called the nictitating membrane, tucked into the inner corner of each eye. You may notice it briefly when your cat is waking up or very relaxed. If it stays visible while your cat is alert, that is more likely to mean something is wrong.

A raised third eyelid often happens because the eye is painful or inflamed. Common causes include conjunctivitis, corneal scratches or ulcers, trauma, foreign material, uveitis, glaucoma, dry eye, and eyelid problems such as entropion. Cornell notes that conjunctivitis can involve swelling and redness of the third eyelid, and VCA lists ulcers, uveitis, glaucoma, and dry eye among conditions that can make the third eyelid more noticeable.

Sometimes the problem is not limited to the eye itself. Cats with dehydration, weight loss, fever, viral illness, parasite-related gastrointestinal upset, or other systemic disease may show both third eyelids. VCA also notes that infectious diseases such as FeLV, FIV, FIP, toxoplasmosis, and fungal disease can be associated with uveitis and visible eye changes.

Another possibility is Haws syndrome, where both third eyelids protrude without obvious eye pain. This is often reported in younger cats and may occur around diarrhea or other digestive upset. Even then, your vet still needs to rule out more serious eye disease first, because a painful ulcer or internal eye inflammation can look similar early on.

When to See the Vet vs. Monitor at Home

See your vet immediately if your cat has a visible third eyelid plus squinting, pawing at the eye, marked redness, thick discharge, cloudiness, a blue or white film, bleeding, unequal pupils, sudden vision changes, or obvious trauma. These signs raise concern for painful conditions like corneal ulcer, uveitis, or glaucoma, and delays can put vision at risk.

You should also book a prompt visit if only one eye is affected, if the third eyelid stays up for more than a few hours while your cat is awake, or if your cat seems lethargic, dehydrated, not eating, losing weight, or having vomiting or diarrhea. A third eyelid showing in both eyes can be a clue that your cat feels unwell overall, not only that the eye is irritated.

It is reasonable to monitor briefly at home only if the third eyelid appears for a moment when your cat is sleepy and then disappears once fully awake, with no redness, discharge, squinting, or behavior change. Take a clear photo in good light. If it happens repeatedly, lasts longer, or your cat seems off in any way, contact your vet.

What Your Vet Will Do

Your vet will start with a full history and physical exam, because a visible third eyelid can come from either an eye problem or a whole-body illness. They will ask whether one eye or both eyes are involved, how long it has been happening, whether there is discharge or squinting, and whether your cat has had upper respiratory signs, diarrhea, appetite changes, weight loss, or recent trauma.

The eye exam often includes checking the eyelids and cornea closely, looking for foreign material, measuring eye pressure, and using fluorescein stain to look for a corneal ulcer. Depending on the case, your vet may also perform tear testing, pupil and nerve checks, and an exam after dilating the pupils. These tests help separate conjunctivitis from more urgent problems like ulceration, glaucoma, or uveitis.

If your vet suspects a broader illness, they may recommend blood work, viral testing such as FeLV or FIV screening, blood pressure measurement, fecal testing if there is diarrhea, or referral to a veterinary ophthalmologist. Treatment depends on the cause. Options may include lubricating drops, pain control, antiviral medication, antibiotic eye medication when indicated, anti-inflammatory treatment, or care aimed at the underlying systemic disease.

Treatment Options

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$90–$180
Best for: Cats that are bright, eating, and stable, especially when both third eyelids are showing without severe pain, cloudiness, or trauma.
  • Office exam with fluorescein stain if available
  • Basic eye assessment to rule out obvious ulcer or trauma
  • Targeted supportive care such as lubricating eye ointment if appropriate
  • Photo monitoring and short recheck plan
  • Focused treatment for mild conjunctivitis or suspected Haws syndrome only after your vet rules out more serious causes
Expected outcome: Often good if the cause is mild conjunctivitis, transient irritation, or Haws syndrome, but only after painful eye disease has been excluded.
Consider: Lower upfront cost, but fewer diagnostics can miss deeper eye disease or systemic illness. A recheck may be needed quickly if signs do not improve.
Most Common

Recommended Standard Treatment

$180–$450
Best for: Most cats with a third eyelid that stays visible while awake, especially if there is redness, discharge, one-eye involvement, or mild whole-body illness.
  • Comprehensive sick visit exam
  • Fluorescein stain and eye pressure testing
  • Tear testing or pupil exam as needed
  • Medication matched to the cause, such as lubricants, pain relief, antiviral therapy, or antibiotic eye medication when indicated
  • Basic lab work or FeLV/FIV testing if your cat seems unwell
Expected outcome: Good to fair in many cases when the cause is identified early. Eye pain and ulcers usually do better with prompt treatment.
Consider: More complete than conservative care, but still may not answer every case if the problem is neurologic, recurrent, or tied to a more complex systemic disease.

Advanced / Critical Care

$500–$2,000
Best for: Cats with severe pain, cloudiness, trauma, suspected glaucoma, deep ulcer, vision loss, neurologic signs, or significant illness beyond the eye.
  • Emergency assessment or same-day urgent care
  • Referral ophthalmology exam, often $185-$520+ for the specialty visit alone
  • Advanced diagnostics such as blood pressure, imaging, infectious disease testing, or sedation for detailed eye exam
  • Intensive treatment for corneal ulcer, severe uveitis, glaucoma, trauma, or systemic disease
  • Hospitalization or surgery if needed
Expected outcome: Varies widely. Some cats recover well with fast treatment, while delayed care can increase the risk of chronic pain or vision loss.
Consider: Highest cost range and more testing, but appropriate when vision, comfort, or overall health may be at immediate risk.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Cat's Third Eyelid Showing

Bring these questions to your vet appointment to get the most out of your visit.

  1. Does this look like a problem in the eye itself, or could it be part of a whole-body illness?
  2. Is the third eyelid showing in one eye or both eyes, and what does that pattern suggest?
  3. Does my cat need fluorescein stain, eye pressure testing, or tear testing today?
  4. Are there signs of a corneal ulcer, uveitis, glaucoma, or conjunctivitis?
  5. Could this be Haws syndrome, and what other causes need to be ruled out first?
  6. What medications are appropriate, and are there any eye drops I should avoid at home?
  7. What changes would mean I should come back urgently or seek emergency care?
  8. What is the expected cost range for today’s exam, testing, and follow-up?

Home Care & Comfort Measures

Do not try to treat a persistently visible third eyelid with leftover pet medication or human eye drops. Steroid-containing eye products can be dangerous if your cat has a corneal ulcer, and even over-the-counter drops may blur the picture your vet needs to see.

Until your appointment, keep your cat indoors and in a calm, dimly lit space if the eye seems painful. Prevent rubbing if you can, trim sharp nails if needed, and gently wipe away discharge from the eyelids with clean gauze or a soft cloth dampened with warm water. Do not press on the eye.

Watch for appetite changes, vomiting, diarrhea, hiding, low energy, or signs of dehydration, because these clues can help your vet decide whether the problem is local to the eye or part of a larger illness. Take photos once or twice a day in the same lighting. That record can be very helpful if the third eyelid comes and goes.

If your cat stops eating, seems painful, develops a cloudy eye, or the third eyelid becomes more prominent instead of less, move from home monitoring to a veterinary visit right away.

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