Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!rutgers!sri-spam!ames!lll-tis!ptsfa!ski!dr From: dr@ski.UUCP (David Robins) Newsgroups: comp.sys.mac Subject: Re: Screens hurt eyes Message-ID: <993@ski.UUCP> Date: Thu, 30-Jul-87 18:30:47 EDT Article-I.D.: ski.993 Posted: Thu Jul 30 18:30:47 1987 Date-Received: Sat, 1-Aug-87 11:11:59 EDT References: <1767@batcomputer.tn.cornell.edu> <6752@dartvax.UUCP> Reply-To: dr@unix.UUCP (David Robins) Organization: Smith-Kettlewell Institute, S.F., CA. Lines: 75 In article <> eric@tcgould.tn.cornell.edu (Eric Fielding) writes: >In article <6752@dartvax.UUCP> earleh@dartvax.UUCP (Earle R. Horton) writes: >>In article <1767@batcomputer.tn.cornell.edu>, dyckman@batcomputer.tn.cornell.edu (Howard L. Dyckman) writes: >>> My eyes have been hurt by some recent Macintosh screens (SE, Plus). >>> Symptoms include sensitivity to light, dryness, grittiness under >>> the eyelids, soreness. A brief exposure produced only soreness. >>These symptoms are identical to those produced by overexposure to ultraviolet >>light. They can be duplicated by spending day in the mountains without one's >>sunglasses. If you obtain a pair of sunglasses with * glass * lenses, this may >>provide some relief. They don't have to be dark, just glass. >>*Earle R. Horton, H.B. 8000, Dartmouth College, Hanover, NH 03755 * > >My sister got a special kind of lenses the last time that she purchased >prescription glasses. They have a coating on them that is designed to >reduce glare from CRT's. They are actually some kind of plastic lenses, as >well. I think that she had had symptoms of dryness before getting the new >glasses, but they have disappeared with the glasses. Unfortunately, the >lenses were more expensive, of course. >++Eric As an ophthalmologist, I have seen many computer-related eye problems. All of them have turned out to be *NOT* due to the computer equipment itself, except when an out-of-focus or flickering system causes eyestrain. A very common problem is "Dry Eye Syndrome" (keratitis sicca). It is due to relative deficiency of lubricating tears one the surface of the eye, not related to one's ability to cry. Staring at anything, but particularly a terminal, reduces the blink rate. Tear evaporation takes place, and air "burns" the conjunctiva and cornea. This leads to dryness, grittyness, foreign body sensation, burning, and sometimes photophobia (light sensitivity). It can feel just like UV keratitis (corneal burn). They can be distinguished by the pattern of the irritation. The corneal tear film is stained with fluoroscein dye, and examined under cobalt blue light at a slit lamp, or with a hand-held long-wave UV source. In UV exposure, the cornea is uniformly stained in the area between the lids. In dry eye syndrome, the stain is mostly along the inferior cornea, just above the lower lid margin and centrally, with very little near the upper lid. Treatment is the same, but UV burn takes 1-2 days to heal, whereas dry eye heals overnight. One uses artificial tears, an over-the-counter preparation, every 1-2 hours, ointment at bedtime optional. I should note that this happens at any concentrated activity; reading, TV, movies, etc. The terminal exacerbation may be due to the dryness of the typical office environment. Another theory is that the machine builds up a static charge. The operator takes on this charge also. It then acts like an electrostatic dust precipitator, and irritants are attracted to the eyes. (Look at your CRT screen someday, it's usually dusty from this cause. Lightly touch the CRT face with the hairs on the back of your hand and feel the static attraction.) Eyestrain is related to the inability of the eye to focus clearly on a plane, leading to fatigue as the focus mechanism "hunts". CRT glasses are promoted to relieve this, basically by increasing contrast, similar to CRT filter anti-glare screens. The color in the glasses also helps reduce overhead glare. They are fairly light color tints. Eyestrain also comes from prolonged focus at a particular distance; the muscles get tired or cramped. This is aided by plus-power lenses (like reading glasses) focused at the distance of the terminal. Also, keep any material being copied from at the same distance and angle as the CRT, by using a copy stand, to reduce the back and forth accommodation changes. -- ==================================================================== David Robins, M.D. Smith-Kettlewell Eye Research Foundation (previously known as: Smith-Kettlewell Institute of Visual Sciences) 2232 Webster St; San Francisco CA 94115 415/561-1705 (voice) {ihnp4,qantel,dual}!ptsfa!ski!dr The opinions expressed herein do not reflect the opinion of the Institute!