Exploration of correlated factors of axial length changes after repeated low-level red-light irradiation in the real world.

Background: To investigate the factors related to the change in axial length after repeated low-level red-light(RLRL) therapy.

Methods: A retrospective case study. A total of 323 children and adolescents who underwent RLRL therapy concurrently with their eye examinations at Wuhan Children's Hospital from 2022 to 2023 were included. The biological eye parameters, including the axial length (AL), spherical equivalent refractive (SER), the subfoveal choroidal thickness (SFCT), intraocular pressure (IOP), corneal curvature and corneal thickness, were recorded at baseline, 3-month, 6-month, 12-month, 12-month, 18-month and 24-month. The factors related to the degree of change in axial length were analyzed.

Results: There was a statistical difference in the amount of AL changes during the follow-up (F = 16.12, P < 0.001), and the amount of AL changes was significant at the 6-month follow-up (△AL=-0.16 ± 0.18), and then gradually decreased with the extension of follow-up time. There was a statistically positive correlation between baseline AL and baseline SER and changes in AL (P < 0.05). The axial regression in high myopia group was significantly greater than that in mild and moderate myopia group (P < 0.05). There was also a statistically positive correlation between age and changes in AL (P < 0.05). At the follow-up of 6 months, 12 months, 18 months, combined with other myopia prevention and control was correlated with the change of AL (P < 0.05). Baseline corneal thickness, baseline corneal curvature and baseline IOP were not correlated with changes in AL (all P > 0.05).

Conclusion: The longer the baseline AL, the higher SER, the thinner SFCT, the older the age and the combination of other myopia prevention and control measures, the more obvious the change of AL. However, the changes of AL were not affected by IOP, corneal curvature and corneal thickness.