A smart solution to vision problems

Smartphone apps and peripherals that simplify the diagnosis of sight problems could help doctors to reach billions of people in low-income countries.
Andrada Fiscutean is a freelance science and technology journalist in Bucharest.

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Ophthalmologist Andrew Bastawrous uses a smartphone application to examine the eye of a woman in Kitale, Kenya.Credit: Rolex/Joan Bardeletti

In 2012, Andrew Bastawrous, an ophthalmologist at the London School of Hygiene and Tropical Medicine, moved to Kenya to study first-hand the causes of vision loss and blindness in low-income countries. He quickly realized that the problem was straightforward — most of the people with poor vision that he examined just needed glasses.

But fixing that problem is harder than it seems. About 2.5 billion people worldwide with poor vision don’t have access to glasses, according to the World Economic Forum. More than three quarters live in lower-income countries where citizens often have limited access to health care. In Kenya, for example, there are only about 100 ophthalmologists to serve a population of almost 50 million people. Even when people do manage to get an eye test and a prescription for glasses, many cannot afford to buy a pair.

In areas where infectious diseases such as AIDS, malaria or tuberculosis are common, and often fatal, correcting poor vision is a low priority. Yet this lack of glasses costs the global economy more than US$200 billion each year through lost productivity. As well as the wider benefits that glasses bring, including higher rates of literacy and improvements in road safety, correcting a person’s vision could increase their income by up to 20%, by improving their productivity and enabling them to perform skilled work.

Bastawrous noticed that many of the people that he encountered with easy-to-correct eye conditions had never consulted a doctor about them. The most vulnerable lived in remote areas, far from health clinics. But he was also aware that many of them had access to smartphones. Could the power of mobile-phone technology be harnessed to help improve people’s vision?

A peek into the future

To answer this question, Bastawrous designed a smartphone application called Peek Acuity, which follows the principles of an eye test conducted by a specialist. The app was developed through the Peek Vision Foundation, a UK-based charity that Bastawrous set up in 2015.

The app is based on the Snellen eye chart, a test for visual acuity developed in 1862 by Herman Snellen, an ophthalmologist from the Netherlands. During a conventional eye test, the person being examined is asked to identify letters in rows on a wall-mounted Snellen eye chart to measure sharpness of vision. The size of the letters is decreased in lower rows. People with vision problems tend to confuse similarly shaped letters such as F and P, or C and O. That test, when coupled with an examination of the eye, is able to screen for common problems such as short-sightedness, which causes blurring of distant objects, or long-sightedness, which leads to blurring of nearby objects.

Because many of those he assessed were young children or adults who couldn’t read, Bastawrous used a simplified version of the Snellen test that relies only on the letter E, in which the arms of the character follow one of four orientations (up, down, left or right). One by one, the letters appear on the screen of the smartphone, and the person being tested points in the direction in which they perceive the E to be pointing. The person giving the test then swipes the screen accordingly. The whole procedure takes an average of 77 seconds, a few seconds less than does a conventional eye test.

Bastawrous designed Peek Acuity so that it could be used by non-specialists to screen large populations. Volunteers with minimal training could travel to remote areas to test the vision of entire communities and then refer individuals with poor sight to a specialist. That way, Kenya’s limited pool of ophthalmologists would have to examine only people in need.

To validate the app, Bastawrous and his team conducted a study in 20,000 children from 50 schools in Trans Nzoia, a county in western Kenya. Students in half of the schools were screened for vision problems using a conventional eye chart, and the other half were screened using the app. Instead of sending a nurse to each school, which would substantially reduce the number of students that could be tested, the team trained teachers to perform the tests. About 5% of the students in the app group and 4% of those in the conventional-chart group were referred to a specialist for a professional examination1.

Guardians of students with vision problems in the app group received a postcard depicting their wards’ blurry view of the world, as well as an image of what they should be able to see. The Peek Acuity team also sent guardians text messages reminding them that the children needed further care. As a result, more than 50% of the children with vision problems that were identified using the app attended a follow-up appointment, compared with just 22% of those in the conventional-chart group.

Out of focus letters on one side, marked "how your child sees", and in-focus letters on the other, marked "normal vision"

Postcards illustrating the vision of students examined using the Peek Acuity smartphone app are sent to students’ guardians.Credit: Peek Vision

The project has since expanded. By November 2018, the Peek Acuity team had screened all 200,000 children in Trans Nzoia. Its next aim is to test everyone in Kenya. Volunteers equipped with solar-powered backpacks that can charge smartphones will be deployed to remote villages to test residents’ vision.

