Overview of Feline Strabismus
Strabismus is misdirection of the eye. Instead of pointing forward in a direction parallel to the nose, the eye is turned either inward towards the nose (esotropia) or outward away from the nose (exotropia). Strabismus may be caused by an abnormality in the muscles behind the eye, or in the nerves that control those muscles. With strabismus, only the direction of the eye is changed; the position of the eye within the orbit (eye socket) is usually normal.
Strabismus may be present in only one eye, or it can occur in both eyes. When both eyes are involved and the eyes are turned to the outside, the strabismus is called divergent. When the eyes are both turned towards the nose and are cross-eyed, the strabismus is called convergent. The eyes may also be deviated downward or upward.
Strabismus can occur in animals of all ages. It may be present at birth and reflect abnormalities in the development of the eye, the muscles of the eye, or the brain. Or strabismus may develop later in life. The onset of strabismus in an adult animal that was previously normal can represent a serious problem behind the eye.
Causes of Strabismus in Cats
- Congenital (present at birth) strabismus. In Siamese, Himalayan and flame point Persian cats, the eyes may be somewhat cross-eyed. This mild convergent strabismus may also be accompanied by a slight bobbling of the eyes (called wandering nystagmus) when the eyes are at rest. The strabismus and nystagmus in these cats are due to some abnormal wiring between the eyes and the brain, that is caused by the influence of the Himalayan gene that the cats carry. These conditions are accepted traits in these cats and do not cause major problems for them. The traits are considered a normal feature of these cats.
- Hydrocephalus (water on the brain) – rare in kittens
- Infection with the feline leukemia virus
- Inflammation of the nerves from infections and inflammation of the inner and middle ear, or the center of the brain that coordinates eye movement, and meningitis.
- Trauma, inflammation or scarring of the extraocular muscles – rare in cats
- Cancer of the brain or nerves to the eye
What to Watch For
- One or both eyes is pointed in an abnormal direction.
- The movement of the two eyes may not be coordinated or one eye may fail to move properly.
- Other neurologic signs may be noticeable, such as differences in pupil size, weakness or difficultly walking, tilting of the head to one side, or falling or turning to one side.
- Possibly mental dullness or seizures
- Possibly lethargy and decreased appetite
Diagnosis of Strabismus in Cats
Complete physical, neurologic, and ophthalmologic examinations are indicated to determine whether the problem is an eye problem or a neurological problem. Diagnostic tests include the following:
- Complete ophthalmic examination including testing of pupillary light reflexes, Schirmer tear test, fluorescein staining of the cornea, tonometry to measure the pressure within the eye, and examination of the interior of the eye under magnification. Of particular importance is the testing of reflexes for the nerves of the eye and the head. Your veterinarian may refer your cat to a veterinary ophthalmologist for further evaluation using specialized instrumentation.
- Complete neurologic examination including testing of various reflexes, observing the animal move about the exam room, and detailed examination of the ears. Your veterinarian may refer your cat to a veterinary neurologist for further evaluation using specialized instrumentation.
Once strabismus is diagnosed in your cat, an extensive search is often required to identify any underlying diseases. Tests to be considered include the following:
- Complete blood count (CBC)
- Biochemical profile
- Blood tests for feline leukemia virus and other infectious diseases
- Skull X-rays
- X-rays of the chest to look for metastatic tumors
- Possibly advanced imaging tests of the brain and eye, such as CT scan or MRI
Treatment of Strabismus in Cats
Treatment is aimed at correcting the underlying cause of the problem, so it is important to reach a specific diagnosis if at all possible. Some causes of strabismus affect only the eye and are not life threatening, while other causes indicate a serious underlying neurologic or systemic problem that requires prompt medical attention. There is no treatment available for the congenital strabismus and nystagmus of Siamese and Himalayan cats.
Home Care and Prevention
There is no way to prevent the development of strabismus. When the strabismus is due to a neurologic problem that affects the middle or inner ear, or area of the brain that coordinates movement, then your cat may also experience severe dizziness (vertigo). Protect him from falling, rolling or otherwise hurting himself.