Correlation between repeated low-level red light-induced afterimage and axial changes in myopia control.

Purpose: To explore the correlation between afterimages induced by repeated low-level red light (RLRL) and changes in refraction.

Method: Patients who used RLRL for myopia control from 2023.02 to 2024.06 were included in this study. The afterimage appeared on a gray background (RGB 217,217,217; Lab 87,0,0). Afterimage color was recorded with CIELAB nomenclature (R, G, B; L, a, b), and afterimage duration (T) was recorded in seconds. Axial length (AL) and axial length-to-corneal radius ratio (AL/CR) were followed up at 1-, and 3-month. Participants were divided into groups based on a = 0 for GroupR (a>0,red bias in afterimage) and GroupG (a<0,green bias in afterimage); b = 0 for GroupY (b>0,yellow bias in afterimage) and GroupB (b<0,blue bias in afterimage), and T = 50.50 for GroupS (T<50.50,shorter afterimage duration) and GroupL (T>50.50,longer afterimage duration).

Results: A total of 52 participants were included in this study, with an age of 9.25 (1.75) years, 27 (51.92 %) males. The T median (P25, P75) was 50.50 (31.25,85.50) s. After RLRL treatment, divided by a = 0, GroupG showed significantly more shortening in the AL changes than GroupR at 1month and 3months (both P<0.05) and the AL/CR changes difference was not significant. Divided by T = 50.50, GroupS showed significantly greater shortening in the AL changes than GroupL at only 1month (P<0.05) and the AL/CR changes difference was not significant. Divided by b = 0, the difference between GroupY and GroupB was not statistically significant (P>0.05).

Conclusion: The change of AL after RLRL treatment showed a correlation to the afterimage. Patients with green afterimage and shorter afterimage duration have a better AL shortening after RLRL treatment. Afterimage may serve as a biomarker for more effective myopia control.