suhre@trwrba.UUCP (Maurice E. Suhre) (07/29/85)
The recent discussion about Bach's vision prompted me to post.
This business about vision being damaged by reading in poor light
has always seemed like an old wive's tale to me. If you try to
take a picture in inadequate light, you get underexposed film.
No damage to the camera. Similarly (it seems to me), the retina
receives an inadequate amount of light to form a sharp image.
It is not clear that having the pupil dilated "trying" to see
is harmful. The lack of light on the retina appears not to be
harmful, otherwise we'd be in real trouble while we were sleeping!
Anybody know what's really happening? Is reading in dim light
harmful, or just an old wive's tale?
Maurice
{decvax,sdcrdcf,hplabs,ucbvax}!trwrb!suhrerbg@cbosgd.UUCP (Richard Goldschmidt) (08/02/85)
In article <1528@trwrba.UUCP>, suhre@trwrba.UUCP (Maurice E. Suhre) writes: > This business about vision being damaged by reading in poor light > has always seemed like an old wive's tale to me. If you try to > is harmful. The lack of light on the retina appears not to be > harmful, otherwise we'd be in real trouble while we were sleeping! > Maurice > {decvax,sdcrdcf,hplabs,ucbvax}!trwrb!suhre My understanding agrees with your intuition, that light level is not a problem. Much more eye strain is likely to be caused by the distance at which you hold your reading matter. The closer the worse, because of the strain on the muscles in the lens of your eye to maintain focus. Rich Goldschmidt {ucbvax,ihnp4,decvax,allegra,seismo} !cbosgd!rbg AT&T Bell Labs ARPA: cbosgd!rbg@seismo or cbosgd!rbg@ucbvax
werner@aecom.UUCP (Craig Werner) (08/03/85)
> This business about vision being damaged by reading in poor light > has always seemed like an old wive's tale to me. In dim light, with the pupil dilated, the lens has to be adjusted more finely due to the reduced depth of field (this is a property of optics, not of medicine) Whether this damages the focusing mechanism, I don't know. The follow anecdote, however, is something I just had to relate to my mother, who has been yelling at me for reading in dim light for years, as soon as I heard it in a lecture from a Retina specialist (a branch of Opthmamology): "The process of projecting the image on the retina and turning into a chemical signal generates a lot of heat, which is helped to dissipate it by the underlying Chorion. However, too intense light can overcome the capacity of the system. So, IT'S PROBABLY NOT A GOOD IDEA TO READ IN TOO *BRIGHT* A LIGHT OR YOU'LL RUIN YOUR EYES." [Emphasis added by me, the cap's is an exact quote, the rest is less so] [The irony need not be added] -- Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes"
geb@cadre.ARPA (Gordon E. Banks) (08/03/85)
In article <1528@trwrba.UUCP> suhre@trwrba.UUCP (Maurice E. Suhre) writes: >Anybody know what's really happening? Is reading in dim light >harmful, or just an old wive's tale? > Old wife's tale.
