In correcting vision problems due to refractive errors, there are two common devices of choice: eyeglasses and contact lenses. These vision problems take place when light isn't focused properly. In getting a prescription device, an eye examination is performed by an optometrist and in some cases by an ophthalmologist too.
Refractive errors come in different types. Nearsightedness (myopia) causes a person to have a hard time seeing objects placed far from eyes. This is because light is focused just before the retina. On the other hand, farsightedness (hyperopia) causes a person to find it hard to see near objects. In this particular situation, the light is focused behind the retina.
Another type of refractive error is called astigmatism. In here the cornea of the eye is shaped in an irregular fashion. The cornea is a transparent covering found in the front of the eyes. It also does a little focusing, much like the lens part. Presbyopia is another problem. Although it also causes blurring of vision, this is primarily due to aging.
Wearing of prescription glasses is the most popular choice in correcting refractive errors. This particular device holds the lenses before the eyes with the help of a frame, resting on the ears and nose of the person. A frame is available in all sorts of shapes and sizes. It's suited for holding many types of lenses. The materials it comes in are varied. To name a few: acrylic, nylon, epoxy, polyamide and cellulose acetate.
Metal frames are preferred by some as they're less noticeable. However, most of them are costlier than plastic counterparts. They can come in stainless steel, aluminum, nickel, titanium alloy, titanium and silver. Some frame models also come rimless, so they're even less noticeable. Directly attached to the lens are the temple and nosepiece frame parts.
The lenses can come in materials like plastic and glasses. The one to pick depends on factors, such as the budget and the problem to correct. Someone with myopia is prescribed with a concave one, wherein the center of the lens is thinner compared to the sides. A convex one, which has a thicker center so it resembles a magnifying lens, is recommended for those with hyperopia. Cylindrical ones, on the other hand, are recommended for individuals with astigmatism. It's also possible to make the glasses more functional by adding anti-UV or anti-reflective coatings.
Placed directly over the corneas of one's eyes are contact lenses. Inconspicuously, they help correct vision problems due to refractive errors. An eye specialist will have to measure the eye's curvature. But there are conditions which may keep a person from using contact lenses, such as those involving the cornea or when the eyes don't produce enough tears for protection.
Contact lenses are available in different types. Some of them are soft lenses for extensive use, soft lenses for daily use, rigid lenses, planned-replacements, and disposable ones. In using them, the person might need some time to adjust, especially if worn for the first time. However, they may not offer the best solutions like eyeglasses do in some cases, such as extreme form of astigmatism.
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