Terry Byland, from Corona, California, was only 37 when retinitis pigmentosa was diagnosed. The degenerative and incurable eye condition, he was told, would slowly but inexorably leave him blind.

When the lights went out seven years later, he assumed that he had seen his son, then 5, for the last time. That was all to change when he volunteered to become the sixth patient to be fitted by Professor Mark Humayun with an experimental artifical retina.

“Aged 37, the last thing you want to hear is that you are going blind — that there’s nothing they can do,” he said. “It was amazing to see something. It was like little specks of light, not even the size of a dime, when they were testing the electrodes one by one.

“At the beginning, it was like seeing assembled dots, now it’s much more than that. Now my visual cortex, which was dormant, is learning to work again.

“We were told before it would be a very slow and very tedious process. Well, we’ve gone far beyond that. It’s such an exciting project.”

He now has a field of view about ten inches (25cm) wide. He cannot recognise faces but can see movement and shapes.

The highlight of his new world has been the ability to see his son again, however dimly. “I was with my son, walking, the first time,” he said. “It was the first time I had seen him since he was 5 years old. I don’t mind saying, there were a few tears wept that day.”

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