A single vision lens has just one power. It is focusing at one range. For a nearsighted person who cannot see far away, the lens is a “minus lens” which is thick on the edge, thin in the middle. For a person who is farsighted or has difficulty reading, the lens is a “plus lens” which is thick in the middle, thin on the edge.
Bifocal lenses are typically for the presbyopic patient who has a hard time seeing both distance and up close. This requires two different vision corrections in the glass. The near and distance pieces of the lenses are called “segments.” The top part of the lens is usually used for distance and the bottom part is used for up-close work.
A popular option is the no-line bifocal in which the line between segments is not visible. This creates a more youthful appearance, although there may be an additional cost for this option.
Trifocal lenses accommodate a person who has a visual need at three distances: far away, at an intermediate distance, and up close.
Lenticular lenses consist of an array of optical elements called lenticules. These lenses are designed to treat eye conditions that are more serious than simple myopia, hyperopia, presbyopia, or astigmatism. They are occasionally prescribed after cataract surgery for patients without intraocular implants; however, advances in surgical procedures have resulted in fewer prescriptions for Lenticular lenses.