Use of the Pulfrich pendulum for detecting abnormal delay in the visual pathway in multiple sclerosis

(1) Pulfrich's pendulum has been developed as a method for detecting abnormal delay in the visual pathway of patients with suspected multiple sclerosis. (2) Forty-one normal subjects gave a mean interocular latency difference of 2-4 +/- 1-8 msec on Pulfrich's pendulum. This mean +2 SD (6 msec) was taken as the limit of normal interocular latency difference by this method. (3) The test was assessed on 58 patients. Eighteen of these had definite multiple sclerosis, 9 had probable multiple sclerosis, and 8 had possible multiple sclerosis, according to clinical criteria. The remaining 23 patients did not conform with clinical criteria for multiple sclerosis, and served as neurological controls. Thirteen of these 23 patients had abnormal signs in the visual system. All the 58 patients also had visual evoked responses (VERs) recorded. (4) Interocular latency difference was outside the normal range in 9/18 with definite multiple sclerosis, in 3/9 with probably multiple sclerosis and in 2/8 with possible multiple sclerosis. (5) Interocular latency difference was outside the normal range in 2/23 patients with other neurological disorders. (6) There was a strong correlation between abnormality on the Pulfrich pendulum and on the VER for the multiple sclerosis group. (7) Individual results are compared with those from the VER. There was no significant correlation of the size and direction of the interocular latency difference obtained from the Pulfrich pendulum with that obtained from the VER, for any group. Possible reasons for this are discussed. (8) It is concluded that Pulfrich's pendulum is an easily performed and potentially useful subjective test for detecting abnormal dealy in the visual pathway in multiple sclerosis.