Close work may have very significant affects on vision. I only found
the below recently and it relates directly to me because I do mountains
of reading, or was until about 4 years ago when my vision went bye bye.
Also, I have ptosis in my good eye, the left one, which is significant
in light of below.

Have you had a thyroid function tested?

John.

http://www.livescience.com/humanbiology/061027_eyelid_vision.html
-->
Eyelids Alter Shape of the Eye

The pressure of the eyelid on the eyeball could cause one of the most
common vision problems, new research shows.
The work builds on previous research showing that heavy reading
(http://www.livescience.com/othernews/060718_illiterate_boys.html) can
change the shape of the eye
(http://www.livescience.com/humanbiology/051128_eye_works.html) during
the day, temporarily degrading eyesight.
Imperfections in the shape of the cornea
(http://www.livescience.com/humanbiology/060719_clear_eyes.html), a
transparent shield that protects and covers the front of the eyeball,
often causes corneal astigmatism. The condition, which affects
somewhere between 33 and 60 percent of all people, can lead to
distorted vision.
The study of 100 normal-sighted young subjects showed that the shape of
the eyelid (http://www.livescience.com/humanbiology/050725_blink.html)
opening at different angles of gaze affected the shape of the cornea,
says Scott Read of Queensland University of Technology, in Brisbane,
Australia.
"It appears eyelids do play a part in determining the shape of the
cornea," Read said. "One explanation is that pressure from the
eyelids is involved in the cause of corneal astigmatism."
The results, announced last week, were published in the journal
Optometry and Vision Science.
It is still unproven that eyelid pressure definitely causes corneal
astigmatism, Read told LiveScience.
"An important next step is for us to develop an accurate and precise
means of measuring the amount of pressure that the eyelids do exert on
the cornea," he said. Then scientists could link those measurements
with the development of astigmatism.
Astigmatism and corneal shape change a lot in young children and older
people, so Read also plans to study the peepers and lids of those
populations to learn more.
Astigmatism takes a few different forms. One way to think of one form
of it is to envision light
(http://www.livescience.com/technology/050819_fastlight.html) coming
into the eye
(http://www.livescience.com/animalworld/051118_animal_eyes.html) along
two perpendicular axes. With astigmatism, the light along one axis is
more in focus than the light along the other. In other cases, the light
fails to line up with the light-receiving axes in the eye.
Heavy readers, take note: Earlier research by Read and his colleagues
shows that downcast eyelids degrade your vision
(http://www.livescience.com/humanbiology/050811_attention_problem.html),
pressing against the cornea and worsening eyesight as the day wears on.
People who read or do close work tend to maintain a downward gaze for a
long time, such that the upper eyelid exerts pressure on the cornea and
actually changes the shape of the eyes throughout the day.
The study found that the shape of the cornea changed significantly
throughout the day, with the eyelid pressure forming horizontal bands
of distortion on the cornea where the eyelid was sitting. The cornea
bounced back by morning.
"As these changes appear to be related to forces from the eyelids
themselves and were more marked in people who spent a lot of time
reading in downward gaze, it is certainly one reason why people's
vision may be slightly worse at the end of the day or after doing a lot
of close work," Read said.
"It suggests," he said, "that people should take a short break
from reading or close work
(http://www.livescience.com/technology/051223_future_office.html) at
least every hour."

Close work may have very significant affects on vision. I only found
the below recently and it relates directly to me because I do mountains
of reading, or was until about 4 years ago when my vision went bye bye.
Also, I have ptosis in my good eye, the left one, which is significant
in light of below.

Have you had a thyroid function tested?

John.

http://www.livescience.com/humanbiology/061027_eyelid_vision.html
-->
Eyelids Alter Shape of the Eye

