what is presbiopia? How it is corrected
Answers
Answer:
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).
Explanation:
Presbyopia is a common defect of vision, which generally occurs at old age. A person suffering from this type of defect of vision cannot see nearby objects clearly and distinctively. 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 can be corrected by focal lens.