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Blue Light And Your Eyes

Main St Optometry Newmarket
18 June 2019
Blue Light and Your Eyes

The eyes are sensitive to a narrow band of light frequencies called the  visible light spectrum.  Blue light has the shortest wavelength of the  visible light spectrum, and blue rays with the shortest wavelengths have  the most energy.  Blue light is generally defined as visible light  ranging from 380 to 500 nanometers (nm).  Since the entire visible  spectrum ranges from 380nm to 700nm, blue light makes up approximately  one-third of all visible light.  

Our main source of blue light is  sunlight, however the number of indoor man-made sources of blue light is  on the rise.  This includes fluorescent lighting, LED lighting, and  display screens such as smart phones, tablets, computers, and flat  screen TVs.  

Despite the fact that the eye is good at blocking UV rays from reaching  the retina, the eye is not very good at blocking blue light.  Virtually  all visible blue light passes through the cornea and lens and reaches  the retina.  The effect of this exposure is cumulative, and the total  number of exposure hours is what matters.  

Exposure to blue light may also contribute to the following:

The human crystalline lens absorbs UV light throughout life and slowly  yellows with time.  By the age of 20, it has yellowed enough to filter  some but not all HEV blue light.  However, it is now believed that this  absorption throughout life is a contributing factor to aging and  cataract formation.

Too much exposure to blue light can damage light sensitive cells in the  retina.  This causes changes that resemble those of macular  degeneration, which can lead to permanent vision loss. Studies have  shown that it is the cumulative effect of this exposure that causes the  damage, and that mainly affects the cones (the photo sensitive cells  responsible for central vision and colour vision) and the retinal  pigment epithelium (cells responsible for nourishing the retinal  cells).  Lutein, a blue blocking pigment, is found in healthy human  retinas and has been shown to protect against the blue light photo  damage.  

Computer screens and other digital devices emit significant amounts of  blue light and people are spending more and more hours looking at them.   The high energy blue light waves scatter more in the eye and is not as  easily focused.  This scatter creates “visual noise” that reduces  contrast and can contribute to digital eye strain.

Certain wavelengths of blue light can help boost mood, alertness,  memory, and cognitive function.  Blue light is also important in the  regulation of the circadian rhythm, the body’s natural sleep/wake  cycle.  Proper and timely exposure to blue light helps the body to  maintain wakefulness, and as the natural blue light (sun) wanes in the  evening the restful cycle begins.  Therefore, exposure to too much blue  light at night through screens and indoor lighting may lead to poor  sleep quality, difficulty falling asleep, and daytime fatigue.

Some lens manufacturers  have developed special glare-reducing lenses and coatings to block blue light.

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