An aspheric lens tends to have a flatter front than traditional lens designs.  The typical reason your optometrist or optician suggests an aspheric lens is to accomplish a flatter front face of the lens.  This is done to reduce edge thickness for myopic (nearsighted – minus range) patients, and reduce the center thickness of the lens for farsighted (plus range) patients.  The flatter design of the aspheric lens allows the same or optical performance of similar high quality lenses with steeper curves while subtracting some of the objectionable problems inherent in solving high minus, high plus range, and presbyopic prescriptions.  In high power (high diopter) prescriptions the use of an aspheric lens will tend to have the benefit of reducing the distortion of the eye appearance when seen by other people.  Because of these qualities, an aspheric lens can help benefit the overall vision improvement mission of your eye care professional while making eyeglasses less objectionable from an appearance and aesthetic point of view. 

Aspheric lenses can be classified as convex (rounded outward), and concave (scooped out appearance).  Concave aspheric lenses are used to correct high myopic conditions (nearsighted).  Convex aspheric lenses are used to correct presbyopic eye conditions (age related need for multifocal lenses) and increase the optical power of the lens over the wider lens area used by the eye.  Whether used in near or far sighted correction situations, the aspheric lens flattens near the edge of the lens to minimize the edge profile more than in traditional lenses.

When conducting your eye care examination the Optometrist will determine if an aspheric lens can help you with sight conditions and possibly help you accomplish a better visual appearance for your Rx.  Since the large majority of aspheric lenses are manufactured specifically for your Rx it should be expected that aspheric lenses are more expensive than most lens types.  Aspheric lenses may be available in just about any lens material but high index plastic values will cost the most, when available.