Provision of Near Glasses Improves Productivity in Indian Tea Pickers: PROSPER Randomized Trial

Abstract

Purpose : Presbyopia is the commonest cause of vision impairment globally, but no randomized trial has addressed the effect of correction on work outcomes. We assessed impact of providing near glasses on productivity among presbyopic tea workers in rural India.

Methods : All permanent tea pickers aged >=40 years at three plantations in Assam underwent eye examinations and assessment of near visual acuity (NVA, 40cm). Eligibility criteria were: Habitual NVA < 6/12 in both eyes, correctable to 6/7.5 with spherical near glasses; uncorrected distance vision >= 6/7.5; no eye disease. Enrolees were randomized (1:1, stratified by age, productivity) to immediately receive free spherical spectacles optimizing NVA at their working distance (Intervention) or to receive glasses at study closeout (Control). The main study outcome, assessed by intention to treat in investigator-masked fashion, was difference between groups in change in mean daily weight of tea picked (productivity), between a 4-week baseline and the 11-week evaluation period. Spectacle wear was assessed at 7 un-announced visits.

Results : Among 2699 permanent workers, 1297 (48.1%) met age criteria and consented for examination, and 751 (57.9%) met vision criteria and underwent randomization to Intervention (n=390, 51.9%, mean age 47.1+/-5.36 years, 76.2% women) or Control (n=361, 48.1%, mean age 47.3+/-5.62 years, 80.1% women). Groups did not differ significantly in baseline characteristics. No participants owned glasses at baseline, all received allocated intervention, and none were lost to follow-up. Intervention group compliance with study glasses was 70.9%. Mean productivity increase in the Intervention group (35.1-25.0=10.1 kg/day) was significantly greater than in Controls (30.1-26.0=4.10 kg/day, difference 6.00 kg/day, 95% CI 5.28, 6.71, P<0.001). In regression models, predictors of greater productivity increase included Intervention group membership (6.23, 95% CI 5.59, 6.86 kg [24.4%], P<0.001), and older age and better compliance in the Intervention group (both P<0.001). Rise in productivity compared to Controls by age was: 16.4% (40-44 years, n=144), 23.2% (45-49 years, n=107), 32.1% (50+ years, n=139, p<0.001).

Conclusions : Provision of near glasses, needed by >50% of workers aged 40+, improved productivity (24%) more than previously reported by other health trials in low-resource areas (nutritional supplements: 0-10%; mosquito nets: 15%).

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.