When someone wakes up (regardless of whether they are blind or not), they should recognize when they are conscious. If you have the ability to sense your environment through other senses, and control your limbs, that is also a good sign.

Uh... how do you know you are awake? How does anyone?

Lol what? If I were asleep, would I have typed out this response?

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Blind doesn’t always mean you don’t see light.

They could set alarms on their phones to wake them up.