I've read here that it's usual for myopia to decrease after say, age
50 but what is the usual shift? How much improvement to myopia is
average or usual? And over what period? Does it stabilise again?

I've read here that it's usual for myopia to decrease after say, age
50 but what is the usual shift? How much improvement to myopia is
average or usual? And over what period? Does it stabilise again?

Any info would be good.. google is not revealing much, probably
because because I'm not using the right terms in the search.

Ann

"Ann" <me@privacy.net> wrote

I've read here that it's usual for myopia to decrease after say, age
50 but what is the usual shift? How much improvement to myopia is
average or usual? And over what period? Does it stabilise again?

After 50, myopic shift is mostly lenticular, driven by changes in chemistry
rather than geometry. For those who experience it, an "average" value might
be -100 over 10 years. But it's accompanied by increasing blur so at some
point there's a net loss of usable vision.

The lens proteins are like the albumin in egg white. Over time, with
oxidation and sunlight and "normal" aging, the lens proteins get hard, the
classic cause of presbyopia. Presbyopia is remarkably predictable - these
proteins seem to hold up remarkably well for the first 40 years. Beyond
that, the changes vary with each individual. Most _monocular_ myopic
excursion after age 50 is presumed to be lenticular.

Wait another decade or two, and circumferential bundles of lens fiber cells
turn white or blue-white. Their shape and location give rise to
crescent-shaped "riders" and wedge-shaped opacities that are fortunately
slow to reach the center.

The oldest (fetal) cells are at the core, like an onion, and often they
behave independently, forming a pill-shaped "nucleus" with different
refractive index or color.

Local variations in refractive index can easily create monocular diplopia,
either from wedge-shaped irregularities or a dichotomy of index in the
center vs the periphery. These may vary dramatically with pupil size.

Myopic shift is how hyperopes and presbyopes get "second sight" up close. No
doubt it contributed to some of Dr. Bates' success-stories.

The lens color usually changes, toward yellow and eventually red. This makes
little old ladies dye their hair blue.

Eventually the whole lens becomes opaque and white, like boiling an egg.

Wait too long (like age 90) and the lens protein liquifies inside the
capsule, producing an allergenic protein mush.

I hope to live long enough to have that problem. Hell I hope to live long
enough to get cataracts.

My vision has improved from -6.25 to -5.25 in exactly
three years. Wearing glasses that are slightly too strong is far more
difficult than wearing glasses that are slighty too weak

The report sent by Robert is interesting but will take a couple of
reads to get my head round.

On Wed, 31 Jan 2007 11:22:52 +0000, Ann <me@privacy.net> wrote:

My vision has improved from -6.25 to -5.25 in exactly
three years. Wearing glasses that are slightly too strong is far more
difficult than wearing glasses that are slighty too weak

Especially for myopes (nearsighted). Even half of that change (.50) can make
reading, intermediate, or the vision in general uncomfortable if you are older
than about age 45.

The report sent by Robert is interesting but will take a couple of
reads to get my head round.

Ann,

In general, it says that myopes over age 50 tend to have a stable distance Rx.
Hyperopes (farsighted) and those with very little distance Rx tend to drift
towards more plus power.