Ocular Transmission of Red and Violet Light: Insights into Light-Based Myopia Therapies

The purpose of this study was to determine transmission of red and violet light through ocular tissues, providing insight into how much light from light-based myopia control instruments reaches each tissue.

Fresh porcine eyes (n = 5, axial length = 22.40 ± 1.52 mm) were dissected to isolate the cornea, lens, retina, retinal pigment epithelium (RPE)/choroid, and sclera. Light transmission was measured for a red laser (654 nm), red light-emitting diodes (LEDs; 660 nm), and violet LEDs (396 nm). Transmission was quantified using a radiometer. Mean transmission values were compared using 1-way ANOVA with Bonferroni post hoc tests.

Corneal, lenticular, and retinal transmission were significantly lower for light emitted from violet LEDs compared with red laser and red LEDs (P < 0.05 for all). Light from the red laser showed reduced retinal transmission relative to the light from the red LEDs (P = 0.03). Power of light incident on the posterior sclera, considering cumulative transmission through the anterior ocular structures, was 1.66 µW (0.6%) for the red laser (with Maxwellian), 0.37 µW (0.6%) for the red laser, 2.79 µW (0.9%) for red LEDs, and 5.85 µW (0.1%) for violet LEDs.

Red light exhibited greater penetration through ocular tissues than violet light. Violet light was more strongly attenuated by the cornea and lens, demonstrating limited retinal delivery. The choroid acted as a major barrier to all light sources.

Understanding transmission efficiency of red and violet light through ocular tissues is a critical first step in finding a mechanistic link to biological pathways underlying light-mediated myopia control strategies.