Anisocoria (Unequal Pupil Sizes) in Dogs

Anisocoria is described as unequal pupil size.

Pupil is an opening at the center of the eye, a circular hole located in the center of the iris that allows light to strike the retina. This expands when there is less light and contracts when there is more light. Anisocoria occurs when one pupil size is smaller than the other. This could be a result of an underlying disease, eye conditions, bacterial and parasitic infections, wounds, injury, inflammation of the eye, nervous system disorders and iris conditions.


There are various factors which can cause Anisocoria such as:
› Nervous system disorders which involve optic nerves, cerebellum
› Inflammation of the eye
› Uveitis
› Bacterial infection
› Parasitic infection
› Eye tumors and cancer
› Eye lesions
› Wounds, trauma and injury
› Glaucoma

Clinical Signs & Symptoms

The severity depends on the underlying disease. Some can be treated with medications, whereas other can be a result of severe conditions. Symptoms seen are:
› Nystagmus (involuntary movement of the eye)
› Twitching of the eye
› Eye pain
› Uveitis (inflammation of the inner pigmented structure of the eye)
› Tearing of eyes
› Conjunctivitis (Inflammation of the eye)
› Unequal size pupil


Veterinarians will require a complete history of your dog which includes medical history, vaccination records, existing health concerns, current and previous medications, onset of symptoms, diet and exercise routine and any information which can help in establishing a correct diagnosis. Diagnosis is done with a combination of tests. These include routine lab examinations and special tests which can detect the underlying cause. They are:

› Physical examination
› Complete Blood Count (CBC)
› Biochemical profile
› Urinalysis
› Eye test
› Cerebrospinal Fluid Tap (CSF)
› CT Scan
› MRI Scan
› Chest Radiograph (X-ray)
› Tonometry test
› Ultrasound
› Electroretinography test (ERG)
› Visual evoked potential (VEP)


Treatments can vary depending on the underlying cause of Anisocoria.
› Anti-inflammatory medications
› Antibacterial medications
› Antibiotic medications
› Topical ointments
› Eye drops


Anisocoria is a symptom of an underlying or secondary disease. Treatments can reduce this symptom.

Home Care

Treatments can range from a few days to weeks. You have to administer and monitor all prescribed medicines as directed by your veterinarian. If you observe any behavioral changes or if the condition does not improve, please contact your veterinarian immediately.

Related posts

Leave a Reply

Your email address will not be published. Required fields are marked *