Cataract - Part 2 Systemic diseases and syndromes

Cataract or opacity of the lens is still the most common cause of blindness. The age-related form affects over 20 million people worldwide.1 It is a multi-factorial trait with both genetic and environmental components. An association has also been found between cataract and certain systemic and syndromic conditions. Some of these diseases will be discussed in more detail in this article.

Diabetes mellitus

Diabetes mellitus is a common metabolic disorder affecting 8 per cent of the world's population.2 It is characterised by abnormally high blood glucose levels or hyperglycaemia. Normally, the hormone insulin is constantly synthesised by b-cells in the pancreas, irrespective of glucose levels in the blood. It is stored in vacuoles and an elevation of blood glucose levels triggers its release. Insulin is one of the hormones involved in the regulation of blood glucose it regulates the uptake of glucose from the blood into cells including skeletal cells and adipose cells and the conversion of glucose to glycogen for storage in liver and muscle cells. When blood glucose drops there is a reduction in the release of insulin and an increase in the secretion of another hormone called glucagon from the a-cells of the pancreas. Glucagon opposes the action of insulin by stimulating the conversion of glycogen to glucose.3