International Classification (ICD) H26.-
Symptoms Decreasing eyesight, impaired spatial vision
Possible causes age-related change of the eye lens, Eye injuries, Congenital malformation, Increased sugar content in the aqueous humor, Chronic inflammation, Radioactivity, UV light, Poisoning, Medication, Malnutrition
Possible risk factors Metabolic disorder, diabetes mellitus


A cataract is a clouding of the lens of the eye. This clouding has the consequence that the affected eye loses more and more visual acuity. People who suffer from a cataract feel as if they are seeing the world through a grey veil that becomes thicker over time.

Often, the clouding of the lens is caused by aging of the eye's lenses - this form is called cataracts and most often occurs after the age of sixty. However, a cataract can also be caused by other factors, such as clouding of the lens of the eye due to eye injuries, eye diseases or as a result of diabetes mellitus (diabetes).

The name "cataract" comes from the Greek and means "waterfall". This name is based on the earlier assumption that the gray haze in the pupil is caused by a clotted fluid. The colloquial name "cataract" originates from the fixed gaze that people develop who are completely blinded by cataracts.

Cataracts affect a large number of people in older age. Surgical treatment is now a routine procedure and is performed frequently.


The most common cause of cataracts is age-related changes in the lens of the eye. In young people, the lens is transparent, soft and flexible. The flexibility ensures that the lens can be adjusted by the eye muscles to provide a sharp image when looking at both near and far objects. The light transmission and flexibility of the lens of the eye is affected by the internal lens fluid. As we age, the composition of this fluid changes. The volume of fluid also increases. As a result, the lens becomes increasingly cloudy and a cataract develops.

In addition to age-related cataracts, there are numerous other triggers, but they occur far less frequently:

  • Cataracta traumatica: eye injuries such as a bruise to the eyeball (from a punch, tennis ball) or stab wounds.
  • Cataracta congenita: congenital eye malformations, for example caused by infections during pregnancy (toxoplasmosis, rubella)
  • Cataracta diabetica: due to an increased sugar content in the aqueous humor, glucose is deposited in the lens, causing lens swelling - this shifts the arrangement of the lens fibers, resulting in lens opacification.
  • Cataracta complicata: lens clouding as a result of chronic inflammation of the interior of the eye.
  • Defects in lens metabolism, UV light, radioactive radiation and malnutrition
  • Medication or poisoning


A cataract is noticeable to those affected by the fact that the ability to see decreases visibly over time. Contrast and colour intensity fade, so that the environment is perceived "as if in a fog". Often the eye reacts very sensitively to light, so that people feel easily dazzled. It also takes longer than usual for the eyes to adjust to brightness or darkness. Sufferers lose spatial vision over time - some sufferers also see double images.

In the final phase of cataracts, vision is reduced to such an extent that the patient virtually goes blind. The clouding of the lens is now even visible to other people from the outside as a grey colouring of the eye.

In the congenital form of cataracts, the development of vision is impaired. In addition, the eyes often adopt a squinting position. Cataract disease does not cause pain.


An initial suspected diagnosis of cataract can be confirmed by the Brückner test. In this test, the eye is illuminated by the ophthalmologist with light - part of the light is normally reflected back evenly from the retina, whereby lens opacities appear as dark spots.

By examining the lens with a slit lamp (a special microscope for the eyes), it is possible to estimate which layer of the lens is affected by the opacity. This may help to determine what form of cataract is present and what may be causing it.

However, since a cataract can also be the first sign of another disease, additional examinations of the skin, blood, and muscles are performed, especially in younger people with cataracts. In this way, other underlying diseases such as diabetes mellitus, tetany (abnormal muscle cramps), galactosemia (galactose intolerance) or Wilson's disease (copper storage disease) can be detected or ruled out.


A cataract can only be corrected with the help of a surgical correction. Cataract surgery is one of the most common surgical procedures and can usually be performed on an outpatient basis. There are no medications for cataracts.

Whether an operation should be carried out depends primarily on the extent to which the person affected is restricted in their everyday life by their reduced visual acuity. In case of additional eye diseases (for example optic nerve or retinal diseases) it has to be clarified whether a good visual acuity can be restored despite a successful cataract operation. Many people also decide against cataract surgery at first because of fear of eye surgery in case of mild symptoms.

If the cataract is very advanced, it must be surgically corrected even if there is no prospect of better vision, because in some cases the swelling of the lens increases very quickly. This can cause the lens capsule to tear, causing lens protein to leak out and triggering an inflammation of the eye (panophthalmitis) with increased eye pressure and severe pain.

