what is Trifocal glasses?

[rimless eyeglasses]

The small aperture eyeglasses is a kind of vision correction glasses with lens have three holes, if you wear this kind of eyeglasses for a while, you can get a clear vision only for a few minutes. At present, the physical therapy eyeglasses have effect to the pseudo myopia, among them with neutrons glass for representative, it uses the principle of the burning and prism to correct vision.