Back Room ...

From Scott Dorsey:
Peter Smith wrote:
David Lesher wrote:

And you now can't buy glass at all, I'm told. There's a new
fracture
requirement or such....

Thats right. Glass lenses are heavy, they break if you drop them,
and
if they are hardened the impact resistance increases - but when they
do
break there's glass powder exploded into your cornea... not fun.
Also a
small scratch or defect can cause the hardened lens to spontaneously

shatter... most people get really ****ed off if that happens.. And
the
hard-coated plastics have scratch resistance comparable to glass
anyway.

You can still get glass, but the requirements for how thin the center
of the lens can be have been increased, so a lot of folks with higher
sphere prescriptions either need to go to a high index glass and pay
$500/lens
or go to plastic.

I strongly recommend the Zeiss high index glass lenses. They have
much
less birefringence than any of the plastic lenses I have ever used.

Regarding the topic of fragments getting stuck in the cornea, the
origins of contact lenses are said to go back to the time when WWII
pilots had polycarbonate canopy fragments splintered into their eye and
optometrists were amazed to see how non-reactive the foreign particles
were. While the contact lens invention had previously been attempted
with glass (as evolved from glass eyes) it was the switch to plastics
that led to the success of contacts.

So we can add contact lenses to the long list of useful inventions that
most people would not think of as being brought about by war.


~ CT

Stuf4 wrote:

Regarding the topic of fragments getting stuck in the cornea,
the origins of contact lenses

demonstrated by Thomas Young c.1800

are said to go back to the time when WWII
pilots had polycarbonate

the canopy material was Perspex (polymethylmethacrylate)

canopy fragments splintered into their eye and
optometrists were amazed to see how non-reactive the foreign particles
were.

polycarbonate is a poor material for longterm bodily implants

While the contact lens invention had previously been attempted
with glass (as evolved from glass eyes) it was the switch to plastics
that led to the success of contacts.

plastic contact lenses were first demonstrated by William Feinbloom in 1936

So we can add contact lenses

Free clue: your story relates to the introduction of acrylic
intra-ocular lenses implanted into the eyeball following cataract
surgery first demonstrated by Dr Ridley in 1949 - rather than contact lenses

to the long list of useful inventions that
most people would not think of as being brought about by war.


~ CT



- Peter

On Wed, 18 May 2005 12:51:56 GMT, Peter Smith
wrote:

Free clue: your story relates to the introduction of acrylic
intra-ocular lenses implanted into the eyeball following cataract
surgery first demonstrated by Dr Ridley in 1949 - rather than contact lenses

....Free clue: killfile the trolling ******* and put him out of our
misery.

Please.

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr

OM wrote:


...Free clue: killfile the trolling ******* and put him out of our
misery.

Point taken.

- Peter

From Peter Smith:
Stuf4 wrote:

Regarding the topic of fragments getting stuck in the cornea,
the origins of contact lenses

demonstrated by Thomas Young c.1800

are said to go back to the time when WWII
pilots had polycarbonate

the canopy material was Perspex (polymethylmethacrylate)

Thanks for this correction. The more advanced polycarbonate canopies
came after WWII.

canopy fragments splintered into their eye and
optometrists were amazed to see how non-reactive the foreign
particles
were.

polycarbonate is a poor material for longterm bodily implants

While the contact lens invention had previously been attempted
with glass (as evolved from glass eyes) it was the switch to
plastics
that led to the success of contacts.

plastic contact lenses were first demonstrated by William Feinbloom
in 1936

Contrary to popular historical accounts, Feinbloom's design actually
used glass lenses. He only used plastic for covering the surrounding
whites of the eyes (sclera). One reference:

"In 1936, New York optometrist William Feinbloom introduced the use of
plastic in contact lens manufacturing. Feinbloom's lenses had a
central portion made of glass that covered the cornea and a peripheral
band of plastic that covered the sclera."
http://www.eyetopics.com/Articles/18...ct-Lenses.aspx

Granted, it was an important step forward, but contacts made with
plastic lenses did not happen with Feinbloom's 1936 invention.

So we can add contact lenses

Free clue: your story relates to the introduction of acrylic
intra-ocular lenses implanted into the eyeball following cataract
surgery first demonstrated by Dr Ridley in 1949 - rather than contact
lenses

I see the mishap of canopy shards getting stuck into pilot's eyeballs
as applying to both inventions, implants and contacts.

to the long list of useful inventions that
most people would not think of as being brought about by war.


It might also be interesting to branch this thread into the history of
contact lens use in spaceflight. There is a long history of official
prohibition to the use of contact lenses for US military pilots. That
changed very quickly in the 1990s when the use of NVGs came into vogue.
(If you thought that those NASA black rim glasses were an effective
form of birth control, NVGs introduced a whole new fad of ugly!) So
who was the first to wear contacts in space? Obviously not John Young
on STS-1:
http://images.jsc.nasa.gov/lores/S81-30419.jpg


~ CT