October 21, 2011
What is Light?
Light is made up of electromagnetic particles that travel in waves. The human eye responds to only a small part of the entire electromagnetic spectrum. From the longest waves (lowest frequency) through the shortest waves (highest frequency), lighting specialists identify the electromagnetic wave regions as 1) radio waves, 2) microwaves and radar, 3) millimeter waves and telemetry, 4) infrared, 5) visible light, 6) ultraviolet, and 7) x-rays and gamma rays.
Is the Blue Light Hazardous?
Sight requires light. As years go by, accumulation of lipofuscin (cellular debris) in the retinal pigment epithelium (RPE) may make the retina more sensitive to damage from chronic light exposure. Retinal light damage has been studied by exposing experimental animals and cell cultures to brilliant light exposures for minutes to hours. According to some of these studies blue light waves may be especially toxic to those who are prone to macular problems due to genetics, nutrition, environment, health habits, and aging. On the other hand, acute retinal phototoxicity experiments such as these can cause retinal injuries, but they cannot simulate a lifetime of normal light exposure. Some researchers have noted strong similarities between photic injury and retinal abnormalities caused by years of overexposure to light. Others have found no similarities. Whereas the shorter wavelengths of UV-A and UV-B are somewhat filtered by the lens and cornea, animal studies have shown that the light spectrum from UV through blue can be harmful. During lengthy exposures of up to 12 hours, toxicity of the retina is known to increase as the light wavelengths grow shorter. More recently, research on human fetal cell tissue has also revealed damage from blue light exposure.Fortunately, healthy retinas have a wide array of built-in chemical defenses against UV-blue light damage. They bear such imposing names as xanthophyll, melanin, superoxide dismutase, catalase, and glutathione peroxidase. And then there are the more familiar agents vitamin E, vitamin C, lutein, and zeaxanthin. Unfortunately, these defenses can weaken with disease, injury, neglect, and age.
Another built-in protective process is that the natural lens takes on a yellowish tint with age, which helps to filter blue light. After cataract surgery, however, patients lose that benefit. Some doctors now recommend replacing the damaged lens with an intraocular lens (IOL) that is tinted to block blue light. The patient should be made aware, however, that this procedure will diminish scotopic (night) vision. According to the CVRL Color & Vision database, light waves measuring approximately 470nm to 400nm in length are seen as the color blue. The blue bands of the visible light spectrum are adjacent to the invisible band of ultraviolet (UV) light. UV is located on the short wave, high frequency end of the visible light spectrum, just out of sight past the color violet. It is divided into three wavelengths called UV-A , UV-B, and UV-C. The effects of UV-C (100nm-290nm) are negligible, as the waves are so short they are filtered by the atmosphere before reaching the eyes. UV-A (320nm-400nm) and UV-B (290nm-320nm) are responsible for damaging material, skin, and eyes, with UV-B getting most of the blame.
When light hits a photoreceptor, the cell bleaches and becomes useless until it has recovered through a metabolic process called the “visual cycle.” Absorption of blue light, however, has been shown to cause a reversal of the process in rodent models. The cell becomes unbleached and responsive again to light before it is ready. This greatly increases the potential for oxidative damage, which leads to a buildup of lipofuscin in the retinal pigment epithelium (RPE) layer. Drusen are then formed from excessive amounts of lipofuscin, hindering the RPE in its ability to provide nutrients to the photoreceptors, which then wither and die. In addition, if the lipofuscin absorbs blue light in high quantities, it becomes phototoxic, which can lead to oxidative damage to the RPE and further cell death (apoptosis).
Blue light is an important element in “natural” lighting, and it may also contribute to psychological health. Research, however, shows that high illumination levels of blue light can be toxic to cellular structures, test animals, and human fetal retinas.The industry has established standards for protecting consumers from extremely bright light and from UV radiation; but no standards address the blue light hazard that may be affecting millions who have retinal problems. Blue light is a duplicitous character who needs to be carefully watched. Until research proves him to be either a friend or a foe, education will help consumers make decisions based upon the facts.
From Artificial Lighting and The Blue Hazard (The Facts about Lighting and Vision)
by Dan Roberts (http://www.mdsupport.org)
Ultimate Blogger Theme By Buywptemplates