Myopia is a kind of ametropia. When the eyes are relaxed, parallel light enters the eyes and focuses in front of the retina, resulting in the inability to form a clear image on the retina, which is called myopia. At this time, checking the optometry will prompt the degree of myopia. For example, it is usually called myopia 50 degrees and recorded as "-0.50D".

When the eyes relax, the parallel light from the outside enters the eyes, and its focus just falls on the retina, forming a clear image, which is called face up; If the focus cannot fall on the retina, it is called ametropia.

Axial myopia and refractive myopia

Axial myopia: the most common is that the anterior and posterior diameter of the eyeball is too long (that is, the axial length of the eye is beyond the normal range), while the refractive power (that is, the refractive performance of other refractive components of the eye such as cornea and lens) is basically within the normal range.

Refractive myopia: the refractive power is beyond the normal range, and the axial length is basically within the normal range, mainly due to excessive curvature of cornea or lens or abnormal combination of refractive components.

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