What is the definition, types, and epidemiology of cataracts?

Cataracts: Definition, Types, and Epidemiology

Definition

A cataract is defined as progressive opacification or clouding of the eye's natural lens, leading to visual disability and potentially blindness if left untreated. 1 This clouding impairs the lens's ability to focus incoming light onto the retina, causing scattered light and deteriorating vision clarity and brightness. 2

Types of Cataracts

Cataracts can be classified based on several factors:

1. Age-related cataracts: The most common type, occurring as part of the aging process

2. Congenital cataracts: Present at birth or developing during early childhood

3. Secondary cataracts: Developing as a result of:

   • Medical conditions (diabetes, galactosemia)
   • Medications (particularly corticosteroids)
   • Ocular trauma
   • Radiation exposure (UV, electromagnetic waves)
   • Inflammatory and degenerative eye diseases 3

4. Traumatic cataracts: Resulting from eye injury

5. Complicated cataracts: Associated with other eye conditions or systemic diseases

Epidemiology

Cataracts represent a significant global health burden:

• Leading cause of blindness worldwide 4
• Affects approximately two-thirds of the population older than 80 years 1
• More than 3.5 million cataract operations are performed annually in the US 1
• The number of people with cataracts in the US is expected to increase to 50 million by 2050 due to the aging population 1
• Globally, cataracts contribute significantly to the 94 million people who are blind or visually impaired 4

Risk Factors

Several factors increase the risk of cataract development:

• Age: Primary risk factor 1
• Genetic predisposition: Hereditary factors 1, 3
• Medical conditions:
  • Uncontrolled diabetes
  • Retinitis pigmentosa
  • Down syndrome
  • Congenital rubella 1
  • Other metabolic disorders like galactosemia 3
• Environmental factors:
  • UV exposure
  • Radiation therapy 1
  • Electromagnetic waves 3
• Medications: Particularly corticosteroids 1
• Lifestyle factors:
  • Smoking
  • Alcohol consumption 3
• Nutritional deficiencies: Including trace metal deficiencies 3
• Oxidative stress: A key mechanism in cataract formation 3, 4
• Trauma: Eye injuries 1, 3

Clinical Impact

Cataracts have significant impacts on health and quality of life:

• Associated with decreased quality of life and reduced life expectancy 4
• Cause painless, progressive blurring of vision and visual glare 1
• Can lead to complete blindness if untreated 4
• Surgical treatment is associated with lower rates of falls (>30%) and dementia (20%-30%) 1

Treatment

Currently, surgery is the only effective treatment for cataracts 2, 5:

• Involves removal of the opacified lens and implantation of an artificial intraocular lens (IOL) 1, 5
• Phacoemulsification with IOL implantation is the preferred method for most patients 4
• Surgery is highly cost-effective and can be performed with topical anesthesia 1, 4
• Advanced technology IOLs can reduce dependence on eyeglasses, though these come with additional costs not covered by insurance 1

Global Challenges

Despite effective treatment options, challenges remain:

• Global inequity in surgical service quality 4
• Insufficient surgical facilities in poor and developing countries 3
• Need for universal health coverage to make services accessible to all 4