The Different Types of Vision
Single Vision
You will need this type of lens if you need to correct one specific distance. This would be the case for hyperopes or farsighted users that need glasses to see up close; myopes of nearsighted users that can see clearly up close but need their glasses to see better at distance; or intermediate vision designed to help you see clearly at your computer screen distance.
The prescription from your optometrist will not include an ADD power for reading but only spherical or astigmatism correction.
Bifocals
These types of lenses offer a standard lined segment at the bottom of your lens for reading up close, as well as you distance vision correction at the top of your lens. Bifocals allow users to use a single pair of glasses for both distance and near vision; however, they will not be a good solution if intermediate distance, such as the computer distance, is part of your daily tasks.
Trifocals
As the name indicates, this type of lens offers three areas of vision correction. The standard distance correction is located at the top of the lens, while the lower section provides vision for your intermediate and up close reading. In order to do this, the lower section is divided into two segments.
Progressive
Also known as the no-line or invisible line bifocals, the lenses allow you to switch from distance to intermediate to near vision with the greatest of ease. The bifocal segment in your lenses isn't even visible and you can that "sweet spot" of your vision for any distance.
Task Specific Lenses
For a variety of eyewear users whose visual daily tasks are predominantly based around near or intermediate work, standard progressive lenses may not be the perfect solution. Regular progressive lenses may offer a more limited field of view so these task specific lenses would be ideal for office workspace settings. These types of lenses are designed to give you more depth and width of vision in your lens without extra head movements