neal@weitek.UUCP (Neal Bedard) (08/06/85)
In article <1360@cbosgd.UUCP>, rbg@cbosgd.UUCP (Richard Goldschmidt) writes: > In article <1528@trwrba.UUCP>, suhre@trwrba.UUCP (Maurice E. Suhre) writes: > > This business about vision being damaged by reading in poor light > > has always seemed like an old wive's tale to me. If you try to > > Maurice > > My understanding agrees with your intuition, that light level is not > a problem. Much more eye strain is likely to be caused by the distance > at which you hold your reading matter. The closer the worse, because of > the strain on the muscles in the lens of your eye to maintain focus. > > Rich Goldschmidt {ucbvax,ihnp4,decvax,allegra,seismo} !cbosgd!rbg With adequate light the pupil is smaller, resulting in a greater depth of field. The net effect is that the eye has to accomodate less - very important in warding off eye strain during extended periods of close work. By the same token, one should not do near work at too close a distance: back away from the work as far as comfortable, and/or use reading glasses. Both tactics reduce the amount of accomodating the eye is required to do. An excessive light level causes annoying glare and afterimages - think of what happens when a television camera is exposed to a spotlight: the image pickup medium is saturated, and its contrast is reduced. Same problem with human vision, the consequence of which is that one is forced to expend more visual effort (rereading what isn't clear, squinting, etc.) resulting in eyestrain. Low light levels also reduce visual contrast, with similar eyestrain results. Then there are video terminals...... -Neal B. -- "mynd you, m00se bytes kann be pretti nasti" UUCP: {ucbvax!dual!turtlevax,ihnp4!resonex,decwrl!amdcad!cae780}!weitek!neal
dr@ski.UUCP (David Robins) (08/06/85)
> The recent discussion about Bach's vision prompted me to post. > > This business about vision being damaged by reading in poor light > has always seemed like an old wive's tale to me. If you try to > take a picture in inadequate light, you get underexposed film. > No damage to the camera. Similarly (it seems to me), the retina > receives an inadequate amount of light to form a sharp image. > It is not clear that having the pupil dilated "trying" to see > is harmful. The lack of light on the retina appears not to be > harmful, otherwise we'd be in real trouble while we were sleeping! > Anybody know what's really happening? Is reading in dim light > harmful, or just an old wive's tale? As far as we know (ie. ophthalmologists), reading in dim light does *not* harm the eyes or the visual system. It can cause eyestrain, a temporary ocular discomfort which may also cause pain around the eyes, headaches, neck aches, etc. This is only temporary, and disap[ears when the offending activity is curtailed. -- ==================================================================== David Robins, M.D. Smith-Kettlewell Institute of Visual Sciences 2232 Webster St; San Francisco CA 94115 415/561-1705 {ihnp4,qantel,dual}!ptsfa!ski!dr
wmartin@brl-tgr.ARPA (Will Martin ) (08/08/85)
Hmm, so when you hold the page far enough away to let your eyes focus at their normal, unstrained distance, you don't have enough light coming from the page to your eye to distinguish the characters, so you bring it closer to make them out, and this strains your eyes. I have just the opposite problem -- in one eye (my right, measured as 20/500 uncorrected), I have clear vision about four inches away from the eye, with a depth of field about 1 1/2 inches. I can read characters or words easily enough with that, but, if I hold a page of text at that distance, the field of view of that eye is far too narrow -- I cannot see enough of the page to read wuth my normal rapid scanning which gives me a good fast reading speed. I would have to move the paper through the eye's field of view, which can't be done steadily for long. An interesting idea for getting some use out of this eye would be to mount some sort of high-contrast small display (that would present a word or phrase of text) in a headset which would hold it in that limited field of vision for that eye, and use tachistoscope techniques to flash the words by at high reading speed. Hmm.. netnews at 1000 wpm while lying in bed... (And, if I could switch off my corpus callosum, I could have a different one for each eye, showing different stuff... Which eye should get the technical groups and which the artistic & frivolous?) Science marches on... Regards, Will
fsks@unc.UUCP (Frank Silbermann) (08/09/85)
In article <247@weitek.UUCP> neal@weitek.UUCP (Neal Bedard) writes: > >With adequate light the pupil is smaller, resulting in a greater depth of >field. The net effect is that the eye has to accomodate less - very >important in warding off eye strain during extended periods of close work. >By the same token, one should not do near work at too close a distance: back >away from the work as far as comfortable, and/or use reading glasses. Both >tactics reduce the amount of accomodating the eye is required to do. > >Low light levels also reduce visual contrast, with similar eyestrain results. > >Then there are video terminals...... > >-Neal B. Doctors disagree on whether close work increases nearsightedness. If close work does actually encourage nearsightedness, then close work under dim light would be even worse, as the reduced depth of field prohibits "cheating" (under bright light, the eye could perhaps focus for 5 feet away and still be sharp enough to read 2 feet away). Frank Silbermann