The principle of the formation of myopia is mainly due to excessive eye use leading to ciliary muscle spasm and lengthening of the eye axis. Myopia can be categorized into two different types: true myopia and pseudomyopia, which are formed by different principles. The formation of pseudomyopia is mainly related to prolonged close-distance eye use, which leads to over-contraction of the ciliary muscle spasm and cannot be relaxed quickly. True myopia is caused by the lengthening of the eye axis, which results in the refractive system of the eye refracting light from the outside environment into the eyeball and then failing to focus on the retinal plane, but focusing on the front of the retina. To differentiate between true myopia and pseudomyopia, it is usually necessary to consult a doctor and have an astigmatic examination to determine the difference.