The risk of damage to the retina from blue light is increased in people with retinal damage, those who use photosensitizing medications or supplements, and older people. Even a young person with a healthy retina faces a significant risk of advancing the onset of macular degeneration and blindness by many years with long term, repetitive exposure to the blue wavelengths of light from a "bright" or blue light therapy unit. Several specialists involved in research of the pathogenesis of macular degeneration now recommend that everyone use sunglasses that block blue visible light in order to limit the amount of blue light reaching the retina over a lifetime.

While the proposition that increased exposure to blue light may double a persons risk of becoming blind in their lifetime may appear to be an overstatement of the degree of risk from the use of bright light and blue light therapy devices, it is not. The two major epidemiological studies on the causes of blindness and visual impairment in the U.S. found that the development of macular degeneration is related to the amount of exposure to visible blue light in the years preceding onset.

Data from the more recent study showed that an increase of 3 hours of daily exposure to sunlight for people in their teens and thirties advances the onset of macular degeneration in these individuals by 10 years.¹ As both papers pointed out, it is established that the only contributing element of sunlight towards the pathogenesis of macular degeneration is from the blue visible light wavelengths.^{1a, 2} More recently, a study using objective measurement of lifetime sunlight exposure also found that the pathogenesis of AMD is linked to cumulative sunlight exposure, i.e. the cumulative exposure to blue visible light wavelengths over a lifetime.³

25% of people in the developed world will have vision problems caused by age-related macular degeneration by age 75, (10% 65-74 and 25% over 75 have severe vision loss). For people with a family history of macular degeneration, the prevalence of severe vision loss increases to 54% at age 75, and 64% at age 85. A 10 year advance in onset of AMD would dramatically affect the lives of a large proportion of light therapy users, and would more than double the likelihood of becoming blind in their lifetime.^{4, 5} 

It is primarily the blue wavelengths of light (400 - 475 nm) in light therapy devices that are of concern. Blue light contributes about 90% of the risk of photochemical retinal damage from fluorescent lamps and sunlight, which is why the term "blue light hazard" is used to describe this risk. Recent studies on light exposure of mammals, as well as in vitro studies and post-mortem analysis of the human retina that examine the mechanisms by which cumulative blue light exposure induces retinal degeneration, all support the thesis that repetitive exposure to blue wavelengths of visible light promotes the development of ARMD.⁶ 

A senior researcher in the field of light therapy who studied spectral sensitivity of light therapy has pointed out that there is no need to use potentially hazardous blue light wavelengths as these wavelengths provide no increase in efficacy over the green light wavelengths in the spectral region of 500 nm. Light therapy devices emiting shorter wavelengths of light should not be used until the potential hazard from blue light from light therapy devices is resolved. In the wordsof this researcher, "It should be noted that broad-spectrum white light, traditionally used for bright light therapy, also contains blue light of potential concern particularly for very high intensity, long-duration exposure. Clearly, the safety of bright light therapy for people needs investigating. In the meantime it would be suggested that light in the 500 to 530 nm wavelength range (blue–green) should still be effective while avoiding the putative blue hazard".⁷

To see the extent of concern regarding the link between blue light exposure and ARMD that is shared by numerous research groups around the world, please see a list of some of the studies presented at the 2006 ARVO meetings that address this matter.  Without exception all these abstarcts, and subsequent abstracts presented at the 2007 and 2008 ARVO meetings, are consistent with the thesis that the blue light exposure contributes to the development of ARMD. See ARVO 2006. Considering 10 million Americans have lost some or all of their vision as a result of ARMD with normal light exposure, it makes sense to avoid additional retinal stress induced by bright and blue light therapy devices if other options are available.  See ENDNOTE below

Sunnex Biotechnologies' Lo-LIGHT technology is a safe, low intensity alternative to bright light therapy. It is the only light therapy device that filters out dangerous high-energy blue light rays. While some "blue light" therapy devices emit wavelength in the 460 - 465 nm range, which is 70-80 % of the maximum blue hazard, the blue-green light ( peak 500 nm) used in the Lo-LIGHT is less than one-tenth as hazardous to the eye as blue light with a wavelength of 440, where the blue hazard peaks according to the International Commission on Non-Ionizing Radiation Protection.

These same authoritative sources also state "we believe that there is support for the long-held belief that light has a role in the pathogenesis of ARMD. That is, the recent findings that antioxidant therapy has a protective effect confirms that oxidative stress has a role in the pathogenesis of AMD and laboratory studies have demonstrated that light, and in particular blue light, is a source of oxidative stress via its interaction with retinal chromophores. Therefore a reduction in blue light exposure might reasonably be expected to reduce progression in ARMD"⁸ This is consistent with other investigators who have explained that "avoiding exposures to bright short-wavelength [blue] light is the simplest preventative measure against light damage".⁹