Andrew Steer asked the Naked Scientists:
When we are tired, possibly on the day following a bad or interrupted
night's sleep, as well as being generally a bit groggy/irritable, why do we
principally feel the tiredness in our eyes?
The eyes may be a bit dry, bloodshot, the eyelids "heavy" (can't keep 'em open) - we are familiar with the symptoms.
Is the effect of lack of sleep on the eyes direct or indirect?
What do you think?