[A simple and precise measurement of ocular torsion].

The instrument, derived from Mariotte's blind-spot experiment, permits the anatomical ocular torsion of each eye to be measured separately in primary position. This method was evaluated in a group of normal subjects, by comparison with measurements on fundus photographs. It was established that it was simpler and more accurate than measurement with the Goldmann perimeter and indirect ophthalmoscopy assessment. It complements subjective methods of measuring torsion by the double Maddox rod test or with the synoptophore.