Presbyopia is an inability to focus on objects that are close to you, and usually occurs after the age of 40.
It can be corrected by using bifocal glasses and lenses.
Presbyopia is thought to be one of the symptoms of the ageing process as it is basically caused by the hardening of the eye's lens.
It becomes noticeable when you start to read menus, newspapers and magazines at arm's length, or feel fatigued when doing close work such as embroidery, other needlework or writing.
Doing such activities may also cause headaches or eyestrain.
If this is happening to you, call your doctor or ophthalmologist and have your eyes checked.
Bifocal glasses can correct presbyopia as can lenses, but there are new processes which can cure it.
One of these is refractive lens exchange, which means that your hardened natural lens in the eye is replaced by a more flexible one that is artificial.
This procedure will give you multi-focal vision.
If you are undergoing surgery for the removal of cataracts, presbyopia can be cured with intraocular lenses, although this treatment is not suitable for all.
However if you are able to have it, you will be able to see clearly over all distances.
There is also a new treatment that is currently being tested, which involves a specially formulated gel which replaces the natural lens and gives the flexibility which has been lost in the natural lens.
The World Health Organization (WHO) has identified presbyopia as a priority area for their global work.
In 2005 over 1 billion people worldwide had the disease, but of those only 517 million had received corrective glasses or lenses.
The rest were untreated.
If presbyopia is not corrected it will eventually cause problems with driving, at work and to your lifestyle.
However it is considered a natural part of the ageing process.
Scientists point out that there is no proven prevention or cure other than those mentioned above for the disease.
It must be treated by an ophthalmologist and not left until it is too late because you though it would be corrected by doing eye exercises or changing your diet.
Clearly if you have a well balanced nutritious diet, you are less likely to suffer from disease than people who don't have such a healthy diet but eating healthily is not a guarantee that you won't get a disease, whether this is related to the eyes or any other part of your body as genetic factors and your environment can also affect your health.