Vertigo of vestibular origin is made more noticeable with eyes closure and may be felt by palpation. Alternatively, Frenzel glasses with +20 diopter can be used to eliminate visual fixation.
Frenzel glasses in-used (Rechargeable battery-operated with head-band).
Frenzel glasses (hand-held battery operated).
Spontaneous nystagmus is defined as nystagmus occurring without optic fixation: eyes under Frenzel glasses, or eyes open in total darkness or eyes closed. It indicates active vestibular-ocular imbalance.
Reference: Gordon B. Hughes. Textbook of Clinical Otology. ISBN 0-86577-183-9.