1. Forum
  2. Usenet
  3. SCI.OPTICS

  • Re: near sighted

    From Jeroen Belleman@21:1/5 to RichD on Mon Mar 21 23:58:05 2022
    On 2022-03-21 23:44, RichD wrote:
    A person with normal vision will become far
    sighted with age; his cornea loses the ability to
    focus at close range.

    But a near sighted person will often retain
    his close range vision, he doesn't need reading glasses.

    Can we explain this through optics? Or is it really a
    ophthalmology issue?

    --
    Rich


    At old age, a person will lose the ability to /change/
    focus. If he was near sighted to begin with, he will
    stay that way. The condition is called presbyopia.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From RichD@21:1/5 to All on Mon Mar 21 15:44:21 2022
    A person with normal vision will become far
    sighted with age; his cornea loses the ability to
    focus at close range.

    But a near sighted person will often retain
    his close range vision, he doesn't need reading glasses.

    Can we explain this through optics? Or is it really a
    ophthalmology issue?

    --
    Rich

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Jeroen Belleman on Fri Mar 25 02:08:12 2022
    Jeroen Belleman wrote:
    On 2022-03-21 23:44, RichD wrote:
    A person with normal vision will become far
    sighted with age; his cornea loses the ability to
    focus at close range.

    But a near sighted person will often retain
    his close range vision, he doesn't need reading glasses.

    Can we explain this through optics?  Or is it really a
    ophthalmology issue?

    --
    Rich


    At old age, a person will lose the ability to /change/
    focus. If he was near sighted to begin with, he will
    stay that way. The condition is called presbyopia.

    Jeroen Belleman



    There's also a tendency for the resting focus to get further away, maybe
    a diopter's worth, along with the reduction in accommodation. Mine sure
    has. I suppose that if your correction is -5 diopters when you're
    young, having it go to -4 when you're old isn't that big a change. Going
    from zero to +0.7 (age 62) is a bigger deal--I'm now on the edge of
    needing glasses to drive.

    Memorizing the eye chart is one of those useful things you can do while
    waiting at the motor vehicles department. ;)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)