Lens Technology: Aspheric lenses

‘Aspheric’ refers to a type of lens design. It is recommended for those high powered reading and magnifying eyeglasses.  There is also an aspheric design for those who are very near-sighted and wear ‘coke-bottle’ lenses in their eyeglasses. You may also see hand-held and stand magnifying lens that are aspheric in design.

The center thickness of a standard lens will increase as the power increases. The result is a very curved and thick looking lens. This very curved and very thick lens has several optical problems, among which they are unattractive. Same issue with the high powered ‘coke bottle’ nearsighted lenses in the other direction: the center is very thin and the edges get very thick.

from Sight Nation
from Sight Nation

What some very smart people figured out was that they could flatten out the lens, making the center or edges less thick, and still maintain the prescribed optical powers. There are some other benefits to aspheric lenses:

  • Flatter, thinner and lighter lenses. , about a third thinner and lighter,
  • Larger field of view in the center versus a standard lens design in the very high-powered prescriptions greater than +8.00,
  • Less distortion away from the center of the lens in the higher powers, and
  • The eyes of the wearer look more normal in size. Regular high powered lenses will make your eyes look either abnormally large or abnormally small, depending on the prescription.

An optometrist or optician will usually recommend a lens material like polycarbonate or high index lenses to  reduce the thickness and weight  of eyeglass lenses. In the high-powered  magnifying lenses, they will also recommend an aspheric design to minimize the thickness, give optimal functionality, and a natural appearance to your eyeglasses.

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