Blindness: WHO Definition, Causes in India, Epidemiological Determinants & Prevention

1. WHO Definition of Blindness (2 marks)

"Visual acuity of less than 3/60 (Snellen) or its equivalent."

2. Causes of Blindness in India (3 marks)

• Cataract remains the single largest cause, accounting for nearly 2/3 of all blindness.
• Emerging causes: Glaucoma, ARMD, diabetic retinopathy, corneal ulcer, and ocular trauma are rising in significance.
• Childhood blindness: Retinopathy of prematurity (ROP) is an emerging cause. Other causes include xerophthalmia, congenital cataract, congenital glaucoma, optic atrophy due to meningitis, and uncorrected refractive errors.
• The prevalence of blindness has fallen from 1.0% (2006-07) to 0.36% (2015-18).

3. Major Epidemiological Determinants of Blindness (4 marks)

• Children/young: Refractive error, trachoma, conjunctivitis, vitamin A deficiency
• Middle age: Cataract, refractive error, glaucoma, diabetes
• All ages: Accidents and injuries (especially 20-40 years)

4. Prevention of Blindness - Interventions at Each Level (National Programme) (6 marks)

A. Primary Prevention (Preventing occurrence of blindness)

1. Vitamin A supplementation: Massive dose vitamin A prophylaxis program (100,000 IU at 6 months; 200,000 IU every 6 months up to 5 years) to prevent xerophthalmia. Integrated into routine immunization (UIP).
2. Immunization: BCG (against TB causing corneal blindness), measles vaccination (measles precipitates Vitamin A deficiency and corneal ulcers in children).
3. Nutrition improvement: School nutrition programmes, balanced diet with beta-carotene-rich foods, mid-day meal schemes, food fortification.
4. Safe water supply and environmental sanitation: To control trachoma and other eye infections. Personal hygiene promotion (separate towels, no eye rubbing).
5. Health education: Awareness of eye safety, avoidance of traditional eye remedies (kajal, etc.), proper use of protective devices in occupational settings.
6. Occupational safety: Enforcement of safety standards, protective eyewear use in industries (welding, cutting, grinding).
7. Trachoma control: Antibiotics (azithromycin) for active trachoma, lid surgery for trichiasis (SAFE strategy - Surgery, Antibiotics, Facial cleanliness, Environmental improvement).
8. Diabetes and hypertension control: Screening and management to prevent diabetic retinopathy and hypertensive retinopathy.

B. Secondary Prevention (Early detection and prompt treatment)

1. School eye screening: Detection of refractive errors, squint, amblyopia, and other eye diseases in school-age children. Provision of spectacles to poor children.
2. Cataract surgical services: Cataract is the leading cause; camps and fixed eye care units perform free surgeries. Target - cataract surgical rate (CSR) to be raised. IOL implantation for aphakia correction.
3. Glaucoma detection: Tonometry and visual field testing in eye camps.
4. Refractive error correction: Provision of corrective spectacles to children and adults.
5. Diabetic retinopathy screening: Fundus examination in diabetic patients; laser photocoagulation for early retinopathy.
6. Mobile eye care units (vision centres): Outreach services to rural/underserved areas, linking primary care to district hospitals.
7. Eye camps: Organized at community level for mass screening and surgery.

C. Tertiary Prevention / Rehabilitation

1. Low vision services: Provision of low-vision aids (magnifiers, telescopic lenses) for those who cannot be fully restored.
2. Corneal transplantation (keratoplasty): Eye donation campaign under the National Eye Bank programme for corneal blindness.
3. Retinopathy of prematurity management: Screening of premature neonates (<30 weeks, <1500 g) and laser/surgical treatment.
4. Rehabilitation of the blind: Braille education, vocational training, white cane distribution (National Association for the Blind - NAB).
5. Optical services: Subsidized spectacles at district hospitals and vision centres.

D. Long-term/Societal Level Measures

• Improvement in socio-economic conditions and living standards
• Safe water, adequate sanitation, poverty alleviation
• Community participation and sustained health education
• Training of ophthalmic assistants and allied eye care workers for peripheral coverage

Vision 2020: The Right to Sight

Prevention of Blindness - Methods of Intervention as per National Programme

Step 1: Initial Assessment

Step 2: Methods of Intervention (4 Levels)

(a) Primary Eye Care - Grass-root / Community Level

• Provided by village health guides, multi-purpose workers (MPWs) - the first contact with the community
• Treats/prevents: acute conjunctivitis, ophthalmia neonatorum, trachoma, superficial foreign bodies, xerophthalmia
• Workers are supplied with: topical tetracycline, vitamin A capsules, eye bandages, shields
• They refer difficult cases (corneal ulcer, penetrating injuries, non-responding infections) to PHC or district hospital
• Promote personal hygiene, sanitation, good dietary habits, and general safety
• Coverage: 1 village health guide per 1,000 population; 2 MPWs per 5,000 population

