An analysis of ocular counter-rolling measured with search coils.

Ocular counter-rolling (OCR) was studied by using a scleral search coil magnetic system in normal subjects and in pathological cases. Normal ocular counter-rolling was 2.7 degrees-7 degrees when the head was tilted 10 to 30 degrees. In most cases of benign paroxysmal positional vertigo, the OCR to the ipsilateral side was reduced, while that to the contralateral side was normal or only slightly reduced. Soon after unilateral labyrinthectomy, the OCR to the ipsilateral side was reduced or was 0, whereas OCR to the contralateral side was normal or slightly reduced. Some 3-5 years after the operation, however, the OCR seemed to depend on the compensation achieved. In cases of acoustic neurinoma, OCR to both sides was reduced, that to the ipsilateral side being more strongly impaired than the OCR to the contralateral side.