A pioneering eye test could save the sight of millions by helping doctors tackle the biggest global cause of permanent blindness.

The test allows early detection of glaucoma so that treatment can start before vision begins to deteriorate.

It also has potential for diagnosing degenerative neurological conditions including Parkinson's, Alzheimer's and multiple sclerosis.

Glaucoma, caused by the death of retinal cells at the back of the eye, affects 60 million people around the world, a tenth of whom are completely blind.

The new technique, called Darc (detection of apoptosing retinal cells) uses a special fluorescent marker which attaches to cell proteins when injected into patients.