1. Improving health worldwide www.iceh.org.uk www.lshtm.ac.uk Calculation of CSR and CSC and visual acuity thresholds Improving health worldwide www.iceh.org.uk www.lshtm.ac.uk IAPB 9GA Hyderabad 2012 G V S Murthy

2. Improving health worldwide www.iceh.org.uk www.lshtm.ac.uk Reader, International Centre for Eye Health, Department of Clinical Research, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine & Director, Indian Institute of Public Health, Public Health Foundation of India, Hyderabad Institutional Affiliation

3. Acknowledgements Dr Hans Limburg Dr B R Shamanna Their inputs were critical to this presentation

4. Characteristics Cataract Surgical Rate (CSR) uses the population as the denominator Cataract Surgical Coverage (CSC) uses operated persons in the community as the denominator. Both can be used in conjunction to compare performance and pending workload at regional/ national level.

5. Cataract Surgical Rate (CSR) Number of cataract operations (eyes) conducted per million population per year Indicator for output on cataract intervention Denominator is total population while cataract occurs mainly in people 50+ Who is operated? (age, sex, 1 st or 2 nd eye, VA?) Depends on accuracy of data collection Risk of over- or under-reporting

6. What data is needed to calculate CSR? Population of administrative area Quantum of cataract surgeries (operated eyes) Time period when above events occur – i.e. specific year Usually obtained from secondary data sources.

7. Cataract Surgical Rate No. of Cataract Surgeries/ Year x 10 6 Population in Defined Area Cataract Surgeries refers to Operated Eyes

8. Cataract Surgical Coverage (CSC) Objective: coverage indicator measures accessibility & utilization of services measures actual community level situation independent of reporting system Assumption: -VA at time of surgery not known: use VA threshold conforming to surgical practice in survey area

9. Cataract Surgical coverage Sources of Data: –Surveys –RACSS/RAAB

10. What data is needed to calculate CSC? No. of cataract blind/visually impaired Quantum of cataract surgeries (eyes/persons) Time period when above events occur – i.e. specific year Valid data generally possible only from primary sources in LMIC. i.e. RAAB

11. Defining CSC Can be calculated at person level or operated eye level Can be calculated at different visual acuity levels (based on a country’s needs/ surgical practices) –VA<3/60: cataract blind eye or person –VA<6/60: severely visually impaired cataract eye or person –VA<6/18: visually impaired cataract eye or person

12. Calculating CSC CSC eyes: (a/a+b) x 100 Where: a = no. (pseudo)aphakic eyes b = no. eyes with operable cataract (BCVA<3/60; <6/60; <6/18) CSC persons: (x + y/x + y + z) x 100 Where: x = persons with bilateral (pseudo)aphakia y = persons with 1 (pseudo)aphakic and 1 operable cataract z = persons with bilateral operable cataract (BCVA<3/60; <6/60; <6/18)

13. THANK YOU