By the end of this lecture the students should
be able to:
 Define blindness, visual impairment & low
vision according to the WHO- ICD-10
classification
 Critically evaluate the definition & its
implications
 Describe the global burden of blindness &
visual impairment
 Identify the major causes of blindness at
global and national level
 Recognize the impact of blindness on the
life of the individual and the society
Why should Ophthalmology
be taught and learnt?
1. Approximately 314 million people
suffer from serious visual
impairment
2. 45 million people are blind and 124
million have low vision
3. 75% of blindness is avoidable - i.e.
treatable and/or preventable
4. 90% of visually impaired people live in
developing countries
5. Infectious causes of blindness are
decreasing. Blinding trachoma now affects
fewer than 80 million people, compared to
360 million in 1985
6. 153 million people’s visual impairment is
due to uncorrected refractive errors. In
most cases, normal vision could be
restored with eyeglasses
7. Aging populations , lifestyle changes
rising incidence of chronic blinding
conditions such as diabetic retinopathy
8. Women face a greater risk of vision loss
than men
9. Without effective, major intervention,
the number of blind people worldwide
is projected to increase to 76 million
by 2020
10. Restorations of sight, and blindness
prevention strategies are among the
most cost-effective interventions in
health care




Why define?
Blindness is defined in different ways in
different countries according to the purpose
of definition i.e legal, social, clinical etc
WHO recommends the ICD-101 –based
definition
In Pakistan we use the same
1. International Statistical Classification of Diseases & related health problems, 10th revision
(ICD-10)
Chapter
Blocks
Title
I
A00-B99
Certain infectious and parasitic diseases
II
C00-D48
Neoplasms
III
D50-D89
Diseases of the blood and blood-forming organs and certain disorders
involving the immune mechanism
IV
E00-E90
Endocrine, nutritional and metabolic diseases
V
F00-F99
Mental and behavioural disorders
VI
G00-G99
Diseases of the nervous system
VII
H00-H59
Diseases of the eye and adnexa
VIII
H60-H95
Diseases of the ear and mastoid process
IX
I00-I99
Diseases of the circulatory system
X
J00-J99
Diseases of the respiratory system
XI
K00-K93
Diseases of the digestive system
XII
L00-L99
Diseases of the skin and subcutaneous tissue
XIII
M00-M99
Diseases of the musculoskeletal system and connective tissue
XIV
N00-N99
Diseases of the genitourinary system
XV
O00-O99
Pregnancy, childbirth and the puerperium
XVI
P00-P96
Certain conditions originating in the perinatal period
XVII
Q00-Q99
Congenital malformations, deformations and chromosomal
abnormalities
XVIII
R00-R99
Symptoms, signs and abnormal clinical and laboratory findings, not
elsewhere classified
XIX
S00-T98
Injury, poisoning and certain other consequences of external causes
XX
V01-Y98
External causes of morbidity and mortality
XXI
Z00-Z99
Factors influencing health status and contact with health services
XXII
U00-U99
Codes for special purposes
http://apps.who.int/classifications/icd10/browse/2010/en
ICD
VA
VF
(degrees)
What it
defines
0
6/6 – 6/18
> 20
Normal
1
<6/18-6/60
< 20
MVI
2
<6/60-3/60
3
<3/60-1/60
4
<1/60-PL
B
5
NPL
B
Category
SVI
<10
B
(ICD-10,Visual impairment (VI)
categories 3, 4 & 5)
 Blindness is defined as a visual acuity
(VA) of less than 3/60 (20/400) in the
better eye with best possible correction
Or
 A visual field in the better eye to less
than 100 from fixation
 Key words?


6
visual acuity
less than 3/60
5
4
3
2
1

6/12
in the better eye
1/60
1/60
Which
one is
the
better
eye?
2/60

best possible correction



visual field loss
Better eye
less than 100
Organ
Individual
IndSociety
Disease ——> Impairment ——> Disability ——> Handicap
Organ
system
Damage
Loss of
performance
Disadvantages
to a person
because of the
impairment &
disability
VA
1
2
3
4
5
Rt eye
(OD)
6/24
6/12
6/6
6/60
2/60
Visual Field
Lt eye
(OS)
2/60
6/9
1/60
PL
2/60
Rt eye
(OD)
Lt eye
(OS)
150
100
Cause
Number of blind
in million
% of total
Cataract
25
50
Glaucoma
6.7
13.4
Refractive error
5
10
Trachoma
3
6
Vitamin A deficiency
0.5
1
Other causes of
childhood blindness
1
2
Age-related macular
degeneration
1
2
Onchocerciasis
0.4
0.8
Leprosy
0.3
0.6
Corneal opacity other
than from Trachoma &
other causes
7.1
14.2
DEVELOPED COUNTRIES DEVELOPING
COUNTRIES
Age-related macular
degeneration (AMD)
Cataract
Diabetic retinopathy &
glaucoma
Glaucoma & corneal
opacity
Cataract
Diabetic eye disease
( emerging) & AMD

Blindness which could be
either treated or prevented by
known, cost-effective means




Cataract
Refractive errors
Diabetic retinopathy
Unavoidable blindness


Retinal causes of childhood blindness
ARMD
?

Vitamin A deficiency
Corneal xerosis
Normal
Keratomalacia
Bitot spot
DIABETIC RETINOPATHY






A person has a visual acuity of
3/60 in the right eye and 6/60
in the left eye according to the
WHO (ICD-10) classification he
Has moderate visual impairment
Is a blind person
Is blind in the left eye
Is blind in the right eye
Is normal

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


http://www.who.int/mediacentre/factsheets/fs282/e
n/ (WHO website)
http://www.v2020.org/page.asp?section=00010001
0002 ( Vision 2020 website)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2486
591/pdf/bullwho00405-0112.pdf
http://www.who.int/classifications/apps/icd/icd10onli
ne/ (ICD-10)
http://www.who.int/blindness/Change%20the%20D
efinition%20of%20Blindness.pdf
Textbook
Johnson GJ, Minassian DC, Weale RA, WestSk
(editors). Prevalence, incidence and distribution of
visual impairment. In The epidemiology of eye
disease, 2nd Ed. London. Arnold 2003; 3-5