RAPID ASSESSMENT OF
REFRACTIVE ERROR (RARE)
Professor Kovin NaidooGlobal Programs Director
IAPB AFRICA CHAIRPERSON
Uncorrected Refractive Error (URE)“The Crisis”
• URE is most common cause of Visual impairment (VI) worldwide and 2nd most common cause of blindness1,2
• URE drives children and adults further into poverty:3 − Limits opportunities to education− Employment− Seriously impacts quality of life and productivity
• Link between poverty and VI due to URE places heavy economic burden on individuals families affected nations
What is the status of URE?4
Prevalence of Visual Impairment• 158 million cases of Distance VI• 544 million cases of Near VI
Human Resources Required• 47000 full-time refractionists• 18000 ophthalmic dispensers
Cost of Human Resource Development• US $20-28 billion
Estimated loss in global GDP due to DVI
US $ 202 billion
Implications
Implications
Historical Situation
• Paucity of Data• Refractive data elicited through:
− RESC studies• From community to school• Children only
− Conventional Population based studies• Prohibitively expensive• High level of expertise• Few and far between• Lag between completion and Program implementation
timelines
CONTEXT SETTING
• Why and where do we need data− National level
• Planning• Evaluation• Awareness• Advocacy
− Regional level• Advocacy• Establish priorities for investment in regions
RAREEvolved out of RACSS and RAABS
Rapid Quick Cost effective
Assessment Simple
Results
Refractive Error
Prevalence Barriers
How does RARE data help?• RARE data can be used in a top-down or bottom-up approach.
Globally
285.389 mil VI
246.024 mil Blind
RARE STUDIES
LOCATE
Blind
and
VI
Regional
RARE
RARE STUDIES
EXPAND to the national or even global context
TOP-DOWN
BOTTOM-UP
METHODOLOGY
Target Group
• RARE studies used to assess prevalence of URE, presbyopia, spectacle coverage, and barriers to uptake of services for refractive errors and presbyopia5
Studies are focused on:• Younger age groups more affected by RE• Presbyopia• 15-49 years
Definitions
Condition Definition
Visual ImpairmentBinocular Presenting
VA<6/12 in the better eye
Uncorrected
Refractive Error
(URE)
Presenting VA<6/12 but
improving ≥6/12 with
pinhole
PresbyopiaBinocular near vision < N8 at
33-35cms
Definition Description
URE
(Unmet need)
Unaided VA <6/12 but improving
to 6/12 or better with pinhole and
no spectacles
Uncorrected
Presbyopia
(Unmet need)
Binocular Unaided near vision <N8
in subjects aged >35 years with no
distance VI and no spectacles
Corrected RE
(Met need)
Unaided VA<6/18 but improved to
6/18 or better with spectacles
Corrected
Presbyopia (Met
need)
Unaided near vision < N8, but
improved to N8 or better with their
spectacles
Definitions
Equipment Purpose
Snellen chart (E, Alphabet optotypes)
Distance Visual Acuity
Measuring tape or String
Measure testing distance: subject and chart
Multiple pinhole occluder
Presenting VA, if VA<6/12
N notation chart Near vision
Torch light External examination
Ready made spectacles (+1.0 to +3.0 Ds)
Best corrected near vision assessment in individuals with presbyopia
RARE Toolkit
OUTPUTS OF RARE STUDIES
Magnitude of RE (uncorrected)
Prevalence of presbyopia
Spectacle coverage and utilisation patterns
Understanding barriers to access of services
Provide baseline information
Trends in prevalence determined on follow up studies
What is the impact of gathering this information? ....
Spectacle Coverage
[met need’ ] .
[(‘met need’ + ‘unmet need’) X 100]
Barriers – URE6
Lack of awareness
Personal reasons
Lack of access
Lack of felt need
Economic reasons
0
5
10
15
20
25
30
35
12.9
16.5 16.5
23
30.9
Current and future RARE studies
• Studies conducted
1. Eritrea
2. Ghana
3. Uganda
4. South Africa
5. Tanzania
• Studies in preparation
6. Mozambique
7. Gambia
8. Zambia
9. Cameroon
10. Ethiopia
11. Malawi
MAJOR BARRIERS IDENTIFIED IN RARE STUDIES CONDUCTED
Affordability of the spectacle exam
Aware of problem but felt no need for consultation
Unaware of problem
Cannot afford the cost of glasses
Comparison of visual impairment and refractive error prevalence across various RARE studies
Eritrea Ghana Uganda Tanzania (South Africa)
0
2
4
6
8
10
12
4.4
2.9
7
10.4
1
6.4 6.6
8.6
5.7
1.2
VIRE
References
1. Resnikoff S, Pascolini D, Mariotti S, Pokharel P. Global magnitude of visual impairment caused by uncorrected refractive errors in 2004. Bull World Health Organ 2008;86:63-70.
2. Holden BA, Fricke T, Ho S, Wong R, Schlenther G, Cronje S, et al. Global vision impairment due to uncorrected presbyopia. Arch Ophthalmol 2008;126:1731-9.
3. Fricke TR, Holden BA, Wilson DA, Schlenther G, Naidoo KS, Resnikoff S and Frick KD. Global cost of correcting vision impairment from uncorrected refractive error.
4. Naidoo KS, Wallace DB, Holden, BA, Minto H, Faal HB, Dube P. The challenge of uncorrected refractive error: driving the agenda of the Durban Declaration on refractive error and service development. Clin Exp Opt 2010: 93(3): 131-136.
5. Marmamula S, Keeffe JE, Rao GN. Uncorrected refractive errors, presbyopia and spectacle coverage: Results from a Rapid Assessment of Refractive Error survey. Ophthalmic Epidemiology 2009;16:269-74.
6. Marmamula et al. Population-based cross-sectional study of barriers to utilisation of refraction services in South India: Rapid Assessment of Refractive Errors (RARE) Study. British Medical Journal.
Acknowledgements
• Pirindha Govender
• Brien Holden Vision Institute (Public Health Division) – Research Department