Presbyopia
is normal age-related loss of ability to focus on things up close. It affects
all of us once we reach our 40s. If you are presbyopic, your eyes will need at
least two different prescriptions: one for far away, and one for up close. An alternative
way to deal with presbyopia is called monovision. In monovision, your dominant
eye is given a distance prescription, while your other eye is given a near
prescription. Contact lens practitioners and refractive surgeons practice
monovision very often to treat their presbyopic patients. While monovision can decrease
the need for reading glasses, it can take some time to get used to. Monovision
can affect depth perception, and you may not
feel comfortable driving or reading for extended periods.
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| Fig:- Presbyopia |
The presbyopia is
corrected with near addition or “add”, the strength of which depends upon the
age, preferred working distance and the best corrected distance visual acuity.
The strength of near “add” increases as the age increases. The preferred
working distance is the distance that an individual like to keep between their
eyes and the near task. Usually a short height person with short arm has closer
working distance than a tall person with longer arms. A person who wants a
closer working distance would need a higher add than a person who wants a
longer working distance. While prescribing near add you must ask his required
near working distance.
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| Fig:- Presbyopia |
Usually this distance is 40cm, but it may be more or
less. Be careful while asking the near working distance. An emerging presbyope
may want longer working distance. He might not be able to tell you exactly his
required near working distance as he becomes used to working at little longer
distance. A good way of asking about near working distance is to ask them where
their arms feel comfortable while holding the near task. The goal is to find
lowest plus that gives clearest vision at required near distance. Usually near
add should be verified with both eyes together and the near acuity should be
equivalent to that of the distance. If not, you may consider increasing the
near add. Ideally the near add for both eyes should be same.
However, near add
should always be responsive to the patient’s visual needs. The final
consideration is patient’s comfort and his satisfaction.
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