Rigid gas permeable contact lens, also known as RGP (Rigid Gas Permeable Contact Lens), is the healthiest type of rigid corneal contact lens, which has the advantages of soft lens, but also has the advantages of super high oxygen permeability, excellent optical properties, easy to clean and care, not easy to produce dry eye disease, etc. It is not easy to occur the above soft lens-related complications, suitable for refractive It is suitable for long-term wear by patients with refractive errors. The use of RGP has become more and more popular in various countries, especially in Japan and Singapore, where RGP has become the first choice for the treatment of myopia in children and adolescents, and is credited with slowing down the progression of myopia in addition to its basic function of vision correction. Clinical work and scientific studies have proven that long-term RGP wear can relatively slow down the growth of myopia in children and adolescents whose myopia is increasing too rapidly. The reason for this may be that RGP improves the quality of retinal imaging, effectively protects the eye, and stops the further increase of the eye axis. Its only drawback is that it is not as comfortable as soft lenses when you first wear it, but you can get used to it if you stick to it for 1~2 weeks. The design of OK lenses is different from that of ordinary contact lenses, the central zone of which is flatter than the human cornea, so that the central zone of the cornea can be temporarily flattened through the mechanical compression of the lenses, thus causing a temporary decrease in refractive power in the whole eye and achieving “correction”. The purpose of “correction” of myopia. It is important to know that this “correction” is temporary, and its effect usually lasts only 1~2 days, if not worn daily, the cornea will regain its own shape through its own elasticity, thus making myopia “rebound” and return to its original myopic state. Studies have found that long-term wear of OK lenses can also effectively slow the progression of myopia. Of course, not every patient is suitable for wearing OK lenses, but patients with less than 150 degrees of corneal astigmatism, less than 600 degrees of myopia, and moderate corneal curvature are more effective. The fitting of OK is very strict. Before fitting, slit lamp examination is required to exclude other eye diseases, corneal curvature, corneal topography, objective optometry and subjective optometry, etc. After fitting, a very close follow-up visit is also required to observe the effect of fitting and the occurrence of complications. Therefore, the fitting of OK lenses can only be done in regular medical units.