Glasses are also known as Spectacles or Eyeglasses, which have lens in it, which help us to clear our eyesight or   to protect our eyes from dust & sun light.

  Glasses or spectacles are typically supported   by pads on the nose & the side of the ears. Glasses are very much useful for those people who have weak sight. Due to the lens fixed in the glasses we can improve our visibility, some people have problems in seeing close object or words whereas other have problem in seeing far away things. So due to the lens fixed in the glasses visibility is improved.

History

The first spectacles were probably made between1268 & 1289, though the name of inventor is unknown. Over the time, lenses were developed to aid variety of visibility problems.

The first lens was used to care farsightedness. And in the 16th century concave lenses were founded to treat nearsightedness.

But in the older days the problem faces was how to keep eye lenses from falling off one’s face lot of experiments were made to keep the eyeglasses from falling off but finally in 1730, London Optician Edward Scarlet solved the problem by developing the rigid side pieces to be placed over the ears. This design spread throughout Europe & become the model for today’s glasses.

Types

There are different types of eyeglasses but depending upon the technology the types are changed. Earlier only eyeglass lenses were made only of glass but now- a- days there are made of high-tech plastics which are light weight & does not break easily as glass lenses.

1. Polycarbonate Lenses

 These lenses are strong & very impact-resistant. This lens provides ultraviolet protection. Basically people involved in sports use these glasses & most of children who easily drop& scratch their glasses.

2. Trivex Lenses

These have similar features as polycarbonate lenses, these lenses are also light-weight, impact resistant & they give better vision than polycarbonate lenses in some people.

3. Aspheric Lenses

These are spherical in shape, which are made up of differing degrees of curvature over its surface due to which the lens becomes flatter & thinner than other lens.

4. Photocromatic Lenses

 Photocromatic Lenses are made either of plastic or glass. The special feature of these lenses is that it changes from clear to tinted when exposed to sunlight & hence we can use this as an alternative for sunglasses.

5. Polarized Sunglasses

Polarized lenses reduce glare on our glass. Light reflects from water or flat surface causes unwanted glare & hence due to polarized lens this glare reduced & they are mainly used for sports & driving.

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