Eyesight: The effect of age

Eyesight deteriorates with age

BBC News Online explains why our eyesight deteriorates as we get older.

Many people have to start wearing glasses between the ages of 40 and 50 because of failing eyesight. Indeed, being able to read without glasses by the time you hit 60 is rare.

The reason for this is a deterioration in the eye's ability to focus as we get older as a result of hardening of the lens and, sometimes, weakening of the eye muscles.

Children are able to focus from the horizon to close to the end of their nose, but this focal point gradually moves away from us with time.

Problems reading?

By the age of 40 or 50 most people are finding it difficult to focus on printed material in front of them, leaving them requiring reading glasses.

People who work in jobs which require them to do a great deal of reading are likely to suffer from the condition, known as presbyopia, and will need glasses earlier.

President of the Royal College of Ophthalmologists Dr Jeffery Jay said: "The ability to focus depends on the ability of the lens to change shape. The ability to change shape gets more restricted as you get older.

"It is partly that the lens gets harder, it may also be that the muscle is getting less effective."

Because the lens is becoming harder, it is less able to change shape and therefore focussing is more difficult.

The lens in glasses brings the focus closer and makes the object you are looking at appear bigger.

Though the need for glasses will be impossible to resist in most people, reading in good light and using clear type will help reduce the strain on the eyes.