Lighting from the right or left of my desk?
The only thing I can think of is that right handed people would probably prefer the light coming from the left&mdash;and vice versa&mdash;so that one's arm is not darkening the paper being written.

As for computer lighting, my 40+ years of experience as a software engineer (a heavy computer user) is that there should be a minimum of lighting around the computer to be able to perceive and enjoy the screen's dynamic luminescence and color range.  Bright lighting causes glare, obscures the images, and reduces the range of colors perceivable.

It may be helpful to have a desklamp beside the computer for when a book, paper, etc., needs to be viewed in the otherwise darkish room.