Correct vision with lenses, prisms, contact lenses, intraocular lenses, etc., to eliminate visual fatigue, protect or treat the eyes. There are many kinds of glasses, and those who correct refractive errors have optical glasses and contact glasses. In addition to correcting aphakic eyes, in addition to contact lenses, artificial lenses can be implanted. In addition, there are various kinds of safety glasses, cosmetic mirrors and visual aids for correcting low vision. All lenses are thin lenses, and the degree is the reciprocal of the focal length (m) of the lens.