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Undoubtedly, contact lenses are used to
correct your eye vision by correcting various eye disorders like
astigmatism, anisometropia, myopia, and alike. Along with correcting
vision, they also provide a natural look which is absent in the case of
spectacles. People wearing contact lenses or spectacles have some degree
of anisometropia.
This is a condition in which
there is a difference of refractive errors between the two eyes. Mostly
this term is used when the difference reaches 2.00 diopters and more.
There is also another form of anisometropia called anitmetropia in which
there is a difference in the power designations between the eyes like
your right eye may have plus power while the left eye may have a minus
one.
When spectacles are used to correct the refractive error,
the problems begin to erupt. Images are displaced by all corrective
lenses. Converging or magnifying lens displace the images towards the
edges of the lens creating magnification whereas diverging or minifying
lens displaced the images towards the center of the lens creating
minification.
Displacement depends upon the power of the lens. In
an anisometropia patient, there is a great difference of displacement
between the eyes. Displacement increases as the wearer moves away from
the center of the lens, sometimes resulting in double vision. So, people
with anisometropia and distance vision have to tilt their head to view
through the center of the lens.
This prism imbalance can be corrected by applying a technique
while making spectacles called bicentric grinding. In this, either your
eye with most minus power or least plus power has prism grown only in
half of the lens therefore creating a visible line bisecting the lens.
The wearer also has option of wearing two set of glasses separately for
reading and distance. But, to avoid this condition, most wearers prefer
to wear contact lenses as they help in reducing the prismatic effect
experienced with spectacle wear.
It is really
difficult to know the exact cause of anisometropia as it could be due to
congenital or could be a result of trauma. In fact, if one of your eye
has remarkable refractive error than the other eye, it becomes more
dominant resulting in loss of vision of the non dominant eye. The
severity of the condition can also lead to other conditions like
amblyopia and strabismus.
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