Glasses (also known as eyeglasses or spectacles), are frames containing lenses (originally made of glass, now also of other materials) that are worn in front of the eyes. Besides their use in vision correction, glasses may be worn for eye protection against physical objects or chemical substances (especially safety glasses), or visible light and near-visible radiation (especially sunglasses, which may preclude some damage from ultraviolet, or UV, radiation, and also allow better vision in the presence of bright visible light). They may also be worn for aesthetic reasons, or for specialized viewing purposes (e.g., stereoscopic glasses).
Physics in vision correction
Images of the visual world are received by the eye as light waves, which enter the eye through the lens, and are projected onto the light-sensitive retina. The image will be inverted, and the brain reinterprets the stimulus to produce what we understand is 'what we see'. For individuals requiring glasses for vision correction, the resultant image may be blurred or out of focus because of the shape of their lenses.
Glasses can correct this by providing a secondary lens that alter the direction of light waves through the shape and refractive index of its glass, improving the quality of the image on the retina and hence the quality of vision.
Experiments have related eyeglasses wearing to lower somatic (bodily) self-esteem . It has been suggested that children who require visual correctives internalize a negative "spectacle image" that is created by the adult world, and propagated by the media.
However, another explanation for the negative self-image for eyeglass wearers is that the eyeglasses themselves are the problem: by altering the appearance of the wearer's eyes, the eyeglasses obscure important nonverbal communication. Eyeglass wearers may learn through simple reinforcement to avoid the gaze of others since the information communicated by their eyes might appear to be at odds with their verbal message. This process may begin as soon as the wearing of eyeglasses begins: it has been found that infant vocalizations were elicited when an adult brought their face close, but only if their eyes were not obscured by dark eyeglasses. This hypothesis may also explain why people wearing eyeglasses are judged by others to have very prominent eyes, while the wearers themselves tend to de-emphasize the importance of their eyes in their appearance.
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