Why do dogs have Googles?

Dogs have evolved over thousands of years to become humanity’s best friends. As our closest animal companions, dogs have developed traits and abilities that allow them to thrive in human society. One notable canine feature is their expressive eyes, which allow dogs to communicate non-verbally with people. However, the structure and function of dogs’ eyes also result in some key differences from human eyes. Understanding why dogs have “googles” provides insight into canine vision, health, and communication.

What are dog googles?

The term “googles” refers to the visible white areas on the inner and outer corners of dogs’ eyes. These white areas are formed by the nictitans membrane, often called the third eyelid or haw. All animals have nictitating membranes, but they are usually not visible. In dogs, horses, and certain other animals, the nictitans is large and includes a cartilage plate that gives it rigidity. When a dog’s third eyelid is visible in the corner of the eye, it looks like they are wearing swim goggles, hence the nickname “dog googles.”

Functions of the third eyelid

The nictitans membrane serves multiple functions for dogs and animals that have it:

  • Protecting the eye: The third eyelid can sweep across the surface of the eye to remove debris and distribute tears/lubrication.
  • Additional lubrication: The third eyelid contains tear glands that provide extra mucus and watery secretions to lubricate the eye.
  • Clear vision: The third eyelid helps spread the tear film across the eye for clear vision.
  • Extra protection: The third eyelid provides additional protection if something strikes or scratches the eye.

In summary, the third eyelid gives dogs an extra safeguard for their valuable eyesight. It enables rapid eye protection and additional lubrication to remove irritants and keep the eyes moist.

When are dog googles visible?

Under normal circumstances, the third eyelid is not visible in dogs. It rests in the inner corner of the eye, hidden behind the lower lid. However, the third eyelid can become exposed and visible if it is pushed out from the eye or the lower lid is pulled down. Reasons this may occur include:

  • Irritation: If something irritates the eye, such as dust, dirt, or an allergen, the third eyelid may be activated to swipe across the surface of the eye and remove the irritant.
  • Illness: Diseases affecting the eye or tear gland system may cause dry eye conditions that make the third eyelid more visible as it tries to lubricate the eye.
  • Injury: Trauma, scratches, or wounds to the eyeball, eyelid, or surrounding tissues can result in swelling or abnormal positioning that exposes the third eyelid.
  • Anatomical factors: Some dogs naturally have more prominent third eyelids that are visible more often.
  • Aging: A dog’s eyes may change as it gets older, sometimes leading to weakening of ligaments and easier third eyelid exposure.

If your dog’s third eyelid starts showing more, it’s a sign something is irritating the eye or there is an underlying health issue that should be addressed. Seek veterinary advice if the googles appear more prominent or frequently.

Why do dogs have prominent third eyelids?

Dogs’ third eyelids are larger and contain more cartilage than human third eyelids. This gives them enhanced eye protection compared to people. There are several evolutionary factors that contribute to dogs’ prominent googles:

Chasing prey

As hunters who chased quick-moving prey, dogs’ ancestors needed effective eye defense mechanisms. The sturdy third eyelid protected their eyes from injuries like branches or claws while running through vegetation.

Close-range interaction

Early dogs worked closely with humans, being within range of tools, debris, and other hazards. The protective third eyelid shielded dogs’ eyes during interactions at close quarters.

Keen eyesight dependence

As pack hunters reliant on vision, dogs could not afford to have their eyes disabled easily. The durable third eyelid ensured eyes stayed lubricated and unharmed.

Low environmental sanitation

Before modern sanitation, dogs encountered more irritants like fecal matter, dirt, and garbage. The self-cleaning third eyelid helped remove abrasive particles.

Limited medical care

Until recent history, veterinary medicine was limited. Dogs’ eyes needed built-in defences as alternative treatments were not available.

Gradual adaptation

Over generations, natural and artificial selection gave dogs enhanced third eyelids. Dogs with the trait thrived and passed it on.

In summary, genetic and environmental pressures made the third eyelid an adaptive advantage for dogs. It continues to protect dogs’ eyes despite modern veterinary care.

Are dog googles a health problem?

In most cases, visible dog googles are completely normal and no cause for alarm. As discussed previously, they may become exposed during irritation, illness, or injury. However, persistent, prominent googles or changes in frequency could indicate an issue such as:

Dry eye

Insufficient tear production causes irritated dry eyes. The third eyelid may be more exposed as it tries to spread tears.

Conformational defects

Eyelid or tear duct deformities can displace or expose the third eyelid. This is more common in brachycephalic (short-nosed) breeds.

Cherry eye

Prolapse of the third eyelid’s tear gland appears as a red mass in the corner of the eye.

Facial nerve paralysis

Damage to the facial nerve impairs eyelid motion, allowing the third eyelid to slip into view.

Eye injury or disease

Trauma, corneal ulcers, glaucoma, and eye growths can all impact eye anatomy and expose the third eyelid.

