Basically the simplest of all lenses, single vision means any lens that do not include a bifocal prescription which only has one option either for reading or distance. In most cases, any prescription for a patient usually under the age of 40. These vision lenses are designed to treat hyperopia (farsightedness), myopia (nearsightedness) or presbyopia including astigmatism. The average plastic lens (CR-39) will be the lens of choice for low prescriptions under + or -4.00. For prescriptions over + or - 4.00. However if you want to go for a thinner lenses which would look better in the frames but would this would meand decreasing the magnification of your eyes (in a farsighted prescription) or minification of your eyes (in a nearsighted prescription).

The thickness of the lens is determined by the number assigned to them called their refractive index.

• 1.498: average plastic lens, thickest option, fine choice for under + or - 4.00.
• 1.59: 20% thinner and 25% lighter and stronger than the average plastic lens, fine for under + or - 6.00.
• 1.67: thinner again, fine for under + or - 10.00 * 1.74: thinner again, fine for under + or - 14.00
• 1.9: the thinnest lens in the world, fine for any high prescription, made of glass therefore not recommended for children.

Other lenses comes with additional options such as;

• scratch resistance coatings
• anti-reflection coatings
• U.V protective coatings
• coloured tints
• polarized tints(prevent glare)

The bifocal lenses are actually 2 prescription lenses fused together usually found on reading sunglasses. Divided in to two segments, the top portion for distance and the bottom portion for near area reading. Although it saves the need to swap between two pairs of glasses, the visible line across them are a great downside on this type of lenses and the lack to support intermediate range of vision is a disadvantage as well. These lenses are normally used once someone reaches their 40's. It is a normal condition that occurs called presbyopia, which happens when the lens in the eye can no longer focus for near vision. 

The trifocal or multifocal lenses are similar to the bifocal lenses however they have three points of focus which gives the user three ranges of visions including the intermediate distances which is essential for computer work or arms length.

1. Distance - such as driving a vehicle or watching television
2. Intermediate - such as working on computer
3. Near - such as reading or other close-up work

A typical computer glasses uses trifocal lenses which has a small portion at the bottom of the lens reserved for your near-vision correction or reading and a small portion at the top is for distance correction including mid range or intermediate vision which is the zone that can be found in between the distance and near vision.

Also known as PALs (progressive addition lenses) or PPLs (progressive power lenses).

The lens blends gradually from the distance prescription at the top to the reading prescription at the bottom or the mid range. One of the advantage of varifocal lenses is that it has no distinct dividing line which some people find the segment line on bifocals or trifocals an annoying distraction, However these type of lenses requires more head movement and are not recommended for all prescriptions.