Presbyopia
When we want to look at something near to us our eyes have to put in more power to focus the light on the retina. This extra power comes from the crystalline lens of the eye which can change shape and become fatter to give more power. When we are very young the lens can put in 20 dioptres of extra power, however as we get older the lens loses the ability to change shape and by the time we reach middle age it may not be able to give us enough extra power to allow clear near vision.
In presbyopia the lens loses its ability to change shape stopping us focussing things close to us
When this begins you may notice that you need to hold things further away to be able to read them but after awhile things have to be held so far away that they are too small to be read.
as we go presbyopic we need to hold things further away to read
In order to give the eye extra power reading glasses need to be worn - there are several choices separate reading glasses, bifocal lenses or varifocal lenses. There are also specific contact lenses for presbyopes.