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By: Gary L. Morgan, OD
I just returned from Vision Expo West, with 5 days of meetings, education and catching up with colleagues. I really enjoy the Vision Expo meetings; I always come away with a renewed sense of excitement for our profession.
I was particularly glad to see the emphasis placed on the new and growing threat of blue light exposure. Many companies in our industry have introduced new products with blue light protection. It is amazing to think that just 3 years ago there was only one product being introduced specifically for this purpose. I welcome this new effort, but there is one trend that I find disturbing.
While it has been a few years since I watched, I recall part of the story line of the television show, “Mad Men,” being the guys in the advertising agency working with the tobacco companies to put a good spin on cigarette smoking, even going as far as to conjure up health benefits. I am reminded of this when I hear some companies discussing “good blue light.”
A favorite quote of mine that I think of when hearing the phrase good blue light is from an editorial by Dr. Charles Czeisler that appeared in the journal,Nature: “Just as the ear has two functions (hearing and balance) so, too, does the eye.” Dr. Czeisler goes on to discuss the function of intrinsically photosensitive retinal ganglion cells (ipRGCs) in regard to regulating circadian rhythm. His point in the article is that light exposure at night, particularly in the wavelengths 459 nm to 484 nm, has decoupled us from the 24-hour-day from which our bodies evolved. Longer wavelength blue light exposure at night is affecting melatonin secretion and limiting our sleep. The resulting sleep disorders have significant health effects, some of which can be life threatening.
As I have discussed previously, when thinking about blue light, we must think in terms of wavelength. Blue light affects the eye in three ways. First, the shortest wavelengths (about 400 nm to 430 nm) have the greatest effect on vision, as they are the most myopically defocused in front of the retina.
Second, short through medium wavelengths (about 400 nm to 460 nm) have the greatest effect in terms of photo-oxidative damage to the retina, contributing to the pathogenesis of AMD.
Third, longer wavelength blue light (about 460 nm to 490 nm) has the most effect on ipRGCs, telling the suprachiasmatic nucleus (our body’s internal clock) to suppress the secretion of melatonin from the pineal gland. It is from this third component where the good blue light inaccuracy stems from.
We need long wavelength blue light exposure during waking hours to suppress melatonin to keep us alert. Seasonal affective disorder (SAD) has been linked to lack of exposure to long wavelength blue light; 460 nm light has been shown to be twice as potent at suppressing melatonin as both 420 nm light and 555 nm light. The sweet spot for melatonin suppression is 459 nm to 484 nm, so this makes sense. So, this longer blue light wavelength range has been linked to making us feel alert and happy. Thus, companies are calling long wavelength blue light good blue light, but is it always good?
Think about it. Is being exposed to 460 nm to 490 nm light after dinner a good idea when it interferes with our ability to fall asleep? How happy are we to be awake at 2 a.m. because we worked on our computer or handheld electronic device until 11 p.m., delaying the onset of melatonin secretion? Are we happy to gain weight, develop diabetes, heart disease and depression and raise our risk of having a stroke or developing cancer? Is it a good thing that our children are not getting enough sleep, which for some may lead to ADHD-like symptoms? None of these implications that are currently being extensively researched sound very good to me.
So while we need exposure to 460 nm to 490 nm light during the day, we don’t need it after sunset. As doctors, we need to take a critical look at what products are claiming and put it into perspective.
A trend I am starting to see, which I feel is a positive step, is that some companies are releasing transmittance curves for their products. Knowing which wavelengths a lens product shields against and the way in which blue light affects the eye goes a long way in our ability to counsel and protect our patients.
Companies who are offering products driven by an understanding of the science of blue light seem to have no problem sharing the spectral transmission information of their products. Because this is the only way to truly assess a blue light protective lens product, it begs the question: Why hasn’t every manufacturer published this information on their products? Could it be that the marketing story of good and bad blue light is really just a distraction from the reality of scientifically proven facts?
Czeisler C. Nature. 2013;497:S13. doi:10.1038/497S13a.