Simple glasses-prescription method

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.

In its simplest form, the test can be carried out using a small, plastic device clipped onto the front of a mobile phone’s screen. To use it, a patient holds it up to the eye, looks into it and uses 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.