Improving health worldwide Calculation of CSR and CSC and visual acuity thresholds Improving health worldwide .

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

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

Acknowledgements

• Dr Hans Limburg

• Dr B R Shamanna

Their inputs were critical to this presentation

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.

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, 1st or 2nd eye, VA?)• Depends on accuracy of data collection• Risk of over- or under-reporting

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.

Cataract Surgical Rate

No. of Cataract Surgeries/ Year x 106

Population in Defined Area

Cataract Surgeries refers to Operated Eyes

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

Cataract Surgical coverage

Sources of Data:

– Surveys

– RACSS/RAAB

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

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

Calculating CSC

CSC eyes: (a/a+b) x 100Where:a = no. (pseudo)aphakic eyesb = no. eyes with operable cataract (BCVA<3/60; <6/60; <6/18)

CSC persons: (x + y/x + y + z) x 100Where:x = persons with bilateral (pseudo)aphakiay = persons with 1 (pseudo)aphakic and 1 operable cataractz = persons with bilateral operable cataract (BCVA<3/60; <6/60; <6/18)

THANK YOU