Eye check-up with a mobile phone developed at MIT

Scientists at Boston's Massachusetts Institute of Technology have developed a snap-on lens that enables a smartphone to give an eye test.

Patients use the phone's controls to move images seen through the lens while the phone analyses responses.

The results can be sent to doctors.

The Netra research team behind the technique believe it will prove useful in developing countries where expensive eye testing equipment is scarce.

Project leader Professor Ramesh Raskar has shown BBC Technology Reporter Jonathan Fildes how the system works.