Recently in a social media post, I read a comment by someone referring to blue light lenses as snake oil. While I disagree, I understand the reason for this skepticism. Thanks to a combination of misleading and poorly understood blue light messaging in the optical industry over the last 10 years, many mistakenly thought that blue light from digital screens was contributing to ocular photodamage linked to age-related macular degeneration. Hopefully, we are now aware that the relatively clear blue filter lenses do not provide the level of protection from the sun or solar blue light to provide any protective benefit for the eye from sun damage and AMD.
There has been a dramatic shift in clear blue light lens messaging to a more reasonable claim that blue filter lenses can help reduce digital eyestrain and improve visual comfort for screen users. But skeptics won’t be convinced so easily this time, so what are current blue filter claims based on, relative to digital eyestrain?
One of the best explanations I have read on the link between digital blue light emission and eyestrain is by Gary Morgan, OD, in his article “Blue Light Refocused – Separating Science from Speculation.” Dr. Morgan explains that “Blue light is detrimental to vision in that shorter wavelengths are out of focus, and the retina lacks processing power for it.” (Our central fovea lacks blue cone receptors and only 2 percent of the remaining macula is comprised of blue cones to process blue light.) He goes on to say “... in the refractively corrected eye, green light is in focus on the macula. Longer wavelength red light is mildly hyperopically defocused, by approximately +0.50D. Shorter wavelength blue light is significantly myopically defocused, by approximately -1.00D. This creates a violet-blue blur circle, or haze around the in focus green component of light. This phenomenon is known as chromatic aberration and significantly affects visual quality. Blue light diminishes visual quality in that its short, out of focus wavelengths reduce contrast… Glare is worsened by blue light as its short wavelengths are scattered the most intraocularly. Blue light sources such as electronic screens or the sun can worsen glare, causing discomfort or disability depending on brightness… When viewing electronic devices, myopically defocused blue light results in what is now termed digital eyestrain.”
Dr. Morgan explains that we view digital devices at a closer range than other reading options such as books. Closer proximity increases demand on our accommodation and vergence systems. And a closer distance increases intensity which can contribute to eye fatigue. (Intensity increases with closer proximity due to the Inverse Square Law--the intensity of a light source is equal to 1 over the distance squared.) Frequency and duration of exposure also affect digital eyestrain symptoms.
Reducing short wavelength blue light screen emissions does no harm and makes it easier for our eyes to focus, increasing comfort for the prolonged time spent staring at blue emitting screens.
• Deborah Kotob
Pro to Pro Director
[email protected]
