Dynamics of the accommodative response under artificially-induced aniseikonia

Aniseikonia has demonstrated to deteriorate the binocular function, however its impact on the accommodative response remains unknown. The present study aimed to analyze the effects of artificially-induced aniseikonia, using afocal magnifiers, on the dynamics of the accommodative response. The magnitude and variability of the accommodative response were objectively measured in 20 young healthy subjects by a binocular open-field autorefractometer. Participants observed a static stimulus for 90 s, under seven degrees of aniseikonia (0%, 1%, 3%, 5%, 8%, 10% and 12%), and at three distances (500 cm, 40 cm and 20 cm). Complementarily, near stereoacuity, and perceived levels of fatigue and visual discomfort were assessed. The degree of induced aniseikonia was associated with the magnitude of the accommodative response (p < 0.001, η_p² = 0.329), obtaining a statistically significant reduced accommodative lag for the induced aniseikonia conditions of 8%, 10% and 12% in comparison to the control condition at 40 cm (p-corrected = 0.019, <0.001 and 0.013, respectively) and at 20 cm (p-corrected < 0.001, <0.001 and 0.003, respectively). However, the degree of induced aniseikonia did not reveal any effect on the variability of accommodation (p > 0.05). We also found a decline in near stereoacuity and an increment of visual symptomatology when inducing aniseikonia (p < 0.05). Our data evidenced that greater degrees of induced aniseikonia cause a heightened accommodative response. These preliminary findings may be of relevance for patients undergoing cataract or refractive surgery procedures in which aniseikonia can be induced.