Overview

• Leading cause of visual impairment and blindness in the world

• Prevalence of acquired cataracts: increases with age

  • > 80 years: ∼70 %

  • 40–80 years: ∼17.5 %

• Sex: ♀ > ♂

• Age-related cataract (> 90%)

• As a result of ocular diseases (complicated cataract)

  • Diabetes mellitus

  • Renal insufficiency (dialysis)

  • Wilson disease

  • Vitreoretinal diseases

  • Retinitis pigmentosa

  • Acute glaucoma

  • Previous retinal detachment

  • Chronic uveitis

  • Heterochromia

• After intraocular surgeries

  • After vitrectomy (especially after silicone oil is inserted)

  • After filtration surgery in glaucoma

• Drug-induced

  • Glucocorticoids (local and systemic)

  • Miotics (cholinesterase inhibitors)

• Chronic alcohol and tobacco use

• Traumatic (traumatic cataract)

  • Bruise injuries (contusion cataract)

  • Perforation injuries

• Eye infections

• Physically related conditions

  • Radiation (x-ray, radioactive radiation)

  • Excessive sunlight or UVB exposure

  • High-voltage current, lightning

  • Infrared radiation (glassblower's and glass worker's cataract)

• Posterior capsule opacification (PCO; or secondary cataract): clouding of capsule sections after extracapsular cataract extraction

• Hereditary congenital cataracts

• Caused by TORCH infections (esp., rubella)

• Associated with the following comorbidities/syndromes:

  • Galactosemia

  • Tetany (hypocalcemia)

  • Myotonic dystrophy

  • Skin diseases

  • Trisomy 21 (in early childhood)

  • Trisomy 13

  • Trisomy 18

  • Alport syndrome

  • Neurofibromatosis type 2

  • Galactokinase deficiency

  • Marfan syndrome

Cataracts are generally classified according to etiology (as above). Age-related cataracts can also be classified according to where they form in the lens (morphology) or how advanced they are.

• Morphological types

  • Cortical cataract (anterior/posterior): the most common type of cataract; characteristically originates at the outer layer of the lens and grows towards the center, forming a wedge-shaped opacity

  • Nuclear cataract: a type of cataract that affects the center of the lens, appearing as a yellow-brown discoloration of this area

  • Subcapsular cataract (anterior/posterior): a type of cataract that manifests directly under the lens capsule; usually in the posterior lens (rapidly progressive) but can also occur in the anterior lens

• Stages of progression

  • Immature cataract

    • Early stage of cataract progression

    • Red reflex is still present, allowing for visualization of the retina.

  • Mature cataract

    • Advanced stage in cataract progression

    • Red reflex is absent.

    • There is a white-yellow discoloration of the lens due to complete clouding.

    • Vision can be reduced to mere light perception.

  • Hypermature cataract

    • End stage of cataract progression

    • There is a complete white clouding of the lens due to liquification of the cortex.

    • The nucleus often sinks in the cortex and appears brown.