Fuzzy Future for Red Light Therapy in Myopia Prevention, Despite Positive Trial

Repeated low-level red light (RLRL) may be a successful preventive treatment to stave off nearsightedness in children, but questions about safety and potential implementation remain.

In a randomized trial of schoolchildren with premyopia, the 12-month myopia incidence reached 40.8% after RLRL treatment, a significant improvement compared with the 61.3% rate in the control group (relative risk 0.67, 95% CI 0.51-0.86, P=0.003), reported Xun Xu, MD, of the Shanghai Vision Health Center & Shanghai Children Myopia Institute, China, and coauthors.

Patients in the RLRL therapy group also experienced a reduction in myopic shifts, as these patients had an average cycloplegic spherical equivalence refraction (SER) of -0.35 diopter (D) compared with -0.76 D in the control group. Average axial length for RLRL patients was 0.30 mm versus 0.47 mm in control patients (P<0.001 for both), according to their publication in JAMA Network Open.

The authors acknowledged that RLRL may not be an option for all patients.

"Based on our data, it might already be too late to treat those with an SER of -0.50 to 0.00 D because their incidence of myopia in 12 months could be as high as 83.1%," they wrote. "Therefore, prophylactic intervention, including RLRL therapy and increased outdoor time, may need to be implemented earlier, at least among those with an SER in the range of 0.01 to 0.50 D, or even earlier."

For the school-based intervention, patients in the treatment group were placed at a desktop, where they received RLRL from semiconductor laser diodes delivering red light at an average wavelength of 650 nm. Therapy was provided five times every week, twice a day, for 12 months. Individual sessions were 3 minutes long and needed to be separated by at least 4 hours. Therapy was typically administered at school, and devices were taken home during the holidays.

Myopia is a common refractive error all over the world. In the U.S., more than 40% of the total population has myopia, with a 36.1% prevalence in children ages 5 to 17 years.

Study coauthor Mingguang He, MD, PhD, ophthalmologist of Hong Kong Polytechnic University, noted that utilizing the study's in-school design could be an option used to identify, and hopefully treat, myopia more successfully.

"The next challenge or consideration for the experts or public to consider is who we should target for adopting this novel technology, given we should not 'prophylactically' treat all normal children," He told MedPage Today.

"Targeting 'premyopia' [in] children is a great idea, but they would have normal vision and therefore won't show up in our clinics. I personally think a school-based prophylactic intervention -- to identify premyopia [in] children or those at greatest risk of developing myopia and organize them for treatment -- is the most feasible strategy to adopt RLRL as a prophylaxis measure for myopia control," according to He.

In the trial, no RLRL recipients experienced any functional damages to their vision; two participants withdrew from the study following reported afterimages, flash blindness, or a glare for any longer than 6 minutes following treatment.

Maria Liu, OD, PhD, a clinical optometrist at the University of California Berkeley, expressed safety concerns over potential use of the treatment for an extended period of time.

"Compared to LED red light, the energy directed to the macular area by the red laser beam is highly condensed in a very small area, rendering a much higher risk of damage than red LED of similar energy," Liu told MedPage Today. "There is also no testing of any potential change at the molecular level. With the redundancy of photoreceptors and RPE [retinal pigment epithelium] cells in the macular area, it takes a lot of damage to those cells before a detectable decrease in the best corrected vision, making it a poor safety measure for such a device."

"Overall, considering the long-term and repeated use of laser energy on the macular area, the young age of the targeted patients, and the lack of short-, intermediate-, and long-term safety testing, I would not prescribe it to my patients either as a preventative or control treatment, as the benefit of the treatment does not justify the risk," she commented.

There were 278 children included in the study, split evenly between treatment and control cohorts. The average patient age in both groups was age 8.3 years, the intervention group had a 51% male population, while the control group had a 49% male population. In order to qualify for the study, participants had to experience a cycloplegic SER of -0.50 to 0.50 D in their eye with greater myopathy, and need to have at least one parent with an SER of -3.00 D.

Among treatment patients who did not have their intervention interrupted due to the COVID-19 pandemic, 12-month myopia incidence was as low as 28.1%, representing a 54.1% relative reduction in incident myopia over 12 months.

In addition to the interruptions due to the COVID-19 pandemic, however, the authors also acknowledged that the open-label nature of the study could have affected results. Moreover, only specific parameters were examined to assess the effects of RLRL treatment.

Researchers encouraged further study to confirm the safety of RLRL treatment, especially given the prevalence of the condition.

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