In trying to answer the question of how blue light affects eye health we need to explore several topics.
Sunlight Exposure and Damage to the Eye
There have been multiple studies over the years that have shown excessive exposure to sunlight might cause damage to the eyes and the eyelids.
There is a very strong association with exposure to ultraviolet light and the incidence of skin cancer on the eyelids.
Research has demonstrated that exposure to sunlight also increases the risk of cataracts.
These studies include:
- Chesapeake Watermen Study (Taylor et al. New Engl J Med. 1988; 391:1429-33.)
- Beaver Dam Eye Study (Cruickshanks et al. Am J Public Health 1992; 82:1658-62)
- Salisbury Eye Evaluation (West et al. J Am Med Assoc. 1998; 280:714-8)
- Blue Mountains Eye Study (Mitchell et al. Ophthalmology 1997; 104:581-8).
The majority of this research implicates the UV portion of sunlight as the source of the damage, not blue light.
So where does the blue light problem come in?
Blue Light and Its Potential Effect on the Retina
Most of the evidence pointing to the potential detrimental effects of blue light has been inferred from an accumulation of several experimental studies, rather than any studies of direct correlation
A study by Han et al. (Nature 1976; 260:153-5) demonstrated that the retina of a rhesus monkey was most sensitive to shorter wavelengths of visible light with a maximum sensitivity at 441 nm, which is in the violet/blue spectrum.
Some of the studies mentioned previously that demonstrated a connection between sunlight exposure and cataracts also showed some increase in the amount of macular degeneration seen later in life in these same patients. Since UV light is almost completely absorbed by our own natural lens, the portion of sunlight that reaches the retina is the visible portion of light. Experimental evidence has shown that it is the blue/violet end of the visual spectrum that is the mostly likely cause of retinal damage.
The Beaver Dam eye study mentioned above showed that people who reported more than five hours of summer sun exposure in their early years had a higher rate of early macular degeneration. And since it appears that the blue/violet end of the visible spectrum causes the most retinal damage, it infers that blue light may be the major culprit.
Blue Light and Sleep
Blue light suppresses melatonin receptors. Suppressing these receptors helps improve “wakefulness,” so exposure to blue light during daylight hours helps keep us awake and attentive.
This same exposure to blue light in the evening may inhibit your ability to get to sleep by suppressing those same receptors.
Therefore, it might be wise to limit your exposure to screens on cell phones, tablets and E-readers in the hour or two before bedtime if you are having trouble falling asleep.
Another alternative is to wear blue-light-blocking lenses when using those devices in the evening. Wearing those same glasses in the daytime might actually decrease your attentiveness.
So What Should You Do?
Remember, the strongest evidence that light causes health problems is still the damage that can be done from the UV spectrum in sunlight. Cataracts and eyelid skin cancer are both strongly correlated with sunlight exposure. A good pair of sunglasses during daylight hours is the most important health benefit you can give yourself when it comes to protecting yourself from light damage.
As far as blue light is concerned, it might make sense to consider blue-light-filtering lenses if you are staring at light-emitting screens all day, particularly in the evening hours when exposure to blue light might throw off your sleeping patterns. The evidence that blue light exposure is a definitive risk factor for macular degeneration, especially at the levels given off by screens as opposed to sunlight, is much less clear.
So the answer is, there some evidence that there are some real possible health risks with exposure to blue light. But the degree of hype the subject is getting - especially by some specialty eyeglass makers - might be out of proportion to the degree of evidence that these effects are truly harmful at the levels to which we are currently being exposed.
Article contributed by Dr. Brian Wnorowski, M.D.
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