Physical Exam

Alternate Cover Test

also known as Cross-cover test, Test of skew

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Video coming September 2026

How to Perform

Ask the patient to fixate on a target. Cover one eye, then move the hand across to the other eye, and repeat back and forth, pausing briefly on each eye; watch the just-uncovered eye for any movement to take up fixation. A refixation movement indicates an ocular deviation, and a vertical movement can indicate a skew deviation.

How to Interpret

Skew Deviation

Upright-supine test positive

Rule in

—

Rule out

HelpfulDerived CI

Evidence:Limited

Stroke

Posterior Circulation Stroke

HINTS exam concerning (central pattern) in a patient with acute vestibular syndrome

Rule in

HelpfulDerived CI

Rule out

Very helpfulDerived CI

Evidence:Strong

Vestibular Dysfunction

Peripheral Vestibular Dysfunction

HINTS exam reassuring (peripheral pattern) in a patient with acute vestibular syndrome

Rule in

Very helpfulDerived CI

Rule out

HelpfulDerived CI

Evidence:Strong

References

Gottlieb M, Peksa GD, Carlson JN. Head impulse, nystagmus, and test of skew examination for diagnosing central causes of acute vestibular syndrome. Cochrane Database Syst Rev. 2023 Nov 2;11(11):CD015089. doi:10.1002/14651858.CD015089.pub2. PMID 37916744. PMC10620998.
Tao WD, Liu M, Fisher M, et al. Posterior versus anterior circulation infarction: how different are the neurologic deficits? Stroke. 2012;43(8):2060-2065. PMID: 22678088.
Wong AMF, Colpa L, Chandrakumar M. Ability of an upright-supine test to differentiate skew deviation from other vertical strabismus causes. Arch Ophthalmol. 2011;129(12):1570-1575. PMID: 22159676.
Holmes JM, Chandler DL, Christiansen SP, Birch EE, Bothun E, Laby D, Melia BM, Repka MX, Silbert DI, Zeto VL. Interobserver reliability of the prism and alternate cover test in children with esotropia. Arch Ophthalmol. 2009;127(1):59-65. doi:10.1001/archophthalmol.2008.548. PMID: 19139339.

Research last updated September 9, 2026.