Differential synthetic illumination based on multi-line detection for resolution and contrast enhancement of line confocal microscopy.

Line confocal (LC) microscopy is a fast 3D imaging technique, but its asymmetric detection slit limits resolution and optical sectioning. To address this, we propose the differential synthetic illumination (DSI) method based on multi-line detection to enhance the spatial resolution and optical sectioning capability of the LC system. The DSI method allows the imaging process to simultaneously accomplish on a single camera, which ensures the rapidity and stability of the imaging process. DSI-LC improves X- and Z-axis resolution by 1.28 and 1.26 times, respectively, and optical sectioning by 2.6 times compared to LC. Furthermore, the spatially resolved power and contrast are also demonstrated by imaging pollen, microtubule, and the fiber of the GFP fluorescence-labeled mouse brain. Finally, Video-rate imaging of zebrafish larval heart beating in a 665.6 × 332.8 µm2 field-of-view is achieved. DSI-LC provides a promising approach for 3D large-scale and functional imaging in vivo with improved resolution, contrast, and robustness.

Effects of LED supplemental lighting on the growth and metabolomic profile of Taxus baccata cultivated in a smart greenhouse.

Light emitting diode (LED) lamps are increasingly being studied in cultivation of horticultural, ornamental and medicinal plants as means to increase yield, quality, stress resistance, and bioactive compounds content. Enhancing the production of metabolites for medicinal or pharmaceutical use by regulating LED intensity and spectra is a challenging subject, where promising results have been achieved. Nevertheless, some species have been poorly investigated, despite their interest as a source of medicinally active substances, with particular reference to LED effects at the plant cultivation level. This study evaluates the effects of supplementary top-light LED treatments on Taxus baccata, one of the main sources of taxane precursors. Blue, red and mixed red-and-blue spectra were tested at 100 µM m-2 s-1. Moreover, 50 and 150 µM m-2 s-1 intensities were tested for the mixed spectrum. All treatments were set for 14 hours a day and were tested against natural light as control treatment, in a controlled environment, from 19 August to 9 December 2019, this latter date representing 112 days after treatment (DAT) began. A smart monitoring and control system powered by environmental and proximal sensors was implemented to assure homogeneity of temperature, humidity, and base natural light for all the treatments. It resulted in negligible deviations from expected values and reliable exclusion of confusing factors. Biometric measurements and 1H-NMR based metabolomic analysis were performed to investigate growth and phytochemical profile throughout the trial. One-way ANOVA showed that supplemental LED lighting increased plant height and number of sprouts. Considering the mixed red-and-blue spectrum, plant height increased almost proportionally from control to 100 µM m-2 s-1 (+20% at 112 DAT), with no further increase at higher intensity. The number of sprouts was strongly enhanced by LED treatments only in the early phase (48.9 vs. 7.5 sprouts in the averaged 50, 100 and 150 µM m-2 s-1 vs. the control at 28 DAT), with no differences related to intensity in the very early stage, and more persisting effects (up to 56 DAT) for higher intensities. After the very early growth stages (28 DAT), plant vigor showed a modest although significant increase over time compared to the control, with no differences related to light intensity (0.81 vs. 0.74 of NDVI in the averaged 50, 100 and 150 µM m-2 s-1 vs. the control, across 56, 84 and 112 DAT). The different spectra tested at 100 µM m-2 s-1 showed no significant differences in growth parameters, except for a slight beneficial influence of blue (alone or with red) compared to only red for sprouting. According to the metabolomic analysis, treated plants at 28 DAT were characterized by the highest content of sucrose and aromatic compounds. Signals of a putative taxane were detected in the 1H NMR profiles of plants, which were compared to the spectrum of baccatin III standard. However, the intensity of these spectral signals was not affected by the treatment, while they increased only slightly during time. Light at 150 µM m-2 s-1 induced the strongest variation in the metabolome. Conversely, light composition did not induce significant differences in the metabolome.

