Last week, at a conference in London, Dr Pearse Keane beamed an image on to the wall of an orange globe with a dark centre, encircled by red storms and a bright moon. It looked like a dying planet in a distant galaxy. In fact, it was a beautifully detailed scan of the back of a human eye, as awesome in its way as the night sky.

These days, Dr Keane said, that single image betrays a lot of information. "We can now look at a retinal photograph and say: 'This is a woman. She's 58, she's a non-smoker. She's not a diabetic, her BMI [body mass index] is around 25. And her blood pressure is 150 over 85. That's pretty amazing."

The Telegraph London