Simple glasses-prescription method

There are two standard systems for determining a prescription for eyeglasses to correct refractive errors such as nearsightedness, farsightedness and astigmatism.

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.

’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,’ said MIT Media Lab’s Visiting Prof Manuel Oliveira.

Apart from the software to run on the phone, all that’s needed is the snap-on plastic device, which Mohan says can be produced at a cost of about $1 (70p) to $2 today, but could cost only a few cents in large quantities.

The team will be field-testing the device in the Boston area this summer and will later test it in developing countries. The team already has applied for a patent on the system, named NETRA (Near-Eye Tool for Refractive Assessment).

The MIT group plans to launch production of the device as a for-profit company called Perfectsight, initially targeting parts of Africa and Asia. Ultimately, they also hope to produce a more advanced version that can incorporate its own higher-resolution display and be able to detect other conditions, such as cataracts.

The team is preparing to conduct clinical trials, but preliminary testing with about 20 people and objective tests using camera lenses has shown that it can achieve results comparable to the standard aberrometer test.