Cataract: Causes

Pathogenesis (development of disease)

Cataract (cataracta senilis) develops due to aging processes by slowing down the metabolism of the lens. This causes the lens to become cloudy.Genetic factors are also thought to influence the development of a cataract.

Etiology (Causes)

Biographic causes

• Genetic burden
  • By parents, grandparents: cataract is usually inherited in an autosomal dominant manner. This means that the offspring of a cataract patient will also be affected during their lifetime with a probability of 50%.
  • Genetic diseases
    • Congenital (congenital) cataract – due to intrauterine rubella infection or hereditary, e.g., myotonic dystrophy type I + II (autosomal dominant), neurofibromatosis type 2 (autosomal dominant), galactosemia (autosomal recessive; see below) [frequency: twice per 10,000 births].
    • Trisomy 21 (Down syndrome; mode of inheritance: mostly sporadic) – special genomic mutation in humans in which the entire 21st chromosome or parts of it are present in triplicate (trisomy). In addition to physical features considered typical for this syndrome, the cognitive abilities of the affected person are usually impaired; about half of those affected develop a cataract
• Age – increasing age (> 60 years): Cataracta senilis.
• Juvenile cataract (developmental cataract).

Behavioral causes

• Nutrition
  • Micronutrient deficiency (vital substances) – the eye lens of healthy patients shows significantly lower concentration of ascorbic acid compared to patients with cataract. In the eye, constant contact with sunlight produces free radicals, which are neutralized by ascorbic acid, preventing oxidation of sensitive proteins. Supplementation of 300-600 mg of vitamin C per day reduces the risk of cataract by a factor of four – see Prevention with micronutrients.
• Consumption of stimulants
  • Tobacco (smoking)
• Physical activity
  • Physical inactivity – Study participants with highest physical activity had 13% lower risk of cataract compared with the most physically inactive quartile (OR/odds ratio of cataract development: 0.87)
• Overweight (BMI ≥ 25; obesity) – the RR (relative risk) for age-related cataracts for overweight and obese adults, respectively, was 1.08 and 1.19

Disease-related causes

• Complication of other eye diseases – e.g. CMV retinitis (retinal inflammation caused by cytomegalovirus), glaucoma (glaucoma), iridocyclitis (inflammation of iris and ciliary body), uveitis (inflammation of the middle eye skin, which consists of the choroid (choroid), ray body (corpus ciliare) and iris).
• Metabolic diseases
  • Diabetes mellitus (so-called cataracta diabetica).
  • Galactosemia (see below “Genetic diseases”) – if this is not treated from childhood by galactose-free diet, a cataract can develop
  • Hypothyroidism (hypothyroidism).
• Injuries to the eyeball – e.g., contusio bulbi, eyeball perforation.

Laboratory diagnoses – laboratory parameters that are considered independent risk factors.

• Hypocalcemia (calcium deficiency) – so-called cataracta tetanica.

Medication

• Glucocorticoids – drugs such as cortisone that are prescribed for allergic reactions and various inflammations.
• Monoclonal antibodies
  • IgG2 anti-RANKL antibody (denosumab).

Environmental exposure – intoxications (poisonings).

• Exposure to electromagnetic energy
• Exposure to radiation – radiation cataract, e.g.
  • Intense solar radiation (UV-A, UV-B, infrared radiation) or infrared radiation – e.g., glass blowers.
  • X-rays – e.g. doctors in the cardiac catheterization laboratory.
• Thermal influences – fire star (infrared radiation).

Other causes

• Foreign body or external injury to the lens of the eye