Effects of six conditions of ocular fixation on caloric nystagmus

Caloric tests were performed on 20 normal volunteers under the following six conditions of ocular fixation: (1) eyes open with lighted +20-diopter lenses; (2) eyes open with lighted +20-diopter lenses plus strobe lighting; (3) eyes open in darkness; (4) eyes closed in darkness; (5) eyes closed in a dimly lighted room; and (6) eyes open with unlighted +20-diopter lenses plus strobe lighting. Latency, amplitude, frequency, duration, and speed of the slow component were measured from a permanent recording. Significant differences were found between the lighted +20-diopter lens conditions and all others for all variables except latency. Tests performed with lighted +20-diopter lenses should be cautiously interpreted due to the noticeable response suppression noted in these conditions. The present procedure of performing caloric tests with the eyes closed in a dimly lighted room was found to be unqeustionably preferable.