Question

What is myopia and hypermetropia? How can they be corrected?

Answer 1

To see clearly, rays of light from an object must be focussed to a point on the retina by the eye lens.

Myopia: If the eyeball is not spherical but slightly elongated, then the rays of light from a distant object converge to a point ahead of the retina. As a result, distant objects appear blurred and unclear. The condition where distant objects are not clearly seen is known as myopia or near sightedness. Myopia can be corrected by using spectacles or contact lens with concave lens. The concave lens cause the light coming from a distant object to diverge slightly before entering the eye so that they are brought to focus on the retina.

Hypermetropia: If the eyeball is slightly compressed, then the rays of light from a near by object do not converge by the time they reach the retina. As a result, near by objects appear blurred and unclear. The condition where near by objects are not clearly seen is known as hypermetropia or far sightedness. Hypermetropia can be corrected using spectacles or contact lens with convex lens so that the light can be brought to focus on the retina.