The pupil cycle time in familial dysautonomia. Further evidence for denervation hypersensitivity.

The pupil cycle time (PCT) was prolonged in 11 subjects with familial dysautonomia. In the younger age group (10-19 years), mean PCT was 872 +/- 88 msec as compared to 15 normal age matched controls (728 +/- 88). In the 3 oldest patients (30-39 years) mean PCT was 980 +/- 133 msec as compared to 13 age matched normals (748 +/- 56). It is proposed that prolongation of PCT in familial dysautonomia may be due to functional denervation of the iris or that it is a result of a structural abnormality of its musculature and/or its neuromuscular junctions.