STRABISMUS

Strabismus is the term for incorrect alignment of the eyes. That is, they do not point in the same direction when looking at an object.

An eye with strabismus may turn inward, outward, upward or downward. Strabismus may be present all the time, or it can come and go. It may occur in one eye only, or it may alternate from eye to eye. Strabismus occurs in about three people in every 100. The condition is commonly called “squint”. If strabismus is present, the brain:

• ignores the image from the affected eye (leading to impaired vision called amblyopia or “lazy eye”), or
• sees two images (double vision).

A person with amblyopia may have difficulty judging the distance between objects (depth perception). To perform most day-to-day activities, good depth perception is helpful.

Causes of strabismus

Each eye has six muscles attached to its white outer layer (sclera), as shown in the illustration. Contraction and relaxation of these muscles control eye movement in all directions. You can ask your ophthalmologist to point out which muscles appear to be affected in your case.

The cause of strabismus is not fully understood. In most cases, it is due to a failure of the visual areas of the brain to control eye alignment. Less commonly, it may be a condition affecting eye muscles. As eye muscles are strong for their size and the work they do, strabismus is rarely due to a “weak muscle”.

Strabismus often runs in families. It can also be caused by disease or injury. Stress or illness can make strabismus more obvious.

Some images and information provided courtesy of RANZCO and Mi-tec Medical Publishing. The complete RANZCO patient education pamphlet is available from your ophthalmologist.