While waiting for my RollerMouse buttons to arrive (see RollerMouse Red Problems, I tried a spare mouse for a day or so before realising it was aggravating my RSI (repetitive strain syndrome). I decided to explore ergonomic alternatives and came across the Evoluent Vertical Mouse, model C.
As the video below explains, it changes the orientation of the arm while using it.
My experience to date is that it does relieve the strain. However, it's best suited to keyboards that lack a numeric keypad, as most laptops do.
My reasoning is that lateral movement still affects the upper arm as the mouse travels across the screen at normal speed.
In my case, I have a three-monitor setup, and the movement becomes excessive. To compensate, I've adjusted the speed to a high rate, so that less movement is needed. However, this reduces the accuracy needed when settling on a precise location.
When I finally revert to my RollerMouse, I shall transfer the Vertical Mouse to my laptop, where it will be most welcome.