Question

explain me about presbyopia?

Answer 1

presbyopia is a condition where, with age the eye exhibits a progressively diminished ability to focus on nearby objects.

Answer 2

presbyopia effects are less noticeable in bright sun light, due to the action of Iris closing to a smaller diameter. People with disease get eyestrain after reading for some time.  Usually after 40 yrs, the eyes become presbyopic and lose their ability to change focus  or accommodate.  Verifocal lenses or bifocal lenses are used to correct prebyopia.
In order to overcome prebyopia, in addition to the optical system of the eye, the visual processing of brain is also to be addressed.