The Effects of Different Outdoor Environments, Sunglasses and Hats on Light Levels: Implications for Myopia Prevention

Light exposure profiles differ between myopes and non-myopes outside school hours

PURPOSE

Considering the putative role of light in myopia, and variations in socioeconomic, lifestyle, educational and environmental factors across ethnicities, we objectively investigated light exposure patterns in Indian school children.

METHODS

The light exposure profile of 143 school children (9-15 years, 50 myopes) recorded using a validated wearable light tracker for six continuous days was analysed. Additional data for non-school days were available for 87 children (26 myopes). The illuminance exposure levels, time spent outdoors and epoch (number of times participant is exposed to a predefined range of lux level per day) were compared between myopes and non-myopes across different light conditions: ≥1000, ≥3000, ≥5000 and ≥10 000 lux. For school days, light exposure profiles during (1) before school, school and after school hours; and (2) class, break and transition (when a student travels to and from school) time were analysed.

RESULTS

The overall median (IQR) daily illuminance exposure level, time spent outdoors and epochs at outdoors (≥1000 lux) were 807 (507-1079) lux/day, 46 (30-64) min/day and 9 (6-12) times/day, respectively. The daily illuminance exposure on non-school days was significantly higher in non-myopes than myopes (6369 (4508-9112) vs 5623 (2616-6929) lux/day, p=0.04). During transition time (school days), non-myopes had significantly higher illuminance exposure (910 (388-1479) vs 550 (263-1098) lux/day, p=0.04), spent more time outdoors (25 (10-43) vs 14 (4-29) min/day, p=0.01) and had higher outdoor epochs (6 (4-11) vs 5 (2-8) times/day, p=0.01) than myopes.

CONCLUSIONS

A small but significant difference in illuminance exposure, time spent outdoors and epoch was noted between myopes and non-myopes during transition time, which may have implications in myopia control.

Effect of artificial natural light on the development of myopia among primary school-age children in China: a three-year longitudinal study

AIM

To assess the efficacy of artificial natural light in preventing incident myopia in primary school-age children.

METHODS

This is a prospective, randomized control, intervention study. A total of 1840 students from 39 classes in 4 primary schools in Foshan participated in this study. The whole randomization method was adopted to include classes as a group according to 1:1 randomized control. Classrooms in the control group were illuminated by usual light, and classrooms in the intervention group were illuminated by artificial natural light. All students received uncorrected visual acuity and best-corrected visual acuity measurement, non-cycloplegic autorefraction, ocular biometric examination, slit lamp and strabismus examination. Three-year follow-up, the students underwent same procedures. Myopia was defined as spherical equivalent refraction ≤ -0.50 D and uncorrected visual acuity <20/20.

RESULTS

There were 894 students in the control group and 946 students in the intervention group with a mean±SD age of 7.50±0.53y. The three-year cumulative incidence rate of myopia was 26.4% (207 incident cases among 784 eligible participants at baseline) in the control group and 21.2% (164 incident cases among 774 eligible participants at baseline) in the intervention group [difference of 5.2% (95%CI, 3.7% to 10.1%); P=0.035]. There was also a significant difference in the three-year change in spherical equivalent refraction for the control group (-0.81 D) compared with the intervention group [-0.63 D; difference of 0.18 D (95%CI, 0.08 to 0.28 D); P<0.001]. Elongation of axial length was significantly different between in the control group (0.77 mm) and the intervention group [0.72 mm; difference of 0.05 mm (95%CI, 0.01 to 0.09 mm); P=0.003].

CONCLUSION

Artificial natural light in the classroom of primary schools can result in reducing incidence rate of myopia during a period of three years.

Promoting adolescent sleep and circadian function: A narrative review on the importance of daylight access in schools

Adolescent sleep disturbances and circadian delays pose significant challenges to mood and daytime functioning. In this narrative review, we explore the impact of light on sleep and highlight the importance of monitoring and managing light exposure in adolescents throughout the day and night. The benefits of daylight exposure in mitigating sleep and circadian disruptions are well-established; however, interventions targeting access to daylight in adolescents remain understudied and underutilized. The primary aim of this narrative review is to bring attention to this gap in the literature and propose the need for institutional-level interventions that promote access to daylight, especially considering adolescents' early school start times and substantial time spent indoors on weekdays. School-led interventions, such as active commuting to school and outdoor curriculums, have promising effects on sleep and circadian rhythms. Additionally, practical measures to optimize natural light in classrooms, including managing blinds and designing conducive environments, should also be considered. While future studies are necessary to facilitate the implementation of interventions, the potential for these school-level interventions to support adolescent sleep health is evident. Aiming for integration of individual-level regulation and institutional-level intervention of light exposure is necessary for optimal outcomes.

