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After the age of forty, we all will begin to
lose the ability to accommodate or focus the lens of our eye. This is a
universal phenomenon and not caused by any disease or illness.
When the ability to accommodate is lost, it means that the
eyes cannot adjust or focus images at different distances. Therefore, different
glasses, at different focal lengths, are required for distance and near vision.
People may find that if they can see well at distance, they now require glasses
to read at near and vice versa.
This problem is called Presbyopia and is usually corrected
with bifocals or glasses with two focal lengths, one for near and one for
distance. Presbyopia may also be corrected with Monovision. Monovision corrects
one eye for distance and one eye for near. Monovision can only be used in
patients who wear contacts or who have refractive surgery. Thus, the need for
glasses with two different focal lengths is resolved by focusing each eye at a
different focal length.
People over 40, who require glasses for distance vision -
nearsighted or myopic individuals - frequently find that they can read up close
quite well without their glasses. Correcting their distance vision to 20/20
almost always means that they will need glasses to be able to read up close.
This is because they can no longer focus or adjust their focal length.
Typically in Monovision, the eye that is correct for distance
is the dominant eye. One can usually determine which eye is dominant by raising
a thumb, holding it out in front of both eyes, and blocking an object with the
thumb while both eyes remain open. Once the object is blocked, close one eye or
the other, and the eye that cannot see the object is the dominant eye.
Patients over forty must make a choice. Either both eyes are
corrected for distance or one eye is corrected for distance and the other for
near. If the patient is unsure of what they would like, contacts can sometimes
be used to simulate post-operative results.
If you are over 40, or wear bifocals or
reading glasses, your LASIK surgeon will want to discuss Monovision as part of
your Consultation in order to make sure you get the best possible
results.
If you are over 50 and do not wish to have
monovision LASIK, you will most likely require reading glasses after your LASIK
surgery. For patients over 50 who wish to have both their far and distance
vision corrected without monovision or using reading glasses, a possible option
to explore in order to effectively manage their presbyopia is Lens
Replacement Surgery.
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