I'm sorry to read of Tom's difficulties. I hope some of the medical folks will have a few helpful things to suggest.

There are lots of ways to set computer browsers and monitors to lessen the brightness. Make the desktop background black, to start with, and look at the browsers that allow you to control settings to do with font size and such. I know IE and Firefox have that (I was looking at them recently as I looked for the way to do something unrelated to those settings, but notice they are there.)

SRS