Smartphone add-on will bring eye test to the masses

HAVING trouble reading your cellphone’s screen? If that’s because you need glasses, your phone itself could be used tell you what strength lenses you need.

Ramesh Raskar of the Camera Culture group at the Massachusetts Institute of Technology has devised a method of providing basic eye tests using only a smartphone and a specially designed eyepiece. It could provide a home-based eye test for millions of people who cannot easily access regular optometry services.

Raskar’s Near-to-Eye Tool for Refractive Assessment (Netra) consists of a viewer that fits over a cellphone’s screen combined with software running on the phone. To test a person’s eyesight, the phone displays an image which the eyepiece converts into a virtual 3D display.

The user is then asked to focus on the image and use the phone’s keyboard to adjust the lines so that they merge. Based on the amount of adjustment needed, the software will show the strength of the corrective lenses required, measured in dioptres.

Unlike a traditional 3D display, which presents a slightly different view to the left and right eyes, Netra presents different views to different parts of the same eye simultaneously. If the user has perfect eyesight, these images will overlap and appear as a single image, says postdoctoral researcher Ankit Mohan, who worked on the design. If their vision needs correcting, they will see parallel lines that they will need to adjust.

Cellphones have reached remote villages in Asia, Latin America and Africa, making them ideal diagnostic devices, says D. Balasubramanian, the director of research at the L. V. Prasad Eye Institute in Hyderabad, India.

In its current form, Netra needs phones that can be programmed and have a high-resolution display, which are less common in remote areas, Balasubramanian adds.

The work will be presented at next month’s Siggraph conference in Los Angeles.