Strabismus is a visual problem in which the eyes are not aligned properly and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward, or downward. The eye turn may be consistent, or it may come and go. Which eye is straight (and which is misaligned) may switch or alternate.
Strabismus is a common condition among children. It can also occur later in life. It may run in families; however, many people with strabismus have no relatives with the problem.
Types of strabismus
Infantile esotropia, where the eye turns inward, is a common type of strabismus in infants. Young children with esotropia cannot use their eyes together. Accommodative esotropia is the most common form of esotropia that occurs in children usually 2 years or older. In this type of strabismus, when the child focuses the eyes to see clearly, the eyes turn inward. This crossing may occur when focusing at a distance, up close or both.
Exotropia, or an outward-turning eye, is another common type of strabismus. This occurs most often when a child is focusing on distant objects. The exotropia may occur only from time to time, particularly when a child is daydreaming, ill or tired. Parents often notice that the child squints one eye in bright sunlight.
To line up and focus both eyes on a single target, all of the muscles in each eye must be balanced and working together. In order for the eyes to move together, the muscles in both eyes must be coordinated. The brain controls these muscles. With normal vision, both eyes aim at the same spot. The brain then combines the two pictures into a single, three-dimensional image. This three-dimensional image gives us depth perception.
When one eye is out of alignment, two different pictures are sent to the brain. In a young child, the brain learns to ignore the image of the misaligned eye and sees only the image from the straight or better-seeing eye. The child then loses depth perception. Adults who develop strabismus often have double vision because their brains have already learned to receive images from both eyes and cannot ignore the image from the turned eye. A child generally does not see double.
Strabismus is especially common among children with disorders that may affect the brain, such as: Cerebral palsy; Down syndrome; Hydrocephalus; Brain tumors; Prematurity.
A cataract or eye injury that affects vision can also cause strabismus. The vast majority of children with strabismus, however, have none of these problems. Many do have a family history of strabismus.
The main sign of strabismus is an eye that is not straight. Sometimes children will squint one eye in bright sunlight or tilt their head to use their eyes together.
Treatment for strabismus works to straighten the eyes and restore binocular (two-eyed) vision. In some cases of strabismus, eyeglasses can be prescribed for your child to straighten the eyes. Other treatments may involve surgery to correct the unbalanced eye muscles or to remove a cataract. Patching or blurring the strong eye to improve amblyopia is often necessary.
Very young children with esotropia usually require surgery to realign the eyes.
For accommodative esotropia, glasses reduce the focusing effort and often straighten the eyes. Sometimes bifocals are needed for close work. If significant crossing of the eyes persists with the glasses, surgery may be required.
With exotropia, though glasses, exercises, patching or prisms may reduce or help control outward-turning of the eye in some children, surgery is often needed.