Presbyopia (or ‘old sight') occurs in middle-aged adults (around 40 years old) where close-range visual tasks becomes increasing difficult. Reading difficulties is a typical complaint, but tired eyes at close work and defocus when working at a computer are also common. It however generally does not affect vision in the far distance.This condition is due to the decrease in the focusing ability of the eye's ‘natural lens' become less flexible due to changes in its protein composition with age. As the ‘natural lens' in the eye can no longer refract light adequately to focus on near objects, people who are already wearing spectacles may need bifocal, multifocal or progressive lenses, whilst those who have never worn spectacles may require reading glasses. (See Below)These are the corrective options for Presbyopia:

Reading Glasses (Single Vision)
Bifocal Spectacles
Progressive (Varifocal) Spectacles 
Multifocal Contact Lenses