We often hear the terms "spherical design" and "aspheric design" used when selecting spectacle lenses. What do these terms mean?
This term refers to ordinary concave or convex lens with a curve that looks as if it has been cut out of a sphere. One of the disadvantages of this kind of lens is that, unlike aspheric design lenses, increased power results in a thick and heavy lens.
This type of lens features an aspherically-designed front surface curvature.
Compared with the spherical design lens, this design makes it possible to produce a thin, lightweight lens with less peripheral blurring.
Clarity: This is a method of evaluating lenses defined to compare how clearly the contours of objects or small characters can be seen when looking through a lens.