Hira Nath Dahal
Optom (IOM), (M.Optom)
This is the age of digitalization. Most of the people are exposed to digital devices. According to the 2015 survey that was done in the US, 60% of the adults are on their digital devices more than six hours per day and 28% of those exceeds 10 hours per day. (1) With increasing accessibility of cell phones, tablets, computers and more for both education, health care providers have to be prepared for the rising tide of significant unintended consequences we don’t yet fully understand. It is a growing concern that our vision and health are adversely affected by our inability to unplug.
In today’s world, particular interest is the effects of short wavelength blue light or High energy blue light (HEV). Great efforts are put to identify and quantify the effects of prolonged exposure to HEV emissions from digital devices, including whether or not smartphones, tablets, and the computer actually give off enough HEV to trigger damage to our visual systems and a decline in our general health. Although there is a great understanding of the effects of ultraviolet (UV: 380nm and below) and infrared (IR, 780nm) light is relatively well developed, we don’t have an adequate understanding of HEV.
What is HEV (High Energy Blue light)?
High energy blue light comprises a violet-blue end of the light spectrum (wavelength between 380nm and 500nm) and it’s everywhere. Although the focus is on digital devices, we shouldn’t forget about the more energy efficient, higher-output ambient lighting system. For e.g. nearly 35% of the cool white light emitting diode (LED) emissions are in the HEV range and 26% of compact fluorescent light. In comparison, incandescent bulbs put out less than 12% of their light in HEV range. Also, we shouldn’t forget that majority of HEV exposure comes from the sun with 25% to 30% of its spectral emissions falling in HEV range. (2)
What are its effects?
Effect of HEV can be divided into three categories:
- Circadian rhythm modulation with associated impacts on systemic health
- Ocular effects
- Medical effects leveraged in the treatment of certain disease processes such as jaundice and dermatological conditions.
HEV exposure is a crucial component that has direct relevance to us because of its influence through the visual system and the specialized cells that regulate our circadian rhythm. These specialized cells known as intrinsically photosensitive retinal ganglion cells (ipRGCs) have a peak spectral sensitivity between 444nm and 486nm which is the upper end of HEV spectral range. With HEV, ipRGCs, depolarize which ultimately inhibits the release of melatonin from the pineal gland. Digital devices are not inherently bad, the problem is their LED light sources have higher outputs of HEV range (roughly 35%) and which light is actually a blue light (peak emission near 450nm) with a yellow phosphor (peak emission around 580nm) and this increase over time). In 2015, the research into the impact of e-readers (e.g. Apple iPad with a peak wavelength emission of 452nm) on circadian disruption compared with traditional books (peak of 612nm) provided telling results. Subjects read from either an e-reader or a book for approximately four hours immediately prior to going to bed, five nights in a row. The author found the e-reader group had a lag in the onset of sleep by about 10 minutes, a REM sleep period that was shorter by approximately 10 minutes and was subjectively more tired the next day. The most significant finding, however, was the delayed increase of melatonin by nearly two hours. (3) While this study couldn’t say whether the findings were due to the light’s wavelength or the intensity of the source itself, a 2017 study confirmed wavelength as the culprit. (4) In this study, subjects were exposed to light sources at either 80 lux or 350 lux and the light spectrum of 460nm or 620nm for two hours before bed. Each night, researchers collected multiple urines and oral temperature samples and evaluated melatonin levels. While the intensity of light had a negligible effect on sleep quality and melatonin production, the shorter wavelength light had a statistically significant impact on both qualities of sleep and melatonin secretion. In addition to documenting delayed sleep and increased next day fatigue, several studies implicate melatonin suppression via HEV-related device exposure in increased levels of insulin resistance, elevated blood pressure, seasonal affective disorder and certain types of cancers. A study found that subject exposed to light boxes with a peak wavelength of 468±8nm for 1.5 hours upon waking and 1.5 hours before bed had increased levels of insulin resistance. The evening HEV exposure, in particular, led to higher peak glucose production and diminished sleepiness compared with the morning exposure or no exposure to HEV. While melatonin plays a vital role in our sleep regulation, blood glucose levels, and blood pressure, it’s also a powerful anti-oxidant with more than just a passing association with certain types of cancer, specifically those related to hormone production such as breast and ovarian.
