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(R) 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.