Swiss optometrist Frederick Brock developed an eye coordination exercise using a 5-foot string with three colored beads to improve focus and coordination.
This is a simple ocular workout where you try to aim at a fixed point with both your eyes. You can also call it a near point of convergence exercises.
This is a common exercise for outward squint eyes. Draw three barrels of progressive size in red lengthwise on one side of a card. Do the same thing in green on the other side.