Night lights: New guidelines put focus on illuminating roadways and sidewalks

Night lights: New guidelines put focus on illuminating roadways and sidewalks

With cities around the nation swapping out their yellow-hued, sodium streetlights for more energy-efficient, light-emitting diodes (LEDs), the AOA continues to monitor the science and will make evidence-based recommendations for the sake of the public and their eye and vision health.

As far as we know, the only significant health effect that would be detrimental to the majority of people is the effect of blue light on sleep cycles.

The blue light-emitting LEDs have been criticized by some for their potential harm to people's health and the environment, especially coupled with the many sources of blue light in people's lives. Some have linked it, for instance, to age-related macular degeneration (AMD) and cataracts.

The AOA supports additional research on the health effects of blue light.

"As far as we know, the only significant health effect that would be detrimental to the majority of people is the effect of blue light on sleep cycles," says Karl Citek, O.D., chair of the AOA's Commission on Ophthalmic Standards, as well as chair of the subcommittee for the American National Standards Institute (ANSI) that sets consumer-protection standards for the manufacture of sunglasses and over-the-counter reading glasses.

Enlightening development

In June, when the American Medical Association (AMA) adopted its new guidance on street lighting for the nation's roads, it recommended that communities select certain LED lighting to minimize potential harm to humans and the environment. Many communities are moving from conventional street lighting to the more energy-efficient LED technology. Some high-intensity LED technology emits blue light, which reaches deeper into the eye and over time can damage the retina.

The AMA's guidance, based on the report, "Human and Environmental Effects of Light-Emitting Diode (LED) Community Lighting," and adopted by its policy-making board, recommended:

  • Supporting the proper conversion to community-based LED lighting, which reduces energy consumption and decreases the use of fossil fuels.
  • Minimizing and controlling blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.
  • Encouraging the use of 3000K or lower lighting for outdoor installations such as roadways. All LED lighting should be properly shielded to minimize glare and detrimental human and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.

There are currently no accepted industry-wide standards for the design and manufacture of light sources, Dr. Citek says. "Most 'standards' for lighting are set by the community and deal with the efficiency of the light source (i.e., converting electricity into light) rather than the type or quality of light, usually specified by its color temperature," adds Dr. Citek. "For instance, cities with astronomical observatories, such as Flagstaff, Arizona, seek to minimize light pollution by requiring low-pressure sodium fixtures in virtually all public spaces (streets, parks and parking lots) and even in most private areas (residential driveways).

"These light sources also happen to be very efficient, therefore low cost for energy," he adds. "But because they only put out a very narrow bandwidth of wavelengths, they provide very poor color rendition. Most objects that reflect this light will take on a sickly, yellowish-green appearance, and most other objects will appear black. High-pressure sodium lighting, used in many other communities, provides slightly better color rendition, but at the price of slightly worse efficiency." By contrast, some communities are switching to LED lighting. "These [LED lights] also are very efficient, and they offer somewhat more full-spectrum lighting (at least significantly better than sodium sources), often mimicking color appearance of daytime sky," Dr. Citek says. "Low-color temperature, around 2500-3000K, would be equivalent to sunlight at dawn or dusk, and is similar to the light quality from an incandescent bulb.

"Color rendition is good for longer wavelengths (yellow, orange, red) but poorer for shorter wavelengths (blue, violet), which can appear black," he adds. "High color temperature, around 6500-7000K, would be equivalent to the bluish-white light coming from the north sky when the sun is directly overhead on a clear day. Color rendition is good for most typical objects (skin, clothing, cars) across the entire spectrum. This type of LED source is what the AMA is concerned about."

Shedding light
Dr. Citek welcomes any recommendations that would minimize blue light for people with photosensitivity or the distracting glare for nighttime drivers.

But the evidence that blue light causes cataracts or AMD "is not there yet," he adds. Dr. Citek says, "The amount of blue light coming from all artificial sources (computer screens, smartphones and even street lights) is significantly less (some estimates say as little as 1/100th) than that coming from the sun during daytime. Yes, it can affect melanin production, and hence change sleep cycles, but no, there is no conclusive evidence yet that it will cause cataracts, macular degeneration, or any other ocular or visual system damage for most normal, healthy people.

"What patients will potentially notice with the new LED sources is glare and/or haze, which they often will characterize as being a 'harsh' light," he adds. "Some will even complain that it looks too bright (even though the amount of light may be the same as with other sources) or that it is painful to view, especially, as I have encountered, for patients with uncorrected hyperopia or binocular problems. Short wavelengths tend to scatter more readily in an optical medium, be it the air in the environment or even within the eye. Patients with very early cataracts are much more prone to this."

Dr. Citek recommends:

  • For driving at night, an anti-reflection coating (on both front and back surfaces of the spectacle lens) to cut down on some of the potential glare. This can be applied even to photochromic lenses.
  • Avoiding looking directly at or toward a light, regardless of the source type or location (e.g., street light, lamppost, headlight from oncoming car).

October 25, 2016

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