Explain the refractive errors of eye.

Explanation

Refractive errors of eye :
1. Myopia (near sighttedness) : 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 diverge the entering light rays and focuses it on the retina.
2. Presbyopia : Due to againg, the lens loses elasticity and the power of acommodation. convex lenses are used to correct this defect.

3. Astigmatism is due to the rough (irregular) curvature of cornea or lens (Cylinderal glasses are used to correct this error.
4. cataract : Due to the change in nature protein, the lens becomes opaque. It can be corrected by surgical procedures.