Dynamic white lighting to aid sleep and vision for persons living with dementia using off-the-shelf LED strips.

Alzheimer disease and related dementias affect 15-20% of elderly people, and 60-70% of these suffer from sleep disturbances. Studies suggest that lighting can improve sleep. The key challenge is how to deliver light effectively. We have designed a lighting system that adjusts spectrum and irradiance on a 24-hour timetable to provide spatially uniform, shadow-free white light with CRI>85 and up to 1000 Lux for day vision and amber light for night vision. To aid sleep, melanopic illuminance varies over 3 orders of magnitude to enable strong suppression of melatonin in the morning/early afternoon, moderate suppression in the evening, and no suppression at night.

Ocular growth and metabolomics are dependent upon the spectral content of ambient white light.

Myopia results from an excessive axial growth of the eye, causing abnormal projection of remote images in front of the retina. Without adequate interventions, myopia is forecasted to affect 50% of the world population by 2050. Exposure to outdoor light plays a critical role in preventing myopia in children, possibly through the brightness and blue-shifted spectral composition of sunlight, which lacks in artificial indoor lighting. Here, we evaluated the impact of moderate levels of ambient standard white (SW: 233.1 lux, 3900 K) and blue-enriched white (BEW: 223.8 lux, 9700 K) lights on ocular growth and metabolomics in a chicken-model of form-deprivation myopia. Compared to SW light, BEW light decreased aberrant ocular axial elongation and accelerated recovery from form-deprivation. Furthermore, the metabolomic profiles in the vitreous and retinas of recovering form-deprived eyes were distinct from control eyes and were dependent on the spectral content of ambient light. For instance, exposure to BEW light was associated with deep lipid remodeling and metabolic changes related to energy production, cell proliferation, collagen turnover and nitric oxide metabolism. This study provides new insight on light-dependent modulations in ocular growth and metabolomics. If replicable in humans, our findings open new potential avenues for spectrally-tailored light-therapy strategies for myopia.

Quantifying risk factors associated with light-induced potato tuber greening in retail stores.

Light conditions in retail stores may contribute to potato greening. In this study, we aimed to develop a potato tuber greening risk rating model for retail stores based on light quality and intensity parameters. This was achieved by firstly exposing three potato varieties (Nicola, Maranca and Kennebec) to seven specific light wavelengths (370, 420, 450, 530, 630, 660 and 735 nm) to determine the tuber greening propensity. Detailed light quality and intensity measurements from 25 retail stores were then combined with the greening propensity data to develop a tuber greening risk rating model. Our study showed that maximum greening occurred under blue light (450 nm), while 53%, 65% and 75% less occurred under green (530 nm), red (660 nm) and orange (630 nm) light, respectively. Greening risk, which varied between stores, was found to be related to light intensity level, and partially explained potato stock loss in stores. Our results from this study suggested that other in-store management practices, including lighting duration, average potato turnover, and light protection during non-retail periods, likely influence tuber greening risk.

Blue-blocking glasses as additive treatment for mania: Effects on actigraphy-derived sleep parameters.

Improvement of sleep is a central treatment goal for patients in a manic state. Blue-blocking (BB) glasses as adjunctive treatment hasten overall recovery from mania. This method is an evolvement from dark therapy and builds on the discovery of the blue-light-sensitive retinal ganglion cell that signals daytime to the brain. We report effects of adjunctive BB glasses on actigraphy-derived sleep parameters for manic inpatients as compared to placebo. Hospitalized patients with bipolar disorder in a manic state aged 18-70 years were recruited from five clinics in Norway from February 2012 to February 2015. The participants were randomly allocated to wearing BB glasses or placebo (clear glasses) as an adjunctive treatment from 18:00 to 08:00 hours for seven consecutive nights. Sleep and wake were monitored by actigraphy. From 32 eligible patients, 10 patients in each group qualified for the group analyses. The BB group's mean sleep efficiency was significantly higher at night 5 as compared to the placebo group (92.6% vs. 83.1%, p = .027). The 95% confidence interval (CI) was 89.4%-95.8% in the BB group and 75.9%-90.3% in the placebo group. There were fewer nights of interrupted sleep in the BB group: 29.6% versus 43.8% in the placebo group. The BB group received less-intensive sleep-promoting pharmacological treatment and showed significantly higher sleep efficiency and more consolidated sleep as compared to the placebo group. Our findings suggest sleep-promoting effects through deactivating mechanisms. Adjunctive BB glasses seem to be useful for improving sleep for manic patients in the hospital setting.

