Abstract
Purpose :
Myopia progression is characterized by axial length (AL) elongation that is considered irreversible. In a recent randomized clinical trial using repeated low-level red-light (RLRL) therapy, we observed significant AL shortening among participants in the intervention group. In this analysis, we intend to report the frequency of this unexpected clinical phenomenon.
Methods :
This analysis was conducted on a randomized, multicenter, single-masked trial (NCT04073238). Two hundred sixty-four myopic children aged 8 to 13 years who were allocated to the RLRL treatment (intervention group) or a single vision spectacle (SVS, control group) were included in this analysis. AL was measured by partial coherence interferometry (IOL-master 500) at baseline, 1-month, 3-month, 6-month and 12-month follow-up visits. The choroidal thickness (ChT) was measured using swept-source optical coherence tomography. AL shortening was defined as AL reduction from baseline to follow-up visits at three cutoffs: >0.05 mm, >0.10mm, and >0.20 mm. Logistic regression analyses identified influential factors for AL shortening at different cutoffs. The primary outcome was the frequency of AL shortening. Analysis was done with intention-to-treat.
Results :
At the 12-month visit, the frequency of AL shortening >0.05 mm was 26/119 (21.85%) and 2/145 (1.38%) for the RLRL group and the control group, respectively. This frequency was 18/119 (15.13%) versus 0/145 (0%) for AL shortening >0.10 mm, respectively, and 7/119 (5.88%) versus 0/145 (0%), for AL shortening >0.20 mm, respectively (P<0.001). Mean AL shortening was -0.156 mm and subfoveal ChT increased by a mean of 0.056 mm in the RLRL group at the 12-month visit. In multivariate analysis, older baseline age was significantly associated with AL shortening.
Conclusions :
Nearly a quarter of children had >0.05 mm AL shortening following 12 months of RLRL therapy, whereas AL shortening rarely occurred amongst controls. Most of the observed AL shortening could not be explained by measurement error and/or choroidal thickening. Further studies are needed to explore underlying biological mechanisms.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.