Strabismus describes an uncommon disorder in dogs in which one or both eyes are not correctly aligned, giving the appearance of crossed eyes or eyes not pointing in the same direction together.
• Strabismus is the result of an underlying disease mechanism affecting the muscles or nerves that control eye movement
• Some causes of strabismus are hereditary and present at birth
• Other causes include injury, inflammation, infection, or neurological disorders
• Additional associated symptoms include difficulty judging distance, bumping into objects, squinting, redness, and pain of the affected eye
• Investigation of strabismus involves in depth physical, ophthalmic, and neurological examinations, blood work, and diagnostic imaging
• Treatment options depend on the severity and underlying disease process
• Some cases are mild and do not require treatment, whereas moderate to severe cases require treatment including topical or oral medication and eye strengthening exercises
Strabismus is an uncommon presentation in dogs and is usually not painful or life threatening in itself. However, it is sometimes a symptom of a more serious underlying disease process.
Strabismus is seen most commonly as a mild, hereditary condition in breeds such as Pugs and Boston Terriers. Hereditary strabismus is usually well tolerated. It is sometimes possible to improve or correct hereditary strabismus with eye strengthening exercises.
Acquired strabismus is sometimes mild and resolves spontaneously such as cases of vestibular disease, but can be linked to severe underlying disease such as inner ear disease or tumors of the eye and brain.
New cases of strabismus warrant prompt veterinary attention.
Many cases of strabismus are not treatable and result in reduced depth perception. Management focuses on changes to the environment such as removal of sharp objects or covering sharp corners to reduce risk of injury.
In general, strabismus indicates abnormal function of the eyes and/or nerves controlling eye movement. Underlying causes of strabismus include:
• Congenital (born with the condition)
• Idiopathic (cause cannot be determined)
• Vestibular disease
• Head or eye injury
• Infectious causes may be related to toxicity such as tick paralysis or botulism
• Middle and inner ear inflammation
• Tumors of the eye or brain
The severity of strabismus varies depending on the underlying cause.
Hereditary conditions in Pugs and Boston Terriers are often mild and not associated with significant vision problems.
Strabismus seen as part of vestibular disease is usually mild to moderate and sometimes resolves spontaneously.
Severe strabismus resulting from injury or a tumor are sometimes progressive and may result in significant vision complications.
Investigation of strabismus involves:
• Physical examination
• Ophthalmic examination
• Neurological examination
• Blood work
• Diagnostic imaging
In mild cases, no treatment, or only supportive treatment may be necessary. Other treatment options include:
• Treatment of the underlying disease. Examples include steroids, anti inflammatory medications, antibiotics/antifungal medications, chemotherapy, and surgery
• Eye exercises strengthen the muscles around the eyes and improve alignment
Other conditions affecting the symmetry of the eyes can appear similar to strabismus. Examples include protrusion of the third eyelid seen in conditions such as Horner’s Syndrome or mild protrusion of the eye (partial proptosis).
Associated symptoms depend on the severity of the strabismus as well as the underlying disease process.
Mild strabismus sometimes has no other symptoms. Severe strabismus results in loss of depth perception and some dogs start tripping over, or bumping into objects.
Other signs that may accompany strabismus from associated conditions include head tilt, head shaking, circling, muscle weakness and atrophy, and lethargy.
Congenital strabismus is not a painful condition but acquired strabismus may present alongside redness, swelling, squinting, or protrusion of the eye.
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