SYMPTOM
Crossed or misaligned eyes
One eye appears to point off to the side, upward, or downward compared with the other, so the two eyes no longer line up together when the pet looks straight ahead.
Congenital Anatomical Variation
In Siamese cats and related breeds, a convergent, inward-pointing strabismus is a well-recognised congenital trait linked to the same genetic pathway responsible for their pointed coat pattern, arising from an unusual routing of the optic nerve fibres to the brain rather than any disease process. It is typically present from a young age, tends to be stable rather than worsening, and does not cause pain or affect general wellbeing.
Vestibular Disturbance
Disease affecting the inner ear or the brain's balance centres can produce a positional strabismus, where one eye deviates, often downward and outward, when the head is tilted back, alongside other signs such as a head tilt, circling, or unsteadiness. This is a common presentation in both dogs and cats and can arise from ear infection, idiopathic geriatric vestibular disease, or, less often, a lesion within the brainstem.
Cranial Nerve Dysfunction
The muscles that hold the eye in normal alignment are controlled by three cranial nerves, and inflammation, infection, or trauma affecting any of these pathways can produce a specific, often predictable pattern of eye deviation. This can occur in isolation or alongside other signs affecting the same side of the face, and the direction the eye deviates can help indicate which pathway is involved.
Orbital Space-Occupying Process
A mass, abscess, or area of inflammation behind or around the eye can physically displace the globe within its socket, producing an eye that appears to point in an abnormal direction along with other changes such as the eye appearing to bulge forward or the third eyelid becoming more visible. When a tumour is responsible this tends to progress steadily over weeks to months and is more often seen in older pets. Infection behind the eye behaves differently: it appears over a day or two, the eye is pushed forward, the area around it is painful, often noticeably so when the mouth is opened, and the pet may be off colour or running a temperature. It occurs at any age, commonly from an infected tooth root or a penetrating injury, and pressure of that kind behind the eye can cost vision if it continues.
Traumatic Displacement
Blunt trauma to the head or orbit, such as from a road traffic incident, a fall, or a cat fight, can disrupt the normal muscle or nerve control of eye position. The resulting change in alignment may resolve as any associated swelling and inflammation settle, or persist if there has been direct damage to the muscles or nerves involved. Because the force needed to shift an eye out of line also reaches the bones of the socket, the eye itself and the skull, a misalignment appearing after a head injury sits alongside the possibility of a fractured socket, injury to the globe, or bleeding and swelling inside the skull, and carries weight on the day it appears rather than over the following week.
Sympathetic Pathway Disruption
Damage to the sympathetic nerve supply to the eye, sometimes following ear disease, chest surgery, or trauma along its long path through the neck, produces a drooping eyelid, an elevated third eyelid, and a smaller-looking pupil. Owners sometimes describe this combination as the eye looking different or misaligned, even though true muscular strabismus is not present. In a substantial proportion of affected dogs, particularly Golden Retrievers, no underlying cause is ever identified, and this idiopathic form typically resolves on its own over some weeks to a few months.
Why timing matters
Early observation
A pattern noticed early in life, present since the pet was first acquired as a kitten or puppy and unchanging since, most often reflects a congenital anatomical trait. This is particularly likely in Siamese and related cat breeds, where it is a recognised and stable feature rather than an evolving problem.
Later presentation
A change that appears for the first time in an adult or older pet, particularly one that develops or worsens over a period of days, weeks or months, more often reflects an acquired process. This can include vestibular disease, nerve involvement, or a structural change around the eye or brain, depending on what other signs accompany it.
Congenital strabismus tends to remain static throughout life, while vestibular and traumatic causes often appear abruptly and may partially resolve as inflammation settles. A mass-related cause, by contrast, tends to progress steadily over a period of weeks to months, so the trajectory over time helps distinguish between these possibilities.
Conditions commonly associated
Vestibular Disease
Disruption to the balance pathways of the inner ear or brainstem commonly produces a positional strabismus alongside a head tilt and unsteadiness.
Otitis Interna
Infection extending into the inner ear can disrupt the vestibular apparatus and produce eye position changes along with balance disturbance.
Otitis Media
Middle ear infection can affect the sympathetic and facial nerves that pass close to the middle ear, producing the drooping eyelid, raised third eyelid and small pupil of Horner's syndrome, which can make the eye look out of line, along with loss of facial muscle tone.
Brain Tumours
A mass affecting the brainstem or the nerve pathways controlling eye movement can produce a gradually progressive change in eye alignment.
Meningioma
This is a common type of brain tumour in older cats and dogs that can compress cranial nerve pathways controlling eye position as it enlarges.
Horner's Syndrome
Disruption of the sympathetic nerve supply to the eye produces eyelid drooping, third eyelid elevation, and pupil changes that owners sometimes describe as the eye looking different or misaligned.
Squamous Cell Carcinoma
In cats this is one of the tumours reported in the eye socket, although lymphoma is reported more often. It usually reaches the socket by spreading inward from neighbouring tissues such as the eyelids, conjunctiva, third eyelid or nose, and as it takes up space behind the eye it can push the globe out of its normal alignment.
Optic Neuritis
Optic neuritis disrupts the transmission of visual signals from the eye to the brain, often leading to partial or complete blindness in the affected eye. The inflammation responsible is often part of a wider process affecting the brain or the tissue behind the eye, which can involve the nerves controlling eye position, so a change in alignment is sometimes seen alongside the loss of vision.
When to explore further
A pattern present since kittenhood or puppyhood, particularly in a Siamese or Siamese-cross cat, that has remained stable and unaccompanied by other signs is more consistent with a congenital variation than an acquired disease process.
Sudden onset over hours alongside a head tilt, circling, or loss of balance suggests a vestibular process affecting the balance pathways rather than a longstanding conformational trait.
A change accompanying eyelid drooping, elevation of the third eyelid, or a smaller pupil on the same side points towards a nerve pathway change distinct from muscular misalignment.
Recent trauma to the head, such as a fall, road incident, or fight wound, occurring shortly before the eye position changed raises the possibility of direct nerve or muscle injury, and of a fractured socket or injury inside the skull, which carry weight within hours rather than days.
Gradual worsening over weeks together with the eye appearing to protrude, reduced appetite, or other neurological changes may point towards a slowly enlarging process within or around the orbit that benefits from characterisation.
Where the pattern is longstanding and the pet is otherwise well, photographs of both eyes taken from directly in front, in consistent lighting and with the pet looking straight ahead, over several days help establish whether the position is constant or changes with head posture. Noting whether the deviation appears only in certain head positions, such as when the head is raised and the neck extended, versus being present at all times adds useful detail. Recording how long the pattern has been present, and whether it coincides with other signs such as a head tilt or eyelid changes, helps build a fuller picture. A misalignment that is new, that follows an injury, or that comes with a painful or bulging eye is a different situation and carries weight on the day it appears rather than after a period of observation.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS