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What's the difference between the upper and lower parts of a bifocal lens?

4 doctors weighed in
Dr. Richard Bensinger
Ophthalmology
3 doctors agree

In brief: Far v. near focus

A classic bifocal (with a line) has an upper portion focused on distance and a lower portion focused on reading and other near things.
A proper eyeglass prescription will allow these two distances to be in focus when the natural lens of the eye stiffens over age 40 in a condition termed presbyopia. Some bifocals (lineless or progressive) have a continuous grind and no visible line.

In brief: Far v. near focus

A classic bifocal (with a line) has an upper portion focused on distance and a lower portion focused on reading and other near things.
A proper eyeglass prescription will allow these two distances to be in focus when the natural lens of the eye stiffens over age 40 in a condition termed presbyopia. Some bifocals (lineless or progressive) have a continuous grind and no visible line.
Dr. Richard Bensinger
Dr. Richard Bensinger
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