Iridodonesis as a cause of recurrent vertigo.

A 56-year-old woman complained of recurrent attacks of vertigo. Attacks lasted no longer than a second and could be easily provoked by abrupt eye movements. Vertigo disappeared when the left eye was covered. Symptoms had begun after left-sided cataract surgery resulting in subluxation of the left lens. The characteristic feature of iridodonesis is the tremulousness of the iris with eye movement (video on the Neurology® Web site at Neurology.org). While in many cases iridodonesis is asymptomatic, we speculate that in our patient, the instability of the optical system results in a trembling image on the retina, which, in turn, causes irritation in downstream brain regions.