| Background: Myopia is visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than on it owing to the fact that the axis oculi is too long or the refractive power is considerably strong when parallel lights enter the eye at a stationary regulation. The patient with myopia is subjected to dry eyes, fatigue in the eyes, dizziness, migraine, etc ; followed by neurasthenia, strabismus, astigmatism such as interference with the studies and daily life of the pupils affected. A joint investigation conducted by both the Ministry of Health and the Ministry of Education revealed that the incidence of myopia among the students in our country was up to 60%, ranking our country the first in the world. The patients with myopia numbered about 60 million, the largest in the world. There is a trend for the patient to be affected at a younger age. The detection rate of myopia in the age group of 7 to 9 years old was significantly increased. Investigations carried out in each province and municipality directly under the central government also indicated that the incidence of myopia in pupils had been increasing in recent years. Myopia is one of the main factors in impairing the pupils' visual health. In recent years, special attention has been given to its prevention as well as its treatment because it has become a serious public problem harmful to pupil' health. Good visual function is a prerequisite for reading and writing as well as for all kinds of activities in children and adolescents. Therefore, it is necessary to protect eyesight in order to prevent myopia in primary school pupils, to grasp the problem well and to begin the work as early as possible.Objectives: To understand the possible predisposing factors in myopia by analyzing the present status of myopia in primary school pupils in the city of Baotou , to provide basis for working out policies of health care to promote the development of prevention and treatment work so as to lower the occurrence rate of myopia in primary school pupils in our city.Methods: An epidemiological study was carried out by sampling at random in the primary school pupils to understand the optical environmental conditions, the present status of eyesight and awareness of prevention of myopia. The basic information was analyzed and the classic case-control study was conducted by Logistic regression. A multi-factor analysis was made on 29 factors to screen the possible predisposing factors in affecting the pupils' eyesight.Main Results: The prevalence rate of myopia in primary school pupils in the city of Baotou is 24.86%, 23.07% in boys and 26.71% in girls. There is no statistical difference between boys and girls (P>0.05). The occurrence rate of myopia in either group increases as they are growing up.In the pupils investigated, 21.18% of them paid little attention to light when they were reading or writing; 20.08% paid no attention to their postures when reading or writing; 23.6% had a habit of reading while lying and 2.20% had a bad habit of reading while walking or riding. Those having good habits of using their eyes had better eyesight than those having bad habits, but there is no significant difference in the habit of using their eyes between boys and girls (P> 0.05). In the three primary schools investigated, the difference in the height between the desktop and the chair is too great in 76.81% (47/62) and too small in 3.23% (2/62), and only 20.96% (13/62) are up to the standard. When the pupils study at home, only 27.92% (356/1,275) have the proper difference in the height between the desktop and the chair. According to the standard issued by the government, the intensity of illumination on the top of the desk for reading and writing should be greater than 150/x, but 30.67% of the pupils (391/1,275) were reading and writing at home in a dim light. In the classrooms of the three schools, 70.97% (44/62) are qualified in the daylighting coefficient; 1.61% (1/62) in the rear-wall reflection coefficient; 69.35% (43/62) in the window-glass and floor area ratio; 74.19% (46/62) in the average intensity of illumination at the desktop; there is no local illumination over the classroom blackboard; 70.97% being qualified in the intensity of illumination, 59.68% (37/62) in the uniformity of illumination, and 95.16% (59/62) in the reflection coefficient. The classrooms are illuminated with fluorescent lamps as light source, and the lamp tubes are all arranged in parallel with the blackboard, none of which meets the hygienic requirements. Studying at home, 13.80% (176/1,275) of the pupils use energy-saving lamp and 35.60% (454/1,275) use fluorescent lamp as light source. When they are watching TV, they should sit at a distance 5 or 6 times the screen diagonal, but 67.06% (855/1,275) sit too near from the screen. Compared with the pupils with normal eyesight, the near-sighted pupils are studying in an environment which is not up to the hygienic standards except that both groups use energy-saving lamps or other kinds of lamps (P<0.05). The home-computer ownership rate is not remarkably different between the two groups of pupils (P> 0.05).The majority of the pupils don't like to wear glasses for they believe that wearing glasses would be unfavorable to their appearances but they are not aware of the disadvantages of wearing glasses. Near-sighted pupils have a lower correctness rate than pupils with normal eyesight as to their viewpoint on glass-wearing. No matter what is the cause of their myopia, they all have a lower awareness rate concerning the causes of myopia except attributing it to the bad posture when they are reading and writing. Also, they are only aware of prevention of myopia by attention to reading and writing posture, they have little knowledge of other preventive measures.Through multi-factor analysis by Logistic regression model, 11 factors were regarded as having correlationship with myopia in primary school pupils: age, viewpoint of wearing glasses, distance for watching TV, whether there is TV at home, what is the longest time they spend watching TV or playing electronic games, whether they pay attention to reading and writing light, whether they pay attention to reading and writing postures, outdoors activity time, whether the mother has myopia, what's the level of mother's education, and desktop-chair height difference.Conclusion and Suggestions: The investigation reveals that the incidence of myopia in the primary school pupils in the city of Baotou has reached a higher level. Some of the pupils have a bad habit of using their eyes. Whether at home or at school, there are many problems in their visual environments. The primary school pupils have little awareness of the causes of myopia, its harm and its prevention apart from some other problems. The main possible predisposing factors in causing myopia are as follows: they often spend long time in front of TV, the mother has myopia, there is a home computer, the difference in height between desktop and chair is too great, they pay little attention to the light and their postures when reading and writing, the mother has a lower level of education, the pupils are growing up, the pupils have incorrect opinion about wearing glasses, the time they spend on outdoor activities is not long enough, and they often watch TV at a short distance. The incidence of myopia in the primary school pupils can be lowered by taking comprehensive preventive measures.The local government departments concerned in the city of Baotou should pay special attention to the prevention of myopia in primary school pupils. They should make the prevention and control work practicable, strengthen the measures of reform and consolidation, improve the visual environment of the pupils, hold lectures to the schoolmaster, teachers and parents of the pupils, and the pupils themselves on the prevention of myopia. Mobilize all those concerned to launch education of protecting eyesight and preventing myopia. First of all, they should change the concept, attitude and behavior of the school leaders, teachers, the parents of the pupils and the pupils towards the prevention of myopia. The desks and chairs should be adjusted to the height of the pupils, and the illumination at home should be improved. Supervision and inspection should be exercised over the setting-up exercises for eyes done by the pupils. Workable measures should be taken to lower the incidence of myopia in the primary school pupils and to lay a good foundation for their having a pair of bright eyes when they are grown-ups.
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