It started in my early forties, and it’s only gotten worse since then. At first, it was a mild annoyance, but now it affects my quality of life and makes it harder to get things done. I’m definitely not alone—almost every middle-aged person I know has the same problem—and maybe you do too: a condition called presbyopia, a type of age-related vision loss that makes it difficult to see things clearly at close distances.

Luckily, the condition is easily and inexpensively treated with reading glasses, widely available at nearly every corner drug store in the United States. Reading glasses work well, and they’re cheap enough that I have them stashed around my house so a pair is always in reach. But an estimated 510 to 826 million people around the world have presbyopia but do not have corrective glasses.¹See Bastawrous, Kassalow, and Watts 2024.

What we know and what we don’t know

We think that providing reading glasses to people who need them is a promising way to improve their employment opportunities and increase their economic well-being. It makes intuitive sense that being able to see better would improve people’s ability to work, particularly for vision-intensive jobs such as crop cultivation and inspection, manufacturing, or retail work.

We’ve looked at two studies of programs that distribute reading glasses—one of tea pickers in India and one of workers in a variety of vision-intensive occupations in Bangladesh, such as tailors and carpenters—and they both suggest that distributing reading glasses has a positive economic effect for the people who receive glasses.²Reddy et al. 2018, Sehrin et al. 2024. Based on those studies, we think it’s likely that providing workers with reading glasses would be a cost-effective use of funding. However, we’re uncertain about how cost-effective it would be, as the studies don’t provide all the information we need.

For example, the study in India was only 11 weeks long, so it wasn’t able to assess the effect of having reading glasses over a longer time frame. It focused on productivity, measured by the average weight of tea picked each day, and we’re not sure how to translate this to increases in consumption for workers with other jobs.

The study in Bangladesh focused on vision-intensive occupations, but most reading glasses distribution programs provide glasses to a wider population. As a result, the real-world effect size is likely to be smaller than what was found in the study, but we’re not sure how much smaller. That study also measured self-reported income rather than consumption. The latter is based on household expenditure rather than earnings, and we think it is likely to be a more reliable indicator of economic well-being in low-income countries.³We think consumption is a better indicator of material well-being than income because:
• In low- and middle-income countries, where many people work in the informal economy, we think that asking people what they purchased over the past week or two (setting aside large, infrequent purchases like a home or a vehicle) is likely to be a better measure of their material well-being than asking people about their income, which might be quite variable because of, for example, seasonality in harvests for those primarily working in agriculture.
• There are more established methodologies for measuring consumption: “Against this backdrop, practical guidelines have been developed to assist researchers and analysts computing broadly comparable and theoretically consistent consumption aggregates and poverty measures from household surveys (Deaton and Zaidi 2002), but much less information is available for low-income countries in terms of looking at income data.” Carletto, Tiberti, and Zezza 2021, p. 2.
• Consumption better captures different potential sources of income and any offsetting effects. For example, if a person works more in one business and less as a casual laborer, their consumption won’t rise as much as one might expect looking only at their business revenues.

What do we want to learn?

Since we’re not as confident as we’d like to be in the effect of distributing reading glasses, we’re co-funding a study to find out more before we allocate significant funding to direct delivery of glasses. We’re recommending a $4.8 million grant for the study. The Livelihood Impact Fund is contributing $1 million of that total. (See our grant page here for more details.)

The randomized controlled trial, which will be carried out by researchers at the London School of Hygiene & Tropical Medicine, will include 20,000 adults with presbyopia in India and Kenya, two countries where we might fund eyeglasses distribution programs in the future. Half of the participants will be randomly assigned to receive free glasses during the study, while the other half will receive glasses at the end of the trial period. The study will be designed to address several of our uncertainties and to fill gaps in the existing evidence:

• Effect on consumption. Among the study’s outcome measures is the effect of eyeglasses on household consumption, which will be measured by asking participants questions about household size and how much they have spent or consumed in a specific period of time, across a range of goods and services such as food (purchased and home-produced), clothing, durable goods like a tin roof, and health expenses.
• Effect over time. The study will measure the effect of glasses at 12 months and 24 months to assess the longer-term effect of eyeglasses and whether that effect decreases over time. The long trial period is useful in part because we’re uncertain about how long eyeglasses typically last.
• Occupation-specific effects. The trial will draw participants from the general population and analyze data from specific subgroups, providing both average effects and effects on those with vision-intensive jobs. This will allow us to think more about program targeting.
• Multiple measures of economic well-being. The study will measure several related outcomes, such as household consumption, self-reported income, and workplace productivity. This will allow us to compare the results and better understand the relationship between them.

The value of learning

Research like this has benefits, regardless of the results. With more and better information, we can more confidently decide where to allocate funding.

If the results of the trial show that eyeglasses increase consumption as much as (or more than) we currently estimate, we would be more confident in allocating additional funding to programs distributing reading glasses.

Conversely, if the results of the trial show that eyeglasses do not increase consumption as much as we expect, we could instead allocate funding to other programs that are more cost-effective. In that case, the funds that we might have allocated to reading glasses distribution would instead be used to fund something even more impactful.

We believe that funding the trial is a cost-effective use of resources: we expect to learn from the results and thus improve our future funding decisions, the study will contribute to the information available to other scholars and organizations about eyeglasses distribution, and we expect the program to directly benefit the 20,000 participants.