Repeated Low-Level Red-Light Therapy (RLRL, 650 nm): Sub-Foveal Choroidal Thickening & Myopia Regression

In the landmark 12-month multicenter randomized controlled trial of 264 children aged 8–13:

$$\begin{cases} \mathbf{\text{Control Group (Glasses Only):}} & \Delta AL = \mathbf{+0.38\ \text{mm/year}} \quad | \quad \Delta D = \mathbf{-0.79\ \text{D/year}} \\ \mathbf{\text{RLRL Group (650 nm Laser):}} & \Delta AL = \mathbf{+0.05\ \text{mm/year}} \quad | \quad \Delta D = \mathbf{-0.11\ \text{D/year}} \ (\mathbf{87.7\% \text{ Reduction!}}) \end{cases}$$

Remarkably, $\mathbf{21.6\% \text{ of children}}$ in the RLRL cohort demonstrated an actual shortening of axial length ($\ge 0.05\ \text{mm}$), an unprecedented clinical outcome in pediatric ophthalmology.

Myopia progression is driven by choroidal thinning and posterior scleral hypoxia. Photobiomodulation via $650\ \text{nm}$ red light functions via:

1. Mitochondrial Cytochrome c Oxidase Activation: Red photons are absorbed by copper centers in Complex IV, boosting ATP synthesis and nitric oxide (NO) vasodilation.
2. Choroidal Blood Flow Surge: Enhanced choriocapillaris perfusion increases Sub-Foveal Choroidal Thickness (SFCT) by $+15\text{ to }+35\ \mu\text{m}$ on OCT within 4 weeks.
3. Scleral Oxygenation: Oxygen diffuses into the posterior sclera, downregulating HIF-1$\alpha$ and stabilizing collagen cross-links.

The treatment utilizes an ultra-low power ($0.29\ \text{mW}$) collimated red laser beam viewed through a $4\ \text{mm}$ pupil aperture for exactly 3 minutes, twice daily (separated by $>4\ \text{hours}$). The optical power density falls well below the ANSI Z136.1 Maximum Permissible Exposure (MPE) limit, with zero structural photoreceptor damage documented across thousands of trial subjects.