NETRA, an add-on for mobile phones, enables users to quickly and inexpensively test their eyesight.
CAMBRIDGE, Mass. — There are two standard systems for determining a prescription for eyeglasses. One is to have the patient look through a large device called a phoropter, fitted with dozens of different lenses that can be swung into place in front of each eye in various combinations, while the patient tries to read a standard eye chart on the wall ahead. The other uses a more expensive system called an aberrometer that shines a laser into the eye and uses an array of tiny lenses to measure its characteristics, with no interaction from the patient.
Now, a team at MIT’s Media Lab has come up with a much quicker, simpler and cheaper way to get the same information — a method that is especially suitable for remote, developing-world locations that lack these expensive systems. According to the World Health Organization, uncorrected refractive errors are the world’s second-highest cause of blindness, affecting some 2 percent of the world’s population, and two billion people have refractive errors; all these people are potential beneficiaries of the new system. The team is preparing to conduct clinical trials, but preliminary testing with about 20 people, and objective tests using camera lenses, have shown that it can achieve results comparable to the standard aberrometer test.
In its simplest form, the test can be carried out using a small, plastic device clipped onto the front of a cellphone’s screen. The patient looks into a small lens, and presses the phone’s arrow keys until sets of parallel green and red lines just overlap. This is repeated eight times, with the lines at different angles, for each eye. The whole process takes less than two minutes, at which point software loaded onto the phone provides the prescription data. The device is described in a paper by MIT Media Lab Associate Professor Ramesh Raskar, Visiting Professor Manuel Oliveira, and Media Lab student Vitor Pamplona (lead author of the paper) and postdoctoral research associate Ankit Mohan, that will be presented in late July at the annual computer-graphics conference SIGGRAPH.
“Our device has the potential to make routine refractive eye exams simpler and cheaper, and, therefore, more accessible to millions of people in developing countries,” Oliveira says.
contact: Jen Hirsch – MIT News Office
written by: David Chandler, MIT News Office