Feline Third Eyelid Protrusion (Haw's Syndrome)

Overview

A visible protrusion of the third eyelid (a normally mostly-hidden protective membrane at the inner corner of the eye) across part of the eye's surface — while a single, mild instance can occasionally be an isolated finding, bilateral (both eyes) protrusion in particular is often a sign of an underlying systemic condition, making this a genuinely useful diagnostic clue rather than something to view as a purely cosmetic finding.

Symptoms

• Visible third eyelid protrusion (mild, very common)
• Accompanying systemic symptoms (bilateral cases) (moderate, common)

Causes

Can result from a local eye problem (pain or irritation in that specific eye causing the third eyelid to protrude protectively), or — particularly when both eyes are affected simultaneously — from an underlying systemic condition affecting the nervous system's control of the third eyelid's position, including certain gastrointestinal conditions, general debility/weight loss from various causes, or specific neurological conditions. Third eyelid protrusion (Haw's syndrome) can occur as an isolated, often self-limiting finding sometimes linked to mild gastrointestinal upset, or as a sign of a more specific underlying problem — pain in the eye itself, Horner's syndrome (a nerve dysfunction affecting eye structures), or general illness/dehydration can all cause the third eyelid to become more visible than its normal barely-noticeable position.

Risk Factors

Any condition causing eye pain or irritation for local, single-eye protrusion; for bilateral protrusion, underlying systemic illness (particularly certain gastrointestinal conditions have a recognized, if not entirely understood, association) is the relevant risk consideration.

Transmission

Not applicable — a sign/finding rather than a disease itself, with transmission considerations depending entirely on any underlying cause identified.

Incubation Period

Not applicable.

Disease Stages & Progression

Depends on the underlying cause — local eye irritation-related protrusion typically resolves as that specific problem is treated, while systemic-illness-related bilateral protrusion persists until the underlying condition is identified and addressed.

Early Warning Signs

Visible third eyelid partially covering the eye, in one or both eyes.

Advanced Symptoms

More complete third eyelid coverage, and depending on the underlying cause, other symptoms related to that specific condition (weight loss, digestive symptoms, or neurological signs, for example).

Diagnostic Methods

Careful eye examination to rule out local causes of irritation first; for bilateral protrusion without an obvious local eye problem, investigation for an underlying systemic cause (particularly gastrointestinal, given the recognized association) is warranted. Because protrusion itself is a sign rather than a diagnosis, a full eye exam ruling out ocular pain or disease, alongside a general physical exam and sometimes bloodwork if the cat seems otherwise unwell, helps identify whether this is an isolated, benign finding or a signal of something else needing attention.

Veterinary Examination Process

Eye examination assessing for local irritation or pain, and general physical examination looking for signs of systemic illness, particularly relevant for bilateral presentations.

Recommended Lab Tests

Depends on suspected underlying cause; general bloodwork and possibly fecal testing (given the gastrointestinal association) may be pursued for unexplained bilateral cases.

Diagnostic Imaging

Not primarily diagnostic for the eyelid finding itself, though imaging may be used to investigate a suspected underlying systemic cause.

Blood Test Indicators

Not specific to this finding itself; general bloodwork may be pursued to investigate a suspected underlying systemic cause, particularly for bilateral cases.

Biopsy / Histopathology

Not typically needed for this finding itself.

Differential Diagnoses

Local eye irritation or pain (for single-eye cases), and a range of systemic conditions including gastrointestinal disease for bilateral cases — distinguishing between local and systemic causes guides the appropriate workup.

Home Monitoring Guidance

Noting whether one or both eyes are affected, and any other accompanying symptoms, provides useful information for your vet — persistent or bilateral protrusion warrants veterinary evaluation rather than assuming it will resolve on its own.

Veterinary Treatment Options

Treatment addresses the underlying cause — managing local eye irritation directly, or investigating and treating an underlying systemic condition for bilateral cases. The third eyelid protrusion itself typically resolves once the underlying cause is appropriately addressed. Isolated, otherwise-well cats with mild bilateral third eyelid protrusion are often simply monitored, since this pattern frequently resolves on its own within days to weeks; treatment otherwise targets whatever underlying cause is identified — pain management for an eye problem, treating an underlying GI issue, or addressing dehydration/illness.

Surgery Requirements

Not typically needed for the protrusion itself.

Recovery Timeline

Depends entirely on the underlying cause and how readily it resolves with treatment.

Possible Complications

Persistent underlying systemic illness if the cause isn't identified and addressed; the protrusion itself doesn't typically cause its own complications beyond reflecting whatever underlying issue is present.

Long-Term Management

Depends on the underlying cause — once identified and treated, ongoing management follows whatever that specific condition requires.

Prevention

No specific prevention for the protrusion itself, given how it's a sign of another underlying process rather than a standalone condition to prevent directly.

Vaccination Availability

Not applicable.

Prognosis

Depends entirely on the underlying cause; generally good once that cause is identified and appropriately treated.

References

American College of Veterinary Ophthalmologists (ACVO); American Association of Feline Practitioners (AAFP).

Medications Used

• Treatment specific to any identified underlying cause (local eye treatment, or treatment for an identified systemic condition)

Estimated Treatment Cost by Country

Frequently Asked Questions