2. Definition of Blindness
• Blindness is the condition of lacking visua
l perception due to physiological or neurol
ogical factors
3. Definition of Blindness
• The 10th Revision of the WHO Internation
al Statistical Classification of Diseases, Inj
uries and Causes of Death gives definition
of blindness
• Blindness is defined as visual acuity of les
s than 3/60, or corresponding visual field l
oss to less than 10 degrees, in the better e
ye with best possible correction.
4. Epidemiology of blindness
• A November 2004 WHO article Magnitude and causes of visual impairm
ent, estimated that in 2002 there were 161 million (about 2.6% of the world
population) visually impaired people in the world, of whom 124 million (abou
t 2%) had low vision and 37 million (about 0.6%) were blind.
• Blindness occurs in both children and in adults but the major causes may dif
fer.
• Blindness occur every where in the world.
– Since the major causes of blindness are inequitably distributed, the burden of bli
ndness is also skewed in favour of the developed countries of the world.
5. Major Causes of Blindness
• Most visual impairment is caused by disease and malnutrition.
• According to WHO estimates in 2002, the most common causes of b
lindness around the world are:
– cataracts (47.8%),
– glaucoma (12.3%),
– uveitis (10.2%),
– age-related macular degeneration (AMD) (8.7%),
– trachoma (3.6%),
– corneal opacity (5.1%), and
– diabetic retinopathy (4.8%), among other causes.
6. Major Causes of Blindness
• Uncorrected refractive errors is an emerging imp
ortant cause of visual impairment are.
• Severe refractive errors have been estimated to
account for about 5 million blind people.
• According to the most recent data available to W
HO, there are an estimated 124 million people in
the world with low vision.
• About a fourth of these would benefit from low vi
sion services
7. Major Causes of Blindness
• People in developing countries are significantly
more likely to experience visual impairment as a
consequence of treatable or preventable conditi
ons than are their counterparts in the developed
world.
• While vision impairment is most common in peo
ple over age 60 across all regions, children in po
orer communities are more likely to be affected b
y blinding diseases than are their more affluent p
eers.
8. Major Causes of Blindness
• The link between poverty and treatable visual im
pairment is most obvious when conducting regio
nal comparisons of cause.
– Most adult visual impairment in North America and W
estern Europe is related to age-related macular dege
neration and diabetic retinopathy.
• While both of these conditions are subject to treatment, neith
er can be cured.
– Another common cause is retinopathy of prematurity.
• In developing countries, wherein people have sh
orter life expectancies, cataracts and water-born
e parasites—both of which can be treated effecti
vely—are most often the culprits.
9. Major Causes of Blindness
• Abnormalities and injuries
– Eye injuries, most often occur in people under
30, are the leading cause of monocular blindn
ess
– Abnormalities such as optic nerve hypoplasia
can lead to decreased visual acuity.
– Injuries to the occipital lobe of the brain, witho
ut direct damage to the eyes and optic nerves
, may still lead to legal or total blindness
10. Treatment of Blindness and visu
al impairment
• This depends on and is mostly directed at the cause.
– Medical treatment is aimed at controlling infections, inflammation
s and other treatable causes of blindness.
• Once blindness has occurred, available options are redu
ced to
– Cure in the limited cases of curable avoidable blindness or
– Rehabilitating the incurably and unavoidably blind.
• Refractive errors can be rectified with appropriate optical
correction while people with low vision may be helped wit
h low vision devices
11. Levels of Prevention of Blindnes
s
• Primary Prevention: this aims at preventi
ng a blinding disease from occurring in an
individual or community.
– Tools for this include health education, immun
ization, personal, Community and environmen
tal sanitation and modification; nutrition and n
utrition education; and poverty alleviation.
12. Levels of Prevention of Blindnes
s
• Secondary Prevention: this aims at treating a b
linding disease that has already occurred in an i
ndividual or prevalent in a community such that it
does not lead to blinding complications or in the
case of a community reducing its prevalence the
reby significantly eliminating blindness attributab
le to it.
– Essential tools for this include health education, perso
nnel training and deployment, establishment of appro
priate health facilities, provision of drugs and supplies
, community mobilization, and strategies targeted at t
he prevention; poverty alleviation and control of specif
ic blinding diseases.
13. Levels of Prevention of Blindnes
s
• Tertiary Prevention: this is aimed at cure of cur
able blindness.
– Provision of safe, high volume surgical services is the
main tool for this.
– Reducing the backlog of cataract-blind mainly require
s training ophthalmic personnel, strengthening the exi
sting health care infrastructure, affordable pricing, and
the availability of surgical supplies.
– Adjuncts include poverty alleviation, community mobili
zation and social marketing techniques.
• For the elimination of avoidable blindness, th
e integration of primary eye care into primary
health care is advocated.
