Stand with your feet hip-width apart. Hold your thumb or object out in front of you at eye level. Make sure you can get clear focus on the object.
Keep the object in focus while you rotate your head from side to side, moving the object at the same speed as you move your head. Move at the highest speed you can while keeping the object in clear focus. The apparent visual movement in the background may make you feel dizzy. Rest if you need to between attempts to allow the dizziness to subside, then return to the exercise.
You can repeat this with the head moving up and down, or in a diagonal pattern.
