Abstracto

Dissociation between the onset times of convergence eye movements and pupillo-constrictions in the near response of humans.

Haruo Toda, Atsuhiko Iijima, Isao Hasegawa

Objective: Among the triad of the near response, the cross-linkages between the convergence eyemovement-related system and the lens accommodation-related system are well known and the accommodative convergence to accommodation (AC/A) ratio is widely used in the diagnosis of strabismus. Conversely, the function of the cross-linkage between the pupillo-constriction-related system and the convergence eye movement-related system is not fully understood. To examine this issue, we utilized an anticipatory convergence paradigm.

Materials and Methods: Nine healthy adult males participated in the experiments. The positions and pupil diameters of both eyes were recorded using a pair of infrared eye cameras, where the participant looked at far and near light emitting diodes (LEDs) that alternately lit at the front of him in a regular interval (1 s) or random interval pattern.

Results: Under the regular interval conditions, convergence eye movements in advance of the onset of near LED (anticipatory convergence) were frequently observed. In contrast, pupillo-constrictions were observed after the onset of near LED even with the anticipatory convergences. This convergenceversus pupil discrepancy was found in all nine participants and the difference in the onset times between convergence eye movement and pupillo-constriction was significant.

Conclusions: Our data suggest the complexity of the near response system in humans. Further neuronal and clinical investigations are required to better understand this concept.