About one person in fifty is affected by diabetes mellitus or 'sugar diabetes'. This means that the body cannot cope normally with sugar and other carbohydrates in the diet.
Diabetes can start in childhood, but it often begins later in life.
It can cause complications which affect different parts of the body. There are two types of diabetes mellitus - one is controlled by insulin injections, and the other by diet or tablets, but they both affect the eyes in the same way. If you have diabetes this does not necessarily mean that your sight will be affected, but there is a higher risk. If your diabetes is well controlled then you are less likely to have problems, or they may be less serious. However if there are complications which affect the eyes then this can result in loss of sight.