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

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.

Prospective, comparative study comprising 600 eyes of 300 children.

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.

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).

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.