Study on the Influence of LED Spectrum on the Visual and Nonvisual Effects in the Interior Zone of Tunnels

Judicious use of lamps is of profound significance to improve the internal traffic safety of tunnels. This study evaluated the biological effects of spectrum on human visual and nonvisual under mesopic vision category. According to the difference of human eyes’ response to the visual and nonvisual biological effects of different wavelengths of light radiation, a method of applying the mesopic visual spectral luminous efficiency curve to the assessment of nonvisual biological effects and blue light hazards is proposed. The results show that, in theory, under mesopic vision category, the spectrum with high correlation color temperature (CCT) and high color rendering index (CRI) has higher blue light content Z-value and has greater impact on human nonvisual effects and blue light radiation damage, but it can also provide higher human perception luminance. The visual effect detection experiment of driving in the interior zones of the tunnel is simulated in the laboratory, and the critical flicker frequency and reaction time are taken as physiological indexes. The results show that the spectrum with high CCT and high CRI corresponds to lower critical flicker frequency drop value and faster reaction time, which has a positive effect on improving driving safety. Therefore, this paper suggests that the LED with high CCT and high CRI (CCT = 6500 K, CRI2012 = 95) should be used in the interior zones of the tunnel with relatively short lighting section, and the CCT and CRI should be appropriately reduced in other road environments with long lighting section to reduce the impact of spectrum on nonvisual photobiology, so as to improve road traffic safety.

Immediate Effects of Different Screen Sizes on Visual Fatigue in Video Display Terminal Users

Objectives: Computer usage has rapidly grown. This is because it helps to resolve problems, i.e., encountered in daily life by individuals. Various monitor screens that have been developed affect the user’s eyes. Screen size is one of the relevant impacts. Thus, this study compared the immediate effects of two computer screen sizes on visual fatigue in Video Display Terminal (VDT) users. Methods: Twenty female VDT users participated in this study. Using a randomized block design for the study, the study participants randomly drew a ballot to determine the order of using an 18.5-inch and 23-inch computer screen size. The research participants were assessed by a visual fatigue score, critical flicker frequency, and dry eye score before and after using both computer screen sizes. They were tested in an ergonomic computer workstation for 2 hours. Besides, where they rested between each workstation for ≥30 minutes or until presetting no eye fatigue symptoms. The relevant data were compared between before and after using the computers and between the two different screen sizes. Results: The collected results suggested no significant difference in the visual fatigue score, critical flicker frequency, and dry eye score between using either computer screen sizes (P>0.05). However, there were significant differences in the visual fatigue score, critical flicker frequency, and dry eye score between before and after computer screen usage (P<0.05). Discussion: Using both computer screen sizes resulted in increased visual fatigue, reduced critical flicker frequency, and increased dry eyes. The present study results can provide information in determining how to reduce risk factors and prevent visual fatigue from continuous computer use for a long time.

The effects of colour and temporal frequency of flickering light on variability of the accommodation response in emmetropes and myopes

Background Myopia is hypothesized to be influenced by environmental light conditions. For example, it has been shown that colour and temporal frequency of flickering light affect emmetropisation in animals. Considering the omnipresence of flickering light in our daily life, we decided to analyze the effect of colour flickers on variability of the accommodation response (VAR) in emmetropes and myopes. Methods We measured the dynamic accommodative responses of 19 emmetropic and 22 myopic adults using a Grand Seiko WAM-5500 open-field autorefractor. The subjects focused for more than 20 s on a black Snellen E target against three different backgrounds made up of three colour flicker combinations (red/green, red/blue and blue/green) and under five frequency conditions (0.20 Hz, 0.50 Hz, 1.00 Hz, 1.67 Hz, and 5.00 Hz). Results Flicker frequency and colour both had a significant effect on VAR. Lower frequencies were associated with larger variability. Colour had an effect only at low frequencies, and red/blue colour flicker resulted in the largest variability. The variability in myopes were larger than those in emmetropes. Conclusions These findings support the hypothesis that further studies on the colour and temporal frequency of flickering light can lead to a better understanding of the development and progression of myopia.