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What
is squint (strabismus)?
Squint is a misalignment of the two eyes so that both
the eyes are not looking in the same direction. This misalignment
may be constant, being present throughout the day, or
it may appear sometimes and the rest of the time the eyes
may be straight.
It is a common condition among children. It may also occur
in adults.
What
causes squint?
The exact cause of squint is not really known. The movement
of each eye is controlled by six muscles. Each of these
muscle acts along with its counterpart in the other eye
to keep both the eyes aligned properly. A loss of coordination
between the muscles of the two eyes leads to misalignment.
This misalignment may be the same in all directions of
gaze, or in some conditions the misalignment may be more
in one direction of gaze, e.g., in squint due to nerve
palsy.
Sometimes a refractive error hypermetropia (long sight)
may lead to inward deviation of the eye. Poor vision in
an eye because of some other eye disease like cataract,
etc. may also cause the eye to deviate. Therefore it is
important in all the cases of squint, especially in children,
to have a thorough eye checkup to rule out any other cause
of loss of vision.
What
is binocular vision?
Under normal circumstances, when both the eyes have good
vision and they are aligned properly, they focus on the
same object. Each of the eyes sends picture of the same
object, viewed from a slightly different angle. These
two images reach the brain, where they are fused to form
a single three-dimensional picture with depth perception.
This is known as binocular single vision.
What
are the problems with squint?
When the eyes are not aligned properly, each of the eyes
is focusing on a different object and sends signal to
the brain. These two different images reaching the brain
lead to confusion and may have either of the two effects:
A child would ignore the image coming from the deviated
eye, and thus sees only one image. But in the process,
he loses the depth perception. This suppression of the
image from the deviating eye results in poor development
of vision in this eye, which is known as amblyopia.
An adult can not ignore the image from either eye, and
therefore has double vision. This can be very annoying
and may interfere with work.
What
are the symptoms of squint?
In a child, the parents may notice the deviation of eyes.
It is important to remember that the eyes of a newborn
are rarely aligned at birth. Most establish alignment
at 3-4 weeks of age. Therefore squint in any child who
is more than one month old must be taken seriously and
should be evaluated by an ophthalmologist.
Adults may notice double vision, or misalignment of the
eyes.
How
is squint diagnosed?
The squint is diagnosed by the ophthalmologist. He or
she would do a few special tests to confirm the squint,
to try and find out the cause and to quantify the amount
of deviation. In some cases there may be a false appearance
of squint due to broad nasal bridge in a child. An ophthalmologist
will be able to differentiate between a true squint and
false squint.
What
is the treatment for squint?
The aims of treatment of squint in order of importance
are:
1. Preserve or restore vision
2. Straighten the eyes
3. Restore binocular vision
First of all, the eyes are checked to see if they have
any refractive error that may be responsible for squint.
If there is any significant refractive error present,
it is treated first. In some cases (accommodative squint)
a correction of refractive error is all that may be required
to treat squint.
Next the eyes are checked for presence of amblyopia. It
is important to treat the amblyopia before the surgery
for squint. The parents are explained about the importance
of this treatment, as their cooperation is very crucial
for the success of this treatment.
The squint is treated by surgery of either one or both
the eyes. The surgery involves weakening or strengthening
of the relevant muscles to restore the balance and to
get a good coordination. In some cases with double vision,
prisms may be added in the glasses to ease the symptoms.
When
should the squint be treated?
In a child, the treatment of squint and any associated
amblyopia should be started as soon as possible. Generally
speaking, the younger the age at which amblyopia is treated;
the better is the chance of recovery of vision. Remember
that the child would never grow out of squint. A delay
in treatment may decrease the chances of getting a good
alignment and the vision.
Are
glasses necessary?
Yes. Surgery can not replace the need for glasses. If
the child has significant refractive error, glasses are
a must. In some cases wearing glasses may correct squint.
In other cases, wearing glasses help the eyes to see clearly.
This clear vision is very important for the treatment
of amblyopia, and also for maintaining the coordination
of eyes, once they have been aligned by surgery. |
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