A smartphone app to diagnose cataracts and other eye-related problems in people in developing countries is undergoing testing.

The Portable Eye Examination Kit or Peek includes an app-based diagnosis tool and clip-on hardware to examine cataracts and retina problems, the London School of Hygiene and Tropic Medicine says on its website.

About 285 million people are visually impaired worldwide and about 90 per cent of them live in developing countries, according to the World Health Organization. Eighty per cent of all visual impairment can be avoided or cured, the agency says.

"What we hope is it'll provide a paradigm shift where no longer are patients who can't afford to come to the hospital not coming, but you've got effectively experts, because they've got this device in hand, going to the front door of the patient," said Dr. Andrew Bastawrous, an ophthalmologist and researcher at the London School of Hygiene and Tropical Medicine who helped design the app.

Bastawrous is testing the technology on 5,000 people in Kenya to see how effective it is compared with hospital equipment. He's looking for scientific evidence of whether it changes practice and increases access to eye care.

The same 5,000 patients will be retested by a mobile team of clinicians to make sure the findings are accurate.

Dr. Iain Livingstone of the Glasgow Centre for Ophthalmic Research is impressed with the technology.

"The idea is that somebody with no training can point this to an eye and take an accurate, high-resolution video sweep of somebody's retina."

Here's how it works:

A health-care worker travels by motorbike or foot to examine patients in remote locations at their homes.

Images of the eye are stored on the phone and can be transmitted to experts anywhere in the world.

Once an issue is diagnosed, treatment can be planned and co-ordinated.

Google Map guides a health-care worker back to the patient to take him or her for the operation to restore vision.

The technology is also being tested in the Antarctic.