Sunlight and its effect on eye health

Times are changing as we become obsessed with the 24/7 proliferation of blue light-emitting LEDs. The U.S. public health authorities are cautioning against sunlight exposure, yet growing members of the scientific community are recognizing the preventive and therapeutic aspects of ocular and dermal (non-burning) natural sunlight exposure. ¹

Avoiding sunlight entirely appears to be misdirected. Melanoma is in fact inversely related to latitude and inadequate acclimation (i.e., increased melanization and epidermal thickening), which carries the risk of melanoma and non-melanoma skin cancer-both common in northern latitudes. 

Balancing risks

The principal non-genetic melanoma risk is excessive and cumulative ultraviolet (UV) radiation. The relationship between melanoma and UV is two-sided: non-burning sun exposure is associated with a reduced risk of melanoma, while sunburns are associated with a doubling of risk.^{1, 2}

Previously from Dr. Richer: OD education must keep up with industry changes

Internal skin protection against melanoma and non-melanoma skin cancer with dietary vitamin D3, carotenoids lycopene, and secondarily lutein and zeaxanthin are underutilized strategies.³ While 1,500 patients die each year from skin cancer, 1,500 patients die each day from other cancers and vitamin D-related chronic diseases according to John Cannell, MD of the Vitamin D Council (https://www.vitamindcouncil.org) and augmented by a recent meta-analysis .⁴ Vitamin D from UV B (290nm to 315nm) sunlight exposure (and diet/supplements) is key to cancer prevention. 

Light effects on myopia

The global epidemic of myopia is upon us-especially in Southeastern Asia where juvenile myopia is an epidemic.⁵According to the National Eye Institute, Caucasian American children saw an increase between 25 to 41 percent in myopia between 1971 and 2004. African-American children saw an increase of 157 percent during the same span.^{1, 6}

Factors involved are bioenvironmental, with recent epidemiological evidence suggesting children who spend more time outdoors (in intense light) are less likely to be or become myopic-regardless of their near work or whether their parents are myopic.⁷ One likely mechanism for this protective effect is visible light-stimulating release of dopamine from the retina. This inhibits increased axial elongation, the structural basis of myopia.

The spectral characteristics of sunlight include abundant short wavelength violet and blue light-suggesting a benefit of sunlight against myopia. New provocative research suggests that violet light (360 nm to 400 nm) suppresses myopia progression.⁸ These scientists demonstrated protection in both an animal model and children provided with violet light-transmitting contact lenses.

Related: How diet and nutrition affect disease

This new research finding isn’t an outlier: autoimmune diseases like type I diabetes, multiple sclerosis, and rheumatoid arthritis-all benefit from UV violet exposure apart from vitamin D3 mediated mechanisms.¹

If confirmed, we may soon need to rethink 24/7 shielding of sunlight with UV tints and window glass. Early morning natural sunlight would be favored over a world of artificial incandescent, fluorescent, and warm LED bulbs.

Sunlight’s potential damage of the ocular lens and macula, can be mitigated with “sufficient” dietary carotenoids that offer natural protection for the retina of sunlight-exposed youngsters. Lutein and zeaxanthin naturally have poor absorption of desirable violet light yet strong protection in the blue- all without topographic interference of the circadian rhythm photoreceptor ganglion complex affecting sleep.

The highest quintile of plasma lutein concentrations has also recently been shown independently to be associated with a 40 percent reduced risk of myopia.⁹ The key word is “sufficient” intake of dietary carotenoids, determined by “opto-metric” determination and evaluation of macular pigment optical density. Only 1% 0f US optometrists currently measure it. 

How sunlight impacts daily health

Psychiatry has embraced the fact that blue light is desirable in the morning for resetting our circadian rhythm and avoiding northern latitude depression. There are other reasons to love natural sunlight and embrace light boxes for use in the winter months as well as warm lighting in the evening.

Related: Nutrition’s role in eye care

Sunlight modulates both serotonin and B endorphins, suggesting an addictive or natural reward mechanism-encouraging sunlight exposure.¹⁰ Light therapy is also commanding respect in the medical community against jet lag, premenstrual syndrome (PMS), sleep disorders, and other conditions related to non-visual biochemical and bioelectrical connections to the hypothalamus and pineal gland.

