Understanding the Causes of a Visible Third Eyelid in Cats
The third eyelid, or nictitating membrane, is a protective tissue in a cat's eye. Normally, it is not visible in healthy cats, appearing only slightly at the eye’s inner corner during sleep or moments of sedation. However, when it becomes prominently visible, it may signal underlying health issues.
What is the Third Eyelid?
The third eyelid performs several essential roles:
- Protects the eye from injury
- Produces tear film to keep the eye lubricated
- Shields the eye from foreign objects and infections
Its movement is involuntary and commonly occurs when the eyeball retracts, such as during sleep or when a cat is sick or startled.
Can Stress Make the Third Eyelid Show?
Yes, stress can be an indirect cause of third eyelid visibility. Stress-related gastrointestinal disturbances can trigger Haws syndrome, a condition where both third eyelids become visible despite no primary eye problems. It often resolves on its own but should still prompt a vet visit.
Common Causes of Third Eyelid Elevation
- Sleepiness or recovery from anesthesia
- Eye injuries or irritation such as corneal ulcers or conjunctivitis
- Viral, bacterial, or fungal infections
- Systemic illnesses like fever or dehydration
- Neurological disorders including Horner’s syndrome
- Gastrointestinal upset (as seen in Haws syndrome)
- Allergic or chemical irritants
- Cherry eye—a gland prolapse requiring surgical correction
Associated Clinical Signs
When the third eyelid is visible due to health problems, additional signs may include:
- Tearing (epiphora)
- Discharge in various colors
- Redness or swelling of the eye
- Squinting or pawing at the eye
- Sunken or bulging appearance of the eyeball
When to See a Vet
If your cat’s third eyelid remains visible for an extended period or occurs alongside other concerning signs, consult your veterinarian. Don’t attempt to medicate the eye at home without professional guidance.
Diagnostic Methods
- Ophthalmic exam for injury or inflammation
- Fluorescein staining to detect ulcers
- Tear production tests
- Phenylephrine challenge to diagnose Haws syndrome
- Blood and urine tests for systemic causes
- Imaging if neurological issues are suspected
Treatment Options
- Temporary cases: Often resolve on their own, especially if due to sleep or sedation
- Eye injuries/infections: Treated with topical or oral antibiotics, antivirals, or anti-inflammatory drugs
- Conjunctivitis: Requires targeted treatments based on infectious or non-infectious causes
- Cherry eye: Requires surgical repositioning of the gland
- Neurological or systemic disorders: Managed through appropriate veterinary therapies
Conjunctivitis and the Third Eyelid
Conjunctivitis in cats is often caused by infections such as feline herpesvirus, calicivirus, or Chlamydophila felis. It can lead to third eyelid exposure, eye discharge, and squinting. Diagnosis and treatment depend on the underlying cause, involving antivirals, antibiotics, and supportive care as needed.
Home Care and Prevention
- Clean the eye area gently using moistened cotton
- Avoid human eye medications
- Keep nails trimmed to prevent accidental eye injury
- Maintain a clean environment to reduce infection risk
- Supervise multi-cat interactions
- Keep cats indoors to limit exposure to trauma or infectious agents
- Quarantine new pets before introducing to household
Conclusion
While stress itself doesn't directly move the third eyelid, stress-related disorders such as gastrointestinal disturbances can indeed cause its elevation. Stay vigilant and seek prompt veterinary care if changes in your cat’s eye appearance persist. Early intervention can prevent complications, including vision loss.
