As the smartphone falls in price while its capabilities improve, it is becoming a valuable tool in the diagnosis of a growing number of diseases and ailments around the world. When Yonatan Adiri's mother fell down a bank and briefly lost consciousness when travelling in China, an initial diagnosis suggested she had a few broken ribs, but nothing more serious. Doctors were keen to fly her to Hong Kong for treatment. But Yonatan's father was worried and took photos of the CT [computerised tomography] scans of the injuries, emailing them to his son. Yonatan showed the images to a trauma doctor, who instantly diagnosed a punctured lung.

"Seven hundred years after glasses were invented there are still 2.5 billion people in the world with poor vision and no access to vision correction," says Hong Kong philanthropist James Chen. Chairman of his family's Nigeria-based manufacturing company, Wahum Group, Chen is funding a contest called the Clearly Vision Prize that will award a total of 250,000 to projects that improve eyesight, especially in poor countries. Thirty-six semifinalists were announced this week (the five winners will be awarded September 15). Among the contenders: 3D printed eyeglass frames, drones that deliver medical supplies, and several smartphone-based technologies. Some of the smartphones help nonexperts test vision, and one uses artificial intelligence to "see" for blind people. The Clearly Vision semifinalists represent just a sampling of the smartphone projects fighting vision loss, a growing field that is bringing critical care to remote regions far from hospitals and doctors offices.