The influence of the environment and lifestyle on myopia

BACKGROUND

Myopia, commonly known as near-sightedness, has emerged as a global epidemic, impacting almost one in three individuals across the world. The increasing prevalence of myopia during early childhood has heightened the risk of developing high myopia and related sight-threatening eye conditions in adulthood. This surge in myopia rates, occurring within a relatively stable genetic framework, underscores the profound influence of environmental and lifestyle factors on this condition. In this comprehensive narrative review, we shed light on both established and potential environmental and lifestyle contributors that affect the development and progression of myopia.

MAIN BODY

Epidemiological and interventional research has consistently revealed a compelling connection between increased outdoor time and a decreased risk of myopia in children. This protective effect may primarily be attributed to exposure to the characteristics of natural light (i.e., sunlight) and the release of retinal dopamine. Conversely, irrespective of outdoor time, excessive engagement in near work can further worsen the onset of myopia. While the exact mechanisms behind this exacerbation are not fully comprehended, it appears to involve shifts in relative peripheral refraction, the overstimulation of accommodation, or a complex interplay of these factors, leading to issues like retinal image defocus, blur, and chromatic aberration. Other potential factors like the spatial frequency of the visual environment, circadian rhythm, sleep, nutrition, smoking, socio-economic status, and education have debatable independent influences on myopia development.

CONCLUSION

The environment exerts a significant influence on the development and progression of myopia. Improving the modifiable key environmental predictors like time spent outdoors and engagement in near work can prevent or slow the progression of myopia. The intricate connections between lifestyle and environmental factors often obscure research findings, making it challenging to disentangle their individual effects. This complexity underscores the necessity for prospective studies that employ objective assessments, such as quantifying light exposure and near work, among others. These studies are crucial for gaining a more comprehensive understanding of how various environmental factors can be modified to prevent or slow the progression of myopia.

Conjunctival ultraviolet autofluorescence as a biomarker of outdoor exposure in myopia: a systematic review and meta-analysis

Outdoor exposure is considered the primary modifiable risk factor in preventing the development of myopia. This effect is thought to be attributed to the light-induced synthesis and release of dopamine in the retina. However, until recent years, there was no objective quantifiable method available to measure the association between time spent outdoors and myopia. It is only recently that the conjunctival ultraviolet autofluorescence (CUVAF) area, serving as a biomarker for sun exposure, has begun to be utilized in numerous studies. To provide a comprehensive summary of the relevant evidence pertaining to the association between the CUVAF area and myopia across different geographic regions and age groups, a systematic review and meta-analysis were conducted. The search encompassed multiple databases, including MEDLINE, SCIENCE DIRECT, GOOGLE SCHOLAR, WEB OF SCIENCE, and SCOPUS, and utilized specific search terms such as "conjunctival ultraviolet autofluorescence", "CUVAF", "UVAF", "objective marker of ocular sun exposure", "myopia", "degenerative myopia", and "high myopia". The bibliographic research included papers published between the years 2006 and 2022. A total of 4051 records were initially identified, and after duplicates were removed, 49 articles underwent full-text review. Nine articles were included in the systematic review. These studies covered myopia and outdoor exposure across different regions (Australia, Europe and India) with a total population of 3615 individuals. They found that myopes generally had smaller CUVAF areas compared to non-myopes. The meta-analysis confirmed this, revealing statistically smaller CUVAF areas in myopic patients, with a mean difference of - 3.30 mm2 (95% CI - 5.53; - 1.06). Additionally, some studies showed a positive correlation between more outdoor exposure and larger CUVAF areas. In terms of outdoor exposure time, myopic patients reported less time outdoors than non-myopic individuals, with a mean difference of - 3.38 h/week (95% CI - 4.66; - 2.09). Overall, these findings highlight the connection between outdoor exposure, CUVAF area and myopia, with regional variations playing a significant role. The results of this meta-analysis validate CUVAF as a quantitative method to objectively measure outdoor exposure in relation with myopia development.

