Eyeglasses

Eyeglasses are devices consisting of hard plastic or glass 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. Eyeglasses are typically used for vision correction, such as with reading glasses and glasses used for nearsightedness.

History

The concept of eyeglasses was first introduced in Italy, around 1290. Initially, they were only used for reading, but with the passage of time, they started being used for seeing things at a distance as well.

Types of Eyeglasses

There are several types of eyeglasses available, each serving a different purpose.

• Single Vision Eyeglasses: These are the most common type of eyeglasses, which can correct for nearsightedness, farsightedness, or astigmatism.

• Bifocal Eyeglasses: These eyeglasses have two different optical powers. They are most commonly prescribed to people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism.

• Trifocal Eyeglasses: These eyeglasses have three different optical powers. They are used to correct distance, intermediate, and near vision.

• Progressive Eyeglasses: These eyeglasses have a gradient of increasing lens power, added to the wearer's correction for the other refractive errors.

Materials

Eyeglasses frames can be made from a variety of materials. The most common materials include metal and plastic.

See Also

• Contact lenses
• Vision correction
• Presbyopia
• Myopia
• Hypermetropia
• Astigmatism

References

Eyeglasses Resources
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