Abstract
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Purpose: To investigate the reading performance in children with Intermittent Exotropia (IXT) under a Virtual Reality (VR) system presenting an image separately to each eye.
Methods: Thirty-eight children aged 8-12 with IXT (17 untreated and 21 treated) were compared to twenty age-matched controls. Eye movements and trajectory of viewing were recorded with a head-mounted infrared video eye-tracker (120 frames/sec) while reading paragraphs of text under VR environment. The trajectory distance of fixation, angle of eye movement, and execution time were evaluated. Interocular difference in each condition was also compared.
Results: Children with IXT (30.8 ± 7.8 prism diopters, PD) showed a significantly longer trajectory of fixation than children treated with IXT (5.7 ± 9.2 PD, 1.4 years after surgery) and controls (p<0.01, 166.8 ± 21.5 voxels, 65.5 ± 27.8 voxels, and 62.0 ± 21.3 voxels, respectively). Angle of eye movement and execution time were also longer in patients with IXT than those treated with IXT and controls, while the differences were not significant (44.4 ± 12.7° vs 40.0 ± 12.1°, 40.2 ± 10.9°, and 75.5 ± 21.2 secs vs 69.9 ± 16.5 secs, 69.1 ± 18.2 secs, respectively). The interocular differences did not differ between the groups. In patients with IXT, the trajectory distance was correlated with fusional control, but not with angle of exodeviation.
Conclusions: Children with IXT showed a longer trajectory and higher binocular disconjugacy during VR reading compared to those treated with IXT and controls, suggesting that IXT is easily manifest under a VR environment.
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