I have Parkinson's and I have tremors in my hands. I was hoping a track ball would help. However; with the trackball on the side of the mouse, I didn't realize how bad my thumb shook when I used the mouse. I cannot control the mouse icon on the screen. This is too bad, as I was hoping this would help me to use my computer. This in no way reflects the quality of the trackball mouse. It did feel more comfortable in my hand then a regular muse and it is heavy enough to stay put in one place. It just won't work for me. Instead of returning it, I know someone who will enjoy using it.