(b) Secondary Care - PHC / District Hospital Level

• Definitive management of common blinding conditions: cataract, trichiasis, entropion, ocular trauma, glaucoma
• Provided at PHCs and district hospitals with eye departments/clinics
• Eye camp approach: Highly successful for cataract surgery (cataract = >62% of blindness); camps also do general health surveys, early detection of visual defects, and mass health education
• Mobile eye clinics extend reach to peripheral areas
• Must be backed by community participation, follow-up, and evaluation

• (i) Trachoma Control: Mass campaigns with topical tetracycline + socio-economic improvement. (Trachoma Control Programme 1963, merged into NPCB 1976)
• (ii) School Eye Health Services: Screening children for refractive errors, squint, amblyopia, trachoma, conjunctivitis; treatment and spectacle provision
• (iii) Vitamin A Prophylaxis: Massive dose supplementation integrated into immunization (UIP) to prevent xerophthalmia
• (iv) Occupational Eye Health Services: Prevention/treatment of eye hazards in industries; education on protective devices; safety features in machines; proper illumination

(c) Tertiary Care - Medical College / National/Regional Institute Level

• Sophisticated eye care not available at secondary centres:
  • Retinal detachment surgery
  • Corneal grafting (Eye Banks established under Corneal Grafting Acts in most states)
  • Other complex surgical management
• Rehabilitation of the blind: Education in special schools (Braille), vocational training, gainful employment
• National Institute for the Blind, Dehradun - central government institution for new strategies

(d) Specific Programmes (cutting across all levels)

Step 3: Long-term Measures

• Improving sanitation and safe water supply
• Adequate nutrition (vitamin A-rich foods)
• Promoting personal hygiene and community participation
• Health education - creating community awareness, motivating acceptance of total eye health care programmes

Step 4: Evaluation

• Measure the extent to which blindness has been alleviated
• Assess how programme activities have been carried out
• Determine other changes produced by the intervention

Prevention of Blindness - Interventions at Each Level (National Programme)

LEVEL 1: Primary Eye Care (Community/Grass-root Level)

• 1 village health guide per 1,000 population; 2 MPWs per 5,000 population

• Treatment and prevention of: acute conjunctivitis, ophthalmia neonatorum, trachoma, superficial foreign bodies, xerophthalmia
• Supplied with essential drugs: topical tetracycline, vitamin A capsules, eye bandages and shields
• Vitamin A prophylaxis - massive dose supplementation integrated into UIP (100,000 IU at 6 months; 200,000 IU every 6 months up to 5 years)
• Promotion of personal hygiene, sanitation, good dietary habits, eye safety
• Referral of difficult cases (corneal ulcer, penetrating injuries, non-responding infections) to PHC/district hospital
• Health education to create community awareness

LEVEL 2: Secondary Care (PHC / District Hospital Level)

• Definitive management of common blinding conditions: cataract, trichiasis, entropion, ocular trauma, glaucoma
• Eye camps: Highly successful approach for cataract surgery (cataract = 66.2% of blindness in India); also conduct general health surveys, early visual defect detection, and mass health education
• Mobile eye clinics: Outreach to rural/underserved peripheral areas
• School eye health services: Screening children for refractive errors, squint, amblyopia, trachoma; provision of spectacles to poor children
• Trachoma control: Mass campaigns using topical tetracycline + facial cleanliness + environmental improvement (SAFE strategy)
• Occupational eye health: Education on protective devices (welding shields, goggles), safety features in factories, proper illumination
• Diabetic and hypertensive retinopathy screening and management
• Refractive error correction - subsidized spectacles

LEVEL 3: Tertiary Care (Medical College / National/Regional Institute Level)

• Sophisticated procedures not available at secondary level:
  • Retinal detachment surgery
  • Corneal grafting (keratoplasty) - Eye Banks established under Corneal Grafting Acts in most states
  • Complex vitreo-retinal surgery, management of ROP, glaucoma surgery
• Rehabilitation of the blind:
  • Braille education in special schools
  • Vocational training and gainful employment
  • White cane distribution
  • Low vision aid provision (magnifiers, telescopic lenses)
• National Institute for the Blind, Dehradun - central government institute for new strategies

LEVEL 4: Long-term / Societal Level Measures

• Improvement in socio-economic conditions and living standards (poverty is a root cause - blindness is twice as prevalent in lower socioeconomic groups)
• Safe water supply and adequate sanitation (to control trachoma)
• Nutrition improvement - vitamin A-rich foods, food fortification, school mid-day meals
• Sustained health education - community awareness, motivation for eye care, community participation
• Inter-sectoral coordination - involving education, agriculture (nutrition), public works (sanitation), and social welfare departments

Supporting Framework