Eyeglasses are frames with lenses. They are worn over the eyes and supported by the ears and nose. Their purpose is to correct vision and protect the eyes. They can also be worn as a fashion accessory. Common forms of glasses are prescription eyeglasses, safety glasses, sunglasses and contact lenses.

A common use for these devices is to correct vision. Prescription eyeglasses have the ability to appropriate refractive errors of the eye. This is accomplished through modifications of the focal length of the lens. Traditional spectacles are able to move the focal point onto the retina to fix visions in area. Changing the thickness or shape of the lens can shift the focal point, as well as altering the depth of curve. Glasses are known to relieve conditions such as myopia, astigmatism, farsightedness, nearsightedness and presbyopia. Another type is pinhole glasses. These specs do not do anything typical glasses do. They come without lenses and therefore are unable to bend light and change focal length. Nonetheless, these lenses are said to correct vision problems.

Safety goggles or glasses are used as eye protection against debris or chemicals in the air. They are usually made from plastic and contain impact-resistant lenses. At the thinnest point they are a minimum of one millimeter thick. Safety goggles or glasses are commonly used in laboratories, industrial work and factories.

Sunglasses can be used to hide the eyes, improve vision while in the direct sunlight and decrease glare. They may even be used just for aesthetic purposes. These glasses can have prescription lenses added to them. Dark lenses are designed to protect the eyes against ultraviolet and visible light. Sunglasses can come in a variety of shapes, sizes and colors.

Devices that create the false appearance of three dimensions are called 3D glasses. These spectacles are used to watch movies or look at items that have specially-prepared images. Originally, these glasses had different colored lenses. One was red the other was cyan or blue. When the 3D lens is polarized, it can make colors and shapes appear as three-dimensional.

People who do not normally need or wear glasses commonly use reading glasses. These devices contain magnifying lenses. The magnification helps with close-up reading. Generally a prescription is not needed, a person should know what degree of magnification they need from experience or by trying on the spectacles. These specs can be purchased at virtually any store. These specs are capable of treating mild conditions of presbyopia and hyperopia. There are two primary styles: half-eyes and full frames. Half-eyes contain thinner lenses, while full frames are the size of normal eyeglasses.

Multifocal lenses are recommended to individuals who struggle to focus. Bifocals and trifocals are the most common forms of these. The devices can have two or three viewing areas in the lens. These horizontal areas allow wearers to change focus without changing glasses. No-line bifocals are popular because they offer a smooth transition between the focal areas.

Contacts are lenses go directly on the eye. They can be for corrective, therapeutic or cosmetic purposes. Corrective contacts act in the same ways as prescription eyeglasses. They are used to improve vision, by focusing light on the retinas. Generally these lenses are used to correct short or nearsightedness, far or longsightedness, astigmatism and presbyopia.

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Category: Education
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