Abstract
Purpose :
Recent studies on humans showed an impact of the light spectrum on ocular growth parameters. However, it deserves further research whether the eye processes chromaticity or rather the defocus being induced by the longitudinal chromatic aberration (LCA) as a growth signal. The current study therefore investigated the influence of defocus-free monochromatic light on choroidal thickness as a rapid biomarker for ocular growth.
Methods :
In total, n=19 left eyes were illuminated for 20min with isoluminant short-wavelength light (“S” 450nm), mid-wavelength light (“M” 550nm), long-wavelength light (“L” 650nm) and polychromatic light (“P” 450nm to 680nm). The right eye was occluded while serving as control eye. A custom-built laser-interference setup generated monochromatic and defocus-free grid patterns with changing spatial frequency content between 3cpd and 18cpd. The patterns covered the central 10° of the retina. Choroidal thickness was measured before and after each exposure period in the illuminated and non-illuminated area using swept-source optical coherence tomography (ZEISS PlexElite 9000, Carl Zeiss Meditec Inc., USA). Paired t-tests and two-factor analysis of variance were performed to compare choroidal reactions from baseline, between eyes, illumination conditions and choroidal regions. Numerical results are reported as mean and standard error and were rounded to full microns.
Results :
As seen in Figure 1, there were no significant pre-vs-post-illumination changes for any light condition in the central, illuminated choroidal regions (S: 0±2µm, M: 0±1µm, L: +2±2µm, P: +1±1µm, all p>0.05). Statistically significant choroidal thinning occurred only in the non-illuminated area after polychromatic light with a mean change of -2±1 µm (p=0.04). No significant effect for "color" (p=0.80), "region" (p=0.29) and the interaction between both factors (p=0.21) was revealed. Furthermore, no differing responses between test eye and control eye could be found (all p>0.05).
Conclusions :
Monochromatic and defocus-free light did not lead to a significant choroidal response after short-term exposure. Therefore, it can be suggested that the LCA-induced defocus, rather than the chromaticity of the light spectrum, presents the primary signal for guiding ocular growth.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.