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 diseasesII C00-D48 NeoplasmsIII D50-D89 Diseases of the blood and blood-forming organs and certain disorders

involving the immune mechanismIV E00-E90 Endocrine, nutritional and metabolic diseasesV F00-F99 Mental and behavioural disordersVI G00-G99 Diseases of the nervous systemVII H00-H59 Diseases of the eye and adnexaVIII H60-H95 Diseases of the ear and mastoid processIX I00-I99 Diseases of the circulatory systemX J00-J99 Diseases of the respiratory systemXI K00-K93 Diseases of the digestive systemXII L00-L99 Diseases of the skin and subcutaneous tissueXIII M00-M99 Diseases of the musculoskeletal system and connective tissueXIV N00-N99 Diseases of the genitourinary systemXV O00-O99 Pregnancy, childbirth and the puerperiumXVI P00-P96 Certain conditions originating in the perinatal periodXVII Q00-Q99 Congenital malformations, deformations and chromosomal

abnormalitiesXVIII R00-R99 Symptoms, signs and abnormal clinical and laboratory findings, not

elsewhere classifiedXIX S00-T98 Injury, poisoning and certain other consequences of external causes

XX V01-Y98 External causes of morbidity and mortalityXXI 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 50Glaucoma 6.7 13.4Refractive error 5 10Trachoma 3 6Vitamin A deficiency 0.5 1Other causes of childhood blindness

1 2

Age-related macular degeneration

1 2

Onchocerciasis 0.4 0.8Leprosy 0.3 0.6Corneal 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