In the eye world, there has been much talk about the positive and negative effects of certain wavelengths of light on the eye, general physiology and even mood. Much of this discussion has been focused on artificial light sources such as electronic screens (smart phones, tablets, monitor displays), indoor and outdoor lighting such as compact fluorescent lights and now the expanding use of light-emitting diode (LED) technology as a primary lighting source.
Multiple, well-funded studies suggest how these light sources may possibly affect the eye from a cellular viewpoint (think age-related macular degeneration or AMD, early cataract formation and even cancer) to how light affects our cognition and levels of wakefulness.
Rather than boring you with all the details of the many studies in this forum, I’ve taken the liberty and distilled down the most current information for you!
- Lighting is now often used in a transmission mode for reading versus reflective (think light reflecting off traditional paper print).
- Newer lighting technologies utilize high brightness LEDs which produce white light from bi-chromatic sources peak around 450-470 nanometers (nm) in the light spectrum.
- The power spectrum of white-light LEDs are considerably different from traditional fluorescent or incandescent white light sources.
- More persons are presenting to eye care providers complaining of eye strain. The idea of “Computer Vision Syndrome” is gaining more credibility.
- In addition, white-light LED devices degrade over time primarily through bleaching of phosphors so that they no longer efficiently absorb blue light. This shifts the color temperature of the device over time, with a corresponding change in the color-rendering index but, more importantly, an increasing blue emission from the device with time.
- Exposure to light within the blue spectrum, approximately around 470-480 nm stimulates retinal production of melanopsin which in turn supresses the hormone melatonin. Melatonin is very important for normal circadian rhythm – think wake and sleep cycles. We are surrounded by blue spectrum emitting devices – even street lights are now LED powered.
With age, the lens becomes more yellowish, and thus, the spectrum of blue light transmission dramatically decreases through the years. It is suspected that one reason older individuals experience sleep problems is the lack of blue light during the daytime. Several investigations have shown that intense exposure to light of specific wavelengths or intensity may induce severe damage to the retina, most likely photo-chemical damage. Many different antioxidants can reduce the damage to the retina, suggesting an oxidative process is causative.
The second type of light-induced photo-chemical damage occurs with longer (12–48 hour) but less intense light exposure. Studies indicated that blue light (400–440 nm) might be more damaging. The severity of light-induced retinal damage changes with the time of the day. For example, rats are three to four times more susceptible to light damage at night than day.
Experimental models suggest exposure to blue light in the 470–490 nm range may be less damaging to the eye compared to blue light in the 400–460 nm range. Therefore, the development of LEDs with a peak emission of around 470–490 nm may represent an important advancement in the safety of LEDs for ocular health in the future.
Light exposure and age-related macular degeneration in humans
A series of studies in many animal models have shown that exposure to blue light may represent a risk for the development of AMD or other retinal pathologies. Individual susceptibility to blue light damage varies significantly among individuals, making the assessment of the risk associated with repeated exposure to blue light in the etiology of AMD difficult.
Ultraviolet (UV) light is a risk factor for age-related macular degeneration. UV is mostly blocked by the cornea or lens; therefore, only visible light can penetrate the eye and reach the retina. A recent study conducted with an animal model reported that blocking UV light and blue light with yellow-tinted intraocular lenses materials (400–450 nm) could protect the retina.
Conclusions and Recommendations
The use of blue light is becoming increasingly prominent in our society and a large segment of the world population is now subjected to daily exposure (from a few minutes to several hours) of artificial light at increasingly longer lengths of time. Light exposure has a cumulative effect and many different characteristics (e.g., wavelength, intensity, duration of the exposure, time of day) are important to consider. Most researchers are convinced that exposure to blue light from LEDs in the range 470–480 nm for a short to medium period (days to a few weeks) should not significantly increase the risk of development of ocular pathologies. However, this conclusion cannot be generalized to a long-term exposure (months to years). Certainly more studies are needed to substantiate cause and effect relationships.
Here’s what I recommend in the mean time: Wear protective eyewear. Outdoors, think sunglasses and a hat. Indoors, for those with significant exposure (greater than four hours) to LED-illuminated screens I strongly suggest wearing eyeglasses with new anti-reflective and coating technologies which significantly reduce the shorter wavelengths below 470 nm. Various trade names include Crizal Prevencia®, Zeiss DuraVision®, Kodak BlueReflect®, Hoya ReCharge® and EyeZen® to name a few. Reduce your screen time in the evening. Don’t use your smartphone in bed. Eat a diet rich in antioxidants – think kale, spinach and brightly colored vegetables. I’d like to see you in person – come visit me at my Boulder, Colorado office!