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I'm curious - can't doctors tell if people are asleep/unconscious by shining light into the eye to look for dilation? Why wouldn't that also wake them?

And on another note, it seems like emergency alarm systems should alert people in a number of different ways. Apparently it's not unusual for kids to sleep through regular household smoke detector alarms.

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The pupillary reflex is a brainstem reflex. As long as there is brainstem activity, you'd expect that reflex to be present (exceptions: brainstem death, cranial nerve damage, depressants/anesthetics, probably a few others).

You can't tell if someone is awake based on pupillary light reflex.

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