Influence of different LED wavelengths on retinal melatonin levels - A rodent study

BACKGROUND

Retinal melatonin is crucial for neuroprotection. Exposure to light-emitting diodes (LEDs) affects retinal neurons, possibly influencing retinal melatonin levels. Hence, we aimed to quantify the retinal melatonin level with different LED wavelengths.

METHOD

A total of 24 Sprague Dawley (SD) male rats were divided into four groups (n = 6 in each group) as normal controls (NC), blue light (BL), white light (WL), and yellow light (YL). The rats in the experimental groups were exposed to different wavelengths of LEDs for 28 days (12:12 h light-dark cycle) with uniform illumination of 450-500 lx. Following exposure, the rats were subjected to behavioral tests such as passive avoidance and elevated plus maze tests. Following the behavior tests, the rats were sacrificed, eyes were enucleated, and retinal tissue was stored at -80 °C. The homogenized retina was used for reactive oxygen species (ROS) and melatonin quantification using an enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS

Passive avoidance test revealed a significant difference across the groups (p < 0.0004). The BL exposure group demonstrated increased latency to enter the dark compartment (DC) and impaired motor memory. The elevated plus maze test revealed a significant difference across all the groups (p < 0.012), where the time spent in the closed arm was greater in the BL exposure group. Comparison of ROS levels revealed a significant difference across the groups (p < 0.0001), with increased nitric oxide concentrations in the experimental groups. Melatonin levels were significantly decreased in the light exposure groups (p < 0.0001) compared to the NC group.

CONCLUSION

Cumulative exposure to different LED wavelengths resulted in increased anxiety with impaired motor activity. This was also complemented by the addition of oxidative stress leading to decreased melatonin levels in the retina, which might trigger retinal neuronal damage.

Sound and Light Waves in Healthy Environments

Architects need the freedom to design their projects with the assurance that they will be inspiring aesthetic as well as healthy places, i.e., buildings, streets, parks, avenues, and squares that offer a complete living experience in an environment that takes into account light, sound, vibration, climate, and all those aspects that can disturb people's well-being. We know that prolonged exposure to noise can cause discomfort and sleep disorders, which affect the quality of life. This noise is not the only pollutant as there are other sound waves such as infrasound and ultrasound that are not perceptible but potentially harmful to health. Not forgetting electromagnetic waves, the light that reaches our bodies and which has regulated our lives throughout the existence of the species. The invention of electric lighting had the consequence that people spend practically all day indoors. Days are poorly illuminated, and the nights have too much light. On the other hand, the intensity of artificial light is a fraction of that of daylight and the spectral composition is also different.

The outdoor environment affects retinal and choroidal thickness

PURPOSE

Accumulating evidence suggests that time outdoors is protective against myopia development and that the choroid may be involved in this effect. The goal of this study was to examine the effect of 2 h of time outdoors in sunlight on retinal and choroidal thickness in adults.

METHODS

Twenty adults, ages 23-46 years, each participated in three experimental sessions on different days, consisting of 2 h of exposure to (1) indoor illumination (350 lux), (2) darkness (<0.1 lux) or (3) outdoor environment (6000-50,000 lux). Spectral-domain optical coherence tomography (SD-OCT) imaging was conducted at baseline, after 1 and 2 h of exposure, and after 1 and 2 h of follow-up. Choroidal, total retinal, photoreceptor outer segment + retinal pigment epithelium (RPE) and photoreceptor inner segment thicknesses were determined.

RESULTS

At 2 h, the choroid was significantly thinner during the outdoor compared with the indoor and dark conditions (p < 0.01) but was not significantly different at follow-up. Total retinal thickness was significantly thicker during and after the outdoor compared with the indoor and dark conditions. The outer segment + RPE was significantly thinner during the outdoor compared with the indoor condition but was not significantly different at follow-up. The inner segment was significantly thicker during the outdoor compared with the indoor and dark conditions during exposure and follow-up.

CONCLUSIONS

Spending 2 h outdoors under high-intensity sunlight resulted in an unexpected thinning of the choroid, which recovered post-exposure. Retinal thickness showed different responses to the outdoor and indoor environments and was sensitive to the duration of exposure.

