Cardboard is built on very basic optic principles and with simple materials. It has been used to provide various virtual reality experiences, games, and has even been used in hospitals to provide 3D analysis without the need for expensive equipment. Now, Cardboard has helped a blind woman see for the first time in years.

The woman, named Bonny, suffers from Stargardt disease. It is a common form of vision loss that causes photoreceptor cells in the retina to die and in rare cases can lead to complete vision loss. Bonny used Cardboard in conjunction with a free app called Near Sighted VR Augmented Aid. The app takes a video feed from a phone’s rear facing camera and delivers the same image to each eye. This is known as a stereoscopic image and how Cardboard already works.

In this particular case, this was enough to help Bonnie see again for the first time in eight years. While the technology is simple in principle, dedicated headsets whose sole purpose is to provide a split screened camera feed are expensive. Most people have a smartphone and Cardboard viewers start at $20, with more durable plastic viewers that have a head strap and can be worn all day costing only a little more.