What are prescription lenses? Can anyone tell me more about Prescription Lenses?

[cheap eyeglasses]

I want to know more about a prescription lens. Is there anyone who have a clear understanding about prescription on lenses?

[Cudahy]

An Rx or prescription lens is an ovular-shaped piece of glass or plastic which is embeded in metal or plastic frames to help those having problems with that improve vision. The lens is aim to make vision clearer so that the glasses wearers can't get eye strain and prevent the eyesight going down. In order to make Rx lenses, an optometrist or ophthalmologist must test vision to determine the right strength or type of lens for the glasses wearers.

[Cudjoe Key]

A prescription lens is made to correct vision problems, such as myopia, presbyopia, hyperopia and astigmatism by an optician. People who have vision problems need to have an eye exam to get prescription lenses to help them see better. The prescription of the lens is an order written by an optometrist.