This is when the lens of the eye loses its flexibility and you lose the ability to change focus from long distance to close up. Its effects start to become apparent at around 40 years of age but it is an ongoing process that has been happening since before you were born and will stop only when you do!
As a child you have a large amount of focussing because the lens is very flexible and quite small. This focussing ability is called accommodation.
One theory for the reduction in lens flexibility is this: As you grow the lens grows. Extra layers are created around the nucleus at the centre of the lens. These layers are not sloughed off like skin cells so they build up on top of each other, a bit like the layers of an onion. Because the lens is inside the eye it reaches a point where it cannot get any bigger, so it starts to compress and get more dense. This is when it loses its flexibility.
Optometrists often see people for the first time at around 40 years of age. The following are a few of the comments that people make when they first experience the effects of presbyopia.
- I don’t need specs, I just need longer arms.
- The print is getting smaller.
- I don’t need glasses, I just need more light to see things now.
- My distance vision is all blurry after I have been reading.
- It takes ages to focus if I look from the TV to my magazine.
- My eyes are sore and tired if I have to read for too long.
People who are short sighted often complain that they have to take their glasses off to read.
Presbyopia can be corrected by reading spectacles, bifocals, or varifocals. It can also be corrected by some types of contact lenses.