Ubiquitous light-emitting diodes: Potential threats to retinal circadian rhythms and refractive development

The use of light-emitting diodes (LEDs) has increased considerably in the 21st century with humans living in a modern photoperiod with brighter nights and dimmer days. Prolonged exposure to LEDs, especially at night, is considered a new source of pollution because it may affect the synthesis and secretion of retinal melatonin and dopamine, resulting in negative impacts on retinal circadian clocks and potentially disrupting retinal circadian rhythms. The control of ocular refraction is believed to be related to retinal circadian rhythms. Moreover, the global prevalence of myopia has increased at an alarming rate in recent decades. The widespread use of LEDs and the rapid increase in the prevalence of myopia overlap, which is unlikely to be a coincidence. The connection among LEDs, retinal circadian rhythms, and refractive development is both fascinating and confusing. In this review, we aim to develop a systematic framework that includes LEDs, retinal circadian rhythms and refractive development. This paper summarizes the possible mechanisms by which LEDs may disrupt retinal circadian rhythms. We propose that prolonged exposure to LEDs may induce myopia by disrupting retinal circadian rhythms. Finally, we suggest several possible countermeasures to prevent LED interference on retinal circadian rhythms, with the hope of reducing the onset and progression of myopia.

The effects of exposure to solar radiation on human health

This assessment by the Environmental Effects Assessment Panel (EEAP) of the Montreal Protocol under the United Nations Environment Programme (UNEP) evaluates the effects of ultraviolet (UV) radiation on human health within the context of the Montreal Protocol and its Amendments. We assess work published since our last comprehensive assessment in 2018. Over the last four years gains have been made in knowledge of the links between sun exposure and health outcomes, mechanisms, and estimates of disease burden, including economic impacts. Of particular note, there is new information about the way in which exposure to UV radiation modulates the immune system, causing both harms and benefits for health. The burden of skin cancer remains high, with many lives lost to melanoma and many more people treated for keratinocyte cancer, but it has been estimated that the Montreal Protocol will prevent 11 million cases of melanoma and 432 million cases of keratinocyte cancer that would otherwise have occurred in the United States in people born between 1890 and 2100. While the incidence of skin cancer continues to rise, rates have stabilised in younger populations in some countries. Mortality has also plateaued, partly due to the use of systemic therapies for advanced disease. However, these therapies are very expensive, contributing to the extremely high economic burden of skin cancer, and emphasising the importance and comparative cost-effectiveness of prevention. Photodermatoses, inflammatory skin conditions induced by exposure to UV radiation, can have a marked detrimental impact on the quality of life of sufferers. More information is emerging about their potential link with commonly used drugs, particularly anti-hypertensives. The eyes are also harmed by over-exposure to UV radiation. The incidence of cataract and pterygium is continuing to rise, and there is now evidence of a link between intraocular melanoma and sun exposure. It has been estimated that the Montreal Protocol will prevent 63 million cases of cataract that would otherwise have occurred in the United States in people born between 1890 and 2100. Despite the clearly established harms, exposure to UV radiation also has benefits for human health. While the best recognised benefit is production of vitamin D, beneficial effects mediated by factors other than vitamin D are emerging. For both sun exposure and vitamin D, there is increasingly convincing evidence of a positive role in diseases related to immune function, including both autoimmune diseases and infection. With its influence on the intensity of UV radiation and global warming, the Montreal Protocol has, and will have, both direct and indirect effects on human health, potentially changing the balance of the risks and benefits of spending time outdoors.

Association of time outdoors and patterns of light exposure with myopia in children

BACKGROUND/AIMS

To evaluate the association of reported time outdoors and light exposure patterns with myopia among children aged 9 years from the Growing Up in Singapore Towards Healthy Outcomes birth cohort.

METHODS

We assessed reported time outdoors (min/day), light exposure patterns and outdoor activities of children aged 9 years (n=483) with a questionnaire, the FitSight watch and a 7-day activity diary. Light levels, the duration, timing and frequency of light exposure were assessed. Cycloplegic spherical equivalent (SE), myopia (SE≤-0.5 D) and axial length (AL) of paired eyes were analysed using generalised estimating equations.

