[Pseudo-spontaneous nystagmus with Frenzel eyeglasses]

The small light sources of Frenzel's glasses can induce Purkinje's figure on the retina. This is a stabilised retinal figure that may elicit an artificial "Leuchtbrillen-Nystagmus" which is easily mistaken for a spontaneous vestibular nystagmus. Provided with special instructions on how to induce Purkinje's figure, 22 of 55 normal subjects were able to produce nystagmus with Frenzel's glasses. This pseudo-spontaneous nystagmus should be avoided by using a pair of glasses, that cannot induce Purkinje's figure. Such glasses are currently being developed in our laboratory.