Effect of VDT task lighting environment on visual health of designers with different constitutions
Lighting in visual display terminal(VDT)offices is considered to be one of the main factors influencing employees'visual health.On the one hand,improper lighting conditions can lead to increased visual fatigue.On the other hand,recent studies reveal that light is not only essential for vision but also achieves important non-visual effects on a host of physiological functions.These effects depend largely on person-specific parameters.Differences between individuals may modulate the effects of light exposure,with some people exhibiting stronger responses than others.Hence,targeted studies to identify susceptible groups and establish a scientific classification method are necessary for delivering appropriate light doses and protecting employees'visual safety.This study investigates the relationship among light environment,the traditional Chinese medicine(TCM)constitution,and visual healthy,and explores the feasibility of identifying susceptible groups using TCM constitutions.Firstly,a field study is conducted on nine architectural design companies with standard management and complete regulations in Chongqing,China.Each company employs more than 100 people,and their working hours are approximately from 9:00 am to 18:00 pm.The lighting environment of 72 visual display terminal(VDT)offices is assessed and measured at these companies.Horizontal illuminance on the working plane,correlated color temperature(CCT)and illuminance uniformity ratio(U0)are selected as the indexes of the visual lighting.Illuminance at the eye,mEDI(melanopic equivalent daylight illuminance),EML(equivalent melanopic lux)and CS(Circadian Scale)are selected as the indexes of circadian lighting.Then,541 young designers with similar workloads,work content,working hours,and lighting environments are recruited from these offices.The TCM physical constitution scale and a self-reported visual health questionnaire are used to evaluate the TCM constitution types and visual fatigue of these young designers.Finally,statistical analysis are performed using SPSS 19.0 software.Descriptive analysis of the distribution of TCM constitutions,myopia rates,and visual fatigue data are conducted.The chi-square test and Fisher's exact test(whenever appropriate)are performed to determine the differences between the groups.The result of lighting environment investigation shows that the average horizontal illuminance on the working plane of 95.8%offices is ranging from 300 lx to 500 lx.These values meets the standard requirement for general offices,but is lower than the standard value of 500 lx recommended for lighting of design offices.The CCT of 62.5%offices is higher than the standard.Data on circadian lighting of typical VDT office shows that the circadian lighting of near window workstations is higher than the corresponding recommended values in the morning,but lower in the afternoon.The circadian lighting of central and far window workstations do not satisfy the recommended values during the day.The results of investigation on the TCM constitution reveal that the balanced constitution(27.2%)is the most common constitution type of young designers,accounting for the highest proportion among 9 constitutions;yang-deficiency constitution(13.7%)is the most common type of unbalanced constitutions.With respect to the association between myopia and constitution,the results implies that participants with yang deficiency(87.8%),qi stagnation(87.2%),and yin deficiency(79.7%)constitutions contribute to the top three myopia rates.The myopia rate of participants with a yang-deficiency constitution is significantly higher than those with a balanced constitution(p<0.05).After working on computers for 8 hours,participants with qi deficiency(77.4%),yang deficiency(74.3%),and qi stagnation(72.3%)constitute contribute to the top three incidences of visual fatigue.In contrast,the incidence of visual fatigue is lowest in participants with balanced constitutions(59.9%).The incidence of visual fatigue in participants with qi deficiency(p<0.05)and yang-deficiency constitution(p<0.05)is significantly higher than those with balanced constitution.The proportion of visual fatigue reported by qi deficiency,yang deficiency,and balanced constitution is highest at 3 h,1 h,and 5 h,respectively.Statistically significant differences in visual fatigue among the three constitutions are found at 1 h and 5 h(p<0.05).Visual fatigue appears earliest(1 h)in the yang-deficient constitution.However,it appears at the latest(5 h)in the balanced constitution.In other words,short-term VDT use may cause more visual fatigue in the yang-deficiency constitution,while longer VDT operation can withstood in a balanced constitution with less visual fatigue.In conclusion,this study provides basic data on the distribution of TCM constitutions among young designers in Chongqing,and reveals a close interaction among myopia,visual fatigue,and TCM constitution.Individuals with yang-deficiency constitution take a significantly increased risk of developing myopia and visual fatigue compared to those with a balanced constitution.The long-term insufficient sunlight exposure and low circadian stimulation in the workplace could easily lead to the transformation of physical fitness to yang-deficiency and increase the risk of visual health.This study provides a potential method to predict individual-level light sensitivity and takes a new approach to develop optimized lighting strategies in workplaces.
task lighting environmentvisual healthvisual display terminal(VDT)traditional Chinese medicine(TCM)constitutionindividual differences
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