Strabismus is a condition in which the eyes don't point in the same direction, also called "squint." It occurs in between 2% and 5% of all children, bothboys and girls, and sometimes runs in families. About half of affected children are born with the condition, which causes one or both eyes to turn:
- Inward (crossed eyes)
- Outward (wall eyes)
- Upward (hypertropia)
- Downward (hypotropia).
Crossed eyes are the most common type of strabismus in infants. One type of this problem develops in children under age 2 who cross their eyes when focusing on nearby objects. This usually happens to children who are moderately toextremely farsighted. Another common form of strabismus (wall eyes), may onlybe noticeable when a child daydreams, looks at far-away objects, or is tiredor sick.
Sometimes the eye turn is always in the same eye, but sometimes the turn alternates from one eye to the other. Most children with strabismus have an unchanging condition; no matter where they look, the degree of deviation doesn't change. In other forms of strabismus, the amount of misalignment depends uponwhich direction the eyes are pointed.
Sometimes a child may have "false strabismus" and seem to have a turned eye;in reality, this appearance may actually be due to:
- Extra skin that covers the inner corner of the eye
- A broad, flat nose
- Eyes setunusually close together or far apart.
False strabismus usually disappears as the child's face grows.
In children with normal vision, both eyes send the brain the same message. It's necessary that both eyes look directly at the same object so that a childcan see in three dimensions with good depth perception. When an eye is misaligned, the brain receives two different images. Young children learn to ignoredistorted messages from a misaligned eye, but adults with strabismus often develop double vision.
Strabismus can be caused by a defect in muscles or the part of the brain thatcontrols eye movement. It's especially common in children who have:
- Brain tumors
- Cerebral palsy
- Down syndrome
Diseases that cause partial or total blindness can cause strabismus. So can extreme farsightedness, cataracts, eye injury, or having much better vision inone eye than the other.
In adults, strabismus is usually caused by:
- Head injury
- Brain tumor
- Other diseases affecting nervesthat control eye muscles.
The most obvious symptom of strabismus is an eye that isn't always straight.The deviation can vary from day to day or during the day. People who have strabismus often squint in bright sunlight or tilt their heads to focus their eyes.
Every baby's eyes should be examined by the age of 6 months; a baby whose eyes haven't straightened by the age of 4 months should be examined to rule outserious disease.
A pediatrician, family doctor or eye specialist can check the health of the eye using drops that widen the pupils and temporarily paralyze eye-focusing muscles. Early diagnosis is important because some uneven eyes may be caused bya tumor, and untreated strabismus may damage vision in the unused eye and cause lazy eye (amblyopia).
Preserving or restoring vision and improving appearance may involve one or more of the following:
- Glasses to help focus and straighten the eye(s)
- Patching to force infants and young children to use and straighten theweaker eye
- Eye drops or ointments as a substitute for patching or glasses, or to make glasses more effective
- Surgery to tighten, relax,or reposition eye muscles
- Medication injected into an overactive eye muscle to allow the opposite muscle to straighten the eye
- Vision training (also called eye exercises).
Early consistent treatment usually improves vision and appearance. The best results are achieved if the condition is corrected before the age of 7.