Exposure to certain colors has been found to affect behavior, mood, and physiological functions.¹¹ Certain wavelengths of electromagnetic radiation directly increase adenosine triphosphate (ATP) levels in the tissues-mainly by activating the mitochondrial enzyme cytochrome c oxidase.¹²

The long wavelengths within sunlight (i.e., 600 nm to 1000 nm or near infrared) have natural inflammation-lowering effects, and mitogenic (mitochondrial enhancing) effects-acting similarly to antioxidant nutrients by modulating wound healing, boosting metabolism, and helping to remove toxins from the body.¹³

One Canadian company has a working instrument prototype that utilizes these biomodulating wavelengths for age-related macular degeneration (AMD) treatment.¹⁴

A sunny summary

Oily cold water fish consumption and vitamin D supplements, while beneficial, are not an effective substitute for sun exposure.¹ Being fortunate to live in lower latitudes, and taking advantage of that privilege, is smart medicine. Regardless of where you live, the dMinder smart-phone app geotags available sunlight exposure, and is a good place for optometrists to start.

Related: Nutritional one-two punch may slow retinitis pigmentosa

References

1. Hoel DG, Berwick M, de Gruij FR, Holick MF. The risks and benefits of sun exposure 2016. Dermatoendocrinol. 2016 Oct 19;8(1):e1248325.

2. Gandini S, Sera F, Cattaruzza MS, Pasquini P, Picconi O, Boyle P, Melchi CF. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005 Jan;41:45-60.

3. Ascenso A, Pedrosa T, Pinho S, Pinho F, de Oliveira, JM, Cabral Marques H, Oliveira H, Simões S, Santos C. The Effect of Lycopene Preexposure on UV-B-Irradiated Human Keratinocytes. Oxid Med Cell Longev. 2016;2016:8214631

4. Vaughan-Shaw PG, O'Sullivan F, Farrington SM, Theodoratou E, Campbell H, Dunlop MG, Zgaga L, The impact of vitamin D pathway genetic variation and circulating 25-hydroxyvitamin D on cancer outcome: systematic review and meta-analysis. Br J Cancer. 2017 Apr 11;116(8):1092-1110. doi: 10.1038/bjc.2017.44. Epub 2017 Mar 16.

5. Leo SW. Scientific Bureau of World Society of Paediatric Ophthalmology and Strabismus (WSPOS). Current approaches to myopia control. Curr Opin Ophthalmol. 2017 May;28(3):267-275.

6. French AN, Ashby RS, Morgan IG, Rose KA. Time outdoors and the prevention of myopia. Exp Eye Res. 2013 Sep;114:58-68.

7. Galvis V, Tello A, Camacho PA, Parra MM, Merayo-Lloves J. Bio-environmental factors associated with myopia: An updated review. Arch Soc Esp Oftalmol. 2017 Feb 2. pii: S0365-6691(17)30012-6.

8. Torii H, Kurihara T, Seko Y, Negishi K, Ohnuma K, Inaba T, Kawashima M, Jiang X, Kondo S, Miyauchi M, Miwa Y, Katada Y, Mori K, Kato K, Tsubota K, Goto H, Oda M9, Hatori M, Tsubota K. Violet Light Exposure Can Be a Preventive Strategy Against Myopia Progression. EBioMedicine. 2017 Feb;15:210-219.

9. Williams KM, Bentham GC, Young IS, McGinty A, McKay GJ, Hogg R, Hammond CJ, Chakravarthy U, Rahu M, Seland J, Soubrane G, Tomazzoli L, Topouzis F, Fletcher AE. Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study. JAMA Ophthalmol. 2017 Jan 1;135(1):47-53.

10. Van der Rhee H, de Vries E, Coomans C, Van de Velde P, Coebergh JW. Sunlight: For better or for worse? A review of positive and negative effects of sun exposure. Cancer Research Frontiers. 2016 May; 2(2): 156-183.

11. College of Syntonic Optometry. What is Syntonics? Available at: http://www.collegeofsyntonicoptometry.com/home.html. Accessed: 4/17/17.

12. Karu TK. Multiple roles of cytochrome c oxidase in mammalian cells under action of red and IR-A radiation. IUBMB Life. 2010 Aug;62(8):607-10. 

13. Sivapathasuntharam C, Sivaprasad S, Hogg C, Jeffery G, Aging retinal function is improved by near infrared light (670 nm) that is associated with corrected mitochondrial decline, Neurobiol Aging. 2017 Apr;52:66-70

14. LumiThera. PhotoBioModulation. Available at: https://www.lumithera.com/research/. Accessed: 4/17/17.

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