If a child has 300 degrees of myopia, it could be due to pseudomyopia, but it could also be due to true myopia. Pseudomyopia is often seen in school-age children and is also known as accommodative myopia. It is usually caused by continuous contraction and spasm of the ciliary muscles in the eye after too much time spent on reading or writing at close range. Generally speaking, pseudomyopia is rarely more than 300 diopters, while pseudomyopia of less than 300 diopters is more common. To determine whether a child’s 300-degree myopia is caused by pseudomyopia, the child needs to go to the ophthalmology department of the hospital for a dilated optometry examination. If the original 300 diopters of myopia disappears completely after the dilated eye exam, then it is due to pseudomyopia. If the original 300-degree myopia does not disappear, it means that it is caused by true myopia. If only part of the myopia disappears, it means that the part of myopia that disappears is false myopia and the part of myopia that does not disappear is true myopia. It is recommended that children with myopia should be seen promptly for evaluation of their condition and treatment as prescribed by the doctor.