RESULTS

In this study, 483 (966 eyes) multiethnic children (50.0% boys, 59.8% Chinese, 42.2% myopic) were included. Reported time outdoors (mean±SD) was 100±93 min/day, and average light levels were 458±228 lux. Of the total duration children spent at light levels of ≥1000 lux (37±19 min/day), 76% were spent below 5000 lux. Peak light exposure occurred at mid-day. Children had 1.7±1.0 light exposure episodes/day. Common outdoor activities were walks, neighbourhood play and swimming. Greater reported time outdoors was associated with lower odds of myopia (OR=0.82, 95% CI 0.70 to 0.95/hour increase daily; p=0.009). Light levels, timing and frequency of light exposures were not associated with myopia, SE or AL (p>0.05).

CONCLUSION

Reported time outdoors, light levels and number of light exposure episodes were low among Singaporean children aged 9 years. Reported time outdoors was protective against myopia but not light levels or specific light measures. A multipronged approach to increase time outdoors is recommended in the combat against the myopia epidemic.

Near work, screen time, outdoor time and myopia in schoolchildren in the Sunflower Myopia AEEC Consortium

PURPOSE

To examine the association between near work, screen time including TV and outdoor time with myopia in children from the Sunflower Myopia Asian Eye Epidemiology Consortium (AEEC).

METHODS

We analysed AEEC cross-sectional data (12 241 children) on risk factors (near work, screen time including TV and outdoor time) and myopia of six population-based studies (China, Hong Kong and Singapore). Cycloplegic refraction and axial length (AL) measurements were included. Risk factors were determined using questionnaires. Data were pooled from each study, and multivariable regression analysis was performed to evaluate the associations between risks factors and myopia, spherical equivalent (SE) and AL.

RESULTS

Among the included children, 52.1% were boys, 98.1% were Chinese and 69.7% lived in urban areas. Mean±standard deviation (SD) for age was 8.8 ± 2.9 years, for SE was -0.14 ± 1.8 D and for AL was 23.3 ± 1.1 mm. Myopia prevalence was 30.6%. In multivariate analysis, more reading and writing (OR = 1.17; 95% CI, 1.11-1.24), more total near work (OR = 1.05; 95% CI, 1.02-1.09) and less outdoor time (OR = 0.82, 95% CI, 0.75-0.88) were associated with myopia (p's < 0.05). These factors were similarly associated with SE and AL (p's < 0.05), except for total near work and AL (p = 0.15). Screen time including TV was not significantly associated with myopia (p = 0.49), SE (p = 0.49) or AL (p = 0.83).

CONCLUSION

In this study, increased reading and writing and decreased outdoor time were associated with myopia. Screen time may be a surrogate factor of near work or outdoor time, but further research is needed to assess its role as an independent risk factor for myopia.

Recovery From Form-Deprivation Myopia in Chicks Is Dependent Upon the Fullness and Correlated Color Temperature of the Light Spectrum

Purpose

The purpose of this study was to evaluate the impact of full-spectrum light-emitting diodes mimicking sunlight (Sunlike LEDs) on ocular growth and refractive error development in a chicken model of myopia.

Methods

One-day old chicks (n = 39) were distributed into 3 groups and raised for 28 days in isoluminant (approximately 285 lux) fluorescent (n = 18, [FL-4000], correlated color temperature [CCT] = 4000 K) or Sunlike LED (n = 12, [SL-4000], CCT = 4000 K; n = 9, [SL-6500], CCT = 6500 K) white lighting environments. Form-deprivation myopia was induced monocularly from day 1 post-hatching (D1) until D14. On D14, form deprivation was halted and the recovery of form-deprived (FD) eyes was monitored until D28. Axial length (AL), refraction, choroidal thickness, and anterior chamber depth were measured in vivo on D1, D7, D14, D22, and D28. Differences in outcome measures between eyes and groups were compared using 2-way repeated-measures ANOVA.

Results

AL and myopic refraction of FD eyes increased similarly among groups during form-deprivation. FD eyes of animals raised under SL-4000 (D22: P < 0.001 and D28: P < 0.001) and SL-6500 (D22: P = 0.006 and D28: P < 0.001) recovered faster from axial elongation compared with animals raised under FL-4000. The refractive status of FD eyes reared under SL-6500, not under FL-4000 or SL-4000, was similar to control eyes on D28 (P > 0.05). However, SL-4000 and SL-6500 exhibited similar refraction on D28 than FL-4000 (P > 0.05). Choroidal thickness was significantly greater in FD eyes of chickens raised under SL-6500 than in animals raised under FL-4000 (P = 0.03).