HEV mediated circadian rhythm modulation has some positive attributes as well, the most encouraging being improved memory and cognition. Light therapy to treat Alzheimer’s disease is not new, but the applications to other neurodegenerative diseases such as Huntington’s and Parkinson’s are also beginning to show promise. (5) Several studies have evaluated the use of blue light in promoting mental alertness. In a study, researchers evaluated the effects of daytime and nighttime blue (460nm) and green (555nm) light exposure. Subjects were exposed to either blue light or green light for 6.5 hours in the middle of a 16 hours wake cycle during a biological day. Compared with green light, exposure to the blue light (either at night or during the day) improved auditory reaction times, with electroencephalography readings showing greater activity associated with heightened alertness. The trade-off, however, was that blue light exposure at night increased sleepiness during the day.
Effect on the eyes
With all the attention on HEV and its effect on our systemic well-being, it’s easy to lose sight of the fact that it also has an impact on our ocular health-issues addresses every day on our clinical care of patients. (6) HEV has a deleterious effect in retinal health. It has been tied to visual changes such as the development of drusen and photoreceptor apoptosis and Digital Vision Syndrome. As the blue light enters the eye, it is absorbed by the photoreceptors outer segment, triggering the conversion of the opsin retinal to all-trans-retinal. Subsequent oxidation of the all-trans retinal leads to the production of reactive oxygen species (ROS) such as singlet oxygen, hydrogen peroxide and other free radicals that accumulate in the photoreceptor outer segment. The ROS has an affinity for breaking down cell membranes causing incomplete phagocytosis of photoreceptor outer segments and build up of lipofuscin in RPE cells. Lipofuscin levels are present early in life and gradually increase over time, becoming measurable around age 10 and peaking around age 70. However, too much can result in drusenoid changes that can lead to age-related macular degeneration (AMD). When lipofuscin and its hydrophobic fluorophore A2E be in amassing in the RPE, the risk of RPE and photoreceptor damage with subsequent death secondary to repeated HEV exposure is at its greatest. To highlight the significance of HEV in the process, a study found that after saturating human RPE cells with A2E and exposing them to blue and green light, researchers found RPE apoptosis only occurred in those exposed to blue light. (7) There are also studies in rat models where the researcher found exposure to blue LEDs and full-spectrum white LEDs for a period as short as nine days cause obvious damage to the outer nuclear layer. (8) The researchers attribute the damage to the generation of ROS during excitation of the photoreceptor cells.
One missing component in much of this research, however, is the role of xanthophyll carotenoids lutein and zeaxanthin. These pigments are not crucial in filtering out short wavelength light before it reaches the photoreceptors and RPE, but also serve as powerful free-radical scavengers. A fortunate part of the aging process is the natural yellowing of the human lens that increases over time (effectively reducing the amount of blue light reaching the retina). Unfortunately, the density of macular pigments decreases leaving the eye increasingly vulnerable to HEV’s phototoxic effect. This inverse relationship is profoundly important when considering risk mitigation strategies because it serves as a natural segue into a conversation with the patient about how loss of the macular pigmentation, a family history of AMD and the ever-changing exposure to HEV (natural and man-made) and fuel the breakdown of the RPE and eventually lead to permanent retinal damage. However, because in spite of all these available researches into a relationship between HEV and AMD, the evidence is still inconclusive. The challenges in establishing a definite link are wide-ranging and include such things as differences in pupil sizes and interpalpebral fissure width, duration, and intensity of light, the distance from the light source and the actual spectral composition of the light source itself.
Digital Vision Syndrome is another effect of HEV exposure and one that may affect many more patients than the HEV-AMD mediated relationship. According to a 2015 meta-analysis of the literature, 64% to 90% of computer users experience digital vision syndrome with symptoms ranging from eye strain and headache/eye ache to blurry vision, diplopia and dry, burning and watering eyes. HEV is now implicated in the sequelae associated with digital vision syndrome because its short wavelength creates a greater propensity for it to scatter as it moves through the ocular tissues, resulting in glare and decreased contrast sensitivity. In addition, this same scatter triggers micro-accommodative changes and consequently changes in the phoric posture- a constant “autofocus” and “auto-depth” that never achieves stability.
