I have a office department of designers working on multiple screens in an area with no natural light but with LED daylight panels in the ceiling.  Is there a source of information that I could use to ensure that I have the correct lighting level compatible to working with screens all day. 

Its worth being aware that most LED units also flicker in the same way as the old fluorescent tubes they replace - this flicker can be the cause headaches and eyestrain in users even though the flicker may be imperceptable.  Once upon a time it was possible to purchase a flicker meter to evaluate the extent the extent of the problem - it helped me solve office based problems a number of times.

Post retirement I still have one in my tool kit.

Martyn