Q: I have clear blue light blocking glasses / blue light filters in my prescription lenses - is this the same? 
A: No. Transparent lenses block maximum 50%, whereas these block 100% of blue light - you need these for night, the others are suitable for daytime.

Q: I don't watch a screen or use my phone in the 2 hours before bed - do I still need them?
A: Yes, because ceiling lights also emit blue light.

Q: Do I wear them to sleep?
A: No, 2 hours before bed, and if / when you wake in the middle of the night.

Q: I use night shift - is this sufficient? 
A: No - it makes a minor difference (4%) in the amount of melatonin your body produces - meaning with or without night shift, your sleepiness hormone is suppressed and it will be hard for you to fall and stay asleep.