At the very back of the eye is a cluster of cells called ipRGCs. They are cells that don’t depend on vision to sense light, and that keep the circadian rhythms of both sighted and non-sighted people in sync with the sun. Without them, we would not feel the pull of sleep at night; we might fall asleep in the middle of the day and we would feel perpetually jet-lagged.

Disagree with half of it, enjoy reading all of it
TRY 3 MONTHS FOR $5
Our magazine articles are for subscribers only. Start your 3-month trial today for just $5 and subscribe to more than one view
Already a subscriber? Log in
Comments
Join the debate for just £1 a month
Be part of the conversation with other Spectator readers by getting your first three months for £3.
UNLOCK ACCESS Just £1 a monthAlready a subscriber? Log in