Light Therapy and Retinal Damage

Experts Caution Against Bright and Blue Light Therapy Lamps

The development of Age-related Macular Degeneration (AMD) is linked to the cumulative lifetime exposure to blue light wavelengths. Dr. S. Beatty, director of the Macular Pigment Research Group stated "It is photo-oxidative stress, or the cumulative exposure to free radicals from blue light over a lifetime that causes AMD".

Studies indicate that a moderate increase in lifetime exposure to blue light can advance the onset of this blinding disease by several years. The European Eye (EUREYE) Study found that "the combination of blue light exposure and low plasma concentrations of antioxidants was also associated with the early stages of AMD, which are common in the population, and that blue light exposure in middle age might be more damaging than at younger ages."

This has led retinal experts to warn against the use of bright and blue light therapy lamps. In Photochemistry and Photobiology, Roberts and Wielgus asserted "Intense visible light sources that do not filter short blue visible light used for phototherapy of circadian imbalance (i.e. Seasonal Affective Disorder) increase the risk for age-related light damage to the retina."

In Behavioral Sleep Medicine Lack and Wright, experts in human spectral sensitivity to light therapy, cautioned users of bright light therapy "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."

Gagne et al, from Ophthalmology Department at Laval University stated, "The main finding of this experiment is that blue light reduces photoreceptor responses after only a single administration. This brings important concerns with regard to blue-enriched light therapy lamps used to treat SAD symptoms and other disorders." [Refs]

Increased risk to light therapy users from AMD

The consequences of AMD for people who use light therapy can be severe. On the 25th anniversary of the development of light therapy, the journal Science reported on the first person treated by bright light therapy for winter depression, who described how light therapy became less and less effective for him over the years as his eyesight faded, and concluded "Now I can hardly see, and all hell has broken loose... I have had periods of depression lasting over a year".
See REF from Science; Is Internal Timing Key to Mental Health?, last paragraph.

The Safe Lo-LIGHT Therapy Lamp

Sunnex Biotechnologies low intensity Lo-LIGHT therapy lamps using GreenLIGHT Technology are the safe alternative. Proven effective in independent studies published in several highly rated peer-reviewed journals by several different research groups, Lo-LIGHT lamps provide light therapy at the intensity and brightness levels normally found in a well-lit office.

In addition to filtering out hazardous UV light, the Lo-LIGHT lamps also screen out the visible light wavelengths that are most hazardous to the retina. Those wavelengths are in the blue portion of the visible light spectrum with a wavelength shorter than 485 nm. Since blue wavelengths are also emitted by white light lamps normally used for indoor lighting, Lo-LIGHT lamps are less hazardous to the eye than regular indoor lighting. Lo-LIGHT do not emit ultraviolet(UV) light, which can damage the lens or cornea and cause cataracts.

It is the combination of low intensity and the filtering out of the hazardous visible blue light wavelengths, {wavelengths shorter than 485 nm}, of the light provided by a Lo-LIGHT lamp that eliminates the risk of eye damage that is inherent in the use of "bright" white light or blue light therapy lamps. However, even the relatively safe wavelengths of light sources providing light wavelengths in the region of 500 nm provided by a Lo-LIGHT may be hazardous at high intensities. Although the soft green glow from a Lo-LIGHT lamp providing less than 400 lux is comfortable, effective, and safe, we believe other commercial light therapy devices that provides 8,000 to 12,000 lux of blue-green light of similar wavelengths may pose a hazard to the eye.

We propose it can now be established that the accumulated exposure of the eye to blue light over a lifetime is a strongly contributing factor to the development of AMD. Studies confirm that the hazardous shorter wavelengths of visible light constituting the blue portion of the spectrum, (i.e visible light with wavelengths shorter than 480 nm) are not more effective for light therapy than the longer wavelengths of visible light in the 555 nm range. Since wavelengths of light in the region of 500 to 505 nm pose much less of a hazard to the retina than blue light wavelengths, and since wavelengths of light around 500 nm have been found to be more than ten times as efficient for light therapy than blue light wavelengths, the use of light therapy lamps that emit high proportions of blue light does not appear to be justifiable.
Read - Blue Light not beneficial for light therapy.