Blindness

What is blindness?

• A compilation published by WHO in 1966 lists 65 definitions of blindness.

• The 25th World Health Assembly in 1972 noted the complexity of the problem and considered the need for generally accepted definition of blindness and visual impairment for national and international comparisons.

Definition of blindness• WHO proposed a uniform criterion and defined

blindness as follows

• “ Visual acuity of LESS THAN 3/60 (Snellen) or its equivalent”

• In order to facilitate the screening of visual acuity by non-specialized personnel, in absence of appropriate vision charts, WHO has now added the “inability to count fingers in daylight at a distance of 3 meters” to indication less than 3/60 or its equivalent.

Categories of visual impairment

CATEGORIES OF VISUAL IMPAIRMENT

VISUAL ACUITY

MAXIMUM LESS THAN

MINIMUM EQUAL TO OR BETTER THAN

LOW VISION 1 6/182 6/60

6/603/60

BLINDNESS 3 3/60 (finger counting at 1 mt)

1/60 (finger countingat 1 mt)

4 1/60 (finger counting at 1 mt)

Light perception

5 No light perception

Problem statement

• An estimated 180 million people worldwide are visually disabled.

• 45 million are blind, four out of five of the are living in developing countries.

• About 80% of blindness is avoidable (treatable or potentially preventable)

India

• Blindness is one of the most significant social problems.

• It is estimated that there is an annual incidence of 2 million cataract induced blindness.

• Approximately 3 million eyes need cornea transplantation.

Causes of blindness

• The most frequent cause of blindness in developed countries are

–Accidents

– Glaucoma

– Diabetes

– Vascular diseases (hypertension)

– Cataract

– Degeneration of ocular tissues especially retina

– Hereditary conditions

Causes of blindness

• In India the most important causes of blindness are as follows

– Cataract (62.6%)

– Refractive errors (19.7%)

– Glaucoma (5.8%)

– Posterior segment pathology (4.7%)

– Corneal opacity (0.9%)

– Other causes (6.2%)

Source : National Survey on Blindness 2001-02

Epidemiological determinant

• Age: about 30% of the blind in India are said to lose their eyesight before they reach the age of 20 years, and many under the age of 5 years.

• Refractive error, trachoma, conjunctivitis and malnutrition (vit “A” deficiency) are important causes of blindness amongst children and younger age groups.

• Cataract, refractive error, glaucoma and diabetes are causes of blindness in middle age group.

• Accidents and injuries can occur in all age groups, but more importantly in the age group 20-40 years.

• Sex: a higher prevalence is reported in females than in males in India. This has been attributed to a higher prevalence of trachoma, conjunctivitis and cataract among females than in males.

• Malnutrition: PEM, Vit A Def.

• Occupation: people working in factories, workshops and cottage industries are prone to eye injuries because of exposure to dust, air borne particles, fumes, radiations, electrical flash. Even doctors are known to have developed premature cataracts while exposed to X-Rays, UV Rays

• Social class: blindness is TWICE more prevalent in lower socio-economic classes, compared to higher.

• Social factors: many people lose their eye sight because of meddlesome ophthalmology by quacks.

• The basic social factors are ignorance, poverty, low standards of personal and environmental hygiene and inadequate health care services.

Changing concepts in eye health care

1. Primary eye care: promotion and protection

2. Epidemiological approach: research

3. Team concept: specialists, ophthalmic assistants, MPWs, Village health workers, NGOs.

4. Establishment of national programme

Prevention of blindness

I. Initial assessment: to assess

1. Magnitude

2. Geographical distribution

3. Causative agents

II. METHODS OF INTERVETION

a. Primary eye care: wide range of eye conditions like

acute conjunctivitis,

ophthalmia neonatorum,

trachoma,

superficial foreign bodies

can be treated/prevented at grass-root level by locally trained primary health workers.

• b. Secondary care: involves definitive management of common blinding conditions such as

• cataract,

• trichiasis,

• entropion,

• ocular trauma,

• glaucoma.

• This care can be given at PHCs, CHCs and district hospitals

c. Tertiary care: to provide sophisticated eye care such as

retinal detachment surgery,

corneal grafting and other complex forms of management.

• These services are established in the national or regional capitals and often associated with medical colleges.

d. Specific programmes

- Trachoma control

- School eye health services

- Vitamin A Prophylaxis

- Occupational eye health services

III. LONG-TERM MEASURE:

- Improving the quality of life

- Modifying or attacking the factors responsible for persistence of eye health problems like poor sanitation, lack of adequate safe water supply, little intake of foods rich in vit A, lack of personal hygiene.

- Health education is an important long term measure,

IV. EVALUATION

NATIONAL AND INTERNATIONAL AGENCIES

• National Association for the Blind (NAB)

• The Royal Commonwealth Society for the Blind

• International Agency for Prevention of Blindness

Vision 2020: the Right to Sight• It is a global initiative to eliminate avoidable

blindness was launched by WHO on 18th Feb 1999.

• Recognition of sight as a fundamental human right by all countries can be an important catalyst of initiatives for the prevention and control of blindness.

• The objectives of Vision 2020 is to assist member countries in developing sustainable systems which will enable them to eliminate avoidable blindness from major causes like cataract, xeropthalmia and other causes of childhood blindness, refractive errors and low vision, trachoma and other causes of corneal blindness by year 2020