Refractive errors of eye
Myopia (near sightedness) : The affected person can see the nearby objects but not the distant objects. This condition may result due to an elongated eyeball or thickened lens, so that the image of distant object is formed in front of the yellow spot. This error can be corrected using concave lens that diverse the entering light rays and focuses it on the retina.
Hypermetropia (long sightedness) : The affected person can see only the distant objects clearly but not the objects nearby. This condition results due to a shortened eyeball and thin lens, show the image of closest object in converged behind the retina. This defect can be overcome by using convex lens that converts the entering light rays on the retina.
Presbyopia : Due to aging comedy the lens loses elasticity and the power of accommodation full stop convex lenses are used to correct this defect.
Astigmatism is due to the rough (irregular) curvature of cornea or. Cylindrical glasses are used to correct this error.
Cataract : due to the changes in nature of protein korma the lens become opaque. It can be corrected by surgical procedures.
