Hereditary causes
These arise through genetic inheritance from parents or grandparents. It has been found that cataracts are mostly inherited autosomal dominant. This means that one loaded gene in the chromosome pair is sufficient to trigger the disease.
As a rule, it can be expected that 50% of the offspring of an inherited cataract sufferer will also suffer from cataracts. A distinction can be made between cataracts in old age, which are caused by genetic predisposition in old age. However, factors of origin remain unknown.
Old-age cataract is the most frequent cataract. In 90% of the cases it concerns an age-related cataract. One calls the age-related cataract also Kataracta senilis.
The age-related cataract has several causes. On the one hand, the composition of the lens fluid changes, which leads to the agglutination of proteins. In addition, oxidative changes caused by radicals can damage and cloud the lens.
There are also osmotic causes, which are caused by the conversion of sugar molecules into alcohol derivatives. As a result, more water remains in the lens. Hereditary cataracts can also occur as a concomitant disease of another disease such as neurodermatitis and Wilson’s disease.
Cataracts also occur in other hereditary diseases, especially of the eyes, but also in other organ diseases. Cataracts can also occur in galactosemia, a hereditary metabolic disorder with a specific enzyme deficiency, but this is reversible. Hereditary cataracts can occur in children and adolescents, which is normally atypical of classic cataract of old age and is therefore rare.Another risk factor for cataracts seems to be Down’s syndrome. Because about 50% of trisomy 21 patients also suffer from cataracts.
Internal and external causes
In addition, there are drugs that can trigger cataracts, such as cortisone. Cataracts are caused by many years of taking cortisone or medicines containing cortisone. With Kortison induced grey cataract it comes to a clouding of the rear lens bowl.
This is caused by infections during pregnancy such as rubella or mumps. The congenital cataract can also be caused by a hereditary disease. These include myotonic dystrophy, neurofibromatosis 2 and galactosemia.
Congenital cataracts are present in less than one percent of newborns. If the cataract already exists at birth or until the eighth week of life, it is a congenital cataract. If a cataract occurs between the ninth week of life and the sixth year of life, it is a juvenile cataract.