Turned Eyes (Strabismus)
What is Strabismus?
Strabismus is the medical term for misalignment of the eyes two eyes
that are not straight. It occurs in at least 5% of the population. There
are three common
types:
- Esotropia, or 'crossed eye'
One eye is turned inward, toward the nose. A child may be born with
this condition, or it may develop a few months after birth or around
age two to three.
- Exotropia, often called 'wall-eye' in the past
One eye is turned outward, away from the nose. Achild is rarely born
with this condition. More often, it develops later.
- Vertical strabismus
The eyes are out of alignment vertically.
Strabismus can cause a couple of different vision problems:
- Defective binocular vision: The eyes need to be straight for the
brain to combine the images seen by the two eyes into a single
picture. This gives us 3-D vision, which allows us to judge depth.
Any turn of the eye can interrupt 3-D vision. As well, if an eye
turns in, it can reduce the total field of vision.
- Vision loss in the turned eye: When a child's eye is turned, he
or she may end up with only partial sight in the turned eye. This
condition is called amblyopia, or 'lazy eye.' This can also happen
if the eyes are unequally focused.
What Causes Strabismus?
Strabismus can run in families. Sometimes the condition is due to the
eyes being out of focus; in this case, eyeglasses are part of the
treatment. Sometimes there is a problem with the eye muscles or nerves.
Strabismus can also be caused by a serious problem inside the eye, such
as a tumour or a cataract, which leads to poor vision.
How is Strabismus Diagnosed?
Achild can be checked at any age to see whether his or her eyes are
properly aligned. If you are not sure whether your child's eyes are
straight, ask your family doctor or a qualified eye care professional,
who may refer you to an ophthalmologist.
Vision Screening in Children
All newborns should have their eyes checked in the hospital for visual
problems, such as cataracts or lack of visual response. All children
should have their vision checked by age three and a half to four and a half to detect common
treatable problems such as strabismus, amblyopia or the need for
glasses.
Is My Child Especially At Risk?
If any member of your immediate family has had strabismus or amblyopia,
it is more likely that your child will have it. In this case, even if
your child's eyes seem straight, he or she should be examined by a
qualified eye care professional by age one and again by age three. Premature
birth, neurological diseases, and a family history of severe eye
diseases are also reasons to have your child's eyes examined early.
How is Strabismus Treated?
The goal of treatment is for your child to have good vision in each eye,
as well as good binocular (3-D) vision. If your child's strabismus has
caused amblyopia, treatment will aim at bringing the vision up to normal
in the 'lazy' eye first. Glasses may help for eyes that are out of
focus, especially when one is much worse than the other. They may also
help straighten the eyes. Surgery on the eye muscles may be necessary,
especially when glasses are not enough to straighten the eyes.
The results of treatment can be excellent. How much your child's vision
improves depends on how early in life and how quickly treatment was
started. This is especially true for amblyopia and for strabismus that
develops in a child who was born with straight eyes. If treatment is
delayed too long, it may not be possible to completely restore your
child's vision. This kind of vision problem can be effectively
prevented, so it is important to seek professional advice as soon as
possible.
© Copyright by the Canadian Ophthalmological Society