What is cataract?

The crystalline lens in the human eye is situated behind the pupil. Its function is to focus light on the retina so that images can be seen clearly. The optic nerve then carries the images to the brain.
When cataract is present the crystalline lens becomes opaque and images are blurred.



The most frequent cause of cataract is the ageing process. The normal protein structure of the crystalline lens is altered thereby and it becomes opaque. Most cataract patients are aged over 60 years.

In 5 % of cases, cataract has some other cause:

  • metabolic diseases such as diabetes
  • eye diseases such as glaucoma or ocular inflammatory diseases (iritis, etc.)
  • extended use of certain types of medication such as cortisone
  • heredity
  • traumas such as a blow on the eye or irradiation.


The way in which cataract affects the daily life of patients can vary, as can the speed at which it develops. One eye may be affected more than the other.
Initially it may be possible to correct changes in vision by adapting the patient’s spectacles. In some cases reading ability may improve while distance vision deteriorates. In other cases double vision develops. Often patients become more sensitive to light, at night spotlights become starry and driving may become dangerous.
In a later stage a cataract patient’s vision may become cloudy, as if looking through a waterfall ! – whence the name “cataract”.


This is made by the ophthalmologist after thorough examination of the eye, using a slitlamp microscope and other diagnostic equipment, to ascertain whether cataract is the cause of the diminishing vision and that no other diseases are involved.

Read all about cataract in our brochure

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