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It is a lens that mainly uses the soft contact lens and colored the contact lens surface by special treatment. It is used for beauty purposes to change the color of the eyes using various colors. Circle lens has the effect of adding color to the edge of the lens (mainly black in our country) to make the eyes look clear and large. This lens is used for cosmetic purposes when the color looks different from normal.
Beauty color lenses are often recognized as cosmetics, not medical supplies. They can even be purchased from unqualified people on Internet sites, use crude products from unauthorized companies, and use them with friends. Is often not done well. However, since cosmetic color lenses are attached directly to the eye like normal contact lenses, they can cause various complications. In addition, colorants are used, which results in lower oxygen transfer rate and rougher surface than other contact lenses. Are more likely to damage. Therefore, long-term wear can cause side effects such as neovascularization, keratitis, corneal ulcer, and corneal edema, and in severe cases, blindness.
Therefore, cosmetic color lenses also require a professional's prescription and instructions. Like contact lenses for vision correction, you must clean them regularly, do not sleep at night, and use the lens with other people. Rather, it is recommended to wear it for a shorter time (within 6 hours a day) compared to normal soft lens.
Classification by form
It is a contact lens that is composed of spherical surface both outside and inside of the lens. You can think of spherical as cutting off a part of a sphere-like a soccer ball.
The cornea of our eye has an elliptical aspherical surface that becomes flat as it goes from the center to the periphery, not the perfect spherical surface. The lens manufactured to correct this is called aspherical lens. The aspheric lens can make the thickness of the lens thinner and can minimize the thickening part in the middle of the lens, making it comfortable to wear and correcting slight presbyopia. Because of the disadvantage that the image is blurred, it is possible to prescribe after the evaluation of the correct fitting condition of the ophthalmologist for the test.
This lens is designed to add circumferential lens effect along the astigmatism axis in patients with severe astigmatism that is difficult to correct with the spherical or aspherical lens. In the case of soft contact lenses, astigmatism of more than 2.0D has a limitation that correction of advanced astigmatism is difficult because vision correction is not good when the axis of astigmatism is slightly rotated.
Classification by material
Used in the early stages of contact lenses, they have been irritated and unsuitable for long-term wear.
PMMA lens (polymethyl methacrylate lens)
It is more convenient to use than glass lenses and contributed to the widespread use of contact lenses. However, the oxygen transmission rate is low, so it is rarely used since the RGP lens was developed.
In the 1960s, soft contact lenses made of hydrogel materials were developed to improve the discomfort of conventional PMMA lenses and the oxygen transmission rate, which was near zero, and thus contributed to the popularization of contact lenses. Lens material. Currently, most soft contact lenses use this material, but since the development of silicone hydrogel material, it has been gradually changed to silicone hydrogel material.
RGP lens (rigid gas permeable lens)
It is a conventional lens that improves oxygen transmittance by combining silicon with PMMA structure, which is a hard lens material (silicone acrylate). It is a kind of hard lens, but it is called RGP lens (oxygen permeable hard lens) to distinguish it from the PMMA lens which was called a hard lens. I am using more expression. The disadvantage is that it takes a period of time to get used to wearing the lens, but the lens surface is relatively hard, which is effective in correcting the refractive power of the cornea, resulting in excellent vision improvement in keratoconus and severe astigmatism. In addition, the oxygen permeability is 5 to 10 times higher than that of the normal soft lens hydrogel lens, which has less side effects such as corneal edema, corneal neovascularization, and dry eye syndrome, and less inflammation or infection caused by the lens.
Silicone hydrogel lens
Since soft contact lenses were invented in the 1960s, hydrogels have been widely used for soft contact lenses. Hydrogel lenses are comfortable to wear initially but have a lower oxygen transmission rate than the newly developed RGP lens.
Silicone hydrogel lens, developed in 1999, is widely used in continuous wear lenses and daily wear lenses by improving the oxygen transmittance.