Eyeglasses
Eyeglasses
Eyeglasses (pronounced: /ˈaɪˌɡlæs, -ˌɡlɑːs/), also known as spectacles or glasses, are devices consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person's eyes, typically using a bridge over the nose and arms which rest over the ears.
Etymology
The term "eyeglasses" is derived from the fact that the devices utilize glass lenses to aid vision. The term "spectacles" originates from the Latin word "spectaculum" which means "show, spectacle".
History
Eyeglasses were invented in Italy, most likely between 1268 and 1289. The exact date and inventor are unknown, but the earliest mentioned use of eyeglasses is in a sermon written by the Dominican friar Giordano da Pisa in 1305.
Types
There are various types of eyeglasses, including:
- Single vision glasses: These have the same corrective power over the entire lens.
- Bifocal glasses: These have two different corrective powers.
- Trifocal glasses: These have three different corrective powers.
- Progressive glasses: These have a gradient of corrective powers.
Related Terms
- Optician: A professional who designs, fits and dispenses corrective lenses for the correction of a person's vision.
- Optometrist: A healthcare professional who provides primary vision care.
- Ophthalmologist: A medical doctor who specializes in eye and vision care.
External links
- Medical encyclopedia article on Eyeglasses
- Wikipedia's article - Eyeglasses
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