Maintain the balance to the exposure
Rather than completely blocking blue light, patients should take a two-pronged approach to ensure the blue light they are exposed to doesn’t become detrimental to their health.
The first patient should eat naturally occurring carotenoids (carrots, sweet potato, spinach), foods high in omega 3 fatty acid and phyto flavinoids (Spinach, Liver and other organ meats, legumes, pumpkin) while decreasing risky behaviors such as diets high in saturated and trans fats, smoking and unprotected sun exposure. By changing a diet to consume foods higher in lutein and zeaxanthin, the body becomes better able to produce additional macular pigmentation that can protect against macular degeneration due to blue light absorption, reduce photo-oxidative stress and subsequently stabilize RPE cell membranes. (9)
Some of the blue light filter lens coatings available include: Essilor’s Prevencia (Peak absorption between 415nm and 455nm), Kodak’s total blue (blocks up to the 80% of the HEV between 380nm and 440nm), Hoya’s Blue control, Zeiss Blue protect (peak absorption between 380nm and 455nm). Also, specially designed lenses are available such as Gunnar Optiks which are specialized computer spectacles designed with peak absorption between 380nm and 470nm. All of these technologies are designed to selectively block harmful HEV allowing the longer wavelength blue light through and are easy for patients to incorporate into their daily regimes. While they are not a panacea for everything HEV, research shows these coatings decrease harmful effect by between 10.6% and 23.6% while reducing symptoms associated with digital vision syndrome in roughly 30% of patients. (2)
Coupling these lens coatings technologies such as f.lux, Apple’s Night Shift or any blue light reducing apps for the Android platform will provide the patients with even more comprehensive benefits in the areas of phototoxic protection and circadian rhythm stabilization, ultimately reducing the ocular and systemic risks associated with HEV exposure.
HEV exposure is inevitable and has many negative and few positive systemic and ocular ramifications. Each source the sun, artificial lighting, and digital devices affects us in a different yet predictable manner depending on the distance, intensity, duration and timing of the exposure.
Our job as an Optometrist is to provide patients with recommendations to balance the good and bad effects of HEV for both their systemic and ocular health. Reducing the risky behavior such as smoking, unprotected sun exposure, and poor diet while increasing healthy behaviors such as dietary intake of naturally occurring carotenoids and phyto flavinoids and incorporating blue-light filtering spectacle lenses and other technologies are all crucial to protecting our patients.
- Adamopoulos D DM, Hildreth E. Digital eye strain in the USA: Overview by the vision council. Points de Vue International Review of Ophthalmic Optics 2015(N72).
- Leung TW LR-h, Kee C. Blue light filtering spectacle lenses: optical and clinical performance. PLos One. 2017;12(1).
- Chang AM AD, Duffy JF, Czeisler C. Evening use of light emitting eReaders negatively affects sleep, circadian timing, and next morning alertness. Proc Natl Acad Sci U S A. 2015;112(2):6.
- Green A C-ZM, Haim A, Dagan Y. Evening light exposure to computer screens disrupts human sleep, biological rhythms, and attention abilities. Chonobiol Int. 2017;34(7):11.
- Tosini G FI, Tsubota K. Effect of blue light on the circadian system and eye physiology. Molecular Vision. 2016;22:12.
- Yang JH BS, Gross RL, Wu SM. Blue light-induced generation of reactive oxygen species in photoreceptor ellipsoids requires mitochondrial electron transport. Invest Ophthalmol Vis Sci. 2003;44(3):9.
- Sparrow JR NK, Parish CA. The lipofuscin Fluophore A2E mediates blue-light-induced damage to retinal pigmented epithelial cells. Invest Ohpthalmol Vis Sci. 2000;41(7):9.
- Shang YM WG, Sliney D, Yand CH, Lee LL. White Light-Emitting Diodes (LEDs) at Domestic Lighting Levels and Retinal Injury in a Rat Model. Environmental Health Perspectives. 2014;122(3):8.
- J KV. Rod and Cone Visual Pigments and Phototransduction through Pharmacological, Genetic and Physiological Approaches. Journal of Biological Chemistry. 2012;257(3):6.
The author is the Optometrist working at Drishti Eye Care System.