A case report.

In the next few months these intermittent symptoms became more constant and the patient noticed vertical diplopia on looking down and to the left and on reading; a Hess chart plotted on August i6, I967, now showed slight but definite evidence of a right superior oblique weakness (Fig. 2, opposite). A fortnight later she complained that the diplopia had suddenly altered, so that she was liow experiencing double vision on looking up and to the left rather than down and to the left. On clinical examination she was found to have restriction of elevationi in adduction of the right eye with a down-drift of the right eye on adduction, and the diagnosis of a superior oblique sheath syndrome was made; this was confirmed by the Hess chart plotted at that time (Fig. 3, opposite). One month later, she complained that the double vision was again evident on looking down and to the left, but this gradually improved, and on January 6, 1968, she complained only of occasional diplopia on looking down and to the left. After another 3 months, however, she complained that the diplopia was more noticeable, although similar in type (i.e. most marked on laevo-depression) and