. What is presbyopia? How is it corrected?
The accommodation of the eye decreases with ageing. It occurs due to the gradual weakening of the ciliary muscles and decreasing flexibility of the crystalline lens. The near point of the eye increases with age. This defect is known as presbyopia. Such a person may suffer from myopia and hypermetropia. This defect can be corrected by using bifocal lenses of suitable focal lengths. The upper part of the lens is concave lens for correction of myopia to see the distant objects and the lower part of the lens has convex lens to correct the hypermetropia to see the nearly objects clearly.