Interaction Between Near Work and Narrowband Light on Choroidal Thickness.

Purpose: To investigate effects of near work performed under short-wavelength "blue" and long-wavelength "red" light on choroidal thickness (CT) and axial length (AL). Methods: Twenty-five participants (9 myopes, 16 nonmyopes), aged 20 to 36 years, completed four visits, consisting of a 30-minute near-work task (5 D demand) under broadband, blue (457 nm), and red (628 nm) light, and a control distance viewing condition under broadband light. Right eye CT and AL were measured before and after the task and after 30-minute recovery using optical coherence tomography (Spectralis) and biometry (Lenstar). Dynamic accommodative responses (n = 11) were recorded under each light condition (Grand Seiko). Results: CT decreased and AL increased after near work in broadband (mean ± SEM CT: -11 ± 2 µm, AL: +10 ± 3 µm, P < 0.01) and red light (CT: -6 ± 1 µm, AL: +7 ± 2 µm, P < 0.01) but not under blue light or the control condition (P > 0.05 for all). After recovery, CT and AL returned to baseline, except in blue light, where AL decreased compared to baseline (AL: -4 ± 2 µm, P = 0.04). The accommodative response was significantly reduced under blue light (P < 0.01). Conclusions: Near work under broadband and red light produced acute choroidal thinning and axial elongation. Blue light was associated with a posttask reduction in axial length and reduced accommodative response. Findings suggest that blue light may mitigate biomechanical stress on the posterior eye that is induced by sustained near work.