A single-vision lens has the same corrective power across its whole surface, so the field of vision is the size of the whole lens. Single-vision lenses work perfectly when there is no need for near vision addition or only a small addition would be required. If stronger near vision addition is needed, single-vision lenses provide limited ability to see things clearly at longer viewing distances.
Bifocal eyeglass lens
The corrective power at the lower part of a bifocal lens is made for the working distance, and the surrounding part can be made for a viewing distance of your choice – typically for instruments or a computer monitor. The benefits of bifocal lenses include wide and clear fields of vision for both viewing distances. On the downside, far distance view may become limited if the surrounding lens part is made with powers for mid distance.
Trifocal eyeglass lens
Trifocal lenses are especially useful when strong near vision addition is required, but you also need to be able to see well at longer distances. The corrective power in the lower part of the lens is made for the working distance, and you can freely choose the viewing distances for the upper areas. Compared to progressive lenses, trifocal lenses have the benefit of wide and clear fields of vision.
Progressive eyeglass lens
The corrective power of the lower part of the lens providing near vision diminishes gradually towards the top of the lens that is used for looking further away. Progressive lenses most suitable for room distances include the so-called enhanced reading glasses and occupational progressive lenses. In these lenses, the narrow field of vision typical to progressive lenses can be widened by leaving out the area for distance vision in the top part of the lens. In addition, this also results in a slower gradual change in the corrective power of the lens, which makes it easier to view various objects.
MeridentOptergo AB Skinnefjällsvägen 1 SE-435 40 MÖLNLYCKE