Abstract
Purpose :
Environmental light regulates ocular growth, through mechanisms that may be mediated by melanopsin retinal ganglion cells (mRGCs). This study aimed to examine the choroidal thickness (ChT) changes following brief stimulation of the melanopsin-expressing axons of the mRGCs at the optic disc with blue light in a group of healthy emmetropic and myopic subjects.
Methods :
The sub-foveal ChT of 10 emmetropic and 10 myopic subjects (ages 28 ± 6 years) was measured with enhanced-depth imaging optical coherence tomography before and during a 60-min period after stimulation of the optic disc with a 15 Hz flickering short-wavelength blue light for 1-min. ChT was also assessed following 1-min of no light stimulation on all subjects and following 1-min of optic disc stimulation with a 15 Hz flickering long-wavelength red light on a subset of subjects (3 emmetropes and 3 myopes). These control conditions were assessed on separate days at a similar time of day. Linear mixed model analysis was performed to examine the main effects and interactions of light, time, and refractive group upon changes in ChT.
Results :
Averaged across all time points post-stimulation, the ChT increased significantly following the optic disc stimulation with blue light (4 ± 1 µm), compared to the no light (0 ± 1 µm) and red light (0 ± 1 µm) conditions (both p < 0.001). Significant choroidal thickening was observed across all measured time points following the stimulation of the optic disc with blue light compared to no light stimulation in emmetropes (change at 60-min post-stimulation, 10 ± 2 µm vs 4 ± 2 µm, p < 0.001), but not in myopes (4 ± 2 µm vs 0 ± 2 µm; p > 0.05). No significant changes in ChT were observed following the stimulation of the optic disc with red light compared to the no light condition in either refractive group (all p > 0.05). The increases in ChT associated with blue light stimulation of the optic disc were significantly greater in emmetropes than myopes after 30 (8 ± 2 µm vs 0 ± 2 µm), and 60 mins (10 ± 2 µm vs 4 ± 2 µm) post-stimulation (both p < 0.05; Fig 1).
Conclusions :
A refractive error-dependent sustained thickening of the human choroid was observed with brief stimulation of the optic disc with blue light. This choroidal response may relate to a short-wavelength sensitive mRGCs’ signaling pathway, given the lack of response of the choroid with red light stimulation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.