Brock String Foundations – Part Two: the ‘Moveable X’ Brock String Technique

The second level of Brock String training, often referred to as the “Moveable X”, advances the patient from static convergence to dynamic vergence shifts. Multiple beads are placed along the string at varying distances and positions. The patient is asked to fixate on these beads in a random, unpredictable order, with the goal of forming a clear, centered “X” immediately upon each shift. This progression trains vergence flexibility, visual spatial judgment, and instantaneous sensory-motor alignment, forming the foundation for efficient binocular vision across environments.

At this level, the task demands more than symmetrical motor alignment; it requires precise integration of central and peripheral visual processing. Central fixation must rapidly locate and lock onto the new bead, while the peripheral visual field must simultaneously register the crossing of the strings to confirm symmetrical eye alignment. The visibility and stability of the “X” pattern serve as both an objective alignment check and a subjective perceptual anchor. A breakdown in peripheral awareness may result in uncalibrated localization, suppression, or visual confusion, reflecting underlying deficiencies in spatial integration or fusion stability.

This exercise is particularly aligned with Skeffington’s “Where am I?” and “Where is it?” circles. The “Where am I?” system, which is concerned with postural and proprioceptive grounding, interacts with the “Where is it?” system, which is responsible for spatial localization of visual targets. As the beads are moved to new positions every few minutes, the visual system is required to recalibrate both its internal map of visual space and its relationship to the environment. This dynamic recalibration is critical for patients with convergence disorders who demonstrate rigidity or spatial disorientation, as it reinforces a more fluid and adaptable visual-motor schema.

A key therapeutic component of the Moveable X is the development of feeling tone; a kinesthetic awareness of correct convergence effort and visual alignment. The patient learns to recognize the sensory “signature” of accurate vergence: the moment when the bead becomes clear and single, and the two strings intersect smoothly at the point of fixation. This internal feedback loop supports self-monitoring and auto-correction, crucial for long-term generalization. Repetition of the experience helps encode the motor-sensory pattern of correct vergence into procedural memory, increasing speed and reducing cognitive load over time.

Therapeutic setup should include positioning the patient in a stable, balanced stance (seated or standing) and encouraging breath awareness and postural alignment. Beads should be repositioned periodically, not just in distance, but also in lateral and vertical space to engage all planes of gaze and prevent habituation. This variability supports vergence adaptability, enhances proprioceptive calibration, and reinforces accurate spatial mapping across the Z-axis. Ultimately, the Moveable X task is not just a convergence exercise; rather, it is a high-level binocular integration activity that cultivates refined spatial awareness, flexible motor control, and efficient sensory feedback.

Ready to bring these techniques to life? Use the official Emergent Brock String—designed with adjustable challenge levels through variable bead sizes and accommodative targets. It also helps reduce suppression using glow-in-the-dark string, glow-in-the-dark beads, and luster discs designed for use with red/green glasses.

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