In most cases, myopia is related to the natural change in eyeball, which changed the focus of light. Light gets focused in front of the retina instead of focusing right on the retina. Myopia is inherited so we can find many little kids wearing glasses for their parents are nearsighted. Some researches say that a lot of upclose vision work might lead to nearsightedness, such as reading, looking at computer monitor, sitting to close to the TV or monitor or bad sitting gesture. Some study suggests that people doing a lot of reading are tending to have a higher degree of myopia. I think it is because that most people reading with a bad gesture, like getting too close to the book or reading with dim light or some people even lying in the bed and reading. All these bad habits of using eyes will accelerate the development of myopia.
Myopia means you cannot see things clearly without eyeglasses and contact lenses. This is the common explanation of myopia. Yes, it's right. Medically, myopia is nearsighted and shortsighted. Reading too much does harmful to eye health, which is easy to cause myopia. Because if your eyes feel tired and uncomfortable during reading, then the nerves that govern eye movements will slow down our brains. Next the signals of images cannot reach the back of eyes complete and you must focus to read something. It is easy to let one of your eyes has much focus than the other one. This time the different clear degree begin to occur and squinting eyes may also company. If this condition lasts in a long time when you read, your eye sight must be much worse day by day, at last you need turn to eyeglasses for help. In order to get myopia during reading, you should form good reading habits and control the time to read.