Reddy PA, et al. - In this randomised trial, researchers determined the impact of near glasses on the productivity of tea workers aged 40 years or older with presbyopia in India. It was noted that the cost of glasses per person, including delivery, was $10.20. In this rural cohort, a substantial productivity increase was achieved by providing glasses to correct presbyopia, with little cost and high intervention uptake.

Methods

• This trial was conducted on tea pickers aged 40 years or older in Assam, India, with unaided near visual acuity (NVA) lower than 6/12 in both eyes, correctable to 6/7.5 with near glasses; unaided distance vision 6/7.5 or greater; and no eye disease.
• Participants in the study were randomly assigned (1:1) to receive free glasses optimising NVA at working distance (cost including delivery US$10.20 per person), either immediately (intervention group) or at closeout (control group).
• By age, sex, and productivity, participants were stratified.
• The difference between groups in the change in mean daily weight of tea picked (productivity) was the primary outcome (investigator-masked), between the 4-week baseline period (June, 2017) and the 11-week evaluation period (July 24, 2017, to Oct 7, 2017).
• Workers' income was tied to their productivity.
• Compliance with study glasses was evaluated at seven unannounced visits.
• Outcomes were analyzed on an intention-to-treat basis.

Results

• One thousand, two hundred ninety-seven (48.1%) of 2699 permanent workers met the age criteria and consented for eye examinations between July 3, 2017, and July 15, 2017.
• Seven hundred fifty-one (57.9%) fulfilled vision criteria and were randomly assigned to the intervention (n=376) or control (n=375) groups.
• In baseline characteristics, groups did not differ substantially.
• They found that no study participants owned glasses at baseline, 707 (94.1%) received the allocated intervention, and all were followed up and analyzed.
• Mean productivity in the intervention group raised from 25.0 kg per day to 34.8 kg per day (an increase of 9.84 kg per day), a significantly higher increase than in the control group (from 26.0 kg per day to 30.6 kg per day; an increase of 4.59 kg per day), corresponding to a between-group difference of 5.25 kg per day (95% CI 4.50–5.99; 21.7% relative productivity increase; effect size 1.01 [95% CI 0.86–1.16]; p < 0.0001) between the baseline and evaluation periods.
• It was observed that intervention-group compliance with study glasses reached 84.5% by closeout.
• Regression model predictors of greater productivity increase involved intervention group membership (5.25 kg per day [95% CI 4.60–5.91], p < 0.0001) and, among intervention participants, older age (p=0.039) and better compliance with the intervention (p < 0.0001).