Procedure of the operation

The principle of surgical treatment of cataracts is to remove the clouded lens and insert an artificial lens instead. In contrast to the surgical technique used in the past, nowadays the entire lens is no longer removed, but the lateral and posterior lens capsule is left in the eye. The new artificial lens must have exactly the same refractive power as the original lens. Using an ultrasound device, the length of the eye and the refractive power of the cornea can be measured, which allows the lens power to be calculated.

If both eyes are affected by a cataract, only one eye is operated on at a time. The second operation is only performed once the other eye that has already been operated on has completely healed. The operation usually takes about half an hour.

In most cases, cataract surgery is performed under local anesthesia. Anesthetics in the form of eye drops are usually used. If the entire eye must be anesthetized and immobilized, an anesthetic can alternatively be injected next to the eye.

The most common procedure today is phacoemulsification. In this procedure, an incision about three millimeters long is made in the cornea, through which the lens nucleus is crushed using an ultrasound device and then suctioned out. The capsular bag of the original lens, however, remains intact - the new artificial lens is now inserted into it. Modern artificial lenses are usually made of elastic materials, which allows them to be rolled up and inserted through the small incision into the capsular bag, where they then unfold. The new lens is automatically centered and secured with the help of two elastic stirrups. The incision usually closes by itself and heals without scarring.

If the cataract is already at a very advanced stage, it may no longer be possible to shatter the lens using an ultrasound device. In these cases, the procedure of nucleus expression is used. In this procedure, the entire lens is removed through an incision about ten millimeters long and replaced by an artificial lens. This is then fixed by the surgeon with very fine sutures.


In the period after the operation, the treated eye is covered with an ointment bandage for better healing. Care must be taken that no soap gets into the eye when showering or washing. In addition, physical exertion must be avoided during the healing process, as well as sports and sauna visits. Reading is possible again about one week after the operation. About six weeks after the operation, a new pair of glasses can be fitted by an optician.

Lens types

After cataract surgery, the artificial lens remains in the eye for the rest of the patient's life - it does not need to be removed or replaced at a later date. Lenses made of different materials are available (e.g. silicones, acrylates), which can be adapted to a certain refractive power of the eye. Before the operation, the patient must decide whether he or she wants to see clearly at a distance or close up - depending on this, "distance glasses" must be used after the operation, but not "reading glasses", or vice versa.

Certain artificial lenses can also be used, which are similar in function to varifocals or multifocals. These ensure good visual acuity both at distance and at near. The disadvantage, however, is that contrast vision may be reduced and there may be more glare (especially at night).

Until recently, hard artificial lenses were the standard in cataract treatment, but nowadays they are hardly ever used.

Surgical risks

Since cataract surgery is one of the most common surgical procedures, complications occur only in rare cases. Nevertheless, as with any surgery, there are risks in general.

If the posterior capsule of the lens tears during the procedure, complications can result. Between the lens capsule and the retina lies the vitreous body (corpus vitreum), which consists of a transparent, gel-like mass. This presses the retina onto its support. If the posterior lens capsule tears, vitreous substance can escape through the tear, which in the worst case can lead to detachment of the retina.

In very rare cases, germs enter the eye during cataract surgery, causing a bacterial inflammation (endophthalmitis). This can lead to blindness of the affected eye.

As a consequence of the surgical removal of the cataract, a so-called secondary cataract may develop. In this case, a clouding of the posterior lens capsule develops over time. While this complication used to occur in up to 50 percent of patients, modern surgical techniques have now reduced the risk to about four percent. By means of a laser, the post-cataract opacity can be removed on an outpatient basis and painlessly, without the need for another operation. The laser treatment immediately restores full vision.


If left untreated, cataract vision deteriorates visibly due to the clouding of the lens and can even lead to complete blindness.

However, cataracts can usually be corrected by surgery, which restores full visual acuity. In most cases, patients can see significantly better after surgery than before. If the cataract is caused by other eye diseases, such as glaucoma, diabetic retinopathy or age-related macular degeneration, the prognosis is much worse.

Editorial principles

All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.
Danilo Glisic

Danilo Glisic

As a biology and mathematics student, he is passionate about writing magazine articles on current medical topics. Due to his affinity for facts, figures and data, his focus is on describing relevant clinical trial results.

The content of this page is an automated and high-quality translation from DeepL. You can find the original content in German here.



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