Light-emitting diodes (LED) for domestic lighting: any risks for the eye?

Over-expression of CNTF in bone marrow mesenchymal stem cells protects RPE cells from short-wavelength, blue-light injury

Increasing evidence has demonstrated that excessive blue-light (BL) with high photochemical energy and phototoxicity could induce apoptosis in retinal pigment epithelium (RPE) cells. RPE apoptosis leads to retina damage and further aggravate age-related macular degeneration (ARMD). Because of their neuroprotective, plasticity, and immunomodulatory ability, bone marrow mesenchymal stem cells (BMSCs) are recognized for retinal neuroprotection. RPE cells possess ciliary neurotrophic factor (CNTF) receptor complexes and can respond to CNTF; hence, we investigated the effects of BMSCs over-expressing CNTF on BL-injured RPE cells. BL-injured RPE cells were co-cultured with CNTF-BMSCs and GFP-BMSCs for 24 and 48 h. Superoxide dismutase and malondialdehyde assays were conducted to examine the effects of CNTF-BMSCs on the oxidative stress of RPE cells. VEGF protein secretion by RPE was determined by ELISA, and western blotting analysis was used to determine apoptotic protein expression and autophagic flux. Immunofluorescence was used to demonstrate the relationship between autophagy and apoptosis. We found that CNTF-BMSCs enhanced antioxidant capacity, decreased VEGF secretion, promoted autophagic flux, and inhibited apoptosis in BL-injured RPE cells, compared to GFP-BMSCs. Our findings suggest that CNTF over-expression enhances the protective effects of BMSCs on RPE cells, thus indicating subretinal-transplantation of CNTF-BMSCs may be a promising therapy for BL-injured retina.

Electronic device generated light increases reactive oxygen species in human fibroblasts

OBJECTIVES

Our skin is constantly exposed to light from solar radiation and electronic devices, which impact skin physiology and aging. The biological altering properties of ultraviolet (UV) solar radiation on skin have been well established. There is significant scientific and public interest on the effects of electronic device generated light (EDGL) on skin. Currently, the effects of EDGL on skin are largely unknown. EDGL includes UV, visible, and infrared light from consumer electronics such as smartphones, computers, and televisions. In this study, we measured the wavelength specific irradiance from electronic devices, and irradiated fibroblasts with white EDGL to determine changes in reactive oxygen species generation, apoptosis, and necrosis.

METHODS

To determine the EDGL output of commonly used consumer electronic devices, we measured the irradiance from electronic devices at the manufacturers' recommended reading distances and at 1 cm. To determine the effect of EDGL on human skin cells, we irradiated AG13145 fibroblasts with EDGL for 1 hour at a distance of 1 cm and measured changes in reactive oxygen species generation, apoptosis, and necrosis.

RESULTS

ROS increased significantly by 81.71%, 85.79%, and 92.98% relative to control following 1 hour of white EDGL from iPhone 8+, iPhone 6, and iPad (first generation), respectively. There was a non-significant change in apoptosis following irradiation with an iPhone 8+, iPhone 6, and iPad. Total necrosis was less than 2% for all treatment and control groups.

CONCLUSIONS

Our results suggest that short exposures of EDGL increase ROS generation, but the long-term effects associated with repeated exposures of EDGL are unknown. As electronic devices become more widely used and integrated into society globally, we anticipate greater scientific research and general public interest on the effects of visible EDGL on skin. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

The potential influence of LED lighting on mental illness

OBJECTIVES

Two recent scientific breakthroughs may alter the treatment of mental illness, as discussed in this narrative review. The first was the invention of white light-emitting diodes (LEDs), which enabled an ongoing, rapid transition to energy-efficient LEDs for lighting, and the use of LEDs to backlight digital devices. The second was the discovery of melanopsin-expressing photosensitive retinal ganglion cells, which detect environmental irradiance and mediate non-image forming (NIF) functions including circadian entrainment, melatonin secretion, alertness, sleep regulation and the pupillary light reflex. These two breakthroughs are interrelated because unlike conventional lighting, white LEDs have a dominant spectral wavelength in the blue light range, near the peak sensitivity for the melanopsin system.

METHODS

Pertinent articles were identified.

RESULTS

Blue light exposure may suppress melatonin, increase alertness, and interfere with sleep in young, healthy volunteers and in animals. Areas of concern in mental illness include the influence of blue light on sleep, other circadian-mediated symptoms, prescribed treatments that target the circadian system, measurement using digital apps and devices, and adolescent sensitivity to blue light.

CONCLUSIONS

While knowledge in both fields is expanding rapidly, future developments must address the potential impact of blue light on NIF functions for healthy individuals and those with mental illness.

Introducing carbon dots to moderate the blue emission from zinc vanadium oxide hydroxide hydrate nanoplates

Adding carbon quantum dots is shown to moderate the blue component of the photoluminescence from vanadium oxide hydroxide hydrate nanoplates.

