best-form spheric vs aspheric

Discussion in 'Optometry Archives' started by infoseeker, May 22, 2007.

  1. infoseeker

    infoseeker Guest

    I was told by my optician that there would always be a slight benefit
    to aspheric lenses. However, my research seems to indicate that a
    true best-form spheric is best. My question is, If someone has a
    prescription filled with a CR-39 lens, would they automatically be
    getting a best-form spheric? If not, how can a person make sure they
    are getting a best-form spheric?
    infoseeker, May 22, 2007
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  2. infoseeker

    Salmon Egg Guest

    The real question is: Best for what? Lens design is always a trade-off. That
    applies even for simple lenses. For example, how much do you value best
    resolution looking straight ahead along the axis of your lens compared to
    facing straight ahead and pivoting your eyes to see in and off-axis

    Lens designers use some kind of merit function that is a weighted average of
    all kinds of performances. Such a merit function is often subjective. With
    that merit function, a lens can be designed to maximize it under whatever
    fabrication constraints there may be. It is like asking what combination of
    spices will give the best taste to chili.

    Fortunately, it is usually not necessary to go to such extremes.

    -- Fermez le Bush--about two years to go.
    Salmon Egg, May 23, 2007
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  3. infoseeker

    infoseeker Guest

    The reason I ask is that my mother has macular degeneration. She can
    still see to carry out daily activities, but she is starting to lose
    central vision. I am trying to determine what type of lens will give
    her the widest field of clear vision.
    infoseeker, May 23, 2007
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