Both parents and three of their seven offspring affected with the tonic pupil illustrate either a dominant type of inheritance or a double recessive with imperfect penetrance in this pupillary disorder. There was an acute onset with loss of accomodation, an initial lack of hypersensitivity to methacholine chloride and a period of postganglionic regeneration during which the pupil became smaller, accommodation returned, and the methacholine chloride test became positive in two of the three affected children. These characteristics are not part of the usual picture of the tonic pupil of inconspicuous onset, which reacts positively to 2.5% methacholine chloride.
Hedges TR. The Tonic PupilFamilial Incidence, Recognition, and Progression. Arch Ophthalmol. 1968;80(1):21-25. doi:10.1001/archopht.1968.00980050023003