Increased outdoor time was found to significantly affect myopia prevention and control, but conflicting evidence was found in relation to these effects on changes in spherical equivalent on patients with myopia vs. those without. Photo: Getty Images. Click image to enlarge.

Researchers from Singapore wanted to review the effectiveness, safety and implementation outcomes of different forms of light treatment as a modality for myopia control in kids. They conducted a systematic review up to January 2024, including a total of 19 interventional studies.

Significant effects on myopia incidence and changes in axial length, spherical equivalent and choroidal thickness were seen with increased outdoor time from three studies, red-light therapy from 13 studies and increased classroom lighting in one study. Violet-light therapy, studied in two reports, was only effective in kids aged eight to 10 without glasses and with less than 180 minutes of near-work time daily. Two red-light therapy reports indicated adverse effects which spontaneously resolved.

Focusing their discussion on red-light therapies, the authors elaborate on some specifics of the studies. In these red-light investigations, therapy ranged from four weeks to 24 months, with consistent findings that the therapy might be effective in inhibiting myopia progression through reduced axial elongation, refraction changes and increasing choroidal thickness. However, they note that only one of these studies investigated the effects over a period longer than 12 months. Other reports indicate red-light therapy to have greater effectivity than other treatments, but with a rebound effect potentially related to its higher efficacy. As the investigators point out, this effect after cessation may make the modality less clinically useful due to reduced sustainability, but the pool of evidence currently makes it hard to draw consistent conclusions. Another roadblock that exists is evidence being uncertain in its effectivity for different age groups and myopia severities.

Safety was another inconsistency seen across the red-light therapy studies, with two reporting minor adverse effects that resolved spontaneously. This does not answer, though, whether long-term adverse effects beyond two years of treatment exist, with concerns about intensity of the light and duration of intervention.

Clearly put, “the uncertain long-term safety evidence for red-light therapy makes it difficult to definitively conclude whether the benefits and effectiveness of this therapy outweigh the risks associated with its administration.”

However, there was data to support significant effectivity of myopia control at powers lower than what is currently adopted for treatment regimen. “Thus…a treatment regimen with a more conservative power can be considered to both control myopia progression and alleviate any potential long-term side effects,” the authors explain.

Looking toward future adoption of the practice, the investigators believe that “with safety concerns, moderately high but wide-ranging compliance rates and other more cost-effective alternatives, red-light therapy has some evidence to suggest potential challenges in scaled implementation.”