Patients sit with their eyes bandaged at an Aravind Eye Care clinic in Madurai, India after cataract surgeries. Aravind performs more than 300,000 cataract surgeries annually. Reinhard Krause/Reuters/Landov hide caption

itoggle caption Reinhard Krause/Reuters/Landov

Sound World Solution's hearing device lets a user customize its settings using a Bluetooth connection and a smartphone. Courtesy of Sound World Solutions hide caption

itoggle caption Courtesy of Sound World Solutions

Composer Richard Einhorn lost most of his hearing several years ago, but that hasn't held him back, thanks to state-of-the-art digital hearing aids. Kevin Rivoli/AP hide caption

itoggle caption Kevin Rivoli/AP