Mechanisms for Positive Bielschowsky Head Tilt Testing in Horizontal Strabismus

ABSTRACT

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.

KEYWORDS:

• Bielchowsky Head Tilt Test
• esotropia
• exotropia

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Supported in part by the Knights Templar Eye Foundation, Flower Mound, TX (Dr Brodsky) and Mayo Foundation. The funding sources had no involvement in this work.