Conclusions

Compared to fluorescent light, moderate intensities of full-spectrum Sunlike LEDs can accelerate recovery from form-deprivation myopia in chickens, potentially through a change in the choroid-mediated pathway.

The effect of spatially-related environmental risk factors in visual scenes on myopia

Myopia, the most common refractive error, is estimated to affect over two billion people worldwide, especially children from East Asian regions. Children with early onset myopia have an increased risk of developing sight threatening complications in later life. In addition to the contribution of genetic factors, of which expression is controversially suggested to be subject to environmental regulation, various environmental factors, such as near-work, outdoor, and living environment, have also been determined to play significant roles in the development of refractive error, especially juvenile myopia. Cues from daily visual scenes, including lighting, spatial frequency, and optical defocus over the field of visual stimuli, are suggested to influence emmetropisation, thereby affecting myopia development and progression. These risk factors in visual scenes of the everyday life may explain the relationship between urbanicity and myopia prevalence. This review first summarises the previously reported associations between myopia development and everyday-life environments, including schooling, urban settings, and outdoors. Then, there is a discussion of the mechanisms hypothesised in the literature about the cues from different visual scenes of urbanicity in relation to myopia development.

Ambient light level varies with different locations and environmental conditions: Potential to impact myopia

PURPOSE

Considering that time spent outdoors is protective for myopia, we investigated how ambient light levels reaching the eye varies across 9 outdoor and 4 indoor locations in 5 different environmental conditions.

METHODS

Illuminance (lux) was recorded using a lux meter under conditions of weather (sunny/cloudy), time of a day (7:00,10:00,13:00, and 16:00 hours), seasons (summer/winter), and sun protection (hat and cap) in outdoor and indoor locations. Nine outdoor locations were "open playground", "under a translucent artificial-shade", "under a porch facing east", "under a porch facing south", "under a big tree", "between three buildings", "within 4 buildings", and "canopy". As a ninth outdoor location, "Under a glass bowl" in the outdoor location was used as a simulation for "glass classroom model" and measurement was taken at the floor level only to determine in overall the illuminance conditions with glass covered on all sides. The 4 indoor locations included "room with multiple large windows", "room with combination light source", "room with multiple artificial lights", and "room with single artificial light".

RESULTS

The overall median illuminance level (median; Q1-Q3) recorded in 9 outdoor locations was 8 times higher than that of all indoor locations (1175;197-5400 lux vs. 179;50-333 lux). Highest illuminance in outdoor locations was recorded in "open playground" (9300;4100-16825 lux), followed by "under a translucent artificial shade (8180;4200-13300 lux) and the lowest in "within 4 buildings" (11;6-20 lux). Illuminance under 'Canopy', 'between three buildings' and 'within four buildings' was similar to that of indoor locations (<1000 lux). Time of the day, weather, season, sensor position and using sun protection did not alter illuminance to change from high to low level (>1000 to <1000 lux). Among indoor locations, illuminance in "room with multiple large windows" crossed 1000 lux at a specific time points on both sunny and cloudy days.

CONCLUSIONS

Illuminance levels in outdoors and indoors varied with location type, but not with other conditions. Given the variation in illuminance in different locations, and the impact it may have on myopia control, appropriate detailed recommendations seems necessary while suggesting time outdoors as an anti-myopia strategy to ensure desired outcomes.

Pandemic of Childhood Myopia. Could New Indoor LED Lighting Be Part of the Solution?

The existence of a growing myopia pandemic is an unquestionable fact for health authorities around the world. Different possible causes have been put forward over the years, such as a possible genetic origin, the current excess of children’s close-up work compared to previous stages in history, insufficient natural light, or a multifactorial cause. Scientists are looking for different possible solutions to alleviate it, such as a reduction of time or a greater distance for children’s work, the use of drugs, optometric correction methods, surgical procedures, and spending more time outdoors. There is a growing number of articles suggesting insufficient natural light as a possible cause of the increasing levels of childhood myopia around the globe. Technological progress in the world of lighting is making it possible to have more monochromatic LED emission peaks, and because of this, it is possible to create spectral distributions of visible light that increasingly resemble natural light in the visible range. The possibility of creating indoor luminaires that emit throughout the visible spectrum from purple to infrared can now be a reality that could offer a new avenue of research to fight this pandemic.

