Causes of Myopia

The myopia rate in our country is now very high, especially among students. Many people are myopic. If we go to school and take a look, we will find that many people are myopic. Some children do not have this feeling when they are young, but with the gradual increase in the amount of study, coupled with some bad study and reading habits, it is easy to develop myopia. Let's take a look at the causes of myopia.

Many people are nearsighted, especially among students, and myopia occurs in childhood. Many children like to lie on the bed when watching TV, and do their homework very close to the bed, which can cause myopia. Everyone should learn more about the causes of myopia and prevent it from occurring.

1. Internal factors

(1) Genetic factors: Myopia has a certain genetic tendency, especially for high myopia. But for general myopia, this tendency is not very obvious. Those with genetic factors tend to develop the disease at an earlier age, mostly above 6.00D. But there are also people with severe myopia who have no family history. High myopia is an autosomal recessive trait, while general myopia is a multifactorial genetic disease.

(2) Developmental factors: Infants are hyperopic because their eyeballs are relatively small. However, as they grow older, the axial length of the eye gradually lengthens and develops normally during puberty. If it develops excessively, it will develop myopia, which is called simple myopia and usually begins during school age. Generally it is lower than 6.00D. It stops developing at around age 20. If the progression is rapid in childhood, it will progress even faster when the child is 15 to 20 years old, and then slow down. This type of myopia is often higher than 6.00D and can reach 20D to 25D or 30D. This type of myopia is called high myopia, progressive myopia or pathological myopia. This type of myopia may develop and degenerate in old age, so vision may gradually deteriorate and glasses cannot correct vision. Few people are born with myopia, but in very rare cases it is congenital.

2. External factors, namely environmental factors

(1) Using your eyes too close. According to relevant reports, myopia in adolescents is mostly caused by long-term use of the eyes at too close a distance. The eyes of teenagers have a strong ability to accommodate objects. They can still see objects clearly when the distance between the book and the eyes is 7-10 cm. However, if they often read or write at this distance, the eye's accommodation will become abnormally tense, which can lead to refractive (accommodative) myopia, the so-called pseudomyopia. If the eye is over-adjusted for a long time, the ciliary muscle cannot stretch and contract flexibly. The convergence effect is enhanced due to the over-adjustment, which causes the extraocular muscles to exert pressure on the eyeball, increasing the intraocular pressure and causing congestion of the intraocular tissue. In addition, the eyeball tissue of teenagers is delicate, and the eyeball wall is gradually stretched under pressure, causing the anterior-posterior axis of the eyeball to lengthen. When it exceeds the normal value, axial myopia is formed, the so-called true myopia. The normal reading distance should be 30-35 cm.

(2) Using eyes for too long. Some teenagers read, write, do homework, watch TV, etc. for 3-4 hours without rest, or even go to bed late at night. This not only affects physical health, but also puts too much burden on the eyes. The muscles inside and outside the eyes are in a tense state for a long time without rest. Over time, when looking into the distance, the eye muscles cannot relax and are in spasm, so that distant vision appears blurred and myopia is formed. This is the reason why some students' eyesight deteriorates significantly after a summer vacation. It is generally recommended that you take a short break or look into the distance after reading, writing or watching TV for 40-50 minutes.

(3) The lighting is too strong or too weak. If the light is too strong, such as sunlight shining on written material, it will cause strong reflection, irritate the eyes, make the eyes uncomfortable, and make it difficult to see the font clearly. On the contrary, if the light is too weak and the written material is insufficiently illuminated, the eyes cannot see the font clearly, and the head will move forward and get close to the book. Both of the above situations can easily cause eye fatigue, excessive adjustment or spasm of the eyes, and form myopia.

(4) Reading while driving or walking. Some young people make full use of their time by reading while walking or in a moving car, which is very bad for their eyes. Because the car is vibrating and the body is swaying, the distance between the eyes and the book cannot be fixed. In addition, the lighting conditions are poor, which increases the burden on the eyes. If this happens frequently, it may cause myopia.

(5) Read while lying down. Many teenagers like to read books lying on the bed, which is a bad habit. Because people's eyes should remain horizontal when reading, so that accommodation and convergence can be consistent, reducing eye fatigue. If you read a book while lying down, your eyes are not level, the distance between your eyes and the book is inconsistent, your eyes' line of sight is inconsistent up and down and left and right, and the illumination on the book is uneven. These will make your eyes' adjustment tense and make it easy to move the book closer to your eyes. This will increase the burden on your eyes by 2-3 times, and cause myopia over time.

(6) Insufficient sleep. When you don’t get enough sleep, you will feel tired and dizzy the next day. Your brain does not get enough rest and fatigue is not eliminated, which increases the burden on your eyes and leads to myopia. Lack of sleep is an important cause of myopia.

(7) The desks do not meet the requirements and the writing posture is incorrect. If the tables and chairs are too low, the head will lean forward, the spine will bend, the chest will be compressed, and the eye adjustment will be relatively tense. Or if the tables and chairs are too high, the feet are suspended in the air, the lower limbs are prone to swinging, and the correct posture cannot be maintained, all of which can cause eye fatigue and easily lead to myopia over time.

(8) The influence of radiation in the current space. Watching TV frequently, especially in rural areas with insufficient signals and low reception rates, without shared antennas, unclear screens, and many snow spots can easily cause eye muscle fatigue. Students who often play video games are more likely to damage their eyesight. The Subor learning machines sold in shopping malls can directly cause students to be nearsighted. Computers are an indispensable course today. Dryness and fatigue of the eyes caused by excessive operation can easily cause myopia, so the usage time must be properly controlled.

There are many reasons for myopia. After understanding how children develop myopia, mothers and fathers should be aware of this. Children should be encouraged to develop good habits and keep a certain distance when studying and watching TV. Children should not read while lying down. It is important to prevent the occurrence of myopia in time. After all, wearing glasses is sometimes inconvenient.