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Dr Ryan Parker
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Refer this article as: Parker, R., Putting the medicine in the lenses : The importance of blocking ultraviolet radiation and blue light, Points de Vue, International Review of Ophthalmic Optics, N71, Autumn 2014

Putting the medicine in the lenses : The importance of blocking ultraviolet radiation and blue light

Date of publication :
10/2014

Advancements in spectacle lens technology have given eyecare providers the ability to blend medical and refractive eyecare in our dispensaries. Lenses can do more than just provide amazing vision, they can be used to prevent or delay the onset of certain ocular disease states. Proper use of Crizal® UV, Crizal® Prevencia® and Xperio® UV will allow us to exceed our patient’s expectations by not only providing superior vision now, but by simply wearing lenses, protect their visual system for years to come.

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My passion for medical optometry

When I think back on my fond memories of optometry school I can still remember the anticipation and excitement that came when it was time to grab that patient chart and get to work. The level of excitement was even more pronounced if the patient happened to be a medical case instead of just a boring refractive patient. So was born the great divide in my mind with my chosen profession, medical optometry vs. refractive optometry. 
As I now enter my tenth year of private practice I know my days will be filled with both medical and refractive cases and that is one of the many things that I believe makes the optometric profession a great one. Now that I have the chance to go lecture to many schools and colleges of optometry I stress to future optometrists that the medical aspect is exciting and challenging but not to forget about that all-important refractive part. The bulk of my day in private practice is filled with patients wanting to see as well as possible, which usually ends up with a refractive solution.

Prevention now is part of the discussion with patients 

The technology wave in optometry seems to be ever-changing and it continues to improve the care that I can deliver to my patients. Thanks to companies like Essilor that understand the importance of re-investing in research and development, I now have optical products that intertwine medical and refractive optometry. Daily I am having conversations with my patients’ that discuss glasses and ocular disease in the same breath. These cutting-edge technological lens advancements are one reason why I have chosen to utilize Essilor products in my practice. 
These products are very exciting to me as an optometric physician because now instead of using products to simply just solve problems, I can use these products to actually prevent and delay the onset of certain conditions. As many other medical professions are having conversations with patients about prevention, I feel it is imperative that we have those same conversations. Due to medical advancements, patients are living longer and as we age, our natural anti-oxidant defense mechanisms naturally decrease. Most diets are not what they should be, with an increase in processed fatty foods and a decrease in nutrient-rich natural foods. This creates the perfect storm: our patients are living longer and they are not getting the proper nutrients, which is why the number of cataract and macular degeneration cases is expected to double over the next twenty years. Thus prevention is critical.

Light is both beneficial and harmful 

How then as eyecare providers do we have the ability to prevent damage to the visual system? To understand that, it is important to remember what gives us sight: light, which is part of the elec-tromagnetic spectrum (see Figure 1). While most of the electromagnetic spectrum is beneficial, parts of it are not, mainly UV radiation and high-energy blue light. 
We all know UV radiation is bad for the skin, but we often forget that it also damages the visual system as well. Only 2% of UV radiation reaches the retina, thanks to the cornea and crystalline lens. Since those structures absorb so much UV radiation, that is where the damage will occur, mainly in the form of cataract formation, ptyregium formation, and some studies suggest dry eye issues [3] . While these issues are many times not sight-threatening and fairly fixable, patients do not want to go through surgery or start dry eye therapy early in life. By educating patients that products exist that not only provide superior vision but limit UV exposure and may prevent ocular disease onset, we are addressing the medical need for proper eyewear. 

While most of the electromagnetic spectrum is beneficial, parts of it are not, mainly UV radiation and high-energy blue light.

The eye treats visible light differently than UV radiation. The visual system is adapted to focus visible light onto the retina, which gives us the ability to see. But not all visible light is good for the visual system. High-energy blue light, which sits next to UV radiation in the electromagnetic spectrum, causes damage to the eye, specifically the cone photoreceptors. To understand how this occurs, we need to remember the chemical reactions that occur during the visual pathway (see Figure 2). We can see that in both the photoreceptor outer segment and RPE, blue light can cause oxidative stress. As we age, and based on our genetics, our anti-oxidant defense mechanisms decrease. We can’t change our genetics, we can take vitamins to help those defense mechanisms, but what about reducing our exposure to damaging blue light?

