Ocular torsion among patients with intermittent exotropia: relationships with disease severity factors.

OBJECTIVE: To investigate the distribution of ocular torsion in patients with intermittent exotropia and to determine possible correlation between the torsion and the severity of intermittent exotropia.
DESIGN: Prospective, comparative study comprising 600 eyes of 300 children.
METHODS: One hundred fifty patients with intermittent exotropia between 4 and 15 years of age and another 150 age-matched normal controls without strabismus were enrolled prospectively. Digital nonmydriatic fundus photographs were obtained from both eyes of each subject and the disc-foveal angle was calculated using digital image software. All photographs also were graded as normal, extorsion, or intorsion. We compared the size of the disc-foveal angle between the normal and intermittent exotropia group. We analyzed possible correlations between the disc-foveal angle and disease severity factors, including amount of exotropia, Titmus stereoacuity, and duration of strabismus.
RESULTS: Mean disc-foveal angle of intermittent exotropia group was significantly larger than that of normal control group (6.13 and 5.13 degrees, respectively; P < .01). Ocular torsion (either extorsion or intorsion) was discovered in 45 (30%) patients among the intermittent exotropia group, whereas it was found in only 16 (11%) individuals among the normal control group (P < .01). The size of disc-foveal angle showed significant positive correlations with the amount of exotropia and the degree of stereoacuity (r = 0.45, P < .01, and r = 0.51, P < .01, respectively).
CONCLUSIONS: Ocular torsion could be found not infrequently in patients with intermittent exotropia. Furthermore, the amount of torsion showed a significant relationship to the disease severity of intermittent exotropia. Assessment of ocular torsion could be used as a supplementary tool for evaluating fusion in patients with intermittent exotropia.