How to distinguish the quality of the lens?

With the increasing number of myopia patients in teenagers, more and more students need to wear myopia glasses. In the face of various types of glasses, many people do not know how to choose, how to distinguish the quality of the lens?

Test the transparency and optical uniformity of the lens:

Hold the lens, and about 30 cm from the front of the eye, observe the distant scene through the lens, if the scene is clear without deformation, and there is no scene jumping when moving the lens slowly, it indicates that the transparency and optical uniformity of the lens are good.

Determine the axial direction of the astigmatic lens:

Draw a cross perpendicular to each other on a piece of white paper, and rotate the lens at 30 cm above the cross figure. It can be seen that the cross in the lens moves cross. When the cross figure inside and outside the lens is connected, the figure is positive cross, and the axis of the mirror is consistent with the straight line. Observe which line is staggered more when moving with the straight line outside the lens, and this line is the direction of the astigmatism axis. Move the lens so that the inside and outside line up, here is the astigmatism axis. After marking the lens, the protractor is used to measure the Angle of the axial and horizontal line at the center of the lens, that is, the axial degree.

Test optical center displacement:

Draw a large cross on white paper with a thin stroke, making clear and straight strokes. The hand lens is placed between the eye and the cross, and the shape of the cross stroke is observed from the mirror with one eye. If the inside of the mirror and the outside of the mirror are not in line, the lens can be moved so that the cross stroke inside the lens is in line with the cross stroke outside the mirror. Use a brush or fountain pen to point a small point at the cross center of the lens, which is the optical center. After both lenses point out the optical center, observe and compare whether the bilateral optical center is symmetrical, and measure whether the distance between the two center points is consistent with the pupil distance prescribed by the prescription with a small ruler. If the cross stroke in the lens is curved, it indicates that the lens has internal stress or uneven optical density.

After understanding the simple test method of the quality of the above lenses, you do not need to worry about how to choose glasses, choose a pair of glasses that suit the characteristics of your eyes, and the protection of vision and eyes is also very important.