Effects of a Tailored Lighting Intervention on Sleep Quality, Rest-Activity, Mood, and Behavior in Older Adults With Alzheimer Disease and Related Dementias: A Randomized Clinical Trial.

STUDY OBJECTIVES: We investigated the effectiveness of a lighting intervention tailored to maximally affect the circadian system as a nonpharmacological therapy for treating problems with sleep, mood, and behavior in persons with Alzheimer disease and related dementias (ADRD). METHODS: This 14-week randomized, placebo-controlled, crossover design clinical trial administered an all-day active or control lighting intervention to 46 patients with ADRD in 8 long-term care facilities for two 4-week periods (separated by a 4-week washout). The study employed wrist-worn actigraphy measures and standardized measures of sleep quality, mood, and behavior. RESULTS: The active intervention significantly improved Pittsburgh Sleep Quality Index scores compared to the active baseline and control intervention (mean ± SEM: 6.67 ± 0.48 after active intervention, 10.30 ± 0.40 at active baseline, 8.41 ± 0.47 after control intervention). The active intervention also resulted in significantly greater active versus control differences in intradaily variability. As for secondary outcomes, the active intervention resulted in significant improvements in Cornell Scale for Depression in Dementia scores (mean ± SEM: 10.30 ± 1.02 at baseline, 7.05 ± 0.67 after active intervention) and significantly greater active versus control differences in Cohen-Mansfield Agitation Inventory scores (mean ± SEM: -5.51 ± 1.03 for the active intervention, -1.50 ± 1.24 for the control intervention). CONCLUSIONS: A lighting intervention tailored to maximally entrain the circadian system can improve sleep, mood, and behavior in patients with dementia living in controlled environments. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov, title: Methodology Issues in a Tailored Light Treatment for Persons With Dementia, URL: https://clinicaltrials.gov/ct2/show/NCT01816152, identifier: NCT01816152.

LEDs for photons, physiology and food.

Lighting based on light-emitting diodes (LEDs) not only is more energy efficient than traditional lighting, but also enables improved performance and control. The colour, intensity and distribution of light can now be controlled with unprecedented precision, enabling light to be used both as a signal for specific physiological responses in humans and plants, and as an efficient fuel for fresh food production. Here we show how a broad and improved understanding of the physiological responses to light will facilitate greater energy savings and provide health and productivity benefits that have not previously been associated with lighting.

Effect of elevated CO2 and spectral quality on whole plant gas exchange patterns in tomatoes.

In controlled environment plant production facilities, elevating either light or CO2 levels generally has led to increased biomass and yield due to enhanced canopy photosynthesis. Today, advancements in light-emitting diodes (LEDs) have made this technology a viable option for both supplementary lighting in greenhouses and a sole lighting source in controlled environment chambers. Our study used tomato plants grown under both ambient CO2 (AC) and elevated CO2 (EC) conditions then exposed them to various CO2 and lighting treatments during both whole plant and leaf level measurements. Plants grown under EC reached the first flower developmental stage 8 days sooner and were approximately 15cm taller than those grown under AC. However, under AC plants had more leaf area while their dry weights were similar. Of note, under EC chlorophyll a and b were lower, as were carotenoids per unit leaf area. Whole plant analyses, under all CO2 challenges, showed that plants exposed to high-pressure sodium (HPS), red-blue LED, and red-white LED had similar photosynthesis, respiration, and daily carbon gain. Under different light qualities, day-time transpiration rates were similar among CO2 conditions. Day-time water-use efficiency (WUE) was higher in plants grown and exposed to EC. Similarly, WUE of plants grown under AC but exposed to short-term elevated CO2 conditions was higher than those grown and tested under AC during all light treatments. Under all CO2 conditions, plants exposed to red-white and red-blue LEDs had lower WUE than those exposed to HPS lighting. Assessing alterations due to CO2 and light quality on a whole plant basis, not merely on an individual leaf basis, furthers our understanding of the interactions between these two parameters during controlled environment production. Principle component analyses of both whole plant and leaf data indicates that increasing CO2 supply has a more dramatic effect on photosynthesis and WUE than on transpiration.

Improved cognitive morning performance in healthy older adults following blue-enriched light exposure on the previous evening.

OBJECTIVES: Exposure to light can have acute alerting and circadian phase-shifting effects. This study investigated the effects of evening exposure to blue-enriched polychromatic white (BEL) vs. polychromatic white light (WL) on sleep inertia dissipation the following morning in older adults. METHODS: Ten healthy older adults (average age = 63.3 yrs; 6F) participated in a 13-day study comprising three baseline days, an initial circadian phase assessment, four days with 2-h evening light exposures, a post light exposure circadian phase assessment and three recovery days. Participants were randomized to either BEL or WL of the same irradiance for the four evening light exposures. On the next mornings at 2, 12, 22 and 32 min after each wake time, the participants completed a 90-s digit-symbol substitution test (DSST) to assess working memory, and objective alertness was assessed using a wake EEG recording. DSST and power density from the wake EEG recordings were compared between the two groups. RESULTS: DSST performance improved with time awake (p < 0.0001) and across study days in both light exposure groups (p < 0.0001). There was no main effect of group, although we observed a significant day x group interaction (p = 0.0004), whereby participants exposed to BEL performed significantly better on the first two mornings after light exposures than participants in WL (post-hoc, p < 0.05). On those days, the BEL group showed higher EEG activity in some of the frequency bins in the sigma and beta range (p < 0.05) on the wake EEG. CONCLUSION: Exposure to blue-enriched white light in the evening significantly improved DSST performance the following morning when compared to polychromatic white light. This was associated with a higher level of objective alertness on the wake EEG, but not with changes in sleep or circadian timing.

Effect of Color Light Stimulation Using LED on Sleep Induction Time.

The effects of color are already being used widely. For this reason, in this study, an attempt was made to use such effects of color to examine the changes in sleep onset through the use of the preferred and nonpreferred color light stimulation. Color light stimulations were randomly presented to the subjects, and based on these colors, the changes in sleep onset were examined through the EEG. Also, to quantify the physiological changes that were caused by each color light stimulation, the changes in the HRV were examined through ECG to determine the level of activation of the autonomous nervous system. The results showed that sleep onset time was changed based on the light stimulation. The result of the EEG analysis showed that sleep onset time was most significantly shortened in preferred color light stimulation. Also, the result of HRV was the fastest change about both the time domain and the frequency domain in the preferred color light stimulation. Therefore, because the preferred color light stimulation activated the parasympathetic nervous system, sleep was induced quickly. Also, by simply using the HRV, the differences in the index of HRV showed changes of sleep onset according to the color light stimulation.

Pretreatment with light-emitting diode therapy reduces ischemic brain injury in mice through endothelial nitric oxide synthase-dependent mechanisms.

Photostimulation with low-level light emitting diode therapy (LED-T) modulates neurological and psychological functions. The purpose of this study was to evaluate the effects of LED-T pretreatment on the mouse brain after ischemia/reperfusion and to investigate the underlying mechanisms. Ischemia/reperfusion brain injury was induced by middle cerebral artery occlusion. The mice received LED-T twice a day for 2 days prior to cerebral ischemia. After reperfusion, the LED-T group showed significantly smaller infarct and edema volumes, fewer behavioral deficits compared to injured mice that did not receive LED-T and significantly higher cerebral blood flow compared to the vehicle group. We observed lower levels of endothelial nitric oxide synthase (eNOS) phosphorylation in the injured mouse brains, but significantly higher eNOS phosphorylation in LED-T-pretreated mice. The enhanced phospho-eNOS was inhibited by LY294002, indicating that the effects of LED-T on the ischemic brain could be attributed to the upregulation of eNOS phosphorylation through the phosphoinositide 3-kinase (PI3K)/Akt pathway. Moreover, no reductions in infarct or edema volume were observed in LED-T-pretreated eNOS-deficient (eNOS-/-) mice. Collectively, we found that pretreatment with LED-T reduced the amount of ischemia-induced brain damage. Importantly, we revealed that these effects were mediated by the stimulation of eNOS phosphorylation via the PI3K/Akt pathway.

Fluorescent incisionless cholangiography as a teaching tool for identification of Calot's triangle.

BACKGROUND: Intraoperative incisionless fluorescent cholangiogram (IOIFC) has been demonstrated to be a useful tool to increase the visualization of Calot's triangle. This study evaluates the identification of extrahepatic biliary structures with IOIFC by medical students and surgery residents. METHODS: Two pictures were taken, one with xenon light and one with near-infrared (NIR) light, at the same stage during dissection of Calot's triangle in ten different cases of laparoscopic cholecystectomy (LC). All twenty pictures were organized in a random fashion to remove any imagery bias. Twenty students and twenty residents were asked to identify the biliary anatomy. RESULTS: Medical students were able to accurately identify the cystic duct on an average 33.8 % under the xenon light versus 86 % under NIR light (p = 0.0001), the common hepatic duct (CHD) on an average 19 % under the xenon light versus 88.5 % under NIR light (p = 0.0001), and the junction on an average 24 % under xenon light versus 80.5 % under NIR light (p = 0.0001). Surgery residents were able to accurately identify the cystic duct on an average 40 % under the xenon light versus 99 % under NIR light (p = 0.0001), the CHD on an average 35 % under the xenon light versus 96 % under NIR light (p = 0.0001), and the junction on an average 24 % under the xenon light versus 95.5 % under NIR light (p = 0.0001). CONCLUSIONS: IOIFC increases the visualization of Calot's triangle structures when compared to xenon light. IOIFC may be a useful teaching tool in residency programs to teach LC.

[Light and Medicine]. / Licht und Medizin.

There would be no life without light. The rotation of the earth around its axis has introduced the development of biological clocks in all living subjects regulating all functions of the body. The rhythms best described are the 24-hour/circadian and the seasonal rhythms. The rhythmic composition around the body clock has great impact on health and disease, both in diagnostics and treatment. Nowadays, bright light, e.g. in seasonal affective disorder, can be regarded as a drug, being even more effective than selective serotonin reuptake inhibitors.

Nonconventional Use of Flash-Lamp Pulsed-Dye Laser in Dermatology.

Flash-lamp pulsed-dye laser (FPDL) is a nonablative technology, typically used in vascular malformation therapy due to its specificity for hemoglobin. FPDL treatments were performed in a large group of patients with persistent and/or recalcitrant different dermatological lesions with cutaneous microvessel involvement. In particular, 149 patients (73 males and 76 females) were treated. They were affected by the following dermatological disorders: angiokeratoma circumscriptum, genital and extragenital viral warts, striae rubrae, basal cell carcinoma, Kaposi's sarcoma, angiolymphoid hyperplasia, and Jessner-Kanof disease. They all underwent various laser sessions. 89 patients (59.7%) achieved excellent clearance, 32 patients (21.4%) achieved good-moderate clearance, 19 patients (12.7%) obtained slight clearance, and 9 subjects (6.1%) had low or no removal of their lesion. In all cases, FPDL was found to be a safe and effective treatment for the abovementioned dermatological lesions in which skin microvessels play a role in pathogenesis or development. Further and single-indication studies, however, are required to assess a standardized and reproducible method for applying this technology to "off-label" indications.

