The GAP identifies two key indicators for cataract – the Cataract Surgical Rate (CSR) and the Cataract Surgical Coverage (CSC) .
CSR data was obtained for 102 countries. All five countries in the South Asia Super Region reported and a good response was obtained from Latin America and the Caribbean with 28 out of a possible 32 countries. At the other end of the spectrum data was obtained for only eight of the 34 High-Income countries.
There was considerable variation in CSR between countries and thus the median, the upper and lower quartiles and the full range have been used to compare results across the Super Regions. Figure 1 summarises this data.
Figure 1: CSR for the 102 countries for which data is available
Updated on 12th Oct 2017
The median global CSR was 1,406 with an Inter Quartile Range of 633 to 2,450. When comparing Super Regions, most notable is the extremely low median CSR of 488 in Sub-Saharan Africa – one third of the global average and 1/13th of that seen in High-Income countries. None of this is a surprise and the reasons are well documented but the results starkly emphasise the inequity of access to Cataract surgery across the world.
In contrast, the CSR of Nepal and India was 4,364 and 4,830 respectively; a performance worthy of note given the modest socio-economic condition of both countries. A significant factor contributing to this success has been the concerted efforts to bring eye health services to the poorest communities and widespread capacity building of sustainable and efficient eye health systems.
Given the variation in the age profile of country populations and in the prevalence of blindness in different continents it is now accepted that CSR targets need to be set on a local basis. However it is still true to say that countries with a CSR of less than 1,000 are almost certainly falling well short of the required number of Cataract surgeries to prevent avoidable Cataract blindness and those with a CSR of less than 500 lamentably so. Of the 102 countries for which we were able to collect CSR data, 19 had a CSR of less than 500 with a further 23 countries between 501 and 1,000.
The CSC is a better indicator than CSR in terms of measuring the extent to which the need for cataract surgery in a population is being met by an eye health system. However, to determine the need a population survey has to be conducted and this limits the number of countries that can provide national-level CSC data – our analysis found 36 such studies. The need can be estimated for those with a visual acuity of <3/60 prior to surgery or for those at <6/18. (See here to understand how visual acuity affects sight.) Figures 2 and 3 below show the CSC (persons) at the two visual acuity cut offs.
At the <3/60 cut off 1/3 of the high- or middle-income countries achieved a coverage rate of 80% or more. Three low-income African countries and Timor Leste had coverage levels of less than 50%, clearly illustrating the inequity of provision across the world. It may be argued if we wish to prevent avoidable blindness and visual impairment from Cataract that the CSC at <6/18 is a more relevant measure. At this level of acuity only two countries attained a coverage rate of ≥80% whilst half the countries failed to achieve 40% coverage. There is still much to be done before we can eliminate avoidable cataract blindness and visual impairment for most of the world’s poorer populations.
80% is the minimum CSC target
The CSC is a better indicator than CSR in terms of
measuring the extent to which the need for cataract surgery
in a population is being met by an eye health system
The data analysis in this online version of the IAPB Vision Atlas represents the most recent available data as of October 2017. Data will be analysed regularly and updated here at regular intervals.
We have also avoided trying to ‘over analyse’ the available data given the limitations of some of the data received. We welcome input to make our data better.