Corneal contact lenses, also known as contact lenses or invisible glasses, are lenses that are attached to the surface of the cornea and move with the movement of the eye. Between the posterior surface of the contact lens and the anterior surface of the cornea, which is usually filled with tear fluid, is called a liquid lens. The refractive index of contact lens, liquid lens, cornea and atrial fluid are very similar, so it can be considered as a refractive intermediate. The surface of this newly formed refractive intermediate, the regular spherical surface of the corneal contact lens, actually acts as a refractive surface. This property can be used to correct refractive errors, including hyperopia, myopia, astigmatism, especially irregular astigmatism, as well as unilateral aphakia and refractive aberrations. Corneal contact lenses are divided into two main types: rigid contact lenses made of methyl methacrylate (PMMA) and soft contact lenses made of hydroxyethyl methacrylate (HEMA) (hydrophilic soft lenses), the latter can absorb water, permeate oxygen, soft and easy to bend, less irritation to the cornea, in line with the requirements of corneal respiratory metabolism. But the mechanical strength is poor, more brittle is not very durable, susceptible to humidity, easy to become exactly the same as the corneal surface, so can not fully correct the astigmatism above 2.00D, and the optical effect is not as good as the hard, disinfection procedures are also more troublesome, in recent years, made of cellulose acetate and other agents of semi-rigid contact lenses, good oxygen permeability, high mechanical strength, but also has a certain softness, is a promising new type of contact lenses. Clinical contact lenses are used for: 1, correction of refractive error, especially corneal astigmatism, high myopia, refractive parallax, aphakic eyes, etc. Certain professions such as athletes, actors, and jobs not suitable for wearing ordinary glasses, contact lenses can often play its unique performance. Contact lenses can eliminate or reduce the trigeminal effect of ordinary eyeglasses, oblique astigmatism, and retinal image magnification in aphakic eyes. It plays a positive role in improving visual acuity as well as monocular function of both eyes, etc. 2, treatment of diseases, mainly hydrophilic soft lenses, can cure large vesicular keratopathy, corneal ulcer, corneal conjunctival dryness, corneal conjunctival burns, corneal penetrating injuries, etc.. It provides a new route of drug delivery by utilizing its properties of adsorption and penetration of drugs. In addition, it can eliminate light irritation for albinos through tinted contact lenses to improve visual acuity; mask defects and improve grooming for corneal leukoplakia patients, etc.