• Clinical science

Cataract

Abstract

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.

Epidemiology

  • 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: >

References:[1][2][3][4]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Clouding of the lens may be congenital or acquired.

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

References:[5][6][7]

Classification

  • Cataracts may be classified according to etiology (as above) or morphology
  • Morphological classification .
    • Anterior/posterior cortical cataract (approx. 50%) :
    • Nuclear cataract (approx. 30%) :
    • Anterior/posterior subcapsular cataract (approx. 20%)
    • Mature senile cataract
    • Hypermature cataract

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
  • 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
  • Hyperopia (in cortical cataract)
  • Change in color perception
  • Special features in traumatic cataract
    • In bulb contusion: anterior rosette-shaped clouding of the lens (contusion cataract)
    • In perforated lens injuries: posterior rosette-shaped clouding of the lens

Special features in congenital cataract

Congenital cataracts usually present with different symptoms than acquired cataracts.

References:[5][1][6][7]

Subtypes and variants

There are different stages of senile cataract:

  • Incipient cataract
  • Intumescent cataract
  • Immature cataract
  • Mature/hypermature cataract
  • Special type: Morganian cataract

Diagnostics

  • Primarily a clinical diagnosis
  • Ocular imaging studies: ultrasonography, computed tomography (CT) scanning, or MRI

References:[1]

Treatment

  • 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
    • Extracapsular cataract extraction (ECCE)
      • Method of choice globally
      • Removal of the lens nucleus by anterior capsulotomy (a surgical opening in the anterior capsule) with retention of posterior capsular integrity, and placement of the intra-ocular lens (IOL) in the posterior chamber.
      • Removal of the lens nucleus in ECCE can be performed manually in standard surgical ECCE or by phacoemulsification:
    • Intracapsular cataract extraction (ICCE, former method of choice):
      • Involves removal of the entire lens, including the posterior capsule. The IOL is implanted in the anterior chamber, sutured to the iris, or surgically fixated in the posterior chamber.
      • More invasive procedure (requires a larger incision) associated with high rate of complications like delayed wound healing, corneal edema, iris incarceration, etc.
      • Can be performed in cases with subluxated or luxated lenses (posttraumatic and hypermature cataracts) or if advanced surgical equipment is unavailable.

Cataract surgery does not require any anticoagulative measures!

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

References:[1][7][8]

Complications

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