Eyeglasses, also known as glasses or spectacles, are devices consisting of lenses mounted in a frame that holds them in front of a person’s eyes. Eyeglasses are typically used for vision correction. Safety Eyeglasses provide eye protection against flying debris or against visible and near-visible light or radiation. Sun Eyeglasses allow better vision in bright daylight, and may protect one’s eyes against damage from high levels of ultraviolet light. Specialized Eyeglasses may be used for viewing specific visual information (such as stereoscopy). Sometimes Eyeglasses are worn simply for aesthetic or fashion purposes. The number of Americans who are nearsighted has doubled since the 1970s and almost 3/4 of the US population wears Eyeglasses. People are more likely to need Eyeglasses the older they get with 93% of people between the age of 65-75 wearing corrective lenses.
Eyeglasses are used to correct refractive errors by bending the light entering the eye in order to alleviate the effects of conditions such as nearsightedness (myopia), farsightedness (Hypermetropia) or astigmatism. Another common condition in patients over forty years old is presbyopia, which is caused by the eye’s crystalline lens losing elasticity, progressively reducing the ability of the lens to accommodate (i.e. to focus on objects close to the eye). Eyeglasses are made to conform to the prescription of an ophthalmologistor optometrist. A lensmeter can be used to verify the specifications of a pair of glasses.
Pinhole Eyeglasses are a type of corrective glasses that do not use a lens. Pinhole Eyeglasses do not actually refract the light or change focal length. Instead, they create a diffraction limited system, which has an increased depth of field, similar to using a small aperture inphotography. This form of Eyeglasses has many limitations that prevent it from gaining popularity in everyday use.
Corrective Eyeglasses can significantly improve the life quality of the wearer. Not only do they enhance the wearer’s visual experience, but can also reduce problems that appear such as headaches or squinting.