Glasses usually with corrective lenses, which are mainly used to come nearsightedness, farsightedness, astigmatism and presbyopia treated. Usually prescribed by an ophthalmologist glasses are part of eyeglasses.
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As eyeglasses, there are different types of lenses. If the view of the entire surface of the lens is the same, they are glasses called "single vision correction lens." In case of "bifocal lens', the upper part for distance vision is used, while the lower part of the glasses used for near vision. If an intermediate layer is also in lens present view objects at a distance by, for example, the remote computer, they as a "corrective lens Trifocal." This type of lens has two segment lines that separate the three regions.
Or progressive glasses variables with the advantage that line segments come and give a smooth transition from distance correction near correction. Glasses with adjustable or variable lens used primarily to prevent the loss of property, which together treat presbyopia.
When it comes to the shape, glasses can be produced in any kind of form, but with corrective lenses convex-concave lenses are the most common. The difference in curvature between the front and rear surfaces leads to the correction power of the lens.
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Although there are many advantages of glasses with corrective lenses, are one of its drawbacks is that it causes facial deformity.
Although there are many advantages of glasses with corrective lenses, are one of its drawbacks is that it causes facial deformity.
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