Dramatic increase in blue light exposure 

I believe that since blue light exposure is cumulative, just like UV radiation, if we can limit exposure, we can prevent disease progression. To limit exposure we must know the sources of blue light. First is the sun. The blue light portion of daylight varies between 25% and 30% [2] . Remember the sun also exposes us to UV radiation in addition to visible light. Blue light also comes from artificial light sources, which have been on a dramatic increase over the past few years. Compact fluorescent bulbs contain 25% harmful blue light [2] . LEDs contain 35% harmful blue light; the cooler white the LED is, the higher the blue light proportion [4] . Many of us have made the switch to these new energy-saving bulbs in our homes and offices, which will cause an increase in blue light exposure. If you still think you and your patients do not have increased blue light exposure, think again: smartphones, tablets and laptops are all sources of blue light exposure as well.

Electromagnetic spectrum
Electromagnetic spectrum and zoom on visible light. 
 

Blue-violet light, the most damaging band 

We must then begin to understand blue light better. Thankfully, the Paris Vision Institute has done some groundbreaking research on that topic. In 2008 they began an eye health research project to better understand blue light. This was the first in vitro test in the ophthalmic industry to split the visible light spectrum into 10nm bands and see which bands of light caused the most damage on swine retinal cells. The results showed maximum cell damage occurs from 415-455nm, with a peak at 435nm +/- 20nm [2, 4] . 
This damaging band of light was termed blue-violet light. Cumulative exposure to blue-violet light will lead to retinal cell death and is one of the risk factors for macular degeneration. Compact fluorescent bulbs, LED sources and sunlight all emit these damaging wavelengths of light. Another important finding was that not all blue light is damaging. Blue-turquoise light ranges from 465-495nm and is essential for sleep/wake cycles, memory, mood, cognitive performance and pupillary constriction [2] . Blue-turquoise light is also needed for visual acuity and color perception. Just because it’s blue does not mean it’s bad.

Scientific assumption
Scientific assumption: phototoxicity mechanisms in the outer retina

Limiting UV exposure with Crizal® UV and Xperio® UV

What can we do as eyecare providers to provide our patients with the clearest sharpest vision possible, while limiting exposure to the damaging part of the electromagnetic spectrum? This is where we can put the medicine or preventive medicine in the lenses. By utilizing the right products in our dispensaries, not only can we provide great vision, we can potentially delay and/or prevent onset of ocular disease. Let’s deal with UV radiation first. Typically when we talk about UV, we think of sunglasses. Sunglasses are important, but our patients receive up to 40% of their UV exposure when they are not in direct sunlight. The UV conversation is important on both the sun pair and everyday pair. 
When I talk with my patients about UV prevention on their everyday pair, I talk about Crizal® UV non-glare lenses. Crizal® UV delivers amazing vision by fighting the five enemies of vision: glare, scratches, smudges, dust and water. In addition to these great features, Crizal® UV greatly reduces the amount of UV radiation that enters the visual system. 
When thinking about UV radiation, we have to think about both sides of the lens. UV entering the front side of the lens can either pass through the lens or be reflected/absorbed. By selecting the proper index of materials, polycarbonate and above, no UV radiation will pass through the lens. But that is only part of the equation; what about UV radiation reflecting off the backside of the lens? Studies suggest that up to 50% of UV exposure can come from reflections off of the back surface of the lens [1]. Crizal® UV lenses reduce the backside UV reflections to 4%, giving it an industry-best eye-sun protection factor (E-SPF®) of 25 for clear lenses. In other words, wearing Crizal® UV lenses means you are 25 times more protected from UV radiation than not wearing any lenses at all. This built-in UV protection separates Crizal® UV from other non-glare lenses on the market and allows me to have medical-focused conversations about preventing ocular damage by wearing glasses. 
What happens when the patients goes outside and is in direct intense sunlight? UV protection is of the upmost importance in this environment. My product of choice for sunwear is Xperio® UV. Similarly to Crizal® UV, Xperio® UV deals with UV radiation on both sides of the lens. The same rules still apply to UV coming through the front of the lens, so proper lens material selection is extremely important. The backside reflections are still present on sunwear and Xperio® UV reduces them to 1.5%, giving the highest E-SPF® available today of 50+. Not only does Xperio® UV limit UV exposure but it is also polarized, which means my patients get the maximum UV protection and best vision possible in their sunglasses. By utilizing these products on my patients’ everyday pair and sun pair, I am protecting their visual system by preventing damage caused by UV radiation. 

