What is presbyopia and explain

Dear student,Presbyopia is a common defect of vision, which generally occurs at old age. Presbyopia is the defect of eye in which a person cannot see further as well as nearer objects clearly. A presbyopic eye has its near point greater than 25 cm and it gradually increases as the eye becomes older. Presbyopia is caused by the 1. weakening of the ciliary muscles 2. reduction in the flexibility of the eye lens A person with presbyopia cannot read letters without spectacles. It may also happen that a person suffers from both myopia and hypermetropia. This type of defect can be corrected by using bi-focal lenses. A bifocal lens consists of both convex lens (to correct hypermetropia) and concave lens (to correct myopia). It is a common misconception among people that the use of spectacles “cures” the defects of vision. However, this is not true as spectacles only “restore” the defects of vision to the normal value. REGARDS.