Question about accommodation and aging

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tjh42@mybluelight.com - 17 Feb 2005 21:28 GMT

I am 43 and starting to have difficulties reading close. From what I
understand, this gets worse with age until you completely lose the
ability to accommodate. So, I got to wondering:

1. Typically, at what age do emmetropic people lose ALL ability to
accommodate?

2. Assuming that you are perfectly emmetropic and have completely lost
the ability to accomodate, what is the nearest that you can look at an
object, and have it still be completely in focus?

Thanks,

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Dr Judy - 17 Feb 2005 21:58 GMT

>I am 43 and starting to have difficulties reading close. From what I
> understand, this gets worse with age until you completely lose the
> ability to accommodate. So, I got to wondering:
>
> 1. Typically, at what age do emmetropic people lose ALL ability to
> accommodate?

Sometime between 45 and 55, 48 to 50 is typical.

> 2. Assuming that you are perfectly emmetropic and have completely lost
> the ability to accomodate, what is the nearest that you can look at an
> object, and have it still be completely in focus?

This depends upon the size of the object and your pupil size. Pupil size
depends upon your individual make up, your excitement level and the amount
of light reflecting off the object of regard.

Dr Judy

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Robert Martellaro - 18 Feb 2005 00:23 GMT

>I am 43 and starting to have difficulties reading close. From what I
>understand, this gets worse with age until you completely lose the
[quoted text clipped - 8 lines]
>
>Thanks,

Some folks can see a difference in their vision when looking through a lens that
has as little as .125 diopters of power (which corresponds to ANSI which allows
+/- .125 grinding tolerance with low to medium lens powers).That translates to
about 26'. Others can see a difference only if the lens power is .25 diopters,
about 13'. Twenty feet is a nice round number so I'll go with 20'.

Hope this helps
Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
robopt@execpc.com
~~~~~~~~~~~~~~~~~~
"If a million people believe a foolish thing, it is still a foolish thing."
- Anatole France

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Mike Tyner - 18 Feb 2005 02:46 GMT

> 1. Typically, at what age do emmetropic people lose ALL ability to
> accommodate?

The mean is about 51 years, and the standard deviation is small. It's pretty
universal by age 55 or so. On a public forum you'll hear astounding stories,
but they're based on something other than "amplitude of accommodation."

> 2. Assuming that you are perfectly emmetropic and have completely lost
> the ability to accomodate, what is the nearest that you can look at an
> object, and have it still be completely in focus?

Some kids can focus to 5-6 cm in bright light. The textbook maximum around
age 10 is 11-12 diopters, about 8 cm. (1/12=0.8)

The rate of change between birth and 50 isn't linear, but it can be
approximated by 18 -(age/3).

-MT, OD

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Mike Tyner - 18 Feb 2005 03:20 GMT

>> 2. Assuming that you are perfectly emmetropic and have completely lost
>> the ability to accomodate, what is the nearest that you can look at an
>> object, and have it still be completely in focus?

Sorry.. I answered a different question.

Functionally it's about 4-5 feet, maybe 3 feet in sunlight. As Judy said, it
varies enormously with pupil size.

Presbyopes like bright light and they squint to increase their depth of
field and they can't read diddly in the dark. They function pretty good in
the daylight but back in the warehouse they carry reading glasses or pocket
magnifiers. Or a big, big torch.

Few people are exactly emmetropic. Superimposing just a little refractive
error alters individual experiences widely.

A little myopia goes a long way, and nature cooperates by giving us some
myopic shift after age 60. And smaller pupils.

-MT

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