Matching glasses generally include short-sighted glasses and old mirrors. Fitting glasses has almost become a necessary daily necessities for students and working people. However, the quality of fitting glasses detection has become a common concern.

The horizontal aberration of the optical center refers to the unilateral deviation of the optical center of the lens from the pupil in the horizontal direction. Although the distance between optical center and pupil distance of some fixed matching glasses is the same (no horizontal deviation), if there is horizontal difference between optical center, the optical center of two lenses is asymmetric, one is on the inside and the other is on the outside, the position of optical center is not the same as the pupil position of the wearer, and the degree of inconsistency between two sides is the horizontal difference of optical center.

If the level deviation of optical center and the level difference of optical center are unqualified, the Danyang eye inspection glasses will produce prism effect. Wearing such glasses will cause displacement of the observed object image. The wearer has to adjust through his own adjustment function, which will aggravate the fatigue of the eyes. If wearing glasses for a long time, it will affect the adjustment function of the eyes, reduce the vision, and even cause serious hair loss Strabismus.

According to 5.3.2 of GB13511-1999, the horizontal mutual difference of optical center of glasses for optometry prescription shall not be greater than 1 / 2 of the optical center horizontal tolerance. That is to say, after checking the value of optical center horizontal deviation tolerance, dividing by 2 is the optical center horizontal tolerance. In the case of Jiangsu glasses inspection in the last section, the horizontal tolerance of optical center is 2 mm, and the horizontal tolerance of optical center is I mm.

In some fixed glasses, the distance between the left and right pupils is not the same, and the horizontal difference of the light step center should also be checked according to the left and right eyes, and the one with large deviation should be taken as the horizontal difference.

[example] od: - 4. 00ds OS: - 6. 50ds RPD: 32 mm LPD: 31 mm

After examination, it was found that the distance from the optical center of the right eye to the midline of the bridge of nose was 34 mm, and the distance from the optical center of the left eye to the midline of the bridge of nose was 33 mm.

That is, the optical center distance of the right eye is 35 mm, and the optical center distance of the left eye is 33 mm.

Analysis: horizontal deviation of optical center: 35 + 33 - (32 + 31) = 5 (mm)

Horizontal cross difference of optical center of right eye R: 35 - 32 = 3 (mm)

Left eye optical center horizontal aberration L: 33 - 31 = 2 (mm)

According to the national standard GB13511-1999, the left and right pre focus are different. Take the large value on the left. According to the calculation of - 6.50ds for the left eye, the allowable optical center deviation is 2 mm, and the horizontal tolerance of optical center is 1 mm, so the above are not in conformity.