Effects of white light-emitting diode (LED) exposure on retinal pigment epithelium in vivo

Ageing and alteration of the functions of the retinal pigment epithelium (RPE) are at the origin of lost of vision seen in age-related macular degeneration (AMD). The RPE is known to be vulnerable to high-energy blue light. The white light-emitting diodes (LED) commercially available have relatively high content of blue light, a feature that suggest that they could be deleterious for this retinal cell layer. The aim of our study was to investigate the effects of "white LED" exposure on RPE. For this, commercially available white LEDs were used for exposure experiments on Wistar rats. Immunohistochemical stain on RPE flat mount, transmission electron microscopy and Western blot were used to exam the RPE. LED-induced RPE damage was evaluated by studying oxidative stress, stress response pathways and cell death pathways as well as the integrity of the outer blood-retinal barrier (BRB). We show that white LED light caused structural alterations leading to the disruption of the outer blood-retinal barrier. We observed an increase in oxidized molecules, disturbance of basal autophagy and cell death by necrosis. We conclude that white LEDs induced strong damages in rat RPE characterized by the breakdown of the BRB and the induction of necrotic cell death.

Age-related adaptive responses of mitochondria of the retinal pigment epithelium to the everyday blue LED lighting

The effect of everyday blue light (λ = 440-460 nm) on mitochondria of the retinal pigment epithelium of different age groups of Japanese quail was studied using electron microscopy, morphometric methods, and biochemical analysis. We have found a significant increase in the number of mitochondria, including those modified, mainly in young birds. In addition, cell metabolic activity increased in response to blue lighting. These changes are assumed to reflect an adaptive response of mitochondria aimed at neutralizing the phototoxic effect of blue light caused by accumulation of lipofuscin granules.

An optical and electrical study of full thermally activated delayed fluorescent white organic light-emitting diodes

We report on the engineering of full thermally activated delayed fluorescence – based white organic light emitting diodes (W-OLEDs) composed of three emitters (2,7-bis(9,9-dimethyl-acridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), 2,7-bis(phenoxazin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DPO-TXO2) and 3,11-di(10H-phenoxazin-10-yl)dibenzo[a,j]phenazine (POZ-DBPHZ) in two different hosts. By controlling the device design through the study of the emission of DDMA-TXO2 and DPO-TXO2, the behaviour of POZ-DBPHZ in a device with more than one emitter, and the combination of the three materials, respectively, we show that external quantum efficiencies as high as 16% can be obtained for a structure with a correlated colour temperature close to warm white, together with colour rendering index close to 80. However it is in their performance stability that provides the true breakthrough: at 1000 cd/m² the efficiencies were still above 10%, which is one of the best for this type of devices.

Smart-Glasses: Exposing and Elucidating the Ethical Issues

The objective of this study is to provide an overview over the ethical issues relevant to the assessment, implementation, and use of smart-glasses. The purpose of the overview is to facilitate deliberation, decision making, and the formation of knowledge and norms for this emerging technology. An axiological question-based method for human cognitive enhancement including an extensive literature search on smart-glasses is used to identify relevant ethical issues. The search is supplemented with relevant ethical issues identified in the literature on human cognitive enhancement (in general) and in the study of the technical aspects of smart-glasses. Identified papers were subject to traditional content analysis: 739 references were identified of which 247 were regarded as relevant for full text examinations, and 155 were included in the study. A wide variety of ethical issues with smart-glasses have been identified, such as issues related to privacy, safety, justice, change in human agency, accountability, responsibility, social interaction, power and ideology. Smart-glasses are envisioned to change individual human identity and behavior as well as social interaction. Taking these issues into account appears to be relevant when developing, deliberating, deciding on, implementing, and using smart-glasses.

Light-emitting-diode induced retinal damage and its wavelength dependency in vivo

AIM

To examine light-emitting-diode (LED)-induced retinal neuronal cell damage and its wavelength-driven pathogenic mechanisms.

METHODS

Sprague-Dawley rats were exposed to blue LEDs (460 nm), green LEDs (530 nm), and red LEDs (620 nm). Electroretinography (ERG), Hematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and immunohistochemical (IHC) staining, Western blotting (WB) and the detection of superoxide anion (O₂^-·), hydrogen peroxide (H₂O₂), total iron, and ferric (Fe³⁺) levels were applied.

RESULTS

ERG results showed the blue LED group induced more functional damage than that of green or red LED groups. H&E staining, TUNEL, IHC, and TEM revealed apoptosis and necrosis of photoreceptors and RPE, which indicated blue LED also induced more photochemical injury. Free radical production and iron-related molecular marker expressions demonstrated that oxidative stress and iron-overload were associated with retinal injury. WB assays correspondingly showed that defense gene expression was up-regulated after the LED light exposure with a wavelength dependency.

CONCLUSION

The study results indicate that LED blue-light exposure poses a great risk of retinal injury in awake, task-oriented rod-dominant animals. The wavelength-dependent effect should be considered carefully when switching to LED lighting applications.

Epidemiology of Myopia

Myopia is not a simple refractive error, but an eyesight-threatening disease. There is a high prevalence of myopia, 80% to 90%, in young adults in East Asia; myopia has become the leading cause of blindness in this area. As the myopic population increases globally, the severity of its impact is predicted. Approximately one fifth of the myopic population has high myopia (≥-6 diopters), which results in irreversible vision loss such as retinal detachment, choroidal neovascularization, cataracts, glaucoma, and macular atrophy. The increasing prevalence of school myopia in the past few decades may be a result of gene-environment interactions. However, earlier school myopia onset would accompany faster myopia progression and greater risk of high myopia later in life. Recently, there have been effective interventions to delay the onset of myopia, such as outdoor activity and decreasing the duration of near work. Hyperopia (≤0.5 diopters) is a predictor of myopia. Pharmacological agents and optic interventions such as low-concentration atropine and orthokeratology may slow progression in myopic children. Novel surgeries and anti-vascular endothelial growth factor drugs could deal with some myopic complications. From available evidence, the prevention, control, and treatment of myopia seem to be promising. However, to reduce the impact of myopia in future decades, more work and effort are still needed, including that by governments and intercountry eye health organizations.

