Epidemiology of Ocular Diseases

Epidemiology Basics - Numbers Game

• Epidemiology: Study of disease distribution & determinants in populations.
• Incidence (I): Rate of new cases. $I = \frac{\text{New cases}}{\text{Person-time at risk}}$
• Prevalence (P): Proportion of all existing cases. $P = \frac{\text{All existing cases}}{\text{Total population}}$
• Key relation: $P \approx I \times D$ (D = average disease duration).
• Blindness (WHO criteria): VA < 3/60 (Snellen) or central visual field < 10° in the better eye with best possible correction.

  ⭐ India: Cataract is the leading cause of blindness (62.6%). (NPCB data)

• Terms: Endemic (constant local presence), Epidemic (sudden ↑ cases regionally), Pandemic (global epidemic).

Key Indian Blinders - Sight Stealers

Key diseases contributing to India's blindness burden, demanding focused public health strategies. Early detection and intervention are crucial.

⭐ Cataract is the leading cause of blindness in India (62.6% as per NPCB Survey 2015-19).

Childhood Blindness & Others - Young Eyes, Old Woes

• Childhood blindness: Visual Acuity <3/60 in better eye (children <16 yrs).
• Major Causes (India):
  • Vitamin A Deficiency (VAD): Xerophthalmia, keratomalacia.
  • Congenital: Cataract, glaucoma.
  • Retinopathy of Prematurity (ROP).
  • Measles/Rubella sequelae.
  • Uncorrected Refractive Errors & Amblyopia.
• Prevention & Control:
  • Vitamin A Prophylaxis:
    • <6 months (if not exclusively breastfed): 50,000 IU.
    • 6-12 months: 100,000 IU.
    • 1-6 years: 200,000 IU (every 6 months).
    • VAD Treatment: Therapeutic doses on day 0, 1, and 14.
  • MMR Vaccination.
  • School Eye Health Programs (screening).
• Trachoma: SAFE Strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement).

⭐ Vitamin A deficiency is the leading preventable cause of childhood blindness globally.

NPCBVI & VISION 2020 - India's Sight Savers

• NPCBVI (National Programme for Control of Blindness & Visual Impairment):
  • Launched 1976; 100% Centrally Sponsored Scheme.
  • Goal: ↓ Blindness prevalence to 0.3% (initial), now <0.25% by 2025.
  • Key Foci: Cataract, Refractive Errors (RE), Diabetic Retinopathy (DR), Glaucoma, Corneal Blindness.
• VISION 2020: The Right to Sight:
  • Global (WHO & IAPB) initiative, launched 1999.
  • Aim: Eliminate avoidable blindness by 2020.
  • India adopted 2001. Key pillars: Disease control, Human Resource Development (HRD), Infrastructure.

⭐ NPCBVI is a 100% Centrally Sponsored Scheme, launched in 1976.

High-Yield Points - ⚡ Biggest Takeaways

• Cataract is the leading cause of blindness in India; uncorrected refractive errors are second.
• Diabetic Retinopathy is a rapidly emerging cause of blindness due to rising diabetes prevalence.
• Glaucoma is a major cause of irreversible blindness, often asymptomatic until advanced stages.
• Corneal Blindness is significantly linked to past Vitamin A deficiency and current infections/trauma.
• Childhood Blindness main causes include congenital anomalies, Retinopathy of Prematurity (ROP), and uncorrected refractive errors.
• The National Programme for Control of Blindness & Visual Impairment (NPCB&VI) is India's key program targeting avoidable blindness reduction, focusing on major diseases like cataract.