Cataracts – when the lens becomes cloudy

Cataracts are one of the most common eye diseases worldwide and are often caused by a natural ageing process.

Natural ageing

In some 90% of cases, the disease is caused by a natural ageing process: over the years, the lens of the eye loses its flexibility, causing it to become cloudy. These age-related cataracts will therefore affect practically everybody at some point in their life.

Diabetes

In people with diabetes, cataracts can be caused by poorly managed blood sugar levels. This is because diabetes leads to a high level of sugar not only in the blood but also in the aqueous humour within the eye. If sugar is deposited in the lens, it can cause it to swell up. This displaces the lens fibres and causes the lens to become cloudy. In the case of pregnant women with diabetes, cataracts can even develop in the unborn child.

Eye injuries

Cataracts can be caused by blows and puncture injuries to the eye, as well as by deeply penetrating foreign bodies or injuries due to high-voltage current.

Medications

Long-term and high-dose use of certain medications, such as cortisone, can also cause the lens to become cloudy.

Nutrient deficiencies

Undernourishment and malnutrition can also be responsible for cataracts. This is a particular problem in developing countries.

Congenital cataracts

It is rare for a baby to enter the world with cataracts. This can happen as a result of a genetic defect, the consumption of alcohol during pregnancy or a disease affecting the expectant mother. For example, if a pregnant woman is infected with rubella or herpes or suffers from diabetes, the unborn child may develop cataracts while still in the womb.

Further risk factors

The development of cataracts can be encouraged by UV, infrared or X-rays and by various metabolic disorders, such as an overactive thyroid (hyperthyroidism) or galactosaemia (a disorder affecting the metabolism of galactose, a sugar found in breast milk). Other triggers include serious short-sightedness and inflammation of the eyes. Smoking also increases the risk of developing cataracts. Moreover, a genetic predisposition also plays a role in some individuals.

When the lens becomes cloudy, it is no longer possible for sufficient light to reach the retina, and the small amount of light that does pass through the lens is scattered. This not only causes the person’s vision to become blurred and indistinct, but also reduces their perception of contrast. Colours appear paler, and sufferers become increasingly sensitive to light, for example when exposed to bright sunlight or car headlights. At an advanced stage, cataracts are visible as a grey clouding of the pupils.

The cloudy lens must be surgically replaced with an artificial lens. This operation takes about 20 to 30 minutes and is generally performed as an outpatient procedure under local anaesthetic. During the operation, a device known as an eyelid retractor holds the eye open. A small primary incision (2.5 mm) and two small auxiliary incisions (1 mm each) are made at the edge of the cornea in order to insert the microinstruments for breaking up the cloudy lens and sucking out the fragments. Once the lens capsule has been completely cleaned out, the artificial lens is implanted at the location from which the natural lens was removed.

The cloudier the natural lens, the harder it becomes – and the harder it becomes, the more difficult it can be to remove. However, because every operation carries a certain degree of risk, surgery should not be performed too early. The level of visual impairment ultimately determines when the operation is performed. There is generally no time pressure.