The Brock string was named after Frederick Brock, who developed it as a tool to help him correct his own vision problem.

When using the brock string, one end is held at the tip of the nose, while the other is tied to a fixed point—often our patients will use a doorknob. Three beads on the string are placed at different distances, and the patient must focus on each of the beads. It helps develop better binocular vision.

One of the most important pieces of equipment for vision exercises when working on convergence is the brock string. It offers instant feedback to the participant if their eyes are working together to focus on an object at various distances.

This is the 20 ft version