|Primary school enrolment rate||63%||Unicef25|
|Secondary school enrolment rate||27%||Unicef25|
|Health state valuation of visual impairment||0.755||Burden of disease study26|
|Remission rate of uncorrected refractive error (without screening or treatment)||0||Assumption*|
|Remission rate of uncorrected refractive error (intervention scenarios)||1.09||Calculation†|
|Compliance with wearing provided glassess||70%||Assumption based on Limburg et al27 in India; Hogeweg et al28 in Nepal‡|
|No of children to screen per teacher (5–10 years old)||165||Limburg et al29 in India¶|
|No of children to screen per teacher (8 years old)||50|
|No of children to screen per teacher (11–15 years old)||165|
|No of children to screen per teacher (13 years old)||100|
|Duration of training (days)||1||Assumption*|
|Repetition of training (every number of years)||5||Assumption*|
|Cost per teacher to train (cost per day)||45||WHO-CHOICE|
|Ratio of true positive:false positive cases||1:3.6||Limburg et al29 in India¶|
|Useful life of glasses (years)||4||Assumption*|
|Screening material costs (tape, card etc)||10||Assumption*|
|Treatment at health clinic:|
|Cost of ophthalmic assistant:|
|Time spent per patient (minutes)||15||Assumption*|
|Costs of ophthalmic equipment:|
|Costs of set||4||WHO-CHOICE|
|Useful life (years)||10||Assumption*|
|Average annual patient load||6400||Assumption*|
|Costs of spectacles:|
|Useful life (years)||4||Assumption*|
|Costs of outpatient visits:|
|No of visits||4.6||Limburg et al29 in India¶|
|Costs of visits at secondary hospital level||500||WHO-CHOICE|
*Based on personal communication with Dr Mariotti (WHO) and Dr Limburg (independent consultant), both specialists in ophthalmology in low and middle income settings.
†Formula is −LN(1−(effectiveness×coverage)), with effectiveness equal to compliance and coverage as defined in intervention. The table lists the remission rate for a coverage of 95%.
‡Estimates based on two studies in the respective regions, and are in line with findings from other studies in China34 and Thailand.35
§The number of teachers to train depends on the number of schoolchildren that one teacher can screen and, ultimately, on school size. In screening of children aged 5–10 years, a trained teacher can serve all classes in the school, on average 165 children. In case only children of aged 8 years are screened, the teacher can screen only that class, on average 50 children. The same logic applies to screening at secondary school.
¶To our knowledge, this is the only study that provides the required details on costs of screening for refractive error in a low income setting and has therefore been used as the basis for our estimates.