Block-building performance test using a virtual reality head-mounted display in children with intermittent exotropia.

purposeTo determine whether childhood intermittent exotropia (IXT) affects distance divergence and performance in block-building tasks within a virtual reality (VR) environment.

methodsThirty-nine children with IXT, aged 6-12 years, who underwent muscle surgery and 37 normal controls were enrolled. Children were instructed to watch the target moving away and perform a block-building task while fitted with a VR head-mounted display equipped with eye- and hand-movement tracking systems. The change in inter-ocular distance with binocular distance viewing, time to stack five cube blocks of different sizes in order, and distance disparities between the largest and farthest cubes were assessed. All children were evaluated at baseline and 3-month time points.

resultsThe patients with IXT exhibited a larger distance divergence than did controls (p = 0.024), which was associated with greater distance angle of deviation and poorer distance control (r = 0.350, p = 0.001 and r = 0.349, p = 0.004). At baseline, the patients with IXT showed larger distance disparities in the block-building task than did controls in terms of the horizontal, vertical, and 3-dimensional (3-D) measurements (all ps < 0.050). Larger horizontal disparity was associated with greater distance angle of deviation (r = 0.383, p = 0.037). Three months after surgery, the horizontal and 3-D disparities in the patients with IXT improved significantly and were not comparably different compared with controls.

conclusionsThese preliminary findings suggest that VR-based block-building task may be useful in testing possible deficits in visuo-motor skills associated with childhood IXT.