cataracts

Introduction

An opacity of the crystalline lens of the eye; a loss of transparency of the lens of the eye or of its capsule.

Etiology

(risk factors)

• aging
• systemic disorders
  • diabetes mellitus
  • hypoparathyroidism
  • hypothyroidism
  • obesity
• genetic abnormalities
• trauma
• pharmacologic causes:
  • busulfan
  • chlorambucil
  • glucocorticoids
  • phenothiazines
  • phospholine iodide
• environmental
  • diets low in antioxidants
  • smoking
  • UV radiation/sunlight
  • ethanol

Epidemiology

• 45-60% of individuals > 75 years of age
  • prevalence may approach 100% in persons age > 90
• most common cause of reversible blindness in USA
• 2nd most common cause of blindness in USA
• among older diabetics, more common cause of visual disability than diabetic retinopathy
• cataract extraction is the most frequently performed surgical intervention on the Medicare population
• more common among persons with lower education & socioeconomic class

Pathology

• damage to the major lens crystallin proteins causes their misfolding & aggregation into insoluble amyloids resulting in opacification of the crystalline lens

Genetics

• defects in CHMP4B associated with autosomal dominant cataract posterior polar type 3

Clinical manifestations

• diminished vision in one or both eyes
• lenticular opacities
• glare sensitivity, halos around lights
• generalized blurry vision
• diminished ability to see objects in dim light (contrast sensitivity)
• increased difficulty with driving at night
• myopic shift in eyeglass prescription
  • need for reading glasses diminished

Laboratory

• ophthalmoscopy - reduction in the red reflex
• slit-lamp examination
• lenticular opacities may be observed with 1 & 2

Complications

• older drivers with cataracts were 2.5 times more likely to have a history of at fault motor vehicle accidents
• angle closure glaucoma
  • cataracts can displace the iris forward, narrowing the angle
• glaucoma, cataracts, & age-related macular degeneration may increase risk of falls in the elderly

Management

• surgery
  • indications:
    • diabetic retinopathy: monitoring requires a clear lens
    • vision worse than 20/40
    • visual function interferes with life function
  • procedures:
    • lens implantation
    • extracapsular approach
      • leaves posterior capsule of lens in place
      • permits posterior chamber lens implants
      • reduces incidence of post-operative complications
    • phacoemulsification
      • ultrasonic vibrations to remove lens
      • requires smaller incision
      • shorter period of post-operative visual rehabilitation
  • YAG laser capsulotomy for post-operative opacification
  • routine perioperative evaluation unnecessary
• tight control of diabetes
• vitamin/mineral supplementation (antioxidants?) may provide some protective benefit
  • vitamin A & beta-carotene, vitamin C, zinc
  • Ocuvite Preservision
  • vit E, riboflavin & thiamine supplements may reduce progression of age-related lens opacification
• use of statins may be associated with reduced risk
• UV light filters (sunglasses)

Comparative biology

• lanosterol reverses protein aggregation in cataracts (in vitro, rabbits, dogs)
• molecules that bind to alpha-crysallin & prevent their misfolding & aggregation may improve crystalline lens transparency

More general terms

• ocular lens disorder
• sign/symptom

More specific terms

• anterior cortical cataract (ACC)
• congenital cataracts
• cortical cataract
• familial cataracts
• glaucomatous flecks; glaukomflecken
• nuclear sclerosis
• nuclear sclerotic cataracts (NSC)
• posterior subcapsular cataract (PSC)

Additional terms

• cataract surgery

Patient information

cataracts patient information