Single Vision Lenses
Single vision lenses are prescribed if you need correction for one field of vision, either for distance, intermediate (computer), or items up close (near vision). Single vision has the same optical focal point or correction over the entire area of the lens.
Progressive or varifocal lenses provide a smooth transition from distance correction to near correction, eliminating segment lines and allowing clear vision at all distances, including intermediate; roughly arms' length.
Clarkson now offers the latest in digital lens technology with the Clarkson Precision Lens.
With a bifocal, the upper part of the lens is generally used for distance vision, while the lower part is used for near vision. Usually, a segment line separates the two. Typically a person with myopia would have one section of a prescription lens that has a certain diverging power while another section of the lens would have a lower diverging power for close-up work. Similarly, a person with hyperopia would have one section of the lens with a certain converging power and another section with a greater power for close-up work.
Trifocal lenses are similar to bifocals, except that the two focal areas are separated by a third middle area with intermediate focus correction. This area is used for intermediate vision; roughly at arms' length, e.g. computer distance. This lens type has two segment lines, dividing the three different correcting segments.