Subject: (Lundquist) John Unn's idea for VDT shielding (fwd) Date: Sat, 5 Dec 1998 062515 -0600 (CST) From: "Roy L. Beavers" <rbeavers@llion.org> To: emfguru <rbeavers@llion.org> -------------------------------------------------- ---------- Forwarded message ---------- Date: Sat, 05 Dec 1998 05:15:31 From: marjlundquist@usa.net To: rbeavers@llion.org Cc: unnsc@hotmail.com Subject: John Unn's idea for VDT shielding John Unn has reported being sensitive to the radiation from his computer monitor, and wants to wrap it in aluminum foil and ground it electrically (with conductive glass over the viewing area, I assume). This is certainly worth a try, but the problem is to cover the view screen with something conductive that nevertheless permits the screen to be viewed. There is one pitfall: where the computer and monitor and keyboard are all one integrated unit, there may be a need for ventilation (in which case there will be a fan present). Wrapping a unit that needs to be ventilated will lead to overheating and possible equipment damage. Modular systems that consist of separate units generally do not have fans, and so can be wrapped. But I would suggest that John try wrapping his monitor COMPLETELY, as a test, and gronding it, to see whether this does indeed reduce his sensitivity to it. Once he knows that the idea of totally enclosing his monitor in an electrically grounded "shell" will accomplish his objective, then the challenge is to find a way to view the screen through the "shell" without losing too much of the protection. Perhaps glass that is coated with a thin layer of metal would work. Or perhaps a wire mesh screen would do the trick. More expensive would be electrically conducting cloth (and there is no guarantee that it would be at all satisfactory, so try to get a free sample). The computer itself should not be overlooked as a source of radiation, so if wrapping the monitor alone does not produce the desired degree of improvement, try wrapping the computer, too, just as a test to see if there is improvement. I have never experienced "gritty, irritated eyes" as John does, but I have indeed experienced a reduction in my visual acuity after using a computer for many hours. (It was self-correcting after perhaps 15-30 minutes.) After doing a lot of research, I figured out what was happening to my eyes. Here is some basic information about refraction of light by the human eye. Most of the refraction takes place at the interface between the air and the front of the eye, because this is where the difference in the refractive index of the two media -- air, and the cornea of the eye -- is greatest. The lens of the eye does some "fine tuning" but -- unlike a camera -- in the human eye it accomplishes only a small part of the job of bending light rays so that they are brought to a focus on the retina. The job of refraction done by the cornea depends on the shape of the front surface of the cornea, because this is the air-cornea interface; and this in turn depends on the thickness of the cornea. Corneal thickness is DYNAMICALLY controlled by the corneal endothelium. (At death, the corneal endothelium stops dynamically controlling corneal thickness, and the cornea "relaxes" to an equilibrium thickness that is different from what it was in life.) The point is, the shape of the air-cornea interface is actively controlled by one particular tissue -- the corneal endothelium -- and anything that interferes with the metabolism of the corneal endothelium will "mess up" its control of the corneal thickness, leading to a non-optimal shape of the air-cornea interface, with a consequent loss of visual acuity. As it happens, a lot of things can interfere with the metabolism of the corneal endothelium. For example, the corneal endothelium gets the oxygen it needs from the air. When people wore the early "hard" contact lenses, these lenses blocked the flow of oxygen to the corneal endothelium, which meant that the corneal thickness of these contact lens wearers changed. This did not affect their vision while they were wearing their contact lenses because the main refracting surface was the interface between the air and the front surface of the contact lens. But as soon as they took these lenses out, their vision was bad because their cornea was the wrong thickness! With the lens out, the flow of oxygen to the corneal endothelium was restored, and as it "got back to normal" in its function, the corneal thickness was gradually corrected. About 15 minutes after taking out the hard contact lens, the person could see much better. (The newer "soft" lenses permit the diffusion of oxygen across them, so there is less distortion of the thickness of the cornea.) >From the example I have just given, it is obvious that the corneal endothelium is very sensitive to the oxygen concentration in the tissues that surround it. It is sensitive to a lot of other agents, too. One of them is non-ionizing radiation (microwave radiation for sure, and possibly other RF as well). I finally realized that when I had lost my visual acuity after working on the computer for many hours, my corneal thickness had changed, and this must have occurred because something associated with the computer had interfered with the proper functioning of my corneal endothelium. In the early 1980s, NIOSH did some questionnaire surveys of computer users, and found a large percentage suffered from what NIOSH called "blurred vision". I have been nearsighted most of my life, and I know that an image is "blurred" when it is out of focus. But I prefer to call the disruption of my visual acuity after working on the computer "fuzzy vision" because it did not look the same as when I simply took off my glasses and look at the world with the eyes of a nearsighted person (who has genuine "blurred vision"). The two conditions are different. It was pretty obvious to me that some type of non-ionizing radiation from my computer was "messing up" the functioning of my corneal endothelium, and this was resulting in a very slight departure of my corneal thickness from its optimal value, which made things look like I was seeing them through a flat piece of glass that had a thin film of petroleum jelly smeared across one surface. After about half an hour away from the computer, I found that my visual acuity had spontaneously returned to normal. John Unn may have other problems with his eyes, but I think it likely that part of his problem with his eyes is a disturbed corneal endothelium with resulting alteration in the thickness of his cornea. The way corneal thickness is altered may be by controlling the flow of water in and out of it; if his cornea is comparatively dehydrated, it may be that this gives rise to the "gritty" sensation he reports. (I am just guessing, but it sounds like one possible explanation.) Interestingly, my problem with my eyes was worst on the very first computer I ever had. The more modern ones have not given me the same problem. Maybe John should consider replacing his computer as one way to deal with this problem. (He may need one that is Y2K compliant in the near future, anyway.) -- Marjorie Lundquist ********************************* Marjorie Lundquist, Ph.D., C.I.H. Bioelectromagnetic Hygienist P. O. Box 11831 Milwaukee, WI 53211-0831 USA ********************************* ____________________________________________________________________ Get free e-mail and a permanent address at http://www.netaddress.com/?N=1 Archive provided courtesy of WaveGuide, http://www.wave-guide.org Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html