near sighted

[RichD]

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

[Jeroen Belleman]

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

[Phil Hobbs]

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