Question

name the corrective measures in myopia & presbyopia​

Answer 1

Answer:

In myopia, concave lens is used.

In presbyopia, bifocals are used.

Answer 2

Explanation:

There are four types of defects of Vision in the human Eye: Myopia, Hypermetropia, Presbyopia and Astigmatism. Below are given the nature of the defect, its causes and corrective measures:-

1.Myopia:

Nearsightedness, also called myopia is a common name for impaired vision in which a person sees near objects clearly while distant objects appear blurred. In such a defective eye, the image of a distant object is formed in front of the retina and not at the retina itself. Consequently, a nearsighted person cannot focus clearly on an object farther away than the far point for the defective eye.

2.Presbyopia, progressive form of farsightedness that affects most people by their early 60s. The power of accommodation of the eye decreases with ageing. Most people find that the near point gradually recedes.

Cause and cure:

It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the crystalline lens. Simple reading eyeglasses with convex lenses correct most cases of presbyopia. Sometimes, a person may suffer from both myopia and hypermetropia. Such people often require bi-focal lenses. In the bi-focal lens, the upper portion of the bifocal lens is a concave lens, used for distant vision. The lower part of the bifocal lens is a convex lens, used for reading purposes.