Impact of Blur and Disparity Cues on Accommodation, Vergence, and Pupil Size in Response to Static Stimuli in Adolescents With and Without Concussion.

PURPOSE: To objectively investigate the effects of blur and disparity cues on accommodative response and microfluctuations (root mean square and low-frequency components), vergence, and pupillary responses to static targets in adolescents with persistent post-concussion symptoms.

METHODS

Thirty-one adolescents with concussions and 32 controls completed the study. Refractive states, eye position (vergence), and pupil size were measured simultaneously using photorefraction (50 Hz) while participants viewed near stimuli for 15 seconds at nine distances ranging from 100 to 25 cm under three viewing conditions: blur and disparity cues (binocular, cartoon movie), blur only (monocular, cartoon movie), and disparity only (binocular, difference of Gaussians target).

RESULTS

Participants with concussions showed less accurate accommodative responses (greater accommodative lag) to targets at ≤33 cm than controls did when the targets provided both blur and disparity cues or blur cues only. When disparity-only cues were provided, no significant between-group differences in the accommodative responses were found, but accommodative microfluctuations in participants with concussion were significantly lower than controls at accommodative demands of ≥2.5 D (≤40 cm) for the root mean square and ≥2.25 D (≤44 cm) for low-frequency components. Vergence and pupillary responses were not significantly different between groups for any viewing conditions or demands.

CONCLUSIONS

Accommodative response to static near targets was impaired in adolescents with persistent post-concussion symptoms when blur cues were provided. In contrast, vergence and pupillary response to static targets were not impacted at habitual near-viewing distances. This study provides mechanistic insights into accommodative dysfunction in concussion.