Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Not just a think tank. An entire army of think.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



Bifocal Laser Surgery

Throw away your bifocal glasses
  [vote for,

For those who aren't able to have conventional laser vision correction because they need different glasses for reading to those required for driving etc.

Simply blast the bottom third of the eye ball to replicate reading glasses and the top two thirds so they are suitable for distance work.

muzza, May 21 2004

Bifocal Contact Lenses http://www.allabout...ntacts/bifocals.htm
[ldischler, Oct 04 2004]


       I'm looking at your idea with reading glasses on. If I move the glasses forward, on the bridge of my nose, and look to the screen over the top Of them, i.e. straight ahead, everything's a blur. Even when I tilt my head back whilst looking straight ahead and the bottom third of my eyes are lined up with the glasses and screen, everything is still out Of focus. Until I fully focus through the reading glasses, nothing is clear. Therefore, I conclude, the whole eye is required to make use of the bottom third of reading glasses and your idea wouldn't work. Having said that, I'm No optometrist and might be wrong.
cromagnon, May 21 2004

       I wouldn't think it would work that well, but since there are bifocal contact lenses on the market, there are probably people who would shell out for this, were it avaliable.
ldischler, May 21 2004

       There is an operation for those needing reading glasses already, but it doesn't involve laser surgery. The surgeon embeds a little ring around your cornea to give it something to push/pull against when focusing. I believe there's no reason why you shouldn't have both operations.
DrCurry, May 21 2004

       Like lasik, corneal rings correct vision by flattening the cornea. It can be removed later, if you don't like it, which is the advantage. (I don't believe either help with focusing at different distances.)
ldischler, May 21 2004

       Kind of like a steel drum eyeball. Hmm.
lostdog, May 21 2004

       [DrC]: I believe that the cornea plays no part in varying the focus on the fly, so to speak (rather the ciliary muscles alter the shape of the crystalline lens), although a device as you describe can provide a different range of focus by changing the shape of the cornea semi-permanently (ie, when it is fitted, in the same way as rigid contact lenses).
angel, May 21 2004

       wouldn't work. Your cornea/lense would move when you moved your eye. It would stay in the same place relative to your center of vision.
DesertFox, May 21 2004

       Contact lenses behave that way also but, as [ldischler] noted, bifocal contacts are available. I cannot figure it out either.
angel, May 21 2004

       I am not an optometrist, this is just my understanding of how the lenses work, as well as some potential drawbacks, based on the descriptions in [ldischler]'s link.   

       The aspheric bifocal contacts behave by creating a "volume" of focus, rather than a "plane" of focus. With this setup, you can improve vision of someone with particularly poor vision, but nothing will be completely crisp.   

       The concentric bifocals perform similar to regular bifocals, but instead of a single plane of focus, there are two. A "focused" image would be formed consisting of the properly focused image from the selected plane overlayed on the slightly blurred image from the other focal plane. When you look at a particular item, it will be sharply focused, but with a blurry halo around it.   

       The translating contacts have a flat surface on the bottom. This flat surface catches on your lower eyelid when you look downward, keeping the lens stationary while your eye rotates downward to look through the near-focus portion of the lens. Gravity does the rest to pull it back into far-focus alignment when you look up again. There may be a "halo" symptom similar to the concentric lens, but it probably won't be quite as prominent.
Freefall, May 21 2004


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle