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Aims. Short-wavelength blue light damaged retina by the oxidative stress in the retinal pigment epithelial (RPE) cells. Filtering blue light from screen could reduce blue hazard, whereas it inevitably altered color-gamut coverage and color-deviation level. Although abnormal fundus-vascular density (FVD) sometimes indicated fundus disease, few researchers noticed its responses to the variation of color-gamut coverage and color-deviation level. Methods. In this study, we performed cellular experiments and analyzed the RPE cell viabilities (CVs) in spectrums with different blue (455-475 nm) ratios to describe the corresponding oxidative-stress levels. Further, we investigated the effects of color-gamut and deviation on FVD variations during the screen-watching task using human factor experiments with 30 participants (university students, including 17 males and 13 females, 21 to 30 years old). Results. RPE CVs were similar in different spectrums, implying that non-oxidative blue filtering hardly contributed to CV improvement. Color-deviation level seems to induce more significant effects on the visual function compared to color-gamut coverage, and MTF and FVD presents similar variation trends during the visual task. Conclusion. Oxidative-free blue filtering contributed little to decrease retinal oxidative stress yet caused color-deviation increase, which caused significant FVD reduction.

Blue crest between the wavelength of 460 nm and 480 nm was reported to present melatonin suppression effects, whereas effects of red light on circadian rhythm regulation remain unclear. Spectrum plays an important role in circadian rhythm regulation, yet a lot of researches focused on the correlated color temperature, although a correlated color temperature value corresponds to various possible spectrums. Here, we performed human factor experiments with 3 lamps on 17 participants, comprising 9 males and 8 females. Our results showed that spectrums with high blue intensity tended to cause abnormal regulations of melatonin and cortisol, while the abnormalities were likely to be compensated by the 606-635-nm red light, which was indispensable for the photo-biological effects concerning circadian rhythm regulation. Abnormal circadian rhythm regulation was also found to be influenced by the illuminance, as abnormalities were significant in 500 lux whereas they were likely to disappear in 250 lux, implying the existence of threshold doses to trigger abnormities concerning circadian rhythm regulation. Furthermore, circadian rhythm responses were distinct between males and females. Our work may have implications for the development of light source, as we suggest that lighting source designers should increase the 606-635-nm intensity for bed room luminaires to decrease melatonin suppression effects.

Light-emitting Diode (LED) has been considered as one of the new generation lighting sources with several merits such as high efficiency, high reliability, long lifespan, high-speed response, and energy saving. The optical performances of an LED luminaire, such as illuminance, luminance, correlated color temperature, and spectra power distribution, determine the lighting environment which can affect the human ocular physiological characteristics. To investigate the effect of optical performances on human vision, previous studies have assessed the subjective perception based on questionnaires. In this paper, we propose a novel method based on the aberrations and accommodations data from 150 human factor measurements on a total of 25 participants. The results show that: 1) optical performances of the LED luminaire have an influence on ocular physiological characteristics during the visual task duration, which can be quantized by the variations of physiological parameters; 2) the desk illuminance and light distribution curve are selected in this study as the optical parameters. The variations of ocular physiological characteristics reach the minimum values when the desk illuminance is 550 lux and the light distribution curve is large beam angle; and 3) ocular physiological characteristics are more sensitive to the light spatial distribution compared to the light quality. Thus, the proposed assessment method based on variations of ocular physiological characteristics in this paper is promising as one of the guidelines for the design and optimization of the LED luminaires.

The illuminance index has been widely used in the field of photometry, although the luminance contains more information on not only light intensity but also light direction. In this study, we clarify which photometric index is more competent to describe the influence of lighting environment on human eye. In this study, we propose a novel methodology to investigate the photo-biological effect of the lighting environment by human factor experiment. With the human factor experiments performed on 20 participants, we compare the variations of ocular responses during the Landolt-rings-counting visual task in lighting environments with similar illuminance while distinct luminance changes. With the same Correlated Color Temperature (CCT) and Spectral Power Distribution (SPD), optical performances with similar illuminance values present quite different influences on ocular responses, and the response variations are found to vary with luminance values. It is implied that the regularity of luminance influence on the ocular responses to lighting environment is likely to be dependent on luminance value instead of illuminance, and the photometric index luminance seems more appropriate to be used to assess the lighting quality in standards.

Excessive elongation of ocular axial length increases the risk of visual impairment such as high myopia. Light is an important factor that influences ocular axial growth. Researchers have performed many experiments on light induced axial elongation, whereas the mechanism of light effect on axial elongation is still unclear. Axial length is determined by sclera growth, which is dependent on the oxygen supply by choroid vessels. Dopamine emitted from retina binds with dopamine transporter and is sent to the choroid layer to control the expansion and contraction of choroid vessels. Combination of dopamine and dopamine transporter has a significant influence on sclera oxygen supply, thus affecting ocular axial length. In this study, computational simulation was performed on the binding of dopamine and dopamine transporter at various temperatures. Configuration of dopamine transporter was calculated by molecular dynamics simulation, and molecular docking of dopamine and dopamine transporter was carried out to clarify docking locations in dopamine transporter. Binding of dopamine and dopamine transporter presents more stable in 37°C than in 40°C and in 43°C, indicating that excessive temperature rise is likely to hamper the binding of dopamine and dopamine transporter. Red light tends to induce temperature rise due to its thermal effect. It is implied that long wavelength light in high intensity is likely to induce axial elongation due to excessive temperature rise inside retina and choroid caused by heat effect.

In this study, we were sought to compare the influence of lighting environment with constant brightness and dynamic brightness on human ocular physiological parameters. We chose 20 participants for the human factor experiments. To measure the influence of lighting environment on ocular physiological parameters, three ocular physiological parameters were used in the current study: far point accommodation, the 4th and the 12th terms of aberrations. It was found that far point accommodation presented more significant response to the lighting environment with constant brightness than that with dynamic brightness, and sphere aberrations presented insensitive to the brightness variation. Both aberrations and far point accommodation could reflect the influence of lighting environment on human eye, while far point accommodation presented higher sensitivity to the lighting environment compared to sphere aberrations.

Correlated color temperature (CCT) is an important feature of the LED luminaire. However, its influence on visual discomfort remains vague due to the lack of a comprehensive study based on ocular physiological parameters and psychological assessment. In this paper, the investigation was carried out by the measurement of ocular parameters and the collection of subjective score. Three physiological parameters were used including higher order aberrations, modulation transfer function, and the ratio of accommodative convergence to accommodation ratio. It is shown that CCT has significance influence on human eye, and the proper CCT for the ocular health of moderate myopia people is near 5000 K. In addition, the results imply that the perception of discomfort is caused by psychological perception rather than ocular fatigue.

Previous studies have shown that liquid crystal display (LCD) can cause visual fatigue to the human eye, but the effect of quantum dot (QD) display has not been explored yet. This study conducted a human factor experiment on the QD display and LCD. The parameters ACC, HOAs and MTF were selected as objective physiological indicators for visual quantification of visual fatigue. 39 participants performed a 45-minute video viewing task. While before and after the visual task, measured the physiological parameters of the participants' eyes. Analysis the effects of QD display and LCD on human physiological characteristics under the same conditions. The results show that: (1) The QD display and LCD have an influence on the physiological characteristics of the human eye during continuous visual task duration. These effects can be quantified by changes in human eye physiological parameters; (2) The effect of QD display on human eye physiological parameters is less than LCD: the VICO index (visual comfort index) is lower, and the participants' color feedback accuracy is higher. This study provides theoretical basis and data support for the subsequent development of quantum dot display.

Blue light in the range of 450~480nm has been proved to induce melatonin depression. However, the dose limit of blue light has seldom been reported in previous study. In this study, human factor experiments have been performed to compare lighting influence on melatonin emitting in lighting environments with correlated color temperature of 3000K and 5000K in ordinary illuminance. It is indicated that blue light below 300lux has little influence on melatonin depression in the lighting environment below 5000K. Consequently, illuminance is an important factor for trigger of non-visual photo-biology effect. In the lighting environment with illuminance below 3001ux, no distinctions can be found in the function of blue light induced melatonin depression between non-visual effect luminaires and ordinary luminaires.

