Long sightedness defect of vision is removed by using convex lens of suitable focal length. External lens converses the rays of light and reduces the focal length of eye lens so that image is formed at retina.
A person who is long sighted can focus clearly on distant objects but cannot focus on near objects. This is because the eyeball is too short. Light from near objects is focussed at a point behind the retina resulting in a blurred image. This defect can be corrected by wearing a convex (converging) spectacle lens.Rays from a nearby object need to be converged more, to form the image on the retina. Long sight is corrected using a converging lens which starts to converge light rays from a nearby object before they enter the eye. Converging (convex) lenses are used in reading glasses.
The simplest, cheapest and safest way to correct long sight is with glasses. Convex prescription lenses (called plus lenses) are used to bend light rays slightly inwards to give a little bit of additional focusing power to the eye.Correction of farsightedness uses a converging lens that compensates for the under convergence by the eye. The converging lens produces an image farther from the eye than the object, so that the farsighted person can see it clearly.
- Glasses. Long-sightedness can usually be corrected simply and safely by wearing glasses with lenses that have been prescribed specifically for you. ...
- Contact lenses. ...
- Laser eye surgery. ...
- Artificial lens implants.