• Clinical science



Cataract is a condition characterized by clouding of the lens of the eye. This condition most frequently occurs due to age-related degenerative processes in the lens, but can also be associated with ocular trauma, metabolic disorders, side-effects of drugs, or congenital infections. The clouding causes distortion of light, as it passes through the lens, resulting in visual impairment and glare. Initially, a cataract presents discretely and may even go unnoticed, but the visual impairment worsens as the cataract grows larger. Diagnosis is typically established on the basis of a thorough history and direct visualization of the cataract (by means of slit-lamp microscopy). Surgery is indicated with significant visual impairment and involves lens extraction and implantation of an artificial lens. Untreated cataracts eventually lead to complete blindness.


  • Leading cause of visual impairment and blindness in the world
  • Prevalence of acquired cataracts
    • Increases with age
      • 40–80 years: ∼ 17.5 %
      • > 80 years: ∼70 %
    • Sex: >


Epidemiological data refers to the US, unless otherwise specified.


Clouding of the lens may be congenital or acquired.

In industrialized countries, cataract is typically age-related! Other causes are rare!


Clinical features

General clinical features

Clinical features usually develop gradually and depend on the localization and cause(s) of corneal clouding.

  • Reduced visual acuity: blurred, clouded, or dim vision, especially at night
  • The impairment of vision is usually painless and often bilateral.
  • Glare: in daylight, in low sunlight, and from car headlights; associated with halos around lights .
  • Second sight
    • A temporary improvement in near vision
    • Myopia (in nuclear cataract) improves presbyopia
  • Opacities within the red reflex, darkening of the red reflex, or obscuration of ocular fundus detail during opthalmoscopy
  • Grey, white, yellow, or brownish clouding of the lens
  • Monocular diplopia: double vision that disappears when the eye with the pathology is covered or shut

Special features in congenital cataract

Congenital cataracts usually present with different symptoms than acquired cataracts.



  • Primarily a clinical diagnosis



  • In most cases conservative treatment and drug therapy for cataract does not exist
  • Indications for surgical treatment
    • To improve vision in cases with significant cataract-related visual disturbances (by far the most frequent indication)
    • Medical indication (e.g., imminent phacolytic glaucoma, or in ocular fundus diseases in order to gain clear insight of the ocular fundus)
  • Surgical techniques

Cataract surgery does not require any anticoagulative measures!

Congenital cataracts should be treated surgically as soon as possible to prevent amblyopia (deprivation amblyopia)!



  • Blindness
  • Complications after cataract surgery are rare

We list the most important complications. The selection is not exhaustive.