Sub-40 fs, 1060-nm Yb-fiber laser enhances penetration depth in nonlinear optical microscopy of human skin.

Advancing the practical utility of nonlinear optical microscopy requires continued improvement in imaging depth and contrast. We evaluated second-harmonic generation (SHG) and third-harmonic generation images from ex vivo human skin and showed that a sub-40 fs, 1060-nm Yb-fiber laser can enhance SHG penetration depth by up to 80% compared to a >100 fs, 800 nm Ti:sapphire source. These results demonstrate the potential of fiber-based laser systems to address a key performance limitation related to nonlinear optical microscopy (NLOM) technology while providing a low-barrier-to-access alternative to Ti:sapphire sources that could help accelerate the movement of NLOM into clinical practice.

Utilization of the tyndall effect for enhanced visual detection of particles in compatibility testing of intravenous fluids: validity and reliability.

PURPOSE: This study investigates the validity, reliability, and detection limit of a visual examination method utilizing the Tyndall effect to enhance visible detection of particles. The suitability of the method for compatibility testing of intravenous fluids in a hospital pharmacy context is discussed. METHODS: A panel of 20 inspectors examined 20 samples, with and without particles, using two light sources (halogen lightbulb in a focused desk lamp and a red pocket laser pointer). The samples contained particles of different origin (precipitate, polystyrene standards), varying size, and concentrations. Light obscuration and turbidimetric measurements were used to obtain numeric references. The samples were divided into rejection probability zones, and the validity (sensitivity, specificity, and likelihood ratios) and reliability (inter-rater agreement coefficients Fleiss' kappa and Gwet's AC1) were estimated. RESULTS: The sensitivity of the laser pointer for detecting microprecipitates was quite high; however, it also showed a high false rejection rate. The specificity was slightly higher for the focused desk lamp than the laser pointer. The likelihood ratios were not within the recommended limits of a useful test, indicating that the method could not securely confirm the presence/absence of particles in the samples. The inter-rater agreement coefficients indicated fair to moderate agreement between the inspectors. CONCLUSIONS: The validity and reliability were not satisfactory for either of the light sources. The visual detection limit seemed to be around 5 µm, although we propose that an exact detection limit is not that relevant for compatibility testing. Based on the current findings, the visual examination method cannot be recommended as the sole method for judging compatibility of parenteral nutrition and drugs, but rather in a program of several methods. In the hospital pharmacy, the method may be a resource, together with theoretical considerations, in situations where other methods are unavailable; however, use of in-line-filters is essential to protect the patient. LAY ABSTRACT: Many patients under intensive care are in need of several intravenous drugs simultaneously. These drugs cannot be given in the same infusion line unless compatibility has been documented. Incompatibilities can result in, for example, precipitation of particles. Injected particles can harm the patient and should be avoided. Visual screening of blends of drugs for possible incompatibility, using a focused light source to enhance visual detection based on the Tyndall effect, could be a quick and easy methodology to identify incompatibility. In the following study the objective was to investigate how reliable visual inspection, with the utilization of the Tyndall effect, is at detecting particles and precipitations in blends of intravenous drugs and parenteral nutrition mixtures. Twenty inspectors each examined 20 different samples with two different light sources. Some of the samples were without particles (clean), and some contained different types and degrees of particle contamination. The inspectors' judgment of the samples was recorded and validity and reliability parameters were calculated to evaluate the method's suitability. The conclusion was that because of false positive and negative findings the visual inspection method alone is not enough to securely document compatibility/incompatibility, but it is more suitable as support together with additional methods.

Ambient versus traditional environment in pediatric emergency department.

