Squinting (Blepharospasm) in Dogs

Key Takeaways

Squinting (blepharospasm) occurs when the eyelids are lowered so that there is only a small space for the eye to look out of.

• Squinting is considered a symptom in dogs if it continues for a prolonged period and is not related to protecting the eyes from bright light

• Squinting is a symptom of several associated conditions related to damage to the eyeball, congenital malformation of the structures of the eye, and infection or inflammation

• Although most associated conditions are not typically life-threatening, some result in blindness if left untreated

• Diagnostic tools include eye examination, usually under sedation

• Treatment depends on the underlying cause, including topical or systemic medications, and in some cases surgery

A Closer Look: What is Squinting in Dogs?

A dog who is squinting is usually experiencing pain in one or both of its eyes. The conditions associated with squinting are not typically life-threatening, however some cause blindness if left untreated. Prompt veterinary attention is required for dogs who are squinting for a prolonged period, especially if they are not in bright light.

Possible Causes

Squinting is typically related to damage to the eyeball, congenital malformation of the structures of the eye, or infection or inflammation. Potential conditions include:

• Injuries

• Foreign bodies

• Eyelid deformities, such as entropion

• Bacterial infections

• Fungal infections

• Corneal ulcers 

• Keratoconjunctivitis sicca

• Uveitis

• Glaucoma

• Cherry eye

• Blepharitis (eyelid inflammation)

Risk Factors

The severity of squinting depends on several factors.

Some underlying conditions, such as trauma, foreign bodies, corneal ulcers, and some types of infections, affect only one eye. Other conditions, such as keratoconjunctivitis sicca, glaucoma, and calicivirus, affect both eyes. 

In some cases, such as with infections, glaucoma, and uveitis, onset of squinting is gradual. In other cases, such as injuries or foreign bodies, the onset is sudden. 

Some underlying conditions, such as most infections and foreign bodies, run their course quickly with treatment. Others, such as cataracts and glaucoma, worsen over time. Some, such as keratoconjunctivitis sicca and corneal ulcers, become chronic under certain conditions. 

At their most severe, some of the causes of squinting cause blindness.

Certain eye conditions are more likely in breeds that have shortened snouts, such as bulldogs and brachycephalic breeds. 

Older dogs, young puppies, and dogs with underlying health conditions, especially autoimmune diseases, are more at risk of some eye diseases associated with squinting.

Testing and Diagnosis

Diagnostic tools to identify the underlying cause leading to squinting include a full ophthalmic (eye) exam including:

• Tear production measurement

• Ocular pressure measurement

• Fluorescein eye stain, to detect foreign bodies or damage to the surface of the eyeball

Other possible diagnostic tools include:

• Physical examination

• Bloodwork

• Diagnostic imaging, such as X-ray or ultrasound

• Allergy testing

• Biopsy

• Cultures

In some cases, the dog must be sedated to perform these tests.

Treatment depends on the diagnosis. Possible treatments include:

• Wound care • Ocular lubricants • Surgery

• Anti-inflammatory medications • Antibiotics

• Glaucoma medications • Cryosurgery

Similar symptoms

Squinting is sometimes mistaken for the normal function of the eyelid as protection against bright lights. It is also possible to mistake squinting for:

• Enophthalmos (where the eyeball sits back further in the eye socket than usual)

• Elevated third eyelid

Associated Symptoms

Symptoms that are commonly noted alongside squinting include:

• Redness of the eye(s)

• Discharge from the eyes

• Swelling

• Itching

• Watery eye(s)

• Crusty skin around the eye(s)

• Small pimples on the skin around the eye(s)

• Loss of hair or pigmentation around the eye(s)

• Loss of vision