Cell Phone App Offers Eye Prescriptions

July 5, 2010— -- Two minutes, two dollars and a cell phone will soon be all it takes to get an eyeglass prescription.

Scientists from the Massachusetts Institute of Technology have developed a new app for smart phones that, when combined with a thin, cheap lens, could give inexpensive and accurate eyeglass prescriptions to smart phone owners. The research could help millions of people around the world see better for less money.

"Most ophthalmalogic devices range from simple eye charts to expensive autorefractors," said Ramesh Raskar, a scientist at MIT who will present the app at the upcoming SIGGRAPH 2010 Conference.

"We are somewhere in between. Here you just use your cell phone and a cheap optical plate to align a series of patterns."

The combined app and screen works like an old, analog camera with a manual focus lens. Unlike today's digital cameras, which focus automatically, the new app and screen requires the user to bring patterns into focus.

After loading the app, a user attaches a short, conical viewfinder (about $2 now, although Raskar thinks that will soon drop to 50 cents) to the screen of their high-resolution cell phones and peers in. A series of patterns appear. The user aligns the patterns by pushing buttons on the phone. The more button is pushed, the worse a person's eyesight.

The app repeats this process four times, one for each axis of the eye. During the process the app also measures other abnormalities, such as astigmatism. Once all the patterns have been lined up, the app spits out a person's eyeglass prescription.

Start to finish it takes about two minutes to deliver a full prescription.

Right now the new method is just as accurate as existing ophthalmalogic machines, and far, far cheaper than many. Within a few months the Near-Eye Tool for Refractive Assessment (or NETRA) system will be more precise than most lenses, said Raskar.

The app does have its limitations. Only cell phones with a high-resolution touch screen, such as the Nexus One or the iPhone, can run the app. The app is also only useful for people who can respond to the directions on the screen; most children could not use the app.