BACKGROUND AND OBJECTIVE: To examine the human visual performance (wavefront aberration) and subjective questionnaire (SQ) of visual fatigue when viewing 2-D and 3-D movies. METHODS: Thirty healthy adults observed 2-D and 3-D movies on the same television from a 3m distances during 2D, 3D-A (with better 3D glasses), and 3D-B (with poorer 3D glasses) viewing conditions. Visual quality index, including modulation transfer function index (MTFI), higher order aberration root mean square (RMS), vertical coma (VC), horizontal coma (HC) and spherical aberration (SA), were assessed before and after each viewing condition. One-way repeated measures ANOVA was performed to assess the changes of each test variable before and after movie viewing. RESULTS: Participants watching movies with 3D-B conditions experienced higher change of MTFI, RMS, VC and HC but smaller SQ, compared with 2D and 3D-A (P< 0.05). Additionally, higher MTFI but smaller SQ was found for 3D-A compared with 2D viewing condition (P< 0.05). CONCLUSIONS: While prolonged viewing 2-D and 3-D movies would lead to poorer visual performance, 3-D glasses with better quality can play the major role in reducing visual ability for users. The change of human eye wavefront aberration might be useful for the evaluation of visual fatigue in the future.

Flicker is the lighting characteristic of electric light sources that is generally harmful to human health. In this study, subjects were set in lighting environments with different flickers, and required to finish the reading task within 45 minutes. Visual fatigue caused by different LED flickers and during the task were recorded and reflected by three visual function parameters: higher order aberrations (HOAs), modulation transfer function (MTF) and the ratio of accommodative convergence to accommodation ratio (AC/A). Significant differences were found to exist between the visual function variations of the subjects in lighting environments with different flickers, and people with higher flicker lighting showed lower variations of visual functions. It is manifested that LED luminaires with reduced flicker frequencies are more likely to cause visual fatigue.

The light emitting diode (LED) has wide applications recently. However, there are few literatures on the investigation for the influences of LED lighting on visual fatigue or its comparison with the fluorescent lighting. The aim of this study is to analyze the influences of different LED lighting conditions on visual fatigue, especially to discuss the impacts by the lighting condition factors of lighting type (LED or fluorescent lamp), illumination level, correlated color temperature (CCT). In this study, the subjective responses of visual fatigue and task performance were evaluated via a numerical verification experiment under LED and fluorescent lighting conditions, respectively. The experimental results indicate that illuminance, CCT and the type of light source indeed have effects on some symptoms of visual fatigue. Particularly, LED lighting can suppress visual fatigue more effectively than fluorescent one. Moreover, the task performance is not influenced by lighting conditions in these experimental setups.

In this work, a psychophysical experiment is implemented to assess the white sensation of light-emitting diode (LED) lighting in illuminant mode via a categorical judgment method by a panel of 10 observers. The visual data indicates that the higher values of white sensation estimations locate near the Planckian locus within a correlated color temperature (CCT) range of 5000–9000 K. A model of white sensation for LED lighting in illuminant mode is proposed, from which the predicted maximal white sensation locates near the Planckian locus with a CCT of 6622 K, and the 95% white sensation covers a narrow two-dimensional region.

The purpose of this study was to assess the visual fatigue after watching 3D TV in wave-front aberration (WFA) test methods. The evaluation method is different from the previous visual fatigue test method (such as accommodation response, subjective assessment and electroencephalography). The self-developed wave-front aberrometer used to collect the data. 60 participants were recruited, who watched 3D TV by wearing two glasses respectively. SPSS18.0 was used for analysis and significance is defined as p < 0.05. The results show that MTF (Modulation Transfer Function) and means of WFA (3rd to 5th) of before and after watching 3D TV had significant differences (p < 0.05) and consistent trends. The RMS (root mean square) of WFA had no significance. Meanwhile, we found that the result of MTF of wearing different glasses had significant differences (p < 0.01). In conclusion, MTF and mean of WFA (3rd to 5th) can be used as the evaluation index of visual fatigue. In follow-up studies, more relationship between changes of higher-order aberrations (6th–35th order) and visual fatigue will be studied.

With the development of freeform ophthalmic lenses, especially the appearance of progressive addition lens, the traditional optical lensometer can’t satisfy the optical power measurement requirements. Freeform ophthalmic lenses involve high resolution technological manufacturing processes, due to the particular non-symmetrical, aspherical form of their convex surface. However, the testing of the optical power is not usually performed using whole-field methods because of the high dynamic range and resolution required for the slope changes in the convex surface. Applying some simple enhancements, a two-dimensional Ronchi test technique can be used to obtain accurate power distribution maps of freeform ophthalmic lenses. In this paper, the principle and optical structure of freeform Lens power map measurement based on two-dimensional Ronchi test techniques is introduced. The system structure is described in detail, and a simulation is made to analyze the influence of distance change which is from the Ronchi grating to ground glass.