The pressure of the eyelid on the eyeball could cause one of the most
common vision problems, new research shows.
The work builds on previous research showing that heavy reading
(http://www.livescience.com/othernews/060718_illiterate_boys.html) can
change the shape of the eye
(http://www.livescience.com/humanbiology/051128_eye_works.html) during
the day, temporarily degrading eyesight.
Imperfections in the shape of the cornea
(http://www.livescience.com/humanbiology/060719_clear_eyes.html), a
transparent shield that protects and covers the front of the eyeball,
often causes corneal astigmatism. The condition, which affects
somewhere between 33 and 60 percent of all people, can lead to
distorted vision.
The study of 100 normal-sighted young subjects showed that the shape of
the eyelid (http://www.livescience.com/humanbiology/050725_blink.html)
opening at different angles of gaze affected the shape of the cornea,
says Scott Read of Queensland University of Technology, in Brisbane,
Australia.
"It appears eyelids do play a part in determining the shape of the
cornea," Read said. "One explanation is that pressure from the
eyelids is involved in the cause of corneal astigmatism."
The results, announced last week, were published in the journal
Optometry and Vision Science.
It is still unproven that eyelid pressure definitely causes corneal
astigmatism, Read told LiveScience.
"An important next step is for us to develop an accurate and precise
means of measuring the amount of pressure that the eyelids do exert on
the cornea," he said. Then scientists could link those measurements
with the development of astigmatism.
Astigmatism and corneal shape change a lot in young children and older
people, so Read also plans to study the peepers and lids of those
populations to learn more.
Astigmatism takes a few different forms. One way to think of one form
of it is to envision light
(http://www.livescience.com/technology/050819_fastlight.html) coming
into the eye
(http://www.livescience.com/animalworld/051118_animal_eyes.html) along
two perpendicular axes. With astigmatism, the light along one axis is
more in focus than the light along the other. In other cases, the light
fails to line up with the light-receiving axes in the eye.
Heavy readers, take note: Earlier research by Read and his colleagues
shows that downcast eyelids degrade your vision
(http://www.livescience.com/humanbiology/050811_attention_problem.html),
pressing against the cornea and worsening eyesight as the day wears on.
People who read or do close work tend to maintain a downward gaze for a
long time, such that the upper eyelid exerts pressure on the cornea and
actually changes the shape of the eyes throughout the day.
The study found that the shape of the cornea changed significantly
throughout the day, with the eyelid pressure forming horizontal bands
of distortion on the cornea where the eyelid was sitting. The cornea
bounced back by morning.
"As these changes appear to be related to forces from the eyelids
themselves and were more marked in people who spent a lot of time
reading in downward gaze, it is certainly one reason why people's
vision may be slightly worse at the end of the day or after doing a lot
of close work," Read said.
"It suggests," he said, "that people should take a short break
from reading or close work
(http://www.livescience.com/technology/051223_future_office.html) at
least every hour."

Dear Simon,

The second-opinion on the natural eye's performance.

You might enjoy this commentary:

http://www.geocities.com/otisbrown17268/SaveEye.html

As is presented, a positive refractive STATE is considered
"long-sighted".  A negative refractive STATE is "short sighted".

Tragically, no one has ever pointed out to this kid that
the natural eye will change its refractive STATE if he
continues to write and read at 6 inches (-6 diopters) -- as
the second-opinion.

Best,

Otis

++++++++

The change from May to Dec 2005 was more significant than crossing some
arbitrary line in 06.

No blood sugar problems? No cataracts?

Did you stop reading between May 04 and May 05? :)

-MT

Were the various refractions done with cycloplegia?  If not, then a
variation of +/- 0.25 (which is what we see) is nothing to be concerned
about.

Judy

Simon Dean says...

I started wearing glasses as a teenager, and got
progressively more nearsighted as time went on.  I got all
the way up to -7.50 in my mid 40's.  I've always done a lot
of reading and closeup work.

It's said that myopia is virtually unknown in non-literate
societies, and that idea has led to the inference that
myopia is largely caused by long periods of the strong
accomodation needed for reading and other closeup work.

The same logic says that the above effect can be largely
avoided by using reading glasses for near vision even if you
can still accomodate to read.  The idea is that with strong
reading glasses, the eyes are back at full distance vision
with no accomodation.

So then we would have everyone using reading glasses, or
bifocals, from an early age at an add of like +2.00 or
+2.25, and in theory that would keep them from becoming
myopic.

My myopia started to reverse a couple years after presbyopia
set in, and I started getting an "add" prescription.  My
most recent Rx is -6.00, and as I said in another thread, my
reading glasses are now my computer glasses, so I'm now down
to something like -5.50, I would guess.  I understand this
is fairly common.

I'm not sure I buy the whole theory, but it seems to me that
wearing +2.00 add reading glasses, even at age 29, is not
likely to hurt you.  It might be worth a try.