Scientists in London have come up with a way to use a mobile phone app to check people's eyesight.
It could mean people in remote parts of the world getting vital help they would otherwise miss out on.
The World Health Organization says 285 million people are blind or visually impaired, and this app could be a massive step forward.
The app, which uses a modified smartphone to diagnose people's eye problems, is being tested in Kenya.
BBC Reporter James Gallagher explains how it works.