Bielschowsky head tilt test
Also called head tilt test, BHTT, Bielschowsky test, step three of the three-step test, Parks-Bielschowsky three-step test
A test that compares a vertical deviation with the head tilted toward each shoulder in turn. It is the third step of the three-step test and tells a weak superior oblique from a weak superior rectus, or a weak inferior oblique from a weak inferior rectus1,4.
Tilting the head toward one shoulder makes the eye on that side intort with its two superior muscles; if the superior oblique is weak, the superior rectus acts alone and its unopposed elevating action lifts the eye, so the hypertropia grows on tilt toward the weak side1,2. In a fourth nerve palsy the deviation is therefore better on tilt to the opposite side1.
More detail
The patient sits upright and fixates a target at 3 m. When the difference between the two tilts is hard to see, it is measured with prism and cover in each position, keeping the prism in its usual relation to the eye3. The test is objective, so it works in children who cannot answer questions and whether or not the patient has binocular vision3. The first two steps of the three-step test, which eye is higher and whether the deviation is worse in right or left gaze, narrow the eight vertical muscles to two before the tilt chooses between them4. The test misleads when more than one muscle is involved.
Sources (4)
- Kanski, Clinical Ophthalmology (2024), ch. 19
- Pickwell's Binocular Vision Anomalies, ch. 17
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 12
- Pickwell's Binocular Vision Anomalies, Appendix, Parks' three-steps method
Reviewed October 2026
Related terms
Nearby in the glossary
- Bagolini striated lenses
- Bielschowsky head tilt test
- bifoveal fixation
- blind-spot esotropia
- Brewster stereoscope