Kinds of lens
Single vision lens
One power across the whole lens, for one viewing distance.
Illustrative · the shape of the principle, not measured data
In more depth
A single vision lens corrects for one viewing distance with one power throughout. It can be made for distance, for a computer at arm's length, or for reading — and because nothing on it changes, it gives the widest clear view and the easiest adaptation of any lens.
Its limit is the distance it was not made for. Once reading needs an addition, one pair of single vision lenses can no longer cover the day, and the choice becomes two pairs, a bifocal, or a progressive.
Related terms
Sphere (SPH)The main power of your prescription, in diopters. Minus corrects nearsightedness, plus corrects farsightedness; further from zero means stronger.BifocalA lens with two distinct zones separated by a visible line, and no intermediate correction between them.Progressive lensA lens whose power changes gradually from distance at the top to reading at the bottom, with no visible line.