Caloric testing. 1. Effect of different conditions of ocular fixation

Twelve normal subjects received standard caloric testing under the following conditions: 1) fixation, 2) Frenzel glasses in a dimly lit room, 3) eyes open in total darkness, and 4) eyes closed. Multiple nystagmus response parameters were evaluated and statistically compared for each condition. Fixation markedly diminished induced nystagmus and produced the largest coefficient of variation for each response parameter. Caloric testing with eyes closed resulted in periodic nystagmus suppression and a less distinct saw-toothed pattern. As with fixation, the coefficient of variation was consistently higher with eyes closed compared to eyes open in darkness or Frenzel glasses. It is concluded that caloric testing of the vestibulo-ocular reflex arc should be performed with eyes open in darkness or with Frenzel glasses.