Lighting on Visual Health

Lighting on Visual Health

Lighting to the eyes

The eyes are an intelligent sensory organ that evolved under natural light. When light enters the eyes, the eyes automatically adjust the pupil size based on the characteristics of the light to control the amount of light entering the eyes, automatically adjust the curvature of the lens so that the image falls on the retina.

For the sake of seeing objects of different distances and brightness clearly, the muscles and photoreceptor cells of the eyes have a very strong ability to adjust automatically. However, when reading or writing under unsafe light (too bright, too dark, uneven, unstable, flickering), the adjustment range and frequency of the eyes are very large and are over-adjusted, which may cause excessive adjustment for a long time. Eye fatigue, which in turn leads to decreased vision. Therefore, you must read and write in safe light!

Problems with lighting uses

1. Do not distinguish between daily lighting and study lighting

Daily life has low requirements on the brightness of light, and the acceptable brightness range is very large (>75-100Lx, and almost no upper limit), the stability of light is not high, and general roof lights are applicable. However, learning (reading or writing) requires close-up eyes, and it lasts for a long time. It requires much more light than ordinary daily life. The brightness of light suitable for learning is only a small range (around 300Lx). General roof lighting will appear dim for study.


Be sure to distinguish between living light and study light. Usually, the roof lamp is used as the main light source in the room for daily life; while the desk lamp or floor lamp modern provides suitable fill light when studying (reading or writing), which is a more reasonable match.

2. An improper use of lighting

a. The light source in the learning environment is not suitable, such as too bright, too dark, uneven, stroboscopic, glare, reflection, etc.
Too bright light source: too bright will appear near the window during the day and on the desktop illuminated by the desk lamp at night, because the natural light on sunny days is generally very strong (it is easy to exceed 10000Lx), and the light in the central area illuminated by the desk lamp is also very strong.
Too dark light source: The too dark conditions are mainly natural light in rainy days and evenings; at night, there is only roof lighting in the room. Dim light from the desk lamp when sitting away from the light resources.
Uneven light: This situation often occurs in shelf lamps or desk lamps, such as the light in the center of a small area is very bright, while other areas are too dark.
Light source strobe flashes: The most serious stroboscopic are mainly old-fashioned fluorescent lamps, some dimming table lamps, and inferior brand lamps.
Glare or Reflection: Glare refers to the dazzling bright spots in the field of view. If the light source is exposed outside the lampshade, there are bright spots on the edge of the lampshade, and the lampshade is facing the eyes, then glare will occur. Reflection is because the book or desktop is too smooth, reflecting the harsh light source directly to the eyes.
b. The light is unstable and varies greatly. At the window, the brightness of natural light varies greatly, especially in the morning and evening, cloudy or rainy weather. If a table lamp is used, because the lighting direction of the table lamp is very strong, and its position and irradiation angle is not fixed, the brightness and uniformity of the light in the irradiation area will also change greatly (about two to five times).

c. Incorrect body posture, blocking light. The head, shoulders, or arms are blocking direct light from the light source, causing the target area to be too dim. Too dim light will further lure the eye closer to the book and increase the accommodation of the eye lens.

Lighting is everywhere affect our life always

Attentions on lighting

1. Overregulation of the eyes

As mentioned in the first section of this article, the eyes have a strong ability to adjust automatically, and can passively "adapt" to changes in light intensity by adjusting the eyes muscles and photoreceptor cells, which is the "passive adaptation" of the eyes. For close-up eyes (reading or writing), if the light is within the range that meets the national standard, the adjustment of the eyes to adapt to the light is moderate. The essence of overregulation is that the eyes are overworked and will not feel abnormal for a short time, so there is a certain "deception", which is the reason why many light problems in learning or living environments are ignored. However, if the eyes are in a state of "over-regulation" due to "passive adaptation" to too dark or too bright light for a long time, it will cause symptoms such as eye fatigue and vision loss, and in severe cases, it will affect the development of the eyes and lead to permanent vision decline.

2. Don't dim by "feel"

Some people like to tell whether the light is suitable by "feeling", but because of the "passive adaptability" of the eyes and changes in people's physiological state, this judgment is extremely biased. For reading or writing with eyes at close range, the appropriate light illumination is only within a small range, so adjusting the light based on personal "feeling" will easily exceed the requirements of proper standards, which is quite risky. Some people think that the effect of light is temporary, so they take it lightly, and unconsciously, it leads to a decline in vision.

Kindly remind: in the current situation of rising myopia rate among teenagers, we must maintain continuous attention to the lighting problem in the living and learning environment.

3. Pay attention when reading or living in the following surroundings

Places close to the window: The natural light incident from the window during the day is very unstable and varies greatly. The light changes especially quickly during the morning and evening hours when it is cloudy and rainy. When using the eyes at close range, too strong or too weak natural light is harmful to the eyes: too weak natural light can easily cause over-regulation of the eyes, resulting in eye fatigue. Whilst too strong natural light will directly damage the retina!

Ordinary residences: Roof lights provide ambient light and are generally dim. The desk lamp is used as a desk fill light, and its directionality is very strong, and the position and illumination angle is not fixed, which is prone to excessive brightness, excessive darkness.

Public places (such as bus, subway, train, or station, etc.): The light difference is very large, and it is not suitable for reading or writing.

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