Visual light effects on mitochondria: The potential implications in relation to glaucoma

Light of different wave-lengths have the potential to interact with four major mitochondrial protein complexes that are involved in the generation of ATP. Neurones of the central nervous system have an absolute dependence on mitochondrial generated ATP. Laboratory studies show that short-wave or blue light (400-480nm) that impinges on the retina affect flavin and cytochrome constituents associated with mitochondria to decrease the rate of ATP formation, stimulate ROS and results in cell death. This suggests that blue light could potentially have a negative influence on retinal ganglion cell (RGC) mitochondria that are abundant and not shielded by macular pigments as occurs for photoreceptor mitochondria. This might be of significance in glaucoma where it is likely that RGC mitochondria are already affected and therefore be more susceptible to blue light. Thus simply filtering out some natural blue light from entering the eye might be beneficial for the treatment of glaucoma. Long-wave or red light (650-800nm) affects mitochondrial complex IV or cytochrome oxidase to increase the rate of formation of ATP and ROS causing the generation of a number of beneficial factors. Significantly, laboratory studies show that increasing the normal amount of natural red light reaching rat RGC mitochondria in situ, subjected to ischemia, proved to be beneficial. A challenge now is to test whether extra red light delivered to the human retina can slow-down RGC loss in glaucoma. Such a methodology has also the advantage of being non-invasive. One very exciting possibility might be in the production of a lens where solar UV light is convertes to add to the amount of natural red light entering the eye.

Light-induced retinal damage using different light sources, protocols and rat strains reveals LED phototoxicity

To save energy, the European directives from the Eco-design of Energy Using Products (2005/32/CE) have recommended the replacement of incandescent lamps by more economic devices such as Light Emitting Diodes (LEDs). However, the emission spectrum of these devices is enriched in blue radiations, known to be potentially dangerous to the retina. Recent studies showed that light exposure contributes to the onset of early stages of age-related macular degeneration (AMD). Here, we investigate, in albinos and pigmented rats, the effects of different exposure protocols. Twenty-four hours exposure at high luminance was compared to a cyclic (dark/light) exposure at domestic levels for 1week and 1month, using different LEDs (Cold-white, blue and green), as well as fluorocompact bulbs and fluorescent tubes. The data suggest that the blue component of the white-LED may cause retinal toxicity at occupational domestic illuminance and not only in extreme experimental conditions, as previously reported. It is important to note that the current regulations and standards have been established on the basis of acute light exposure and do not take into account the effects of repeated exposure.

Influence of Light Emitting Diode-Derived Blue Light Overexposure on Mouse Ocular Surface

Purpose

To investigate the influence of overexposure to light emitting diode (LED)-derived light with various wavelengths on mouse ocular surface.

Methods

LEDs with various wavelengths were used to irradiate C57BL/6 mice at an energy dose of 50 J/cm², twice a day, for 10 consecutive days. The red, green, and blue groups represented wavelengths of 630 nm, 525 nm, and 410 nm, respectively. The untouched group (UT) was not exposed to LED light and served as the untreated control. Tear volume, tear film break-up time (TBUT), and corneal fluorescein staining scores were measured on days 1, 3, 5, 7, and 10. Levels of interferon (IFN)-γ, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were measured in the cornea and conjunctiva using a multiplex immunobead assay at day 10. Levels of malondialdehyde (MDA) were measured with an enzyme-linked immunosorbent assay. Flow cytometry, 2’7’-dichlorofluorescein diacetate (DCF-DA) assay, histologic analysis, immunohistochemistry with 4-hydroxynonenal, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining were also performed.

Results

TBUT of the blue group showed significant decreases at days 7 and 10, compared with the UT and red groups. Corneal fluorescein staining scores significantly increased in the blue group when compared with UT, red, and green groups at days 5, 7, and 10. A significant increase in the corneal levels of IL-1β and IL-6 was observed in the blue group, compared with the other groups. The blue group showed significantly increased reactive oxygen species production in the DCF-DA assay and increased inflammatory T cells in the flow cytometry. A significantly increased TUNEL positive cells was identified in the blue group.

Conclusions

Overexposure to blue light with short wavelengths can induce oxidative damage and apoptosis to the cornea, which may manifest as increased ocular surface inflammation and resultant dry eye.

