Possible danger in using SoLux lights?
After having my web page about SAD lighting up for a couple of years, I received email from a SoLux distributor in Finland warning about a possible danger of using SoLux bulbs for this purpose. I haven't had a change to go over this email with an ophthalmologist to evaluate the possibility of danger; if anyone with expertise in this area could do so, I'd appreciate hearing from you. In the meanwhile, I'll just post what I received and let you make your own evaluation.
If I'm understanding, the writer is recommending not using light therapy at all. I need to look into the matter more thoroughly, since I think I can reasonably state that light therapy has been helpful in treating my winter depression.
UPDATE: The letter from the guy in Finland might not even be legitimate; see the follow-up letter at the very end of this page.
Dear Sean,
I wrote to you first time already on Sun, 24 May 1998. Although our company is selling SoLux, we do not recommend it to light therapy. The reason was the very high surface brightness.
Now I have learned more about this. I never recommend to have light therapy, if the lux amount is 10,000. There is a risk for macular degeneration, because there is blue wavelengths in SoLux more than in light which is not full spectrum.
The real problem is with the visible light that penetrates to the retina (which is why it is called visible - we can detect it). There are two different types of risk from high intensity visible light, acute and 1) Acute retinal damage appears to be caused by light induced oxidation that exceeds the repair mechanism's ability to repair the damage. This is wavelength dependant and the risk diminishes with increasing wavelength with the greatest risk in the blue region, from 400-480 nm. This type of damage can also be caused by lasers or by looking at the sun - often during an eclipse. This results in lesions and scarring in the retina. It can also be caused by bright light therapy units, as described in the reference in our web site, in which case lesions appeared in both retina of a closely monitored individual within 5 days of using a bright light therapy unit.
My friend in the U.S. has recently been contacted by a person using a commercial 10,000 lux unit in the U.S. since 1995, who has developed retinal scarring to such an extent that she is now legally blind. This case is not yet published, as the ophthalmologists were not aware of her use of bright light therapy while her condition developed, until recently. They are currently re-assessing her damage, and I expect will publish her case in the near future.
2) long term retinal damage which is cumulative over time and may be caused by repeated oxidative insult from bright visible light. It may also be caused by light damage to the retinal pigment epithelium which causes a break in the blood-retinal barrier and allows microphage from the body's immune system to invade the retina where they can live up to five years, attacking and destroying photoreceptor cells- which they don't recognize as "self". Over time this can result age related macular degeneration and permanent blindness. The wavelengths to which this damage is most susceptible is around 430-460 nm.
The reason for stating earlier that their units appear to have greater risk than others is because of the small size of the lamp and the lack of a diffuser. Thus the image formed on the retina is very small and bright, and it is the intensity or brightness (number of photons per cm2) of the retinal image of the light source that is related to its potential retinal hazard.
The most thorough summary regarding the ocular risks of bright light is "Bright Light Therapy for Winter Depression: Potential Ocular Effects and Theoretical Implications" in Photochemistry and Photobiology 1990; 51(6):781-792 by Terman et al. You might also find the paper "Long Term Light-Induced Retinal Degeneration in the Miniature Pig" by Dureau interesting- It can be found at http://www.emory.edu/molvis/v2/dureau
Relevant recent papers are
"Bright Light Therapy in Focus: Lamp Emission Spectra and Ocular Safety" by Reme et al in Technology and Health Care 1996;4:403-413
"Light History and Age-Related Changes in Retinal light Damage" by Organisiak at al in Investigative Ophthalmology and Visual science 1998; 39(7): 1107-1116
"Light Damage Revisited: Converging Evidence, Diverging Views?" by Reme et al, in Graefes Archives of Clinical and Experimental Ophthalmology 1996; 234:2-11
Regarding wavelengths that are most damaging to the retina and retinal pigment epithelium "Blue Light Induced Dysfunction of the Blood-Retinal Barrier at the Pigment Epithelium in Albino vs Pigmented Rabbits" by Putting et al Exp Eye Res 1994; 358; 31- 40 lists 439 +/- 6 nm as the most damaging. In an earlier paper "Spectral Sensitivity of the Blood Retinal Barrier at the Retinal Pigment Epithelium for Blue Light in the 400 to 500 nm Range" in Graefes Archives of Clinical and Experimental Ophthalmology 1993; 231:600-06 he found that the RPE is most sensitive to damage at about 420 nm.
Re humans, in "Blue Light Induced Reactivity of Retinal Age Pigment" in The Journal of Biological Chemistry 1995; 270(32):18825-18830 Rozanowska et al the abstract state "Exposure to the eye to intense light, particularly blue light, can cause irreversible, oxygen-dependent damage to the retina. We have found that illumination of human retinal pigment epithelium cells induces significant uptake of oxygen that is both wavelength and age dependent...and contribute to the development of age-related maculopathy" You should be able to find this abstract on Medline or possibly at the Journal of Biological Chemistry web site.
In summary retinal damage primarily dependant on the number and energy of photons that impact on a portion of the retina.
Blue light under 450 nm is the most hazardous.
The retinal risk from light depends on the brightness the image of the light source on the retina, regardless of whether it provides a reading of 1,000, 10,000, or 50,000 lux on a light meter. Thus a narrow beam from a laser can cause irreversible retinal damage even if it doesn't produce a high reading on a light meter. It just provides very bright illumination on a small area of the retina where it causes damage.
There are studies, which show, that 400 lux of special green light is as effective as 4000 - 6000 lux of cool white or broad spectrum white light in inducing a response in the light sensitive areas of the brain not involved in vision. On the following page is also useful information. Although I do not think that the Sunnex method is the best because we need all the colors of daylight, they have some very interesting info: http://www.sunnexbiotech.com/frames/bright.html
I hope that you find this helpful.
Best regards
Ilkka Pekanheimo
Finland
On 21 Feb 2000, Phil Bradfield (PBradfield@aol.com) from Tailored Lighting Inc. (the vendor of SoLux) wrote the following response:
Dear Mr. Crist,
Did you ask the guy from Finland if he also recommends avoiding the blue sky of a cloudless day?
Just don't stare at SoLux bulbs and you'll be fine.
Phil Bradfield
Tailored Lighting Inc.
www.solux.net
On 15 Sep 2000, I received the following message from Kevin P. McGuire, President of Tailored Lighting Inc.
Dear Mr. Crist:
I would recommend to anyone using a MR-16 point source at close range, regardless of the manufacturer to consider using a diffuser to reduce glare. In fact, on all the SoLux task and clip on lights we sell provide a diffuser.
Also, as a matter of fact, SoLux does not emit any more blue light than our competitors, we emit less of the other wavelengths in order to provide the perfect balance of light found in the daylight spectrum. Therefore, SoLux does not posses any more health risk than an ordinary bulb.
Please forward this letter to Ilkka Pekanheimo, Finland.
Regards,
Kevin P. McGuire
President
Tailored Lighting Inc.
On 17 Jan 2001, I received the following message from Kevin P. McGuire, President of Tailored Lighting Inc.
Dear Sean:
One additional note about the letter that Ilkka Pekanheimo from Finland sent you. A visitor to our web site noted that you referred to Ilkka Pekanheimo as a distributor of SoLux. In fact, we do not at this time have a distributor of SoLux in Finland, and Ilkka Pekanheimo is not to our knowledge an authorized distributor of our product. Please correct this in your web site.
Regards,
Kevin P. McGuire
President
Tailored Lighting Inc.