by the end of this lecture the students should be able to: define blindness, visual impairment...
TRANSCRIPT
Ayesha Abdullah 03.09.2013
LEARNING OBJECTIVES
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?
Global distribution
BLINDNESS & VI / LOW VISION10 important facts
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
10 important facts
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
10 important facts
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
10 important facts
Definition of blindness
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)
http://apps.who.int/classifications/icd10/browse/2010/en
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
ICDCategory
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 SVI
3 <3/60-1/60 <10 B
4 <1/60-PL B
5 NPL B
Definition of blindness
(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?
visual acuity less than 3/60
6 5 4 3 2 1
in the better eye
1/606/12 2/601/60
Which one is
the better eye?
best possible correction
visual field loss Better eye less than 100
Disease ——> Impairment ——> Disability ——> Handicap
Organ systemDamage Loss of
performance
Disadvantages to a person
because of the impairment &
disability
Organ IndividualInd-
Society
Let’s examine a few scenarios
VA Visual Field
Rt eye (OD)
Lt eye (OS)
Rt eye (OD)
Lt eye (OS)
1 6/24 2/602 6/12 6/9 150 100
3 6/6 1/604 6/60 PL5 2/60 2/60
EPIDEMIOLOGY OF BLINDNESS AND VISUAL IMPAIRMENT; MAGNITUDE AND CAUSES
Causes of blindness- Global level
Global causes of blindnessCause 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
Distribution of causes of blindness
DEVELOPED COUNTRIES DEVELOPING COUNTRIES
Age-related macular degeneration (AMD)
Cataract
Diabetic retinopathy & glaucoma
Glaucoma & corneal opacity
Cataract Diabetic eye disease ( emerging) & AMD
“ Avoidable & unavoidable blindness”
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
Prevalence & major causes of blindness in Pakistan
?
Cataract
Glaucoma
Corneal opacity
Childhood blindnessmortality & morbidity
Vitamin A deficiency
Keratomalacia
Corneal xerosis
Bitot spot
Normal
Trachoma
Age-related macular degeneration
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
learning resources
http://www.who.int/mediacentre/factsheets/fs282/en/ (WHO website)
http://www.v2020.org/page.asp?section=000100010002 ( Vision 2020 website)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2486591/pdf/bullwho00405-0112.pdf
http://www.who.int/classifications/apps/icd/icd10online/ (ICD-10)
http://www.who.int/blindness/Change%20the%20Definition%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