Limiting blue light exposure with Crizal® Prevencia® 

What about reducing blue light? I have the blue light conversation with my patients that have a strong family history of macular degeneration, have signs of macular degeneration or have a high exposure to blue light. In my practice Crizal® Prevencia® is my lens of choice when it comes to reducing blue light exposure. This product is superior to the competition because it blocks more of the damaging blue-violet light and UV radiation than anything on the market today. It has patented LightScan TM technology that selectively filters out harmful blue-violet light and UV radiation, including backside reflections. It also allows beneficial blue-turquoise light to pass through the lens while maintaining excellent lens transparency. Crizal® Prevencia® No- Glare lenses are able to deflect 20% of the harmful blue-violet light that our patients are exposed to on a daily basis [2].

With Crizal® UV, Crizal® Prevencia® and Xperio® UV, we now have the power to blend the medical and refractive sides of optometry.

The Paris Vision Institute showed that this amount of deflection reduced retinal cell death by 25% [2] . On the surface, those numbers may not sound amazing, but it is greater than any other product on the market, and that 25% protection is very similar to what we expect when we discuss AREDs vitamin formulations with our patients [2]. With Crizal® Prevencia® you can expect it to perform like the other Crizal® UV products. It has an E-SPF® of 25 and virtually eliminates backside UV reflections and features complete protection from the enemies of clear vision: glare, scratches, smudges, dust and water. 

Conclusion 

Our goal in the eyecare profession is simple, to provide our patients with the best vision possible. We strive to accomplish this goal daily by providing patients with the best medical eyecare they can get and/or by providing them with the best means of correcting their refractive error. This type of care has become standard and patients expect this when they visit their eyecare providers. 
How then can we exceed our patient’s expectations? I believe by using the technological advancements that are available in today’s spectacle lenses we can do more than we have ever been able to do before. We now have the power to blend the medical and refractive sides of optometry. We can do more than just deliver the best vision possible; we can now put the medicine in the lenses and have conversations with our patients about prevention of future ocular diseases by simply wearing the right lenses in the correct environment. Essilor has given my dispensary the tools to do just that. I talk about Crizal® UV to all my patients on their everyday pair, Xperio® UV on their sun pair, and for those patients that have risk of macular degeneration or high exposure to damaging blue light, Crizal® Prevencia® is the answer. I encourage you to explore the benefits of these practice-changing products and begin having these same conversations with your patients and exceed their expectations.

Key Takeaways

• Patients receive up to 40% of their UV exposure when they are not in direct sunlight.
• UV conversation is important on both the sun pair and everyday pair.
• Crizal® UV lenses (everyday pair) with E-SPF® of 25 protect 25 times more from UV radiation than not wearing any lenses at all.
• Xperio® UV polarized lenses (sun pair) deal with UV radiation on both sides of the lens, giving the highest E-SPF® available today of 50+.
• Blue light conversation is important with all patients and particularly with patients who have a strong family history of macular degeneration, already have signs of it or have a high exposure to blue light.
• Crizal® Prevencia® lenses (everyday pair) selectively filter out harmful blue-violet light and UV radiation, while allowing beneficial blue-turquoise light to pass through.

References

01. Citek, Karl. Anti-reflective coatings reflect ultraviolet radiation(2008). Faculty Scholarship (COO). Paper 5.
02. Barrau C, et al. Blue Light Scientific Discovery. Essilor White Paper 1.0. 2013
03. Camus KM et al. Antioxidant content and ultraviolet absorption characteristics of human tears. Optometry and Vision Science. 2011 April; 88 (4): 507-11
04. Arnault E, Barrau C, Nanteau C, Gondouin P, Bigot K, et al. Phototoxic Action Spectrum on a Retinal Pigment Epithelium Model of Age-Related Macular Degeneration Exposed to Sunlight Normalized Conditions. PloS One,23 August 2013, 8(8)

 

 

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Dr Ryan Parker
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This article has been read 409 times
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Refer this article as: Parker, R., Putting the medicine in the lenses : The importance of blocking ultraviolet radiation and blue light, Points de Vue, International Review of Ophthalmic Optics, N71, Autumn 2014

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