Types of Lenses
Single vision lenses: These are used to correct common vision defects such as myopia, hypermetropia and astigmatism.
Reading glasses: People with presbyopia, or nearsightedness associated with age, are prescribed these. They correct near vision but objects at a distance may be blurred.
Some users of reading glasses may use two pairs of spectacles. One for reading and the other for seeing distant objects.
Bifocals: These lenses combine both near and distant requirements. There is an obvious line in the middle that shows where the two lenses blend.
They are quite thick and indicate the age of the wearer. Until recently, however users of spectacles had to be satisfied with these as the best solution to presbyopia.
Progressive Lenses: Like the bifocals, progressive lenses combine both near vision and distant vision requirements. But unlike bifocals they are divided into three zones: near, distant and intermediate and this division is seamless with the power computed for each zone of the lens and the transitional areas as well.
Of late these lenses are available in compact sizes, enabling users to have smaller, smarter spectacles frames.