OBJECTIVE: We sought to examine the effect of exposure to an ambient environment in a pediatric emergency department. We hypothesized that passive distraction from ambient lighting in an emergency department would lead to reduction in patient pain and anxiety and increased caregiver satisfaction with services. BACKGROUND: Passive distraction has been associated with lower anxiety and pain in patients and affects perception of wait time. A pediatric ED was designed that optimized passive distraction techniques using colorful ambient lighting. METHODS: Participants were nonrandomly assigned to either an ambient ED environment or a traditional ED environment. Entry and exit questionnaires assessed caregiver expectations and experiences. Pain ratings were obtained with age-appropriate scales, and wait times were recorded. RESULTS: A total of 70 participants were assessed across conditions, that is, 40 in the ambient ED group and 30 in the traditional ED group. Caregivers in the traditional ED group expected a longer wait, had higher anxiety pretreatment, and felt more scared than those in the ambient ED group. Caregivers in the ambient ED group felt more included in the care of their child and rated quality of care higher than caregivers in the traditional ED group. Pain ratings and administrations of pain medication were lower in the ambient ED group. CONCLUSIONS: Mean scores for the ambient ED group were in the expected direction on several items measuring satisfaction with ED experiences. Results were suggestive of less stress in caregivers, less pain in patients, and higher satisfaction levels in the ambient ED group.

How synthetic biology will reconsider natural bioluminescence and its applications.

As our understanding of natural biological systems grows, so too does our ability to alter and rebuild them. Synthetic biology is the application of engineering principles to biology in order to design and construct novel biological systems for specific applications. Bioluminescent organisms offer a treasure trove of light-emitting enzymes that may have applications in many areas of bioengineering, from biosensors to lighting. A few select bioluminescent organisms have been well researched and the molecular and genetic basis of their luminescent abilities elucidated, with work underway to understand the basis of luminescence in many others. Synthetic biology will aim to package these light-emitting systems as self-contained biological modules, characterize their properties, and then optimize them for use in other chassis organisms. As this catalog of biological parts grows, synthetic biologists will be able to engineer complex biological systems with the ability to emit light. These may use luminescence for an array of disparate functions, from providing illumination to conveying information or allowing communication between organisms.

The impact of modulated, colored light on the autonomic nervous system.

CONTEXT: Scientists are now finding that light acts on individuals through multiple pathways, most notably the optic nerve that links to the brain's visual cortex, providing a pathway for the visual effects of light. The optic nerve also links to the more recently discovered retinohypothalamic tract, providing a pathway for the nonvisual effects of light. However, specific effects have not yet been widely evaluated clinically, especially in relationship to chromotherapy (ie, therapy based on colored light). OBJECTIVE: The purpose of this study was to evaluate the impact of modulated-light projections, perceived through the eyes, on the autonomic nervous system (ANS). DESIGN: The research team designed a randomized, controlled, partially blinded study with three intervention groups and one control group. SETTING: The study took place in two locations: (1) Midwestern State University, Wichita Falls, Texas, USA (40 participants) and Centre de Santé Satori, Québec, Canada (77 participants). PARTICIPANTS: The research team recruited 117 individuals, 89 women and 28 men, to participate in the study. Participants were normal healthy individuals who were 19 to 72 y old (average age = 43 y). INTERVENTION: Three types of light projections, each containing both specific colors and specific modulations in the frequency range of brainwaves, were tested, in addition to a placebo projection consisting of nonmodulated white light. OUTCOME MEASURES: Evaluation was done using a combination of physiological measures-heart rate (HR), heart rate variability (HRV), and skin conductance (SC)- and psychological tests: the Profile of Mood States (POMS) and a subjective evaluation questionnaire. RESULTS: The research team observed significant differences in the effects of light-modulation projections from baseline to postsession as compared with an equivalent intensity of white light, including decreased HR, increased HRV standard deviations of normalized NN (beat-to-beat) intervals (SDNN), very low (VLF) and low frequency (LF) levels, and decreased POMS total mood disturbance (TMD). Also, the different colors of modulated light were found to result in different ANS effects. CONCLUSIONS: Interest is growing in the therapeutic potential of light. The effects demonstrated in the current study indicate that colored light could significantly enrich the therapeutic potential of light, and further research into chromotherapy is warranted.