Reversal of pupillary atonia after encircling band removal

The authors describe a patient who developed an atonic pupil after placement of an encircling band during retinal detachment surgery. When the band was removed 18 months later, the pupil signs showed partial recovery, demonstrating reversibility of the parasympathetic paresis.

The patient was a 23-year-old woman who underwent surgery for a macula-off rhegmatogenous retinal detachment in her left eye. The surgery, performed under general anesthesia, involved placement of a circumferential silicone explant (buckle) between the 11 o’clock and 4 o’clock meridians, placement of a 2.5-mm diameter 360° encircling band, and transscleral cryopexy.

After removal of her eye patch the following day, she noticed the left pupil was dilated. It remained dilated and nonreactive to light.

Eighteen months later, visual acuity was 20/20 in the right eye and 20/200 in the left eye, and the left pupil remained larger than the right, with no observable light response.

She underwent surgery to remove both segmental and encircling buckles. During the procedure, the left pupil became smaller. Two weeks later, it reacted to light but was smaller than the right pupil and remained so four months later.

The authors say the pupillary changes the patient experienced suggest that surgery caused a marked efferent blockade of parasympathetic impulses to the iris sphincter muscle. They speculate that mechanical deformation of the sclera by the encircling band produced a conduction block of the short posterior ciliary nerve fibers as they pass through the underlying suprachoroidal space.

The authors conclude that the lack of any pupil signs that might indicate aberrant regeneration further supports their view that the short posterior ciliary nerves were preserved but nonfunctioning between the first and second operations.