MIT Media Lab researchers have created a quick, simple, and inexpensive way to use mobile phones to measure refractive errors of the eye, including nearsightedness, farsightedness, astigmatism, and age-related vision loss. Until now, these measurements have only been possible using specialized equipment operated by a trained professional.

This new system, called NETRA (Near-Eye Tool for Refractive Assessment), is a project of the Media Lab's Camera Culture research group. A small plastic device—which currently can be produced for less than US$2—is easily clipped onto a mobile phone screen. To use it, simply hold the device up to the eye, look into it, and use the phone’s keypad until two patterns overlap. This is repeated several times per eye, with the patterns at different angles. The whole process takes about two minutes, during which time software loaded onto the phone computes and provides the data needed to create a prescription.

The small size and low cost of the device make it especially well-suited for use in the developing world. As many as two billion people worldwide have refractive errors of the eye, and according to the World Health Organization, these errors, left uncorrected, are the world's second-highest cause of blindness.

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