Spectral composition of artificial illuminants and their effect on eye growth in chicks

In broadband light, longitudinal chromatic aberration (LCA) provides emmetropization signals from both wavelength defocus and the resulting chromatic cues. Indoor illuminants vary in their spectral output, potentially limiting the signals from LCA. Our aim is to investigate the effect that artificial illuminants with different spectral outputs have on chick emmetropization with and without low temporal frequency modulation. In Experiment 1, two-week-old chicks were exposed to 0.2 Hz, square-wave luminance modulation for 3 days. There were 4 spectral conditions: LED strips that simulated General Electric (GE) LED "Soft" (n = 13), GE LED "Daylight" (n = 12), a novel "Equal" condition (n = 12), and a novel "High S" condition (n = 10). These conditions were all tested at a mean level of 985 lux. In Experiment 2, the effect of intensity on the "Equal" condition was tested at two other light levels (70 lux: n = 10; 680 lux: n = 7). In Experiment 3, the effect of temporal modulation on the "Equal" condition was tested by comparing the 0.2 Hz condition with 0 Hz (steady). Significant differences were found in axial growth across lighting conditions. At 985 lux, birds exposed to the "Equal" condition showed a greater reduction in axial growth (both p < 0.01) and a greater hyperopic shift compared to "Soft" and "Daylight" (both p < 0.01). The "High S" birds experienced more axial growth compared to "Equal" (p < 0.01) but less than in "Soft" and "Daylight" (p < 0.01). Axial changes in "Equal" were only observed at 985 lux with 0.2 Hz temporal modulation, and not with lower light levels or steady light. We conclude that axial growth and refraction were dependent on the lighting condition in a manner predicted by wavelength defocus signals arising from LCA.

Light and myopia: from epidemiological studies to neurobiological mechanisms

Myopia is far beyond its inconvenience and represents a true, highly prevalent, sight-threatening ocular condition, especially in Asia. Without adequate interventions, the current epidemic of myopia is projected to affect 50% of the world population by 2050, becoming the leading cause of irreversible blindness. Although blurred vision, the predominant symptom of myopia, can be improved by contact lenses, glasses or refractive surgery, corrected myopia, particularly high myopia, still carries the risk of secondary blinding complications such as glaucoma, myopic maculopathy and retinal detachment, prompting the need for prevention. Epidemiological studies have reported an association between outdoor time and myopia prevention in children. The protective effect of time spent outdoors could be due to the unique characteristics (intensity, spectral distribution, temporal pattern, etc.) of sunlight that are lacking in artificial lighting. Concomitantly, studies in animal models have highlighted the efficacy of light and its components in delaying or even stopping the development of myopia and endeavoured to elucidate possible mechanisms involved in this process. In this narrative review, we (1) summarize the current knowledge concerning light modulation of ocular growth and refractive error development based on studies in human and animal models, (2) summarize potential neurobiological mechanisms involved in the effects of light on ocular growth and emmetropization and (3) highlight a potential pathway for the translational development of noninvasive light-therapy strategies for myopia prevention in children.

Electronic Sun Journal Versus Self-report Sun Diary: A Comparison of Recording Personal Sunlight Exposure Methods

This research compared personal sunlight exposure times monitored electronically within suburban Australian environments against self-report paper journals for determining the timing and total duration of individual exposure to daily solar radiation. A total of 90 Electronic Sun Journal (ESJ) daily readings and self-report timing and duration estimates of exposure for weekend and weekdays were compared. A Wilcoxon ranked sign test showed a significant difference (V = 157, P < 0.001) between the duration of exposure recorded electronically and the duration of exposure that was self-reported in a diary. There was also found to be a statistically significant difference between total exposure time measured using both methods for weekends (V = 10, P < 0.001) and weekdays (V = 87, P < 0.001). General trends in outdoor exposure timing confirmed that the most frequent daily exposures received over the weekend occurred between 1 and 2 h earlier than the most frequent exposures received on weekdays. This preliminary research found that exposure durations as recorded by the ESJ were longer on the weekends compared to weekdays (W = 402, P < 0.001) and confirmed that the ESJ is a viable alternative to self-reporting diaries.

