Therefore, a qualified discountglasses lens optical design should take into account the relative position between the human eye and the lens for "compensation", which is the so-called optimization.

Pupil height and pupillary distance are based on the fact that the optical center of the lens design needs to be placed directly in front of the pupil, otherwise, it will introduce a lot of additional aberrations. Eye contact is very important! Including single discountglasses lenses.

Posterior vertex distance, the distance between the human cornea and the posterior surface of the lens, is usually deeper and larger in the eye socket. The tilt angle is the angle between the plane of the discountglasses lens and the normal plane of the principal line of sight (myopia can be understood as the face plane). Usually, the higher the nose bridge, the smaller the inclination angle, and vice versa.

Mirror curvature is the angle between the planes of two lenses, usually derived from the curvature of the frame itself. Usually, the curvature of most mirror frames is not too large.

Some people may ask, what impact do these parameters have on the obtained lens power? I used it quite well when I didn't know it before.

The larger the distance between the lens and the eye, that is, the farther the lens is from the eye, the higher the degree of presbyopia. I don't know if you have such experience, but the farther you look at an object with a magnifying glass, the greater the magnification, and the same principle applies. The same applies to myopia.

Why is the prescription of contact lenses usually different from that of frame glasses? Because the eye distance of contact lenses is 0. Modern advanced optical designs analyze and optimize the object mirror eye as a whole, so like all optical systems, their relative position is also an important parameter.