High-index and aspheric lenses are recommended by opticians for very
strong prescriptions that often require very thick lenses. High-index plastics
make it possible for strong prescription lenses to be thinner and lighter. The
materials used in high-index lenses are dense, using less lens material to
achieve the same degree of vision correction. High-index plastic can be used to
correct nearsightedness, An aspheric lens, unlike a spherical lens, which
has constant continuous curvature, has varying degrees of curvature over its
surface. This design makes the lens flatter and appear thinner. An aspheric
lens's optical properties provide the wearer with a larger, more usable portion
of the lens and a clearer view throughout the lens than a conventional
spherical design. They are ideal for strong prescriptions to correct
farsightedness and in those patients who had cataract removal without replacing
the eye's lens with an intraocular lens implant.