Many things can go wrong when you try to improve lighting. For example:
you could create glare or too contrast between much light and dark areas by installing a more powerful lamp
you could create heat and glare from an improperly designed and placed skylight
you could create glare and distraction by placing a worker facing a window cleaning windows,
you could improve the situation by skylights and lamp fixtures only to have the same problem return in a few weeks because of the lack of regular cleaning
you could increase the quantity of light when the real problem is the direction of light or the task background