The dental curing light: A potential health risk

Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition, many dental personnel use magnification loupes. This study measured the effect of magnification loupes on the "blue light hazard" when the light from a dental curing light was reflected off a human tooth. Loupes with 3.5x magnification (Design for Vision, Carl Zeiss, and Quality Aspirator) and 2.5x magnification (Design for Vision and Quality Aspirator) were placed at the entrance of an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A model with human teeth was placed 40 cm away and in line with this sphere. The light guide tip of a broad-spectrum Sapphire Plus (Den-Mat) curing light was positioned at a 45° angle from the facial surface of the central incisor. The spectral radiant power reflected from the teeth was recorded five times with the loupes over the entrance into the sphere. The maximum permissible cumulative exposure times in an 8-hr day were calculated using guidelines set by the ACGIH. It was concluded that at a 40 cm distance, the maximum permissible cumulative daily exposure time to light reflected from the tooth was approximately 11 min without loupes. The weighted blue irradiance values were significantly different for each brand of loupe (Fisher's PLSD p < 0.05) and were up to eight times greater at the pupil than when loupes were not used. However, since the linear dimensions of the resulting images would be 2.5 to 3.5x larger on the retina, the image area was increased by the square of the magnification and the effective blue light hazard was reduced compared to without the loupes. Thus, although using magnification loupes increased the irradiance received at the pupil, the maximum cumulative daily exposure time to reflected light was increased up to 28 min. Further studies are required to determine the ocular hazards of a focused stare when using magnification loupes and the effects of other curing lights used in the dental office.

[The dangers of blue light: True story!]

The dangers of the blue light are the object of numerous publications, for both the scientific community and the general public. The new prolific development of light sources emitting potentially toxic blue light (415-455nm) ranges from LED (Light Emitting Diodes) lamps for interior lighting to television screens, computers, digital tablets and smartphones using OLED (Organic Light Emitting Diode) or AMOLED (Active-Matrix Organic Light Emitting Diode) technology. First we will review some technical terms and the main characteristics of light perceived by the human eye. Then we will discuss scientific proof of the toxicity of blue light to the eye, which may cause cataract or macular degeneration. Analysis of the light spectra of several light sources, from natural light to LED lamps, will allow us to specify even better the dangers related to each light source. LED lamps, whether used as components for interior lighting or screens, are of concern if they are used for extended viewing times and at short distance. While we can protect ourselves from natural blue light by wearing colored glasses which filter out, on both front and back surfaces, the toxic wavelengths, it is more difficult to protect oneself from LED lamps in internal lighting, the use of which should be restricted to "white warmth" lamps (2700K). As far as OLED or AMOLED screens are concerned, the only effective protection consists of using them occasionally and only for a short period of time.

Upregulation of GADD45α in light-damaged retinal pigment epithelial cells

To better understand the molecular mechanisms responsible for light-induced damage in retinal pigmented epithelial (RPE) cells, we developed an automated device to recapitulate intense light exposure. When compared with human fibroblasts, ARPE-19 cells that had been exposed to blue-rich light-emitting diode-light of 10 000 Lux at 37 °C for 9 h displayed dramatic cellular apoptosis. Collectively, gene expression profiling and qPCR demonstrated that growth arrest and DNA damage-45α (GADD45α) expression was markedly upregulated. Transient knockdown of GADD45α partially attenuated light-damage-induced apoptosis in ARPE-19 cells, whereas GADD45α overexpression dramatically increased it. These results demonstrate the critical function of GADD45α in light-induced RPE cellular apoptosis. Quantitative reverse transcription-PCR and western blotting revealed that the upregulation of GADD45α was under direct control of p53. Moreover, treatment with Ly294002, an inhibitor of AKT phosphorylation, further promoted GADD45α gene transcription in both non-light and light-damaged ARPE-19 cells. Treatment also exacerbated RPE cellular apoptosis after light exposure, confirming that inhibition of Akt phosphorylation increases GADD45α expression. Collectively, our findings reveal that light irrigation induces human RPE cellular apoptosis through upregulation of GADD45α expression mediated through both the p53 and phosphatidylinositol 3-kinase-AKT signaling pathways. These results provide new insights into human retinal diseases elicited by light damage and open a new avenue for disease prevention and treatment.

LED Light Characteristics for Surgical Shadowless Lamps and Surgical Loupes

Background:

Blue light has more energy than longer wavelength light and can penetrate the eye to reach the retina. When surgeons use magnifying loupes under intensive surgical shadowless lamps for better view of the surgical field, the total luminance is about 200 times brighter than that of typical office lighting. In this study, the effects of 2 types of shadowless lamps were compared. Moreover, the effect of various eyeglasses, which support magnifying loupes, on both the light energy and color rendering was considered.

Methods:

The light intensity and color rendering were measured on 3 variables: light transmittance, light intensity, and color rendering.

Results:

Under shadowless lamps, the light energy increased with low-magnification loupes and decreased with high-magnification loupes. Filtering eyeglasses reduced the energy, especially in conditions where the low-magnification loupe was used. The best color-rendering index values were obtained with computer eyeglasses under conventional light-emitting diode shadowless lamps and with no glass and with lightly yellow-tinted lenses under less-blue light-emitting diode.

Conclusions:

Microsurgeons are exposed to strong lighting throughout their career, and proper color rendering must be considered for easier recognition. Light toxicity and loss of color rendering can be reduced with an appropriate combination of shadowless lamps and colored eyeglasses.

Light damage to the retina: an historical approach

A brief review of retinal light damage is presented. Thermal damage requires a local rise in temperature of at least 10 °C, causing an instant denaturation of proteins. The primary absorber is melanin. Photochemical damage occurs at body temperature and involves cellular damage by reactive forms of oxygen. The photosensitizers are photoproducts of the visual pigments. First indications that non-thermal damage might exist, in particular in the case of eclipse blindness, was presented by Vos in 1962. Attribution thereof to photochemical action was presented in 1966 by Noell et al who also measured the first action spectrum, in rat. It turned out to be identical to the absorption spectrum of rhodopsin. However, in 1976 and 1982 Ham et al found a quite different spectrum in monkeys, peaking at short wavelengths. The latter spectrum, but not the former, was confirmed since in numerous publications with animal models including rat. In ophthalmological practice a 'sunburn' was at first the only complaint caused by light damage. To avoid this, patients with dilated pupils should always be advised to wear sunglasses. Since the invention of the laser accidents have been reported, the most recent development is youth playfully pointing a strong laser pen in their eyes with marked consequences. The operation microscope and endoilluminators should always be used as brief as possible to avoid photochemical damage. Arguments for implant lenses that block not only the UV but also part of the visible spectrum seem too weak to justify extra costs.

