Question

How are 4d glasses different than 3. 75 lens in stores.

Answer 1

Since eyeglasses are usually
about 12 millimeters from the
eye, the prescriptive power of a
contact lens
which is
positioned directly on the tear
film of the eye
- will be slightly
less nearsighted. This becomes
significantly different with
prescriptions of 4D or greater.
Therefore, in our example, the
power of a contact lens will be
less than the eyeglass
prescription for the right eye.