External Angle

The external opening angle of the glasses frame refers to the included angle between the connecting line of the two hinge axes and the glasses leg when the glasses leg is fully extended. Generally about 80-100 degrees. In actual use, it can be properly adjusted according to the wearer's face and the bending of the glasses frame.

How the external opening angle changes:

When new glasses are delivered to customers, the external opening angle is generally adjusted properly. But before long, the external angle will change. In the words of customers, it is "the more you wear, the more relaxed you become". Why?

The causes of improper external opening angle:

1. Wearing glasses with one hand causes inconsistent external opening angles, resulting in horizontal deviation of lens frame during wearing, which affects binocular vision.

2. If the selection box is inappropriate and small, the external opening angle will be expanded beyond the reasonable range, and large inward compression force will be automatically generated when wearing; If it is too large, in order to ensure that it will not fall off, deliberately reduce the external opening angle and use the inward pressure to prevent slipping; As a result, no matter whether the external opening angle is enlarged or reduced, after wearing for a little longer, two traces will be drawn on the cheek and make the temples feel dizzy, which affects the wearer's mental outlook, appearance and comfort.

3. Wearing glasses from the top of the head causes the external opening angle to become larger, which will often slide during wearing, breeding the habitual unconscious action of supporting the nose.

Specular Angle

It refers to the angle between the left and right lens planes. Generally 170-180 degrees. That is, the specular angle should be within 10 degrees, and the specular angle of sports glasses will be larger. 

Influence of Specular Angle:

If the specular angle is too large or too small, in addition to not fitting the face shape and affecting the beauty, the more important thing is that different prism effects will be produced when facing and side looking, and the focus can not correctly fall on the correct position of the retina, resulting in the wearer's wrong judgment of distance, perspective relationship, size and shape.

When fitting aspheric and progressive multifocal lenses, accurate mirror angle is particularly important, which will reduce the fuzziness of objects in the left and right eyes.

As for professional opticians, when customers have finished matching glasses, they should timely observe and ask customers about their wearing comfort, and have the obligation to remind the wearer to return to the store regularly to maintain and maintain the glasses to ensure their wearing comfort.