By Adam Adel

The primary functions of the crystalline lens are to transmit incident light and to focus it on the retina. This requires that the lens is transparent, a condition dependent on the highly regular organization of the cells of the lens and the high degree of order of the proteins in the lens cytoplasm. The protein concentration in lens fibre cells is extremely high, resulting in an index of refraction significantly greater than that of the surrounding fluids, and so enabling the lens to refract incident light. Cataract occurs when the lens loses its transparency by either scattering or absorbing light such that visual acuity is compromised. Cataracts can result from genetic, metabolic, nutritional or environmental insults, or they may be secondary to other ocular or systemic diseases such as diabetes or retinal degenerative diseases (see box). By far the most important risk factor is age; aging-related cataract constitutes the great majority of all cataracts and is a major public health problem worldwide. In developing countries, where the availability of surgical facilities is limited, aging-related cataract is the leading cause of blindness. Because at present there is no efficacious non-surgical therapy for cataract, the problem is expected to increase in magnitude in coming decades as the world population becomes progressively older.

Causes of cataracts

• Aging

• Inheritance

• Metabolic disorders, e.g. Lowe’s syndrome, hypocalcaemia

• Diabetes

• Toxicity, e.g. drug-induced (steroids, amiodarone), chemical, metal ions

• Nutrition

• Physical dehydration Read the rest of this entry »