If you’re 50 or older and reading this article, chances are you are wearing a pair of inexpensive reading glasses to correct your presbyopia, or farsightedness, the age-related decline in vision that makes it progressively more difficult to see fine print and tiny objects.

Eventually, everyone gets the condition.

But for nearly a billion people in the developing world, reading glasses are a luxury that many cannot afford. According to the World Health Organization, the lack of access to corrective eyewear inhibits learning among young students, increases the likelihood of traffic accidents and forces millions of middle-age factory workers and farmers to leave the work force too early.

Uncorrected presbyopia, not surprisingly, makes it harder for breadwinners to support their families. That’s the conclusion of a new study which found that garment workers, artisans and tailors in Bangladesh who were provided with free reading glasses experienced a 33 percent increase in income compared to those who were not given glasses.

The study, published on Wednesday in the journal PLOS One, included more than 800 adults in rural Bangladesh, many of whom work in jobs that require intense attention to detail. Half of the participants — a mix of tea pickers, weavers and seamstresses between 35 and 65 — were randomly chosen to receive a free pair of reading glasses. The others were not given glasses.

Researchers followed up eight months later and found that the group with glasses had experienced a significant bump in income, receiving an average monthly income of $47.10, compared to $35.30 for the participants who did not have glasses.

The study subjects were evenly divided between male and female, and slightly more than a third were literate.

Dr. Nathan Congdon, the study’s lead author and an ophthalmologist at Queen’s University Belfast in Northern Ireland, said the results added to a mounting body of evidence that quantifies the economic impact of uncorrected vision in parts of the world where the roughly $1.50 it costs to buy a pair of so-called readers is out of reach for many.

“All of us would be happy with a 33 percent jump in income,” said Dr. Congdon, who specializes in low-cost models of eye care delivery. “But what makes the results especially exciting is the potential to convince governments that vision care interventions are as inexpensive, cost effective and life-changing as anything else that we can offer in health care.”

Dr. David S. Friedman, a professor of ophthalmology at Harvard Medical School who was not involved with the study, said he was struck by the results and hoped future studies would confirm the findings. “These economic impacts are large, real and could have a substantial impact on people’s lives,” he said.

Eye care has long been the neglected stepchild of public health in the developing world; infectious diseases like tuberculosis, malaria and AIDS tend to draw more robust government and philanthropic support. But vision impairment is a serious global issue, with a projected cost of more than $400 billion in lost productivity, according to the W.H.O.

Experts say spending on eye care can have a considerable impact on communities, both in terms of increased economic output and improved quality of life. Compared to other, more intractable health problems, addressing presbyopia is fairly inexpensive. Glasses can often be produced for less than $2 a pair, and fittings are usually carried out by community workers who can be trained in just a day.

Misha Mahjabeen, the Bangladesh country director for VisionSpring, a nonprofit organization that participated in the study, said a lack of resources was just one impediment to the increased distribution of reading glasses. In many Bangladeshi villages, she said, community workers must contend with the social stigma associated with wearing glasses, especially for women.

Overall, the health needs of women in Bangladesh take a back seat to those of men. “In our male-dominated society, when the man has a problem, it requires immediate attention, but women, they can wait,” she said.

But the effects of declining vision can be especially pronounced for women, who are often responsible for earning extra income for their families in addition to the child care and household chores, Ms. Mahjabeen said. “When it takes longer to sew and clean, or you can’t pick out all the stones from the rice, in some households it results in domestic violence,” she said.

VisionSpring distributes more than two million pairs of glasses a year throughout South Asia and Africa, up from 300,000 in 2018.

The study in PLOS One builds on previous research involving tea pickers in India that found a significant jump in productivity among study participants given reading glasses. The paper, a randomized study published in The Lancet Global Health in 2018, documented a 22-percent increase in productivity among workers who had been given glasses. For those over 50, productivity increased by nearly 32 percent.

Agad Ali, 57, a Bangladeshi tailor in the town of Manikganj, was among those who received a pair of glasses as part of the study that was published this week. In an interview conducted by a community health worker and sent via email, he described how worsening presbyopia had made it increasingly hard to thread needles and stitch clothing, adding to the time required to finish each tailoring job. Over time, he said, some customers went elsewhere, and his income began to decline. “It made me feel very helpless,” he said.

Since receiving the glasses, he said, his income had doubled. “These glasses are like my lifeline,” he told the community health worker. “I could not do my job without them.”