Do Dogs Have Two Eyelids? Anatomy, Third Eyelid Health & Eye Care Tips

The Quick Answer: Do Dogs Have Two Eyelids?

Dogs actually have three eyelids, not two. The upper and lower eyelids function much like ours — blinking to spread tears and protect the eye from debris. But dogs also possess a third eyelid called the nictitating membrane, a thin, triangular fold of tissue tucked in the inner corner of each eye. This membrane sweeps horizontally across the cornea to provide additional moisture, protection, and immune defense.

If you've noticed a pink or reddish tissue appearing in the corner of your dog's eye, you're likely seeing this third eyelid. In most cases, brief visibility is normal — it may protrude slightly when your dog is sleepy, relaxed, or just waking up. However, persistent exposure or swelling warrants veterinary attention.

Understanding Canine Eyelid Anatomy

The canine eye is protected by a sophisticated three-lid system that goes beyond what humans have. Here's how each component works:

The third eyelid's lacrimal gland is particularly important — according to the Merck Veterinary Manual, it produces a significant portion of the eye's aqueous tear film. Removing this gland surgically (an outdated practice) can lead to keratoconjunctivitis sicca (dry eye), a chronic condition requiring lifelong medication.

Why Does the Third Eyelid Move?

Unlike the upper and lower lids, the third eyelid doesn't have voluntary muscle control in most dogs. It moves passively through a combination of:

• Retraction of the eyeball: When the retractor bulbi muscle pulls the eye slightly backward, the third eyelid is pushed forward passively.
• Sympathetic nervous system tone: When your dog is alert, sympathetic tone keeps the membrane retracted. During sleep or deep relaxation, this tone decreases and the membrane may drift across the eye.
• Active smooth muscle contraction: Some breeds have smooth muscle fibers within the membrane that allow limited active movement.

Common Third Eyelid Problems in Dogs

While the third eyelid is a normal structure, several conditions can affect it. Recognizing these early can save your dog discomfort and you an expensive emergency visit.

Cherry Eye (Prolapsed Gland of the Third Eyelid)

This is the most common third eyelid disorder, particularly in brachycephalic breeds and dogs under 2 years old. The connective tissue holding the lacrimal gland weakens, causing it to prolapse and appear as a red, fleshy mass in the inner corner of the eye.

Breeds most commonly affected: English Bulldogs, Beagles, Boston Terriers, Cocker Spaniels, Shar-Peis, and Bloodhounds. The American Kennel Club notes that cherry eye can occur in one or both eyes and typically requires surgical correction where the gland is repositioned (never removed).

Treatment cost range: $300–$800 per eye for surgical correction at a general practice; $800–$2,500+ at a veterinary ophthalmology specialist.

Cartilage Eversion ("Scrolled" Third Eyelid)

The T-shaped cartilage within the third eyelid bends outward, causing the membrane to flip and expose its inner surface. This is most common in giant breeds like Great Danes, Saint Bernards, and Newfoundlands. Surgical trimming of the deformed cartilage section usually resolves the issue.

Third Eyelid Protrusion (Haws)

Bilateral protrusion of both third eyelids simultaneously often signals an underlying systemic issue rather than a local eye problem. Potential causes include:

• Gastrointestinal upset or parasitic infection
• Dehydration or significant weight loss
• Neurological conditions (Horner's syndrome, dysautonomia)
• Systemic illness causing enophthalmos (sunken eyes)

Third Eyelid Tumors

Though uncommon, adenocarcinomas and other neoplasms can develop in the third eyelid gland, typically in older dogs (8+ years). These present as firm, irregular masses and may require complete excision of the third eyelid — which then necessitates lifelong dry eye management with medications like cyclosporine or tacrolimus.

When to Call the Vet About Your Dog's Third Eyelid

Breed-Specific Eyelid Concerns

Your dog's skull shape significantly influences their eyelid health risks. Understanding your breed's predispositions helps you monitor proactively.