Protective Effect of Fucoxanthin Isolated from Laminaria japonica against Visible Light-Induced Retinal Damage Both in Vitro and in Vivo

With increasingly serious eye exposure to light stresses, such as light-emitting diodes, computers, and widescreen mobile phones, efficient natural compounds for preventing visible light-induced retinal damages are becoming compelling needs in the modern society. Fucoxanthin, as the main light absorption system in marine algae, may possess an outstanding bioactivity in vision protection because of its filtration of blue light and excellent antioxidative activity. In this work, both in vitro and in vivo simulated visible light-induced retinal damage models were employed. The in vitro results revealed that fucoxanthin exhibited better bioactivities than lutein, zeaxanthin, and blueberry anthocyanins in inhibiting overexpression of vascular endothelial growth factor, resisting senescence, improving phagocytic function, and clearing intracellular reactive oxygen species in retinal pigment epithelium cells. The in vivo experiment also confirmed the superiority of fucoxanthin than lutein in protecting retina against photoinduced damage. This excellent bioactivity may be attributed to its unique structural features, including allenic, epoxide, and acetyl groups. Fucoxanthin is expected to be an important ocular nutrient in the future.

Functional and morphological evaluation of blue light-emitting diode-induced retinal degeneration in mice

PURPOSE

The purpose of this study was to evaluate a retinal degeneration (RD) model induced by exposing mice to a blue light-emitting diode (LED), which led to photoreceptor cell death.

METHODS

RD was induced in BALB/c mice by exposure to a blue LED (460 nm) for 2 hours. Retinal function was examined using scotopic electroretinography (ERG). Histopathological changes were assessed by hematoxylin and eosin (H&E) staining and electron microscopy. Apoptotic cell death was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. In addition, retinal inflammation and oxidative stress were evaluated by immunohistochemistry with anti-glial fibrillary acidic protein (GFAP) and anti-8-hydroxy-2'-deoxyguanosine (8-OHdG), respectively.

RESULTS

Scotopic ERG showed that blue LED exposure resulted in a decrease in both a-waves and b-waves in mice retinas in an illuminance-dependent manner. H&E, TUNEL assay, and electron microscopy revealed massive photoreceptor cell death by apoptosis in the central region of the retina. Retinal stress and inflammation were detected by increased expression of GFAP and by electron microscopy findings demonstrating microglia infiltration in the outer nuclear layer and subretinal space. In addition, increased labeling of 8-OHdG was observed in the retinas from blue LED exposure.

CONCLUSIONS

These results suggest that blue LED-induced RD may be a useful animal model in which to study the pathogenesis of RD, including age-related macular degeneration, and to evaluate the effects of new therapeutic agents prior to clinical trials, where oxidative stress and inflammation are the underlying RD mechanisms.

Blue Light Protects Against Temporal Frequency Sensitive Refractive Changes

PURPOSE

Time spent outdoors is protective against myopia. The outdoors allows exposure to short-wavelength (blue light) rich sunlight, while indoor illuminants can be deficient at short-wavelengths. In the current experiment, we investigate the role of blue light, and temporal sensitivity, in the emmetropization response.

METHODS

Five-day-old chicks were exposed to sinusoidal luminance modulation of white light (with blue; N = 82) or yellow light (without blue; N = 83) at 80% contrast, at one of six temporal frequencies: 0, 0.2, 1, 2, 5, 10 Hz daily for 3 days. Mean illumination was 680 lux. Changes in ocular components and corneal curvature were measured.

RESULTS

Refraction, eye length, and choroidal changes were dependent on the presence of blue light (P < 0.03, all) and on temporal frequency (P < 0.03, all). In the presence of blue light, refraction did not change across frequencies (mean change -0.24 [diopters] D), while in the absence of blue light, we observed a hyperopic shift (>1 D) at high frequencies, and a myopic shift (>-0.6 D) at low frequencies. With blue light there was little difference in eye growth across frequencies (77 μm), while in the absence of blue light, eyes grew more at low temporal frequencies and less at high temporal frequencies (10 vs. 0.2 Hz: 145 μm; P < 0.003). Overall, neonatal astigmatism was reduced with blue light.

CONCLUSIONS

Illuminants rich in blue light can protect against myopic eye growth when the eye is exposed to slow changes in luminance contrast as might occur with near work.

