A lens is a transmissive optical device that focuses or disperses a light beam by means of
refrection. A simple lens consists of a single piece of transparent meterial, while a compound
lens consists of several simle lenses, usually arrange along a common axis.Lenses are made from
materials such as glass or plastic, and are ground and polish or moulded to a desired shape.
A lens can focus light to form an image, unlike a prism, which refrects light without focusing.
Devices that similary focus or disperse waves and radiation other than visible light are also
called lenses, such as microwavelenses,electron lenses,acoustic lenses, or explosive lenses.
We have generally the following lenses in our optical center. The lenses are usually
prescribed by the Optomatrist. There could be more but there are important..
Peaple suffering from farsightrdness or hypermetropia cannot see nearby objects clearly rather, they cannot focus them clearly on ratina. So these converging lenses are prescribed. Depending on requirment, plano convex or double convex be prescribed.
Peaple suffering from shortsightedness or myopia focus objects from distence, at a location in front of ratina. So they are prescribed diverging lnses. Depending on requirment, plano concave or double concave may be prescribed.
Peaple suffering from astigmatism have a trouble that they cannot focus correctly the object in all directions. Objects in vertical direction and horizontal direction are not both focused correctly at the same time. Depending on requirment plano cylindrical or total cylindrical lenses may be prescribed. It also possible that peaple are given bifocal lenses with two lensescombined in one spectale.