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Cataract

Basics

  • Lens opacity or discoloration that impairs vision.
  • Leading cause of blindness worldwide (~20 million affected).
  • Types:
  • Age-related (90% of cases)
  • Metabolic (e.g., diabetes, hypocalcemia, Wilson disease)
  • Congenital (1 in 250 newborns; 10-38% childhood blindness)
  • Secondary/complicated (uveitis, tumors)
  • Traumatic (heat, radiation, injury)

  • Toxic/nutritional (corticosteroids)

  • Morphologic types:

  • Nuclear: central hardening; may cause myopia ("second sight").
  • Cortical: radial, spoke-like outer lens opacities.

  • Subcapsular: posterior location with greater visual impact.

  • Affects nervous system function (vision).

Epidemiology

  • Age-related cataracts prevalent in 50% of ages 65-74; 70% over 75.
  • Major cause of treatable blindness globally.

Etiology and Pathophysiology

  • Aging causes lens fiber layer addition and dehydration → opacity.
  • Biochemical/osmotic imbalances disrupt lens clarity.
  • Congenital causes include metabolic disorders, infections, drugs, and genetics.

Risk Factors

  • Aging
  • Smoking
  • UV exposure
  • Diabetes
  • High-dose steroids
  • Family history
  • Alcohol

Prevention

  • UV protective eyewear
  • Smoking cessation
  • Good diabetic control
  • Caution with long-term high-dose steroids

Associated Conditions

  • Diabetes, myotonic dystrophy, atopic dermatitis, neurofibromatosis type 2
  • Secondary cataracts from eye diseases, trauma, drugs

Diagnosis

History

  • Visual acuity decline: blurred vision, distortion, ghosting.
  • Congenital cataracts present with leukocoria, strabismus.

Physical Exam

  • Visual acuity testing
  • Lens opacity on slit-lamp exam
  • Glare and contrast sensitivity testing

Differential Diagnosis

  • Corneal opacities, tumors, retinal detachment.
  • Other causes of vision loss (macular degeneration).

Diagnostic Tests

  • Optical biometry and corneal topography for surgical planning.

Treatment

  • Surgical extraction indicated if vision impairment affects lifestyle or safety.
  • Surgery usually via phacoemulsification with intraocular lens implant.
  • Laser-assisted cataract surgery available.
  • Congenital cataracts require early surgery and amblyopia treatment.

Ongoing Care

  • Postoperative care includes eye protection, topical antibiotics, NSAIDs, steroids.
  • Refractive correction after surgery as needed.

Prognosis

  • Good visual outcomes in healthy eyes (94% achieve 20/40 or better).
  • Posterior capsular opacification common post-op, treated with Nd:YAG laser.
  • Congenital cataracts have poorer prognosis due to amblyopia risk.

Complications

  • Posterior capsular rupture (rare but significant)
  • Visual discomfort, delayed recovery, blindness (rare)

Clinical Pearls

  • Cataracts are the leading cause of blindness worldwide.
  • Visual impairment and lifestyle impact guide surgical timing.
  • Rule out ocular tumors in congenital cataracts (retinoblastoma).

References

  1. Asbell PA, Dualan I, Mindel J, et al. Age-related cataract. Lancet. 2005;365(9459):599-609.
  2. Riaz Y, Mehta JS, Wormald R, et al. Surgical interventions for age-related cataract. Cochrane Database Syst Rev. 2006;(4):CD001323.
  3. Kolb CM, Shajari M, Mathys L, et al. Comparison of femtosecond laser-assisted cataract surgery and conventional cataract surgery: meta-analysis. J Cataract Refract Surg. 2020;46(8):1075-1085.
  4. Biber JM, Sandoval HP, Trivedi RH, et al. Posterior capsule opacification: incidence and significance. J Cataract Refract Surg. 2009;35(7):1234-1238.
  5. Lundström M, Barry P, Henry Y, et al. Visual outcome of cataract surgery: European Registry study. J Cataract Refract Surg. 2013;39(5):673-679.