Healthy lighting science│Natural light stimulation can prevent the occurrence of myopia

There are many reasons for myopia, and eye fatigue is certainly one of them. However, I personally think that the reason for the sudden increase in myopia rate is the lack of natural light in the human eye. Human Eyes From the agricultural era, industrial era, to the current Internet of Things era, the biggest change in the social environment is lighting. What enters the eyes has changed from the long-term outdoor reflected natural light in the past to the current indoor direct screen artificial light.

It took hundreds of millions of years for the eyes to adapt to natural light, while artificial light only appeared for a few decades. How could the eyes evolve to adapt to artificial light in such a short period of time? Such an unfavorable light environment will naturally cause damage to the eyes.

In studies of myopia in humans and animals, there is growing evidence that ambient light exposure is an important factor in regulating eye growth.

The refractive development of chickens raised under a normal day/night light/dark cycle is also affected by light levels. The degree of myopia of chicks raised under high light levels (10,000lux) is significantly lower than that of chicks raised under low light levels (50lux) every day.

In addition, a new study by Michael J. Collins and others from the School of Optometry and Visual Sciences at Queensland University of Technology in Australia was published in the international authoritative basic research journal "IOVS" in ophthalmology in October 2015. An observational study was conducted on 101 children aged 10-15 years (41 myopic and 60 non-myopic) for 18 months. The average daily exposure of each child during these 18 months was collected through light sensors on the wrist.

The results are shown in the figure above. It was found that children without myopia received significantly higher average daily light exposure than children with myopia. Over these eighteen months, the axial length of the eyes of myopic children (red line) increased by an average of 0.19mm, while that of non-myopic children (blue line) only increased by an average of 0.05mm. The average axial growth rate of the medium and high light groups was reduced by 59% compared with the low exposure group. The growth rate of the axial length of the myopic children who lacked light was significantly faster than that of non-myopic children with higher average daily light exposure. This shows that exposure to a higher average daily light amount can delay the growth of the axial length of the eye.

Myopia occurs because the eye axis grows too fast, stretching the eyeball and causing the retina to move backward, causing the distance between the light focus and the retina to become longer, resulting in blurred images.

Generally speaking, the intensity of outdoor natural light is between 11080-18176 lux. Even if you are in the shade of a tree, the intensity is 5556-7876 lux. Wearing a hat also has 4112-8156 lux. Wearing sunglasses, the light intensity level is between 1792-6800 lux. However, the light intensity of the indoor artificial light environment is only 112-156 lux. People work indoors for a long time, and their eyes have no chance to receive high-intensity natural light outdoors, causing the eye axis to grow rapidly.

Outdoor natural light is a full-spectrum, high-intensity light that is beneficial to promoting dopamine secretion. Dopamine mediates ocular growth inhibition, acting upstream of the choroid, causing a transient increase in choroidal thickness. Intravitreal injection of the nonspecific dopamine agonists apomorphine and quinpirole was found to cause a significant increase in choroidal thickness in myopic eyes. As shown below.

Changes in choroidal thickness within 3 hours after injection of dopamine agonist in eyes wearing -10D lenses

Choroidal thickness is negatively correlated with axial length of the eye. The thicker the choroid, the shorter the axial length of the eye will be. The thickening of the choroid seems to be a signal to slow down the growth of the axial length of the eye. As long as the choroid is thickened, the growth of the axial length of the eye will slow down.

When people do not have free time to go outdoors due to work or study, the eyes are exposed to high-intensity natural light stimulation, which leads to reduced dopamine secretion, resulting in thinning of the choroid and accelerated growth of the axial length of the eye, promoting the occurrence and development of myopia. In addition, insufficient natural light stimulation can also lead to abnormal development of the eyeball and cornea, which can also induce myopia.

Nowadays, myopia has tended to develop at a younger age. More and more children and adolescents suffer from myopia at an early age, and adults directly progress to high myopia. Therefore, children are encouraged to go outdoors for more activities. The focus is not on activities, but on adding natural light stimulation to the eyes to prevent the occurrence and development of myopia. Giving students time for outdoor activities every day needs urgent attention.