Brock String Foundations – Part One: Where the Strings Cross

When introducing the Brock String, begin with the most foundational setup: one bead placed at a comfortable distance from the patient’s nose. Have the patient either sit or stand with the string held at the tip of the nose and secured at the other end to a fixed object like a doorknob. Make sure the string is taut and straight. This first level is all about helping the patient experience proper convergence and develop awareness of physiological diplopia.

Coach the patient to look directly at the closest bead with both eyes open. They should see one clear bead and two strings forming an “X” that crosses precisely at the bead. As a Vision

Therapist, this is your cue that both eyes are contributing and that the patient is achieving

simultaneous perception and motor fusion. Reinforce the importance of the “X” shape - not just that it’s present, but that the crossing point aligns exactly with the bead they’re fixating on.

If the patient isn’t seeing the correct response, this is where your role becomes diagnostic as well as therapeutic. For example, if they report seeing only one string, they are likely suppressing one eye. Encourage them to blink, gently touch the string or bead, or shift their weight for better proprioceptive input; they might even benefit from wiggling the string. If the strings intersect in front of the bead, they’re over-converging. Prompt them to focus just beyond the bead—often using a finger placed slightly behind it. If the strings cross behind the bead, they’re under-converging; in that case, have them focus in front of the bead using a similar tactile cue.

Sometimes, patients will report that the two strings don’t intersect at all and appear vertically

misaligned. First, check that the head is level. A simple head tilt can distort perception. If

alignment still appears off after postural adjustments, it may indicate a vertical deviation that

warrants further investigation or modification of the activity. This is an opportunity to gather

clinical information that may inform the broader therapy plan.

The first level of Brock String work is about building foundational awareness and control of the binocular system. Your job at this stage is to slow things down and make sure the patient truly understands what they’re seeing—and what it means. Before moving on to greater distances or adding multiple bead targets, ensure consistency and confidence here. This level sets the tone for everything that follows, and getting it right pays dividends throughout the therapy process.

As you build fluency at this introductory level, stay tuned for upcoming posts where we’ll

explore how to gradually increase the level of difficulty, including shifting between multiple

beads and adding movement. We’ll also look at how to integrate the Brock String into sports

vision training, helping athletes improve eye-hand coordination, depth perception, and spatial awareness, and how this deceptively simple tool can be used to scaffold toward more advanced visual demands.

Check back soon for practical strategies, troubleshooting tips, and a whole lot of talk about how peripheral awareness is key with this activity!