Presbyopia is synonymous with middle age, and has been called ‘vision after 40’. It is the slow loss in accommodation due to hardening of the natural lens.
One notices presbyopia once the accommodative amplitude is insufficient to allow a person to read and carry out near vision work comfortably. The age of onset may vary from person-to-person and depends on the current error of refraction, pupil size (depth of focus), lighting, visual tasks, etc.
Convex lenses found in reading glasses are the most common interventions available.