University of Otago ophthalmologist Associate Professor Gordon Sanderson explains that one of the eye problems associated with ageing is a condition called presbyopia. This involves a deteriorating ability to change the shape of the lens. As a result, viewing near objects such as the print in a book or newspaper becomes blurred or out of focus.
ASSOCIATE PROFESSOR GORDON SANDERSON
As we get old, unfortunately we lose the ability to change the shape of our lens, so this lens that was capable of changing its shape from a relatively flat shape to a much more convex shape, we lose that ability with age.
It doesn’t happen overnight – it starts to happen gradually. And you notice that people who are in their 40s are starting to read things a little bit further away, by the time they’re 45, they’re further away again, and by the time they’re 50, they’re putting the newspaper on the floor and they’re sort of standing there trying to read it at that distance. That’s referred to as presbyopia, and presbyopia literally means ‘old eye’. Now the only way to solve the problem with presbyopia is to take another convex lens in the form of reading spectacles and put it in front of your eyes and put them on to read. But when you want to see in the distance, you have to look over the top of them or you have to take them off again, as you can’t focus in two places at once.
If you’re already wearing glasses for distance vision and you gradually discover that you can no longer read, it’s possible to get the reading lens put at the bottom, and some people have got two lenses in one pair of spectacles, and they’re referred to as bifocals.