Name the defect of vision in which a person uses a bifocal lenses?
Presbyopia is caused when the centre of the eye lens hardens making it unable to accommodate near vision. This condition generally affects almost everyone over the age of 50 - even those with myopia. Eyeglasses with bifocal or progressive lenses are prescribed to correct or improve the condition. The contact lenses used by presbyopes are multifocal lenses.
Hope this clarifies your doubt.