PROductivity Study of Presbyopia Elimination in Rural-dwellers (PROSPER)

Main research question being addressed: To establish, using a randomized, controlled design, the impact of near eyesight correction on the productivity of presbyopic agricultural workers in India, as measured by weight of tea picked.

Primary outcomes to be measured: Change in mean daily weight of tea picked per worker during a 12 weeks period after randomisation compared to a 4 weeks baseline period prior to randomisation. (See details below under Main Outcome.)

I. Background: Importance of research topic, Particular Features of setting Uncorrected presbyopia is an expensive problem for the world. Lost productivity among adults who need eyeglasses has been estimated to cost the global economy $227 billion every year, [1,2] and illiteracy may lead to a further $3 trillion in annual global economic losses. It has been shown that 74% of illiterate adults failed one or more parts of a vision screening. [3] However, in order to motivate governments, industry and other key stakeholders to invest in solving the problem of uncorrected near vision in adults, higher-quality data on the productivity impact of correction are needed. Current studies are suggestive, but carefully-performed randomized trials are still lacking in the published literature.

An unpublished University of Michigan (USA) working paper found that correcting near-vision loss with glasses yields an increase in productivity of up to 34%, though no control group was included, and the outcome assessed was not precisely defined. An unpublished impact assessment conducted by Building Resources Across Communities (BRAC), the world's largest NGO in the number of staff, concluded that 90% of individuals experiencing near-vision loss in Bangladesh encountered problems with their daily work; and, on average, 23% reported that their income was compromised.[4] In Rwanda, Lifetime Consulting & Partners found that workers with poor vision who did not wear glasses were three times more likely to be asked by supervisors to repeat their work of sorting coffee beans than after receiving and wearing glasses.[4] Again, no control group was included, and this work has not been published. Furthermore, a Dalberg Global Development Advisors study of adults in India who had their vision corrected with glasses found that 65% reported an increase in independence in movement and travel, and 59% reported improved work productivity, [5] but these outcomes were not confirmed quantitatively or objectively. Finally, a population study of 1008 older adults in Shenyang, northern China, found that those with uncorrected presbyopia (69%) were more likely to report diminished accomplishment due to vision (P = 0.01, adjusted for age, sex, education, and distance vision) than were those without presbyopia. [6] The impact of correcting presbyopia was not studied in a prospective fashion.

In summary, available data are consistent with the idea that correcting presbyopia can lead to significant improvements in productivity among adult workers. However, in the absence of high-quality randomized trials, it is very difficult to be certain about cause and effect: it is equally plausible that the economic burden of poverty could result in failure to purchase glasses, rather than the reverse. Lack of control groups and carefully-defined productivity outcomes in many studies further hinder interpretation. Policy makers and industry partners require more convincing data in order to commit to the support of programs of vision correction.