Cataract (gray star)

A cataract (gray star) gradually turns the lens of the eye cloudy. The sight of sufferers becomes increasingly blurred, as if looking through a veil or fog. Sometimes the person's sight is only slightly affected, while in other people the deterioration is worse. In the long term, only an operation will help.

At a glance

  • A cataract, also known as gray star, is an eye disease in which the lens of the eye becomes clouded.
  • The sight of sufferers becomes increasingly blurred, as if looking through a veil or fog.
  • Sometimes the person's sight is only slightly affected, while in other people the deterioration is worse.
  • Cataracts usually occur in the over-50s.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

What is a cataract?

A cataract is an eye disease in which the lens of the eye becomes clouded. This impairs the sufferer's vision. Then detail, in particular, can no longer be seen clearly. An older popular term for cataract is “gray star”.

The disease is called “gray star” because the lens is gray and those affected more severely often develop a stare. However, vision is only slightly affected in some people with a cataract. In others the impairment is worse and they lose their sight quickly. How the disease progresses depends, for one thing, on the type of cataract.

Cataracts usually occurs in the second half of a person's life. It is usually over-50s who get it. The risk increases over time: around 20 of every 100 people aged between 65 and 74 are affected. In the case of over-74s the figure is over half.

People over 50 are most likely to have a cataract.

Cataracts are the main cause of blindness in developing countries. In industrialized countries far fewer people go blind as operations can often save the person's sight here. In this procedure, the clouded lens is removed and replaced by an artificial one.

What are the symptoms of a cataract?

With a cataract, the person's vision gradually disappears. Creeping sight loss is the only symptom: there are no other ill effects. The sight of people with a cataract is always more blurred and less clear, as if looking through a veil or fog. Over time, images lose their contrast and colors fade. Some sufferers develop great sensitivity to glaring light, for example from the sun or other bright light sources. Driving also becomes more troublesome, especially at night. The impaired vision increases the risk of falling and injury. The person's spacial vision also declines.

A cataract sometimes also has unexpected effects: some spectacle wearers suddenly see better without their glasses. This is because the disease changes the focal power of the eye and, thus, the ability to clearly see things that are at different distances. However, this effect does not last long.

What causes a cataract?

Around 90 percent of all those affected suffer from age-related cataracts. Doctors then speak of a senile cataract. The reason for the gradual clouding of the lens of the eye in these cases is the aging process. The lens normally bundles the incoming light and provides a clear image on the retina – both near and distant objects then appear sharp. With a cataract the function of the lens is impaired.

In some people the risk of suffering from a cataract is greater for hereditary reasons. The disease is very rarely congenital. It may be, for example, that a child is born with a cataract when the mother has been infected with measles or rubella during pregnancy.

Faktoren, die das Risiko erhöhen können, an einem Grauen Star (Katerakt) zu erkranken, sind Unterernährung, das Alter, eine Entzündung oder ein verletztes Auge, Medikamente, Rauchen, Diabetes und UV-Licht.

There is evidence that certain factors can increase the risk of cataracts These include, for example, UV light and X-rays, but also smoking. Diabetes sufferers are also affected more often.

The disease can also be the consequence of eye inflammations or eye injuries. Eye operations can also result in a cataract. The same applies to certain medications, for example cortisone, if it is used for lengthy periods.

How does a cataract develop?

The sight of a person who gets a cataract gets gradually worse. The impairments initially show up as short-sightedness. Then people who used to be far-sighted (hyperopic) spectacle wearers can briefly see better without glasses. As the disease progresses, the sight of sufferers becomes increasingly clouded and blurred. If left untreated, a cataract can lead to blindness. However this does not need to be so. Both eyes are usually affected. However, a cataract can progress more rapidly in one eye than the other.

Cataracts can progress in different ways. Some sufferers lose their vision quite quickly. Others find that their sight is hardly affected at all. A distinction is drawn between the following types:

  • Cortical cataract: someone affected by this type does not just have blurred vision, but also reacts more sensitively to glaring light, for example when driving at night.
  • Posterior subcapsular cataract: this type more frequently affects younger people. It progresses relatively quickly.
  • Nuclear sclerotic cataract: the far-sightedness of people with a nuclear sclerotic cataract is more impaired than their near vision. Sometimes the person's vision is only slightly impaired. This type of cataract only deteriorates rather slowly.

Can a cataract be prevented?

There is no scientific evidence to show that particular preventive measures reduce the risk of a cataract. It is thought that smoking increases the risk. If the person stops smoking, the risk could fall back again. Rays such as UV light could also possibly help a cataract occur. People who are exposed to UV light can ensure they have good sun protection and protect their eyes from solar radiation, for example with sunglasses. Certain medications containing cortisone can also increase the risk of a cataract. A person using this type of product can check whether they can switch to another medication.

The advertising for some dietary supplements claims that they can prevent eye diseases. However, studies show that these dietary supplements have no effect on cataracts.

How is a cataract diagnosed?

If a person's sight deteriorates, there may be a number of reasons. So to diagnose a cataract the eye specialist will first exclude other possible causes. To do this the patient will be asked about their symptoms and their medical history. Eye tests and eye examinations are used to determine how badly the vision is affected and what the cause could be.

The examination also involves assessing the lens of the eye with a slit lamp. With this special light microscope the specialist can see into the eye. It involves lighting up the eye with a slit-shaped beam of light so that the specialist can assess the lens and the sections of the eye behind it. This examination is pain-free.

To have the rear sections of the eye examined, patients usually take a drug which dilates the pupils. This drug can cause the person to see less clearly and be more easily dazzled for a couple of hours. So driving should be avoided for around four to five hours. However, the drug's effects sometimes last longer: so in case of doubt, it is better to avoid driving.

How is a cataract treated?

Some people with a cataract can compensate for their impaired vision for some time, or even over the long term, by wearing glasses or contact lenses. Cataracts cannot be treated with medication.

The only effective treatment option is an operation. In this procedure, the clouded lens is removed and replaced by an artificial lens.

Whether and when an operation is a good idea depends very much on how badly the loss of vision affects the sufferer's life. Another factor is whether someone has other (eye) diseases that could affect the operation.

For more information, for example on the operation for a cataract, go to

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen) (IQWiG).

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