Sunwear and the science of light
How new lens technology enhances your patients’ visual experience
Light is both a particle and a wave, it has healing energy and harmful energy, and it is so fast that it travels the 24,901 miles around the earth seven and one half times in one second.1 In order for us to understand how to best manage light with sunglasses, we first have to understand some basic science of light.
Breaking down the light
Visible light is a part of the electromagnetic spectrum, which is composed of energized photons, a massless energized particle that travels in waves. The electromagnetic spectrum ranges from radio waves at the longest wavelengths, to visible light, to gamma rays at the shortest wavelengths. As the wavelength goes from longer to shorter, the energy level of the photons increases.
Only the portion of the electromagnetic spectrum called the visible spectrum stimulates the human eye.2 Wavelengths in this part of the electromagnetic spectrum are measured in nanometers (nm), which are one billionth of a meter. Visible light ranges between 400nm to 700 nm.
Other parts of the spectrum are also important for our health, including the ultraviolet (UV) portion of the spectrum. UV rays are separated into three groups:
– UVC runs from 200 nm to 280 nm and is extremely hazardous to the skin and eyes. Fortunately UVC is blocked out by the protective ozone layer of the atmosphere.
– UVB has wavelengths from 280 nm to 315 nm. These rays cause sunburn and are linked to skin cancer. The cornea and most lens materials absorb these rays.3
– UVA is closest to the visible spectrum at 31 nm to 380 nm. Long-term exposure can lead to pterygium growth and is linked to cataract development.4,5
Related: The growing green trend in optical
Portions of the visible light spectrum can also be damaging to our health. High-energy violet (HEV) light is often referred to as high-energy blue light. The extreme violet end of the spectrum (380 nm to 430 nm) is the highest energy visible light that reaches the retina. Long-term exposure is linked to retina damage, increasing the likelihood of macular degeneration.6 Short-wave high-energy blue light also creates scatter and haze, making objects appear somewhat blurry.7 Blue light in wavelengths from 430 nm to 465 nm is also linked to sleep deprivation and melatonin suppression.8
The human eye has three different light-detecting cells which function in higher (daytime) lighting levels. Each of these “cone” cells is sensitive to a different range of wavelengths (blue, green, or red). Because the human visual system extrapolates colors from what it detects at just three basic wavelengths, it can easily be fooled. By optimizing these specific wavelengths, better color perception and clarity can be achieved.9
The human eye in daylight conditions has peak sensitivity around 555 nm with all three cone cell types working together.9 By emphasizing this peak when managing light, we achieve the best clarity of vision.