Myopia is usually caused by genetic and environmental factors and is categorized as mild, moderate and severe. Mild is under 300 degrees, moderate is 300-600 degrees and severe is over 600 degrees. If a parent has myopia, but it is mild myopia, then the chances of the child being myopic may be less. If one parent has myopia of 600 degrees or more, then the chances of the child having myopia are much greater than for a child with neither parent having myopia. If both parents are highly nearsighted, the child’s chances of having myopia are even greater, and generally the higher the degree of the parent, the higher the probability of inheritance. Therefore, myopia is closely related to heredity, but acquired habits of improper eye use may also cause patients to develop myopia. It is recommended that myopic patients seek prompt medical attention to evaluate their condition and follow medical advice for treatment and genetic counseling.