Light pollution: the possible consequences of excessive illumination on retina

Light is the visible part of the electromagnetic radiation within a range of 380-780 nm; (400-700 on primates retina). In vertebrates, the retina is adapted to capturing light photons and transmitting this information to other structures in the central nervous system. In mammals, light acts directly on the retina to fulfill two important roles: (1) the visual function through rod and cone photoreceptor cells and (2) non-image forming tasks, such as the synchronization of circadian rhythms to a 24 h solar cycle, pineal melatonin suppression and pupil light reflexes. However, the excess of illumination may cause retinal degeneration or accelerate genetic retinal diseases. In the last century human society has increased its exposure to artificial illumination, producing changes in the Light/Dark cycle, as well as in light wavelengths and intensities. Although, the consequences of unnatural illumination or light pollution have been underestimated by modern society in its way of life, light pollution may have a strong impact on people's health. The effects of artificial light sources could have direct consequences on retinal health. Constant exposure to different wavelengths and intensities of light promoted by light pollution may produce retinal degeneration as a consequence of photoreceptor or retinal pigment epithelium cells death. In this review we summarize the different mechanisms of retinal damage related to the light exposure, which generates light pollution.

Photoinduced changes in subcellular structures of the retinal pigment epithelium from the Japanese quail Coturnix japonica

Fifteen-week-old sexually mature female Japanese quails (Coturnix japonica) grown under various lighting conditions were used in the study. It was found that the number of mitochondria and phagosomes was increased by 1.5-fold in the retinal pigment epithelium from birds reared for 95 days under blue light (440-470 nm) vs. reduced blue light component conditions. Also, it was found that egg production was increased by 15% in birds reared under blue light compared to other lightning conditions. Thus, we concluded that blue light conditions resulted in elevating metabolic activity and accelerating pace of life in Japanese quails. It is assumed that the blue light-induced effects are probably due to inhibition of melatonin synthesis.

Carrier modulation layer-enhanced organic light-emitting diodes

Organic light-emitting diode (OLED)-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML), also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI) for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance.

Retinal damage induced by commercial light emitting diodes (LEDs)

Spectra of "white LEDs" are characterized by an intense emission in the blue region of the visible spectrum, absent in daylight spectra. This blue component and the high intensity of emission are the main sources of concern about the health risks of LEDs with respect to their toxicity to the eye and the retina. The aim of our study was to elucidate the role of blue light from LEDs in retinal damage. Commercially available white LEDs and four different blue LEDs (507, 473, 467, and 449nm) were used for exposure experiments on Wistar rats. Immunohistochemical stain, transmission electron microscopy, and Western blot were used to exam the retinas. We evaluated LED-induced retinal cell damage by studying oxidative stress, stress response pathways, and the identification of cell death pathways. LED light caused a state of suffering of the retina with oxidative damage and retinal injury. We observed a loss of photoreceptors and the activation of caspase-independent apoptosis, necroptosis, and necrosis. A wavelength dependence of the effects was observed. Phototoxicity of LEDs on the retina is characterized by a strong damage of photoreceptors and by the induction of necrosis.

Enabling a blue-hazard free general lighting based on candle light-style OLED

Increasing studies report blue light to possess a potential hazard to the retina of human eyes, secretion of melatonin and artworks. To devise a human- and artwork-friendly light source and to also trigger a "Lighting Renaissance", we demonstrate here how to enable a quality, blue-hazard free general lighting source on the basis of low color-temperature organic light emitting diodes. With the use of multiple candlelight complementary emitters, the sensationally warm candle light-style emission is proven to be also drivable by electricity. To be energy-saving, highly efficient candle-light emission is demanded. The device shows, at 100 cd m^-2 for example, an efficacy of 85.4 lm W^-1, an external quantum efficiency of 27.4%, with a 79 spectrum resemblance index and 2,279 K color temperature. The high efficiency may be attributed to the candlelight emitting dyes with a high quantum yield, and the host molecules facilitating an effective host-to-guest energy transfer, as well as effective carrier injection balance.

Novel composite layer based on electrospun polymer nanofibers for efficient light scattering

We fabricated a PAN (polyacrylonitrile) NF (nanofiber)-embedded composite layer to adjust the light-control layer in light-emitting-diode (LED) and organic-light-emitting-diode (OLED) lighting systems with unique optical characteristics, for effective light scattering. The newly designed light-control composite layers with a composition of PAN NF/SU-8 exhibited a change in the optical properties, which was identified by the diameter control of the NF using a simple process. The change in the optical properties was largely dependent on the embedded NF's features. Therefore, the NF can be applied in different types of lighting systems, depending on each lighting device's purpose.

Photo-damage, photo-protection and age-related macular degeneration

The course of Age-related Macular Degeneration (AMD) is described as the effect of light (400–580 nm) on various molecular targets in photoreceptors and the retinal pigment epithelium (RPE). Photo-damage is followed by inflammation, increasing oxidative stress and, probably, unveiling new photosensitive molecules.

Energy efficiency and color quality limits in artificial light sources emulating natural illumination

We present in this work a calculation of the theoretical limits attainable for natural light emulation with regard to the joint optimization of the Luminous Efficacy of Radiation and color fidelity by using multiple reflectance spectra datasets, along with an implementation of a physical device that approaches these limits. A reduced visible spectrum of blackbody radiators is introduced and demonstrated which allows lamps designed to emulate natural light to operate with excellent color fidelity and higher efficiency as compared to full visible spectrum sources. It is shown that even though 3,000K and 5,500K blackbody sources have maximum efficacies of 21 lm/W and 89 lm/W, respectively, reduced-spectrum artificial light sources can exceed those values up to 363 lm/W and 313 lm/W, respectively, while retaining excellent color fidelity. Experimental demonstration approaching these values is accomplished through the design and implementation of a 12-channel light engine which emits arbitrarily-tunable spectra. The color fidelity of the designed spectra is assessed through Color Rendering Maps, showing that color fidelity is preserved uniformly over a large spectral reflectance dataset, unlike other approaches to generate white light.

