1. The contribution of rapid and non-rapid studies to the GBD Hans Limburg MD, PhD, DCEH

2. Rapid Assessment of Avoidable Blindness (RAAB) Population based survey Focus on people aged 50+ –High prevalence  lower sample size Standardised survey form Special software –Calculation of sample size –Random selection of clusters with pps –Data entry with consistency checks –Automatic generation of reports –Results comparable worldwide

3. How representative is RAAB? Survey area with population 0.5 - 5.0 million Cluster size: 50 residents age 50+ Usually 50 to 100 clusters Random selection of population units from sampling frame with PPS Selection of 50 eligible persons from population unit with compact segment sampling In-build data cleaning functions Age and sex adjustment of prevalence

4. RA versus conventional Survey Blindness survey Focus >1 risk group –lower prevalence Sample size >15,000 Detailed examination Disease intervention Expert staff Large survey population (10-100 m) Custom data analysis Takes long (years) Expensive (0.5-10 mln) Rapid assessment Focus on 1 risk group –higher prevalence Sample size 2500-5000 Basic examination Planning and follow-up Local staff Smaller survey population (0.5-5 mil.) Automatic data analysis Rapid (months) Cheap (20-40,000 US$)

5. The Gambia: Blindness by age 85% of blindness in people aged 50+

6. The Gambia: Causes of blindness Cause of blindness Total population Population 50+ Cataract46%48% Aphakia13%15% Trachoma/CO22%17% Glaucoma9%11% Other11%9% Causes in people 50+ reflect causes in total population

7. Other rapid assessments in eye care CauseRapid assessment CataractRACSS TrachomaTRA; ASTRA OnchocerciasisREMO; RAPLOA Childhood blindnessCBS RE & low visionRARE Diabetic retinopathyDR module in RAAB

8. Where surveys were done RAABRACSS Custom survey

9. Web-based repository for results from blindness surveys Increasingly difficult to publish results Not all results in publication Risk of losing original data and reports Study results in public domain Enable researchers to combine data Permission: –Address principal investigator –Reports generated by software –Original data as Excel file