What is amblyopia?
Amblyopia (lazy eye) is poor vision in an eye that did not develop
normally during childhood. It commonly affects one eye but may also
involve both eyes. It is generally caused by lack of use of one eye,
when brain 'favors' one eye over the other.
What causes amblyopia?
The visual system of the child is not fully developed at birth. The
visual brain cells of a child are developing during their first decade
of life. Any insult to the child's vision during this time period can
lead to amblyopia.
Following are the common causes of amblyopia:
- Squint: This is the commonest
cause of amblyopia. The brain to avoid double vision ignores the
image from the deviating eye. This leads to poor visual development
of the deviating eye and hence amblyopia.
- Unequal
refractive error (anisometropia): In this condition, the
two eyes have different refractive errors. Because the brain can not
"balance" this difference, it picks the eye that is "easier"
to use and develops a preference for this eye only. The eye with
greater refractive error is suppressed and thus gets amblyopic. An
early treatment by giving the right glasses for correction can
prevent and correct this problem.
- Stimulus deprivation: Any form of stimulus derivation to
either one or both eyes in early childhood may lead to a severe form
of amblyopia. These causes for stimulus deprivation may be ptosis,
cataract, glaucoma, patching or any
other obstacle that blocks the vision in the eye.
How can we detect if the child has amblyopia?
Detecting
amblyopia in child is difficult, as the child may not be aware of having
one strong eye and one weak eye. If the child has a
squint or some other abnormality, the parents
may notice that something is wrong. The vision of the child can be
tested by the ophthalmologist by special tests. Poor vision in an eye
may point towards a possibility of amblyopia. Remember, poor vision in
an eye does not always mean amblyopia. It is important to rule out other
causes of
poor vision in child.
Is it treatable?
Yes. In most of the cases the amblyopia is treatable. The treatment
involves 'forcing' the brain to use the weaker eye and thus stimulating
its visual development. This is done by patching the better eye. The
schedule of patching is decided by the ophthalmologist depending upon
the degree of amblyopia and the age of child.
When should it be treated?
As soon as possible. The earlier the amblyopia is detected and the
treatment started, the better are the results. The aim is to stimulate
the brain to use the suppressed eye before permanent change has
occurred, so that it gets a chance of normal development. Generally
speaking, an amblyopia that is not treated by 10 years of age has a poor
chance of recovering the vision.
Why is it important to treat amblyopia?
If an amblyopic eye is not treated by 10 years of age, the amblyopic
eye may permanently stay weak. This has many disadvantages like:
- Both eyes can not be used simultaneously and hence depth
perception (three-dimensional vision) is not present. Many
occupations are not open for people who have good vision in one eye
only.
- It is important to give best possible vision to the amblyopic eye
even if the other eye is seeing well. The importance of this becomes
obvious, in case the person loses the other (better) eye, sometime
later due to some injury or disease.
What are the factors that determine the success of
treatment?
The success of amblyopia treatment largely depends upon the motivation
of parents and the cooperation of the child. Patching of the better eye,
especially when the amblyopic eye has very poor vision is not tolerated
well by the child. The parents have to understand the importance of this
treatment and should explain the same to the child to ensure better
cooperation.
The other factors that determine the success of treatment are:
- The severity (depth) of amblyopia
- The age at which the treatment is started: The earlier the
treatment is started, the better are the results
- Any other complicating factor in the eye preventing sufficient
gain of vision, e.g., glaucoma, cataract, retinal or optic nerve
disorders
My child has squint and amblyopia. Which should be
treated first?
Amblyopia has to be treated first in all these cases. Once the
amblyopia has been taken care of, the surgery may be done for squint
correction.
