Single Vision Lenses
Single vision glasses are glasses that correct for 1 focal distance. Depending on your own eye's focussing power 1 pair may be adequate for all distances. As you get older your focussing power decreases and you may need to get separate glasses for different focal distances i.e. usually distance and reading.
Multifocals are the best all-round glasses for presbyopes (people who are over 40 and require a different prescription for distance to reading). Some people in the past may have had trouble getting used to their multifocals and generally it does take a bit of time to get used to your first pair but the newer free form designs reduce the amount of distortion visible through the lenses and many people who once could not adapt to multifocals are happily wearing the newer versions. Multifocals do not have a defining line between distance and near portions so look better than bifocals or trifocals.
Bifocals are good for people who do not use a computer often (or have a separate pair of computer glasses) and cannot handle the distortion in multifocal glasses.
Trifocals are like bifocals but have 2 near portions - 1 for intermediate/computer distance and 1 for reading. These are good for patients who can't get used to multifocals but would like to have an intermediate portion (usually for the computer) in their everyday glasses.
Transitions are lenses that change between clear and tinted lenses depending on sunlight. They are useful for people who don't like to have to carry an extra pair of sunglasses and are great for overcast weather when you don't need such a dark tint.
Prescription Sunglass Lenses
Prescription sunglass lenses can be tinted to almost any colour, though higher index lenses may be more limited. The most common tints are green (like the traditional Rayban® G15), grey or brown. They can be tinted to different darknesses and can also be made to be a graduated tint. Graduated tints are good for those who would like to read through their sunglasses.
Prescription sunglass lenses can also be polarised. Polarised lenses are great for people who are glare sensitive as they cut out light bouncing off horizontal surfaces. They are especially good for people who are near water and can enable you to see through the water rather than be affected by the glare bouncing off the surface. There are a small percentage of people who experience visual disturbances when looking through polarised lenses through a windshield.
Anti-reflective Coating on Lenses
This is a must for people driving at night or using the computer or with astigmatism. However, it is beneficial to most patients because it minimises the reflections from the lenses allowing more light to pass through so you can see better. This coating also helps with transitions as it allows more light to transmit to activate the lens to go darker.
High Index Lenses
High index lenses are lenses that have a higher refractive index than basic CR39 plastic lenses. The higher the refractive index, the more it bends light and the thinner the lens can be.
Grind lenses are lenses that are specially made usually because they are out of the stocked range but are often used for plus lenses so they can be made thinner. This will depend on the prescription, size and shape of the frame.