Intermittent exotropia with a positive Bielschowsky head-tilt test

Mechanisms for Positive Bielschowsky Head Tilt Testing in Horizontal Strabismus

PURPOSE

To elucidate the induced effects of horizontal strabismus on the Bielschowsky Head Tilt Test (BHTT).

DESIGN

Prospective clinical study.

METHODS

Prospective analysis of BHTT testing in 85 patients with exotropia and 71 patients with esotropia who were examined in a strabismus clinic.

RESULTS

Eighty-four of 85 patients with exotropia (98.82%) showed a positive BHTT with an induced hyperdeviation on the side of the tilt (to both sides in 67% and to one side in 32%). Fifty-seven of 71 patients with esotropia (80.2%) showed a positive BHTT with an induced hypodeviation on the side of the tilt (to both sides in 57.7% and to one side in 22.5%). These induced vertical deviations were greater in patients with larger horizontal deviations and in those with constant rather than intermittent deviations; however, they were not influenced by the presence or absence of associated primary oblique muscle overaction.

CONCLUSIONS

Exotropia and esotropia produce hyperdeviations during BHTT testing, with a hyperdeviation on the side of the tilt observed in patients with exotropia, and hypotropia on the side of the tilt observed in patients with esotropia. These diametrical results are not attributable to any preexistent alteration of neurologic output inherent to these two forms of horizontal strabismus or to associated torsion. Rather, they arise directly from the altered anatomical positions of the two eyes, which cause the eyes to approximate their visual axes more closely to the vertical rectus muscles (in exotropia) and the oblique muscles (in esotropia), enabling the vertical actions of specific cyclovertical muscles to predominate in response to altered utricular output generated by the BHTT.

Range of forced cyclorotation in superior oblique palsy and V-pattern strabismus

PURPOSE

To quantify a passive range of cyclorotation using a smartphone application and evaluate its associations with fundus torsion and rectus muscle cyclorotation in superior oblique palsy (SOP) and V-pattern strabismus.

METHODS

Fifty-two patients showing overelevation in adduction (30 with congenital SOP and 22 with V-pattern strabismus) underwent forced cyclorotation on the photographs. A photograph of the globe was taken in maximally excyclorotated and incyclorotated positions after marking at the 6 and 12 o'clock limbus under general anaesthesia, and the rotational alignment of these markings was read using the toriCAM application. The degrees of forced cyclorotation were compared between the two groups. Disc-fovea angle on fundus photographs and rectus muscle cyclorotation in the coronal view on orbital computed tomography were correlated with the range of forced excyclorotation.

RESULTS

The range of forced excyclorotation was greater in V-pattern strabismus than that in SOP (58.5° vs. 46.8°, p < 0.001), whereas the ranges of incyclorotation were similar between the two groups (39.0° vs. 39.0°, p = 0.543). Regression analysis revealed a significant increase in the range of excyclorotation with the degree of rectus muscle excyclorotation, after accounting for age and angle of hypertropia (r² = 0.475, p = 0.001). The range of excyclorotation did not correlate with the amount of fundus extorsion and grade of overelevation in adduction.

CONCLUSIONS

The range of excyclorotation was correlated with the rectus muscle excyclorotation in these populations, suggesting that the results from this forced cyclorotation test may reflect orbital alignment and oblique muscle status.