Daily Eye Care Routine for Dogs

Keeping your dog's eyes healthy involves simple daily habits. Here's a practical maintenance protocol:

1. Visual inspection (daily): In good lighting, gently pull down the lower lid and look at the conjunctiva (should be pink, not bright red or pale). Check that the third eyelid is not protruding. Look for discharge, cloudiness, or squinting.
2. Gentle cleaning (as needed): Use a sterile, vet-approved eye wash or plain sterile saline (not contact lens solution) on a soft gauze pad. Wipe from the inner corner outward. Use a fresh pad for each eye to avoid cross-contamination.
3. Hair trimming (every 2–4 weeks): Keep hair around the eyes trimmed short to prevent mechanical irritation. Use blunt-tipped grooming scissors — never sharp scissors near the eye.
4. Tear stain management (breed-dependent): For breeds prone to porphyrin staining (Maltese, Bichons, Shih Tzus), wipe the area daily with a damp cloth. Commercial tear stain removers containing boric acid can help, but avoid getting any product in the eye itself.

Products to avoid: Human eye drops (Visine, Clear Eyes), hydrogen peroxide near eyes, apple cider vinegar solutions, or any product containing steroids without veterinary prescription. Steroid-containing drops can cause corneal ulcer perforation if an ulcer is already present.

When Third Eyelid Visibility Is Normal vs. Concerning

Frequently Asked Questions About Dog Eyelids

Can dogs close their third eyelid voluntarily?

No. Unlike the upper and lower eyelids, which dogs control through the orbicularis oculi muscle, the third eyelid moves primarily through passive mechanisms — retraction of the eyeball into the orbit and changes in sympathetic nervous system tone. Some species (cats, for example) have more active control, but in dogs the movement is largely involuntary.

Why does my dog's third eyelid show when they're sick?

Several mechanisms explain this. Dehydration and weight loss reduce the fat pad behind the eye, causing the globe to sink slightly (enophthalmos), which pushes the third eyelid forward. Additionally, systemic illness can alter autonomic nervous system balance, reducing the sympathetic tone that normally keeps the membrane retracted. If both third eyelids are protruding, it often indicates a body-wide issue rather than a local eye problem.

Should I let the vet remove my dog's prolapsed third eyelid gland?

Modern veterinary ophthalmology strongly recommends repositioning (gland-preserving surgery) rather than removal. The gland of the third eyelid produces an estimated 30–50% of the aqueous tear film. Removal significantly increases the risk of keratoconjunctivitis sicca (dry eye), which requires lifelong daily medication and can lead to corneal scarring and vision loss. The American Veterinary Medical Association supports referral to a veterinary ophthalmologist for gland-preserving procedures when available.

Do all dog breeds have a visible third eyelid?

All dogs have a third eyelid — it's a universal anatomical feature. However, visibility varies. Breeds with prominent eyes and shallow orbits (brachycephalic breeds) tend to show the third eyelid more frequently. Some breeds also have pigmented (dark) third eyelids that are less noticeable when they briefly cross the eye, while others have pale pink membranes that are more conspicuous.

How much does a veterinary eye exam cost?

A general practice eye examination typically costs $50–$150 as part of a standard office visit ($65–$120 in most US markets in 2026). If your vet recommends referral to a veterinary ophthalmologist, expect a specialist consultation fee of $150–$300, plus diagnostic tests: Schirmer tear test ($25–$50), fluorescein staining ($20–$40), tonometry for glaucoma screening ($30–$60), and potentially an ocular ultrasound ($200–$400).

Can I use human artificial tears on my dog's eyes?

Plain, preservative-free artificial tears (such as those containing carboxymethylcellulose or hydroxypropyl guar without added medications) can be used as a temporary lubricant while awaiting a vet appointment. However, avoid any product containing vasoconstrictors (tetrahydrozoline, naphazoline), steroids, or antibiotics unless prescribed by your veterinarian. Always consult your veterinarian before applying any product to your dog's eyes.