Lighting hazards, youth vision killer?

The Beijing Municipal Education Commission recently released an official Weibo news that this year the city will allocate a special amount of 96.352 million yuan to support 16 districts and counties of primary and secondary schools in the end of August to complete classroom and blackboard lighting renovation, improve classroom lighting effects to protect students' eye health.

The reporter learned that the "Beijing 2010 National Fitness Survey Results Bulletin" shows that the city's primary and secondary school students with poor vision detection rate of 60.2%, of which 81.89% of high school students, junior high school students 71.89%, 43.5% of primary school students. Compared with the results of the 5th National Student Physical and Health Survey in 2005, the rate of bad eyesight among high, middle and primary school students in Beijing has increased by 7%, 19%, and 27% respectively.

Is there a direct connection between lighting and teen myopia? What is scientific and healthy lighting? The China Science Journal interviewed experts in the fields of medicine, architecture, and optics.

The human eye requires "light health"

On May 1, 2011, China began to implement the "Hidden Standards for Lighting and Lighting of Classrooms in Primary and Secondary Schools." It requires that the illuminance of classroom classroom desks should reach 300Lx, and that of blackboards should reach 500Lx.

However, the Beijing and district disease control centers in the city’s elementary and middle school classrooms have shown that the lighting conditions of the classroom lighting environment indicate that there are 1,496 schools that have failed to meet the classroom or blackboard lighting conditions. The average pass rate of desktop illumination for classrooms in primary and secondary schools in the city was 60.3%, and the average pass rate for blackboards was only 22.9%.

“Light health emphasizes a more scientific lighting method. In addition to meeting the functional requirements of the most basic lighting, we must also consider the physiological and psychological health requirements, such as UV protection, anti-glare and so on.” Beijing Anzhen Hospital Ophthalmology Director Wang Jun told the China Science Journal.

“From a physiological point of view, the human eye is like a sophisticated 'optical instrument' that can sense an extremely wide range of brightness and can distinguish objects ranging from a few thousandths of a nit to many millions of nits.” he said .

During the daytime, when the ambient brightness reaches 10,000 nits, the human eye can distinguish approximately 200 to 20,000 nits of brightness, and the brightness below 200 nits will be perceived as black; when the nighttime environment is 30 nits, The resolution of the brightness ranged from 1 to 200 nits, at which time the brightness of 100 nits caused a rather bright sensation, and only a brightness below 1 nit caused a black sensation.

Human visual perception depends on the regulation of the pupil and light-sensitive cells. The pupil adjusts its size according to the intensity of the outside light. Light-sensitive cells are divided into cone cells and rod cells. The sensitivity of the latter is 10,000 times that of the former. In strong light and low light, the pupil and light-sensitive cells adjust to each other, so that the flux of light striking the retina remains moderate. Therefore, the light is too strong or too weak to have an adverse effect on the eyes.

“Everyday lighting must comply with human visual laws and eye health. When lighting quality is not reduced, less energy is used to realize 'green lighting'. This is the scientific and healthy lighting.” China Building Research Institute Architectural Optics A surnamed expert in the research room said.

The daily "light hidden trouble"

“Healthy lighting emphasizes the brightness and spectrum of light. From a functional point of view, when the light is too dark, people will instinctively approach the visual target. As time passes, it will naturally change the refractive system of the eye and cause myopia to occur.” Wang Jun Say.

However, too much light can also damage vision. In daily life, only 100 meters of candlelight are needed to read and write. While reading in the sun, the illumination can reach 80,000 to 120,000 meters, which is 800 to 1,000 times the daily illumination.

Long-term reading under strong light, excessive regulation of the intraocular muscles will promote the occurrence and development of myopia. The strong light will cause damage to the retina, especially the macular area, which will reduce the visual acuity and even cause permanent vision loss.

Long-term reading work with a strobe light source can also make the pupillary sphincter and retina fatigue, soreness and even damage the optic nerve due to excessive use, leading to dizziness, headache, upset nervousness, and even tachycardia.

The waveform of our country's AC grid has 50 ups and downs per second (ie, a frequency of 50 Hz). Fluorescent tubes use 50 Hz of commercial power, and there will be 100 bright and dark flashes every second. The bright and dark “strobe” caused by the alternating current frequency can cause great harm to the eyes of people who work in this kind of light environment for a long time.

If the computer is used under the light, usually the strobe of the fluorescent ballast of the inductive ballast overlaps with the frame of the fluorescent screen to form an optical resonance, which is more harmful to the human visual system. Therefore, as early as 1997, the European Electrotechnical Commission banned the installation of fluorescent ballasts for fluorescent lamps.

The spectrum of lighting fixtures can also affect vision. The spectrum of the sun is 100 Ra, and the object can display real colors under sunlight. At present, the architectural lighting design standards require that the light spectrum reach 80Ra in homes and offices. Even so, under the illumination of the electric light source, the color will still have different degrees of distortion.

“From a technical point of view, the spectrum of the lighting spectrum is as close as possible to the spectrum of the sun. However, it is difficult for a single light source to have such a spectral range. Many incandescent lamps, including LED lighting sources, do not conform to the spectral composition of the Sun. It is also unhealthy for the human eye to be exposed to this environment for a long time,” said Bai Tingzhu, a professor of optoelectronics at the Beijing Institute of Technology.

At the same time, indoor lighting must avoid or reduce glare interference. If the brightness of a lamp, window, or other area is much higher than the brightness of an ordinary indoor environment, people will experience glare, causing eye pain, tearing, and reduced vision. Curtains need to be installed in the classroom to prepare for glare and avoid glare.

“Hidden” out of lighting hazard lighting conditions will not have an adverse impact on vision, however, the popularity of digital life is so that many people are exposed to unhealthy lighting environment every day.

"Now most school classrooms use fluorescent light, and it is still a good light source. At present, there is no more reasonable and economical light source that can replace it," said a surnamed Zhang researcher.

He believes that it is important to use light and develop good study habits. Compared with the 1960s and 1970s, students now spend more time in the house than in the past, and they spend a lot of their leisure time on eye activities and lack outdoor activities. This is the problem.

“The root cause of myopia in adolescents is not that the conditions of light cannot be achieved, but rather that they should be liberated from the pressure of learning and the high-intensity eye-use environment,” said Bing-ting.

“Light is also an electromagnetic wave, which is both volatile and particulate. Particles have a penetrating effect and can damage human tissue when passing through the human body. Illumination light penetration is very weak. In a short time, people Eyes may not feel the light source's stimuli, but there is a long-term hazard." Bing-ting added.