The latest technical report CIE released, to analyze the effect that lighting environment has on human’s visual function

Source: EVERFINE photoelectric time: 2017-10-23 10:27 [edit: JamesWen]

 

    Recently, CIE released a new report “Lighting for Older People Technology and People with Visual Impairment in Buildings” (CIE – 227), analyzing the effect lighting environment has on visual function (such as visual acuity, contrast sensitivity, color vision), and presenting some designed lighting methods for the elderly and low vision people in the office, public places, elderly and residential buildings.

    When people’s age is over 45, their light scattering in the eye gradually increases, their sensitivity of spatial contrast and the retinal illuminance gradually decrease. Their capability of dark adaptation becomes weaker. They have weaker color sense and weaker eyesight. According to the statistics of WHO, there are more than 285 million people suffering from visual impairment all over the world in 2017. And with the problem of aging population becoming increasingly serious in the world (as shown in Figure 1), social labor is gradually aging as well, the design of lighting for the elderly and low vision persons can not be ignored.

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Figure 1

aging population (above 65 years) and estimated aging population in the future  of each country

    In the previous report, CIE123 1997 describes the effect lighting environment has on visual function (such as visual acuity, contrast sensitivity vision and color vision), and puts forward some suggestions for the lighting design which can be applied in people with low vision.  ANSI / IES RP – 28 – 07 put forward the overall lighting design scheme for the elderly on the specific spots such as elevator, corridor, bedroom and bathroom.  CIE 196:2011 analyzed the  calculation model of the contrast sensitivity of different age (CSF) to provide design scheme of the lighting of the elderly and the design of visually impaired people for designers and engineers.

    This technical report is based on the existing research, combined with the current social situation, and carries out the following improvements:

(1) the dividing line of the elderly and the young was reduced from 65 to 50 years old, and the lighting design requirements for the elderly and the low vision people in the public places such as offices were increased;

(2)Systematically analyzes the illumination level, brightness contrast of environmental lighting which influence people who cannot stand the dazzle light and to what degree lighting will influence, to provide corresponding suggestions;

(3)The design methods of lighting and its color in different places are analyzed more concretely in the form of examples.

    According to the analysis of the technical report, with the increase of age, while people tend to have lower sense of the contrast of lighting source and background, the increase of light scattering in the eye will directly increase the imaging size of the light source in the retina. From the model of unified glare index UGR, the larger the size of the light source is, the higher  the level of discomfort glare is. So the higher peoples age is, the more obvious impact disability glare and discomfort glare will have on the his vision.

    As shown in Figure 2, under the same brightness of the computer, the elderly suffer more from dazzling light than young people do.

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Figure 2  

the same brightness a computer presenting in the eyes of young people (left) and the elderly (right)

    Apart from visual function, human eye also has non-visual function which has important influence on circadian rhythm system of human body. The lighting illumination level, spectrum, light distribution, frequency and time length of illumination affect the mood and sleeping quality of human beings. Therefore, in order to protect the eyesight and health of the elderly and the low vision people, the influence that illumination has on the visual and non-visual effects of the human eye should be taken into account when people design the environmental lighting.


Post time: Oct-27-2017
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