Cataract is the term used to describe any form of clouding of the lens of the eye. About 17 million people worldwide suffer from cataracts–that’s about half of all people with low vision. Cataract is by far the most common cause of vision loss. Every year, there are about 150,000 operations in Germany due to cataracts. Cataracta senilis (senile cataract) is the most common form of the disease, accounting for about 90%. There are two main forms of senile cataract – cortical cataract and nuclear cataract. The crystalline lens consists of two components – cortex and nucleus. Consequently, in cortical cataract, the outer part of the lens, the cortex, is affected by the clouding. This leads to problems with both near and distance vision. With nuclear cataract, on the other hand, myopia often develops, which limits distance vision much more than near vision. There are different stages of cataract, which gradually merge into one another:
- Incipient cataract – minor clouding of the lens.
- Advanced cataract – significant opacity of the lens.
- Premature cataract – far advanced lens opacity.
- Maturer (mature) cataract – both the lens cortex, but more so the nucleus are opacified.
- Hypermature (overripe) cataract – the soft lens cortex material is absorbed, the lens capsule is shrunken; risk of phacolytic glaucoma (glaucoma).
Risk factors
Regular examinations for early detection of cataract should be performed if one or more of the following risk factors are present.
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), the ray body (corpus ciliare) and the 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.
Diagnostics
For the diagnosis of cataracts, a so-called slit lamp is used. If necessary, mydriasis (dilation of the pupil) is also performed by prior administration of special eye drops. In this way, the doctor is able to observe and analyze the lens of the eye in detail, and the diagnosis can be made in a simple way.
Benefit
Regular cataract screening examinations every 2 years between the ages of 40 and 50, and annually after the age of 50, are necessary to diagnose cataract early. Your eyesight is one of the most precious things you have. Help keep your eyes healthy for as long as possible by getting regular preventive care.