The Role of Daylight for Humans: Gaps in Current Knowledge

Daylight stems solely from direct, scattered and reflected sunlight, and undergoes dynamic changes in irradiance and spectral power composition due to latitude, time of day, time of year and the nature of the physical environment (reflections, buildings and vegetation). Humans and their ancestors evolved under these natural day/night cycles over millions of years. Electric light, a relatively recent invention, interacts and competes with the natural light-dark cycle to impact human biology. What are the consequences of living in industrialised urban areas with much less daylight and more use of electric light, throughout the day (and at night), on general health and quality of life? In this workshop report, we have classified key gaps of knowledge in daylight research into three main groups: (I) uncertainty as to daylight quantity and quality needed for "optimal" physiological and psychological functioning, (II) lack of consensus on practical measurement and assessment methods and tools for monitoring real (day) light exposure across multiple time scales, and (III) insufficient integration and exchange of daylight knowledge bases from different disciplines. Crucial short and long-term objectives to fill these gaps are proposed.

Effect of light and diurnal variation on macular thickness in X-linked retinoschisis: a case series

BACKGROUND

Diurnal variations in foveal thickness have been reported in several ocular pathologies including X-linked retinoschisis (XLRS), but its underlying mechanism is poorly understood. Rods are active under scotopic conditions with high metabolic demand, and its decrease may have positive effect on metabolic activity and macular thickness. The purpose of this study is to evaluate whether exposure to light and diurnal variation influence macular thickness in XLRS patients.

METHODS

Five patients with clinical suspicion of XLRS underwent RS1 gene sequencing and optical coherence tomography measurements at three consecutive times: morning following sleep in a dark room, morning following sleep in an illuminated room, and late afternoon following sleep in an illuminated room. Central macular thickness (CMT) was compared between measurements, and molecular analysis was performed.

RESULTS

Five RS1 mutations were identified: p.Gly140Arg, p.Arg141Cys, p.Gly109Glu, p.Pro193Leu, and p.Arg200His in patients 1-5, respectively. Two patients (4-5) had atrophied macula and were excluded from macular thickness variation analysis. A significant decrease in CMT between morning and afternoon measurements was observed in all patients (1-3: mean: 455.0 ± 32 μm to 342.17 ± 39 μm, 25%). Morning measurements following sleep in an illuminated room show a CMT reduction in all eyes of all patients with a mean reduction of 113 μm (mean: 547.17 ± 105 μm to 455.0 ± 32 μm, 17%).

CONCLUSIONS

Among XLRS patients, CMT decreased at the afternoon compared to the morning of the same day and may be reduced following sleep in an illuminated room. These results help shed light on the pathophysiologic process underlying intraretinal fluid accumulation involved with the disease.

How does spending time outdoors protect against myopia? A review

Myopia is an increasingly common condition that is associated with significant costs to individuals and society. Moreover, myopia is associated with increased risk of glaucoma, retinal detachment and myopic maculopathy, which in turn can lead to blindness. It is now well established that spending more time outdoors during childhood lowers the risk of developing myopia and may delay progression of myopia. There has been great interest in further exploring this relationship and exploiting it as a public health intervention aimed at preventing myopia in children. However, spending more time outdoors can have detrimental effects, such as increased risk of melanoma, cataract and pterygium. Understanding how spending more time outdoors prevents myopia could advance development of more targeted interventions for myopia. We reviewed the evidence for and against eight facets of spending time outdoors that may protect against myopia: brighter light, reduced peripheral defocus, higher vitamin D levels, differing chromatic spectrum of light, higher physical activity, entrained circadian rhythms, less near work and greater high spatial frequency (SF) energies. There is solid evidence that exposure to brighter light can reduce risk of myopia. Peripheral defocus is able to regulate eye growth but whether spending time outdoors substantially changes peripheral defocus patterns and how this could affect myopia risk is unclear. Spectrum of light, circadian rhythms and SF characteristics are plausible factors, but there is a lack of solid evidence from human studies. Vitamin D, physical activity and near work appear unlikely to mediate the relationship between time spent outdoors and myopia.