I know that gnome has special high contrast themes, also in Ubuntu 7.10 (Gutsy) compiz fusion is enable by default (when you have the right video card!), there is a zoom function there which works very nice, I use it holding the windows key and then scrolling with the mouse to zoom in and out. The screen automatically moves with the mouse so you can work like that quite comfortably actually.
Good luck and don't hesitate to ask more although I'm not a specialist...
edit: You can also set in the pointer option menu that pressing alt highlights the pointer so it is easier to find.
Last edited by teek; 12-20-2007 at 05:15 AM.