Question

Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens a certain defect of vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens.

Answer 1

The defect caused due to a gradual weakening of ciliary muscles and diminishing flexibility of the eye lens is presbyopia. 

The type of lens required by such person to improve the vision is the bifocal lens. A bifocal lens consists of both convex lens and concave lenses. The convex lens used in bifocal lens is used to correct hypermetropia (far-sightedness) and concave lens is used to correct myopia (shortsightedness).