The achievements of Peek Acuity show that, when used in an innovative way, smartphones have the potential to change the lives of billions of people in low-income countries. “Smartphones are a very powerful tool to help people access eye care, particularly in markets where there’s a lack of well-trained eye doctors,” says Jordan Kassalow, the founder of VisionSpring, a social enterprise in New York City that helps people in developing countries to access affordable glasses, and co-founder of EYElliance, a non-profit organization in New York City dedicated to supporting eye-health initiatives in schools.

The full prescription

In addition to vision-testing apps, some companies have created devices that can be attached to smartphones to churn out not just a referral, but a prescription for glasses. Such devices make a visit to the ophthalmologist unnecessary for people with simple vision problems.

A leader in this arena is EyeNetra in Cambridge, Massachusetts. Its device, called NETRA, comprises a virtual-reality headset to which a smartphone is attached. When a person puts on the headset, instead of reciting the letters of an eye chart, they must align red and green shapes that are visible on the smartphone’s screen. People with poor vision are unable to complete the task. The types of error that they make enable the device to identify their specific vision problem. Similar to Peek Acuity, NETRA screens for short-sightedness, long-sightedness and astigmatism, which is caused by irregularly shaped corneas. But NETRA also collects measurements such as the distance between pupils — information that is crucial for determining where to centre each lens inside the frame of the glasses. The eye test — which takes 2–3 minutes to complete — provides the information necessary for a full glasses prescription.

The headset works in tandem with two other EyeNetra devices. For people who already wear glasses, Netrometer can measure the lenses to help confirm that their existing prescription is correct. Meanwhile, Netropter provides a full-range of lenses through which a person can look, to verify and refine the digital prescription that they receive during the NETRA test.

Vitor Pamplona, chief executive of EyeNetra, says that the devices could be used away from medical centres, especially in pharmacies, which are more common than medical centres in low-income countries. “Any pharmacist in a small village in India would be able to use [the devices] and get some glasses to the people who need them,” he says.

Bastawrous and his team are building on the success of their vision-testing app with a device called Peek Retina, which can be attached to a smartphone camera to take detailed pictures of the retina. Abnormalities in these images can indicate serious eye conditions such as diabetic retinopathy, a disease that can arise when high blood-sugar levels damage blood vessels in the retina.

The diversity and complexity of smartphone-based solutions for vision testing is likely to increase in years to come, potentially enabling fully automated eye tests. “In regions with limited budgets, and where there is limited access to traditional eye-care equipment, good-quality smartphone apps hold a lot of promise,” says Peter Holland, chief executive of the International Agency for the Prevention of Blindness in London.

Glasses for all

But apps and devices for diagnosis cannot alone remediate vision problems in low-income countries: people still need to be able to access treatment. Kassalow estimates that 75% of blindness and sight impairment worldwide is caused either by cataracts, which require a straightforward surgical procedure, or by an uncorrected refractive error that could be fixed simply with glasses. His organization, VisionSpring, has distributed more than 4.4 million pairs of glasses in lower-income countries since 2001. Although a pair of glasses can cost less than $1, that’s still too steep for many, Kassalow says.

A schoolgirl tries on some glasses while her friends look on

Correcting poor vision can bring educational advantages such as higher rates of literacy.Credit: Sandeep Biswas/VisionSpring

Prioritizing aid for correcting vision is challenging in the face of other, more pressing problems. EYElliance found that, in 2015, only $37 million was spent on providing access to glasses to people in the developing world. That’s less than 1% of the resources allocated to addressing all other global health and development problems, including malaria and access to clean water — or about 2 cents per person in need of glasses.

Governments, businesses, philanthropists and technology professionals, including app developers and data scientists, need to work together to solve the crisis of poor vision, says Tracy Matchinski, president of Volunteer Optometric Services to Humanity International, a non-governmental organization in Omaha, Nebraska, that sets up temporary eye-care clinics in areas of need.

Bastawrous understands that his app benefits only people who have access to glasses. So he partners with governments and organizations that can provide study participants with eyewear. Every child in Trans Nzoia who was tested during the Peek Acuity study, and then visited a specialist about a vision problem, walked away with a free pair of glasses.

doi: 10.1038/d41586-019-01110-z

This article is part of Nature Outlook: The eye, an editorially independent supplement.


  1. 1.

    Rono, H. K. et al. Lancet Glob. Health 6, e924–e932 (2018).

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