MIT Media Lab researchers have developed a mobile-phone application that, coupled with a small plastic device held over the screen, can determine users' eyeglass prescriptions. Called NETRA or near-eye tool for refractive assessment, the system asks users to align lines on the phone's screen while looking through a small plastic cube.
"So imagine if you could use your mobile phone, hold it right next to your eye, click a few buttons, say calculate and get your prescription for your glasses," said Ramesh Raskar, an associate professor at the MIT Media Lab.
He said that the reason the technology works is because the resolution on phones is improving dramatically. "That allows us to create a waveform that's coming out of your display by simply adding a small optical film," he said. "Drop it on top so that the waveform that's coming out of it can be manipulated to effectively compensate for the aberrations in your eye."
The application shows two lines on the phone's screen. It asks users to align them using the phone's arrow keys while looking through the small plastic device placed atop the screen. The test is repeated eight times with the lines in different places on the screen, after which the application calculates the user's prescription. The whole process takes about two minutes.
The plastic pieces cost about $1 to $2 now, but the group thinks that mass production could drive them down to only a few cents each.
The World Health Organisation estimates that 2 billion people have refractive errors and that uncorrected refractive errors are the world's second-highest cause of blindness.
Eye prescriptions are typically diagnosed using a phoropter or an aberrometer. The former uses a bulky case of trial lenses that are swung in front of each eye in various combinations. The latter shines a laser into the eye and measures its characteristics with no interaction from the patient.
Raskar said that the phoropter method isn't reliable because "deciding what your prescription should be based on when it looks most clear is not a very objective measurement."
Compared to the traditional methods, NETRA is less expensive and more portable. The team plans to commercialise the system and initially target parts of Africa and Asia. Prior to that they will begin field testing it in Boston in the coming months.
In addition to Raskar, visiting professor Manuel Oliveira, Media Lab student Vitor Pamplona and postdoctoral research associate Ankit Mohan worked on the project as part of the lab's Camera Culture Group. The research will be presented in late July at the annual computer graphics conference SIGGRAPH.
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