If your dog develops persistent googles, take note of any other symptoms and talk to your veterinarian to diagnose and address the underlying issue.

Do dog googles impact vision?

The third eyelid is a normal eye component in dogs, so visible googles themselves do not affect vision or cause blindness. However, conditions that lead to excessive third eyelid exposure can impair sight:

  • Dry eye: Insufficient tear film causes irritated dry corneas and blurred vision.
  • Injuries: Lacerations, scratches, or trauma to the eyeball can damage visual function.
  • Corneal ulcers: Ulcers on the transparent cornea obstruct light entering the eye.
  • Cataracts: Lens protein clumping reduces visual acuity and causes blindness.
  • Glaucoma: Excess eye pressure damages the optic nerve and retinal cells.

These conditions may secondarily expose the third eyelid as the eye tries to respond. Vision impairment results from the underlying disease rather than the presence of googles themselves. Prompt diagnosis and treatment of eye conditions is key to restoring normal comfort and vision for dogs.

How are excessive dog googles treated?

Treatment for persistent or problematic dog googles depends on the underlying cause. Some options include:


Eye drops, ointments, pills, or injections to reduce inflammation, treat infections, control pressure, or restore tear function.


Procedures to reduce, remove, or reposition extra eyelid tissue, correct structural defects, or improve drainage.

Topical therapy

Eye solutions to lubricate, flush out irritants, and protect the ocular surface.

Environmental management

Minimizing exposure to eye irritants through grooming, air filters, avoiding certain environments, etc.

Supportive care

Cold compresses, massage, antibiotics, and tranquilizers to make the patient comfortable during recovery.

With appropriate treatment guided by a veterinary ophthalmologist, most conditions causing excessive dog googles can be effectively managed for good vision and comfort.

Key takeaways on dog googles

In review, the key points to understand about dog googles include:

  • Googles are the visible third eyelid tissue in the corner of dogs’ eyes.
  • The third eyelid protects, lubricates, and clears debris from the eye.
  • Dogs have large, prominent third eyelids as an evolutionary adaptation.
  • Common causes of visible googles include irritation, illness, and injury.
  • Persistent googles may indicate an underlying health issue needing veterinary attention.
  • Visible googles alone don’t impair vision, but related eye diseases can.
  • Treatment depends on diagnosing and managing the underlying condition.

While googles are normal for dogs, changes in frequency or severity warrant inspection. With prompt care, excellent canine vision and comfort can be maintained.

Frequently asked questions about dog googles

What is cherry eye?

Cherry eye refers to prolapse and swelling of the third eyelid’s tear gland, causing a red, cherry-like mass to bulge from the inner corner of the dog’s eye.

When do puppies open their eyes?

Puppies’ eyes typically open between 10-14 days after birth. Their vision will be blurry at first but improve steadily as they grow.

Do dogs see color?

Dogs see less color than humans since they only have two color-detecting cone cells. Their vision is dichromatic, allowing them to see blue, yellow, and gray tones.

Why do dogs’ eyes glow green or red?

When light enters dogs’ eyes, it reflects off a structure behind the retina called the tapetum lucidum. This alters the color, causing eyeshine that appears greenish-yellow or red.

Can dogs be blind?

Yes, dogs can experience partial or complete blindness due to birth defects, injuries, cataracts, glaucoma, retinal atrophy, and other eye disorders.

Do dog eyes keep growing?

A dog’s eyes stop growing proportionally to their skull by 16 weeks of age. Their eyes don’t continue enlarging indefinitely through adulthood like some believe.

Why do dogs’ eyes water?

Excessive tearing or eye drainage can be caused by irritation, infection, blockage of drainage ducts, foreign objects, corneal ulcers, ingrown eyelashes, and facial nerve paralysis.

Why do dogs close their eyes when you pet them?

Dogs may gently close their eyes while being pet as a sign of pleasure and contentment. It helps them focus on the enjoyable sensation of petting and touch.

Do dogs need eye drops?

Dogs may require prescription eye drops to treat conditions like dry eye, allergies, ulcers, glaucoma, and infections. Over-the-counter eye drops can also provide relief for minor irritation.

Can dogs get eye infections?

Yes, bacterial, viral, and fungal infections can cause conjunctivitis, inflammation, and discharge in dogs’ eyes. Prompt treatment with medication is important.

Why do older dogs’ eyes turn blue?

A bluish, cloudy haze on older dogs’ eyes results from nuclear sclerosis, a condition causing the lens to harden and take on a blue tint as cells accumulate.


The prominent “googles” on dogs’ eyes provide special benefits—and quirks! The third eyelid gives dogs extra protection for their valuable vision. Changes in this structure can indicate eye trouble and prompt veterinary care. While googles themselves don’t impact sight, underlying conditions linked with them can. With a strong grasp of canine eye anatomy and health, dog owners can partner with their veterinarian to keep their pup’s peepers in peak condition!

Leave a Comment