Meredith Plumb, after the accident that damaged her sight
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I have no sense of time

12 May 2014 Last updated at 09:27 BST

Meredith Plumb's eyes were badly damaged when a chemistry experiment exploded in her face when she was 11 years old.

Now, almost fifty years later, she has no sense of light or darkness, and therefore no external sense of time.

Here she tells the BBC how it feels to have no body clock, and how listening to the radio helps her stay connected with the world around her.

Video journalist: Victoria Gill