Last reviewed 01/2018

Cataract is defined as an opacity of the crystalline lens of the eye or its capsule, resulting in changes of the transparency and refractive index of the lens (1).

  • person’s vision may become blurred or cloudy and may experience problems with glare from the sun or other bright lights (2)
  • variations in the refractive index can be due to changes in lens cell structure or changes in lens protein constituents (high-molecular-weight protein aggregates) or both (1)

Immature cataracts are defined as cataracts through which a red reflex can still be seen.

Mature cataract have obscured red reflex and often are associated with weakness of the suspensory ligament of the lens.

Hypermature cataracts have leaked protein as a result of the action of endopeptidases, resulting in a wrinkled lens. This sort of lens ought to be removed before it causes a lens-induced uveitis or glaucoma.

Cataracts can be divided according to the segment of the lens that is affected:

  • nuclear cataract
  • cortical cataract 
  • subcapsular cataract (3)

Cataracts (4):

  • most commonly affect adults as a result of biological ageing (age-related cataracts)

  • can also occur in children, and may be classified according to the age of onset (congenital or infantile/juvenile cataracts)

  • may occur secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, and exposure to radiation

  • lifestyle factors such as tobacco smoking and high alcohol intake are associated with an increased risk of developing age-related cataracts

  • most cataracts are progressive, although the decline in visual function may be variable and unpredictable. The natural history of cataracts depends on the type and severity of the cataract and the presence of comorbid ocular conditions. In severe, untreated cases, cataracts can lead to significant reduction in vision, which is reversible with cataract surgery, although some level of visual impairment may persist

  • cataract surgery has a high success rate in improving visual function, with low morbidity and mortality. It is the most common operation performed in the NHS, with an ever growing need as the population ages.