Question
Mon December 26, 2011 By:

Where image will form in an eye suffering from Presbyopia????? How it is corrected by Bi-focal lens??????? Explain with diagram.

Expert Reply
Tue December 27, 2011
Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age.
one suffering from presbyopia can not focus the image of distant as well as near objects on retina.
so bifocal lens ie which has lower part for focusing the near objects and the upper part for focussing distant objects.or separate lens for focussing these.
the working of these separate lens are exactly the same as we know separately for concave and convex lens.

Corrective lenses provide a range of vision correction, some as high as +4.0 diopter. Some with presbyopia choose bifocal lenses to eliminate the need for a separate pair of reading glasses; while specialized bifocal preparations usually require the services of an optometrist.

Contact lenses can also been used to correct the focusing loss that comes along with presbyopia. Some people choose contact lenses to correct one eye for near and one eye for far with a method called monovision, which can interfere with depth perception due to loss of focusing ability in the other eye. There are also newer bifocal or multifocal contact lenses that attempt to correct both near and far vision with the same lens.
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