High-performance lighting evaluated by photobiological parameters

The human reception of light includes image-forming and non-image-forming effects which are triggered by spectral distribution and intensity of light. Ideal lighting is similar to daylight, which could be evaluated by spectral or chromaticity match. LED-based and CFL-based lighting were analyzed here, proposed according to spectral and chromaticity match, respectively. The photobiological effects were expressed by effectiveness for blue light hazard, cirtopic activity, and photopic vision. Good spectral match provides light with more similar effects to those obtained by the chromaticity match. The new parameters are useful for better evaluation of complex human responses caused by lighting.

Neuroglobin - a potential biological marker of retinal damage induced by LED light

Neuroglobin (NGB), a protein highly expressed in the retina, has been shown to be up-regulated to protect neurons from hypoxic and ischemic injuries. It exhibits neuroprotective functions and plays an important role in the survival of neurons. Recent studies show that light-emitting diode (LED) white light emitted significant amounts of blue light (short-wavelength), which may be harmful to retinal cells, but the studies about biomarkers for evaluating the damage from LED white light are still insufficient. In our study, we found that NGB levels in the retina showed a twofold increase and peaked at 1h after a 1-h exposure to blue light (453 nm) which did not cause damage to the retina. However, retinal damage was observed after 2h of blue-light irradiation, which induced an approximate sevenfold increase of NGB levels as confirmed by Western blot and RT-PCR analysis. Immunofluorescence study demonstrated that NGB was predominantly up-regulated in the ganglion cell layer (GCL), plexiform layer (PL) and photoreceptor layer (PRL). We also examined Ngb mRNA and protein expression in the damaged retina induced by light of other wavelengths given equal photon fluxes. The LED red light (625 nm), green light (527 nm) and blue light (453 nm) increased the expression of NGB and caused TdT-mediated dUTP nick-end labeling-positive cells, especially in the blue-light group. In addition, a negative correlation between NGB and rhodopsin was observed. These findings suggested that there was a correlation between NGB expression and the severity of the retinal damage, indicating NGB's potential function as a biological marker of retinal damage induced by LED light.

Taurine: the comeback of a neutraceutical in the prevention of retinal degenerations

Taurine is the most abundant amino acid in the retina. In the 1970s, it was thought to be involved in retinal diseases with photoreceptor degeneration, because cats on a taurine-free diet presented photoreceptor loss. However, with the exception of its introduction into baby milk and parenteral nutrition, taurine has not yet been incorporated into any commercial treatment with the aim of slowing photoreceptor degeneration. Our recent discovery that taurine depletion is involved in the retinal toxicity of the antiepileptic drug vigabatrin has returned taurine to the limelight in the field of neuroprotection. However, although the retinal toxicity of vigabatrin principally involves a deleterious effect on photoreceptors, retinal ganglion cells (RGCs) are also affected. These findings led us to investigate the possible role of taurine depletion in retinal diseases with RGC degeneration, such as glaucoma and diabetic retinopathy. The major antioxidant properties of taurine may influence disease processes. In addition, the efficacy of taurine is dependent on its uptake into retinal cells, microvascular endothelial cells and the retinal pigment epithelium. Disturbances of retinal vascular perfusion in these retinal diseases may therefore affect the retinal uptake of taurine, resulting in local depletion. The low plasma taurine concentrations observed in diabetic patients may further enhance such local decreases in taurine concentration. We here review the evidence for a role of taurine in retinal ganglion cell survival and studies suggesting that this compound may be involved in the pathophysiology of glaucoma or diabetic retinopathy. Along with other antioxidant molecules, taurine should therefore be seriously reconsidered as a potential treatment for such retinal diseases.

White light-emitting diodes (LEDs) at domestic lighting levels and retinal injury in a rat model

BACKGROUND

Light-emitting diodes (LEDs) deliver higher levels of blue light to the retina than do conventional domestic light sources. Chronic exposure to high-intensity light (2,000-10,000 lux) has previously been found to result in light-induced retinal injury, but chronic exposure to relatively low-intensity (750 lux) light has not been previously assessed with LEDs in a rodent model.

OBJECTIVE

We examined LED-induced retinal neuronal cell damage in the Sprague-Dawley rat using functional, histological, and biochemical measurements.

METHODS

We used blue LEDs (460 nm) and full-spectrum white LEDs, coupled with matching compact fluorescent lights, for exposures. Pathological examinations included electroretinogram, hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), and transmission electron microscopy (TEM). We also measured free radical production in the retina to determine the oxidative stress level.

RESULTS

H&E staining and TEM revealed apoptosis and necrosis of photoreceptors, which indicated blue-light induced photochemical injury of the retina. Free radical production in the retina was increased in LED-exposed groups. IHC staining demonstrated that oxidative stress was associated with retinal injury. Although we found serious retinal light injury in LED groups, the compact fluorescent lamp (CFL) groups showed moderate to mild injury.

CONCLUSION

Our results raise questions about adverse effects on the retina from chronic exposure to LED light compared with other light sources that have less blue light. Thus, we suggest a precautionary approach with regard to the use of blue-rich "white" LEDs for general lighting.

