To see objects at different distances the eye changes it’s power just like a camera lens. In the eye this is achieved by a structure called the crystalline lens which is attached by very fine fibres to a circular muscle. When this muscle constricts, the lens bulges out becoming more powerful and close objects come into focus.
When we are young the crystalline lens is very flexible, like a sack full of jelly, but as we get older it grows larger and becomes increasingly more inflexible. This process is called Presbyopia – an unflattering term derived from Greek presbys meaning old man and ops meaning to see like.
Because the lens material is stiffer it takes more effort to change it’s shape and increase it’s power – and the closest point that we can easily focus for reading gradually gets further and further away from us. As a result most people over the age of 40 – 45 require glasses in order to read at a comfortable distance.
It is also more difficult to relax focusing effort and return the lens to it’s less powerful shape for distance and one of the first changes many people notice is a delay in adjusting focus back to distance space after concentrating in near space for any length of time. For example they may notice that they cannot see as clearly driving home from work after a day in the office.
The stiffening of the crystalline lens is a continuous process and so every two to four years reading glasses will needs updating to give increasing focusing support – unless you want to read with a selfie stick!
In time you will need to wear your so called reading glasses for must activities in near space – including computer work, looking at your tablet or phone, cooking, eating, and maybe even ironing. As you start to wear them more you may want to consider some of the more advance and comprehensive lens solutions available.