This pilot study is a randomized controlled trial 2 by 2 design to allocated randomly the Frenzel lens and the diagnostic algorithm. There is no use of sham lens. The usual care opposed to the diagnostic algorithm will be questionned only on the perception of nystagmus by the clinician and the use of repositionning particules technique. The only blindings will be the patients about the use of the algorithm and the outcomes assessor about the use or not of Frenzel lens and the use or not of the diagnostic algorithm.
This pilot study is perfomed to validate and document faisability of the use of Frenzel lens and the use of a diagnostic algorithm for the assessment of a special sign (nystagmus) observe in the eyes of patients consulting in the emergency department for an acute episode of vertigo/dizziness/imbalance.