• In most persons with Adie's syndrome, the affected pupil shows some residual light reaction. This residual reaction is always a segmental contraction of the iris sphincter. Most of these pupils have lost more than half of their sphincter function and continue to lose more with the passage of time. The loss of light reaction in the denervated pupils seems to occur randomly around the sphincter without any clear predilection for one quadrant. Segmental palsies of the iris sphincter are characteristic of Adie's syndrome, but they are not pathognomonic. They can also be due to partial damage to the preganglionic oculomotor nerve or to its nucleus in the midbrain.
Thompson HS. Segmental Palsy of the Iris Sphincter in Adie's Syndrome. Arch Ophthalmol. 1978;96(9):1615-1620. doi:10.1001/archopht.1978.03910060249012