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.
The app should not replace trips to optometrist, said Raskar. Optometrists incorporate a patient's medical history and other factors into a final eyeglass prescription. Beyond the accuracy of a patient's glasses though, optometrists also check for eye diseases like macular degeneration and cataracts.
The MIT app can't test for diseases that would rob a person of their sight, at least not right now, said Raskar. Adding disease detection to the app is one goal of the group.
The first step was developing the app. The next step is to deploy it, first in the United States and then across the world. MIT is working with various NGOs in different countries to help distribute both the app and the screen, which together will be known as PerfectSight. Within three to six months Raskar hopes to have everything ready to roll out worldwide.
"What's really cool about this project is that it can be deployed worldwide," said David Brady, a optics expert and professor at the Duke University. "People might not have good access to high-quality ophthalmologic equipment, but throughout the world there is good access to cell phones."
"It's an amazingly simple strategy that give you a pretty good estimate" of a person's eye prescription, he said.