Misconceptions on Light
Following is a guest post by Gary L. Morgan, OD, who emphasizes medical eye care in his practice, Eye Tech Eye Associates. Dr. Morgan is also an early adopter of new technology, and he's published and lectured on the clinical advantages of incorporating technology into optometric practice.
Wow! When I got the invitation to be a guest writer for Dr Mannen’s blog regarding blue light and UNITY Lenses with BluTech, I was truly honored. And, I am excited, as I’ve got something to say…
I have spent the last few years digging through research trying to educate myself on what is harmful to the eye. What I have discovered may surprise some of you reading this.
Open any of our trade publications and you will see product ads and articles touting UV protection, which is important, but only to a certain extent. You see, UV protection will not stop children from developing ADHD-like symptoms. UV protection will not protect those that work the night shift or spend long hours at night working on computers from sleep disorders, diabetes, obesity, heart disease, depression, stroke, cancer, or blindness. But as eye care professionals, we can play a part in protecting the public, our patients, from these maladies.
I often ask the question of my colleagues: what is more dangerous to the eye, UV light or visible light? The answer is visible light and, in particular, the blue end of the visible spectrum, herein referred to as blue light.
UV light can cause cancers of the eyelid, photokeratitis, pterygia, pinguecula, and may contribute to cataract. In general, people in the developed world do not go blind from these conditions. Except in the very young human eye and at a narrow band of 320 nm, the cornea and lens block UV light. Only visible light reaches the retina and it is blue light, ranging of 400-500 nm, that we need to start protecting our patients from.
Outdoors, the sky is blue, plenty of blue light there. However, our indoor world has turned blue as well with CFL light bulbs replacing traditional incandescent bulbs. LCD displays of televisions, computers, tablets, and smartphones are all back lit by fluorescent light, bulbs which have a high blue spectral emission.
- When we refract, the sweet spot of the spectrum is green light. (We were taught to refract “one into the green,” right?) As blue wavelengths are shorter than green, they are focused in front of the retina, creating blur or chromatic aberration. In fact, blue light is up to -1.00D out of focus. This creates glare and decreased contrast sensitivity, diminishing visual performance
- Light from 459-484 nm falling on intrinsically photosensitive retinal ganglion cells containing the photopigment melanopsin enables resetting of our circadian rhythm. Exposure to these wavelengths after dark triggers the suprachiasmatic nucleus (our brain’s master circadian clock) to suppress the pineal gland from secreting melatonin. The resulting sleep disturbance has been linked to the diseases described above. In fact, the WHO International Agency for Research on Cancer has added night-shift work to its list of known and probable carcinogens.
- Light from 400-460 nm has been implicated in oxidation occurring in the visual cycle that leads to increased lipofuscin production in RPE cells, the precursor to age-related macular degeneration (AMD). AMD is the leading cause of blindness for those over age 55 in the U.S., with 2 million people per year developing dry AMD and 550 new cases of CNV each day.
Wouldn’t all of your patients benefit from filtering out these wavelengths?
UNITY Lenses with BluTech block UV and filter blue light commensurate with damage across the blue light spectrum. This allows for protection against the most harmful blue light while also filtering the blue light that can affect the sleep-wake cycle. They incorporate ocular lens pigment (OLP) and melanin into the matrix of the lens, essentially enhancing the natural protective components of the eye.
OLP forms in the lens from exposure to light and oxygen over time. This protection peaks around age 65, essentially filtering all light below 500 nm. However, a decline in lens clarity begins ultimately leading to cataract removal and loss of protection, as even blue filtering IOLs only replace about 50% of the blue light protection of a 65 year old lens. But what about the 2-year-old with an iPad 8" from their face? A 30-year-old?
Ocular melanin is found in the iris, RPE and choroid. In the iris, melanin acts as a photo-screen, with light absorption being greatest at shorter wavelengths. In the RPE and choroid, melanin serves as an antioxidant. Due to constant exposure to light and oxygen with age, melanin loses its antioxidant effect becoming pro-oxidant, which can lead to increased lipofuscin formation in RPE cells. Dark-colored eyes contain a greater amount of uveal melanin and therefore maintain antioxidant properties protecting the RPE until a later point in the aging process. This effect could explain the decrease in the incidence of AMD in the dark-colored eye.
So I will ask my question again, which light, UV or visible, is more damaging and more important to protect our patients from? Is there a patient on the planet that would not benefit from blue light protection? What if you could protect your patients and enhance your practice’s bottom line?
UNITY Lenses incorporated BluTech into their product line in April 2013. For VSP Optics Group to introduce this product strongly indicates the importance they place on BluTech to protect their covered lives, our patients. As I See It, it is up to each of us as providers to help in this endeavor.
Learn more about the science behind blue light. Join Bill Nye at Vision Expo West as he simplifies the science behind the lens technology at the VSP Global booth #22087, or visit vspopticsgroup.com/unity for more information.
References and Further Reading:
Cziesler, Charles. Casting light on sleep deficiency. Nature, Vol. 497, May 2013
Albert R. Wielgus, Joan E. Roberts. Retinal Photodamage by Endogenous and Xenobiotic Agents. Photochemistry and Photobiology, 2012, 88: 1320–1345
Algvere PV, Marshall J, Seregard S. Review Article: Age-Related Maculopathy and the Impact of Blue Light Hazard. Acta Ophthalmologica Scandinavica 2006; 84(1):4-15
Lockley SW, Brainard GC, Czeisler,CA. High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light. J Clin Endocrinol Metab. 2003 Sep;88(9):4502-5
Brainard GC, Sliney D, et.al. Sensitivity of the human circadian system to short-wavelength (420-nm) light. J Biol Rhythms. 2008 Oct;23(5):379-86
James Loughman, Peter A. Davison, John M. Nolan, Mukunda C. Akkali, Stephen Beatty. Macular pigment and its contribution to visual performance and experience. J Optom. 2010;3(2):74-90
Roberts, J.E. (2011) Photobiology of the Human Lens. Original research article, FordhamUniversity, Department of Natural Sciences, New York, NY
Mainster, MA. Violet and blue light blocking intraocular lenses: photoprotection versus photoreception. Br J Ophthalmol 2006;90:784–792
Hu, Dan-Ning Simon, John D; Sarna, Tadeusz (2008) Role of Ocular Melanin in Ophthalmic Physiology and Pathology Photochemistry and Photobiology vol. 84 issue 3 639-644