1. Lens Transmittance and Optical Uniformity Test Method: The hand-held lens is about 30 mm away from the eye, and the distance is observed from the lens. If the object is clear, there is no deformation, and there is no vibriation when moving slowly, indicating that the transparency and optical uniformity of the lens are better.
2.optical center position test method: draw a large cross with thin lines on white paper, strokes should be clear and straight. Hold the lens and observe the shape of the cross stroke from the lens with one eye. If the strokes outside the mirror are not on a line, the lens can be moved so that the cross-stroke inside the lens is connected to the outside of the mirror. Use a mark pen to point a small point at the center of the cross observed in the lens. This is the optical center. After the two lenses are out of the optical center, observe whether the optical centers on both sides are symmetrical, and then use a ruler to measure whether the distance between the two center points is consistent with the prescribed pupil distance. If the cross stroke in the lens is curved, there is a quality problem with the lens.
3.Buy glasses from brand shops,shopping mall,glasses stores or onlin shops who can provide professional suggestions and after-sales services.