CITATION

Shang YM, Wang GS, Sliney D, Yang CH, Lee LL. 2014. White light-emitting diodes (LEDs) at domestic lighting levels and retinal injury in a rat model. Environ Health Perspect 122:269-276; http://dx.doi.org/10.1289/ehp.1307294.

Effects of white light-emitting diode (LED) light exposure with different correlated color temperatures (CCTs) on human lens epithelial cells in culture

Cataract is the major cause for legal blindness in the world. Oxidative stress on the lens epithelial cells (hLECs) is the most important factor in cataract formation. Cumulative light-exposure from widely used light-emitting diodes (LEDs) may pose a potential oxidative threat to the lens epithelium, due to the high-energy blue light component in the white-light emission from diodes. In the interest of perfecting biosafety standards for LED domestic lighting, this study analyzed the photobiological effect of white LED light with different correlated color temperatures (CCTs) on cultured hLECs. The hLECs were cultured and cumulatively exposed to multichromatic white LED light with CCTs of 2954, 5624, and 7378 K. Cell viability of hLECs was measured by Cell Counting Kit-8 (CCK-8) assay. DNA damage was determined by alkaline comet assay. Intracellular reactive oxygen species (ROS) generation, cell cycle, and apoptosis were quantified by flow cytometry. Compared with 2954 and 5624 K LED light, LED light having a CCT of 7378 K caused overproduction of intracellular ROS and severe DNA damage, which triggered G2 /M arrest and apoptosis. These results indicate that white LEDs with a high CCT could cause significant photobiological damage to hLECs.

Ultraviolet damage to the eye revisited: eye-sun protection factor (E-SPF®), a new ultraviolet protection label for eyewear

Ultraviolet (UV) radiation potentially damages the skin, the immune system, and structures of the eye. A useful UV sun protection for the skin has been established. Since a remarkable body of evidence shows an association between UV radiation and damage to structures of the eye, eye protection is important, but a reliable and practical tool to assess and compare the UV-protective properties of lenses has been lacking. Among the general lay public, misconceptions on eye-sun protection have been identified. For example, sun protection is mainly ascribed to sunglasses, but less so to clear lenses. Skin malignancies in the periorbital region are frequent, but usual topical skin protection does not include the lids. Recent research utilized exact dosimetry and demonstrated relevant differences in UV burden to the eye and skin at a given ambient irradiation. Chronic UV effects on the cornea and lens are cumulative, so effective UV protection of the eyes is important for all age groups and should be used systematically. Protection of children's eyes is especially important, because UV transmittance is higher at a very young age, allowing higher levels of UV radiation to reach the crystalline lens and even the retina. Sunglasses as well as clear lenses (plano and prescription) effectively reduce transmittance of UV radiation. However, an important share of the UV burden to the eye is explained by back reflection of radiation from lenses to the eye. UV radiation incident from an angle of 135°-150° behind a lens wearer is reflected from the back side of lenses. The usual antireflective coatings considerably increase reflection of UV radiation. To provide reliable labeling of the protective potential of lenses, an eye-sun protection factor (E-SPF®) has been developed. It integrates UV transmission as well as UV reflectance of lenses. The E-SPF® compares well with established skin-sun protection factors and provides clear messages to eye health care providers and to lay consumers.

Genetic advances in ophthalmology: the role of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells in the circadian organization of the visual system

Daily changes in the light-dark cycle are the principal environmental signal that enables organisms to synchronize their internal biology with the 24-hour day-night cycle. In humans, the visual system is integral to photoentrainment and is primarily driven by a specialized class of intrinsically photosensitive retinal ganglion cells (ipRGCs) that express the photopigment melanopsin (OPN4) in the inner retina. These cells project through the retinohypothalamic tract (RHT) to the suprachiasmatic nuclei (SCN) of the hypothalamus, which serves as the body's master biological clock. At the same time, the retina itself possesses intrinsic circadian oscillations, exemplified by diurnal fluctuations in visual sensitivity, neurotransmitter levels, and outer segment turnover rates. Recently, it has been noted that both central and peripheral oscillators share a molecular clock consisting of an endogenous, circadian-driven, transcription-translation feedback loop that cycles with a periodicity of approximately 24 hours. This review will cover the role that melanopsin and ipRGCs play in the circadian organization of the visual system.

Photodynamic therapy: occupational hazards and preventative recommendations for clinical administration by healthcare providers

OBJECTIVE

Photodynamic therapy (PDT) as a medical treatment for cancers is an increasing practice in clinical settings, as new photosensitizing chemicals and light source technologies are developed and applied. PDT involves dosing patients with photosensitizing drugs, and then exposing them to light using a directed energy device in order to manifest a therapeutic effect. Healthcare professionals providing PDT should be aware of potential occupational health and safety hazards posed by these treatment devices and photosensitizing agents administered to patients.

MATERIALS AND METHODS

Here we outline and identify pertinent health and safety considerations to be taken by healthcare staff during PDT procedures.

RESULTS

Physical hazards (for example, non-ionizing radiation generated by the light-emitting device, with potential for skin and eye exposure) and chemical hazards (including the photosensitizing agents administered to patients that have the potential for exposure via skin, subcutaneous, ingestion, or inhalation routes) must be considered for safe use of PDT by the healthcare professional.

CONCLUSIONS

Engineering, administrative, and personal protective equipment controls are recommendations for the safe use and handling of PDT agents and light-emitting technologies.