What is presbyopia? State its cause. How is it corrected?

Hint: Defect in vision where a person is unable to distinctly see things close and far apart. Presbyopia is a popular vision defect that typically develops at old age.

Complete step by step answer:
First we should know about defects of the eye to answer this question. Vision is called the capacity to see. It's called eyesight, too. Often an individual's eye does not accurately concentrate an object’s image on the retina. In such situations, a person's vision gets distorted and he does not easily and clearly see either distant objects or surrounding objects. The person is said to have a vision defect. Vision defects are known as eye defects. There are three common vision defects and they are Myopia, which is near-sightedness or short-sightedness, hypermetropia, which is a long-sightedness or far-sightedness, and presbyopia.
An individual suffering from this form of vision defect does not easily and distinctively see surrounding or far objects. A presbyopic eye has a point of closure greater than 25 cm and as the eye gets older, it steadily rises.
Presbyopia is caused by:
1. Weakening of the muscles of the ciliaris
2. Reduction of eye lens versatility
Without spectacles, a person with Presbyopia can't read letters. There may also be an individual suffering from both myopia and hypermetropia. Using bi-focal lenses can correct this type of defect. Both convex (to fix hypermetropia) and concave (to rectify myopia) lenses are made of a bifocal lens.

Note:
Difficulty reading fine print, particularly in low light environments, eye strain while reading for long periods, blurring of close objects or temporarily impaired vision while adjusting the viewing distance are the first signs most people experience. Some serious Presbyopia complain that their arms have grown "too short" for a reasonable distance to hold reading content. Presbyopia becomes less visible under direct sunlight, as other focal imperfections, as the pupil becomes smaller.