Is red light therapy safe and effective for myopia control?

A randomized controlled trial undertaken in 5 hospital centres in China has shown that over one year, repeated low-level red light (RLRL) therapy was effective in slowing myopia progression. The theory of RLRL therapy is to create a time effective alternative to increasing bright light exposure in children for myopia control. The 650nm emitting instrument has already been used for amblyopia treatment in China.

• Participants: Chinese children aged 8-13 years with myopia of -1.00 to -5.00D, astigmatism no more than 2.50D, anisometropia no more than 1.50D and best corrected acuity of at least 20/20 equivalent. All wore single vision spectacles and had not undergone any myopia control treatment previously.
• The control group had no intervention. Around 80% completed 12 months and showed 0.38mm axial length growth and -0.79D refractive progression.
• The treatment group used the desktop light therapy device (Eyerising) under parental supervision for no more than 3 minutes, twice per day with a break of at least 4 hours between treatments, 5 days per week. The web-linked system tracked compliance and limited treatment to the specific protocol. Around 93% completed 12 months, and the group mean was 0.13mm axial length growth and -0.20D refractive progression. This represents a 66% axial and 75% refractive myopia control effect over 12 months.
• Notably, around 40% of RLRL-treated children showed axial length shortening of >0.05mm "exceeding that as a result of measurement error" at 3 months. At 12 months, just over 20% showed this same finding. Changes in choroidal thickness did not fully account for this shortening, indicating some other mechanism at play.
• Best-corrected acuity was similar in both groups, with most being at least 20/20, and no treatment related adverse effects were reported. A subset of children (n=72) in the RLRL group had OCT data which showed "no structural damage on the photosensory layer."
• Discontinuations from the RLRL group were 1 child who switched to orthokeratology treatment, and 5 more who cited "that the light is too bright" or were not compliant.
• Compliance with the treatment protocol overall was 75%. For those whose compliance was over 75%, small improvements in the mean efficacy were found.

In summary, the results of this one-year clinical trial are no doubt impressive, and indicate a powerful potential tool in the myopia control armament. Since then, a two-year study has been published where control group children were switched to RLRL, and some RLRL treated children were discontinued. Some children were also continued with SV spectacles (SVS) or RLRL from the first year, for comparison. RLRL treatment showed an impressive control effect again, with 57% less axial elongation in the two-year RLRL group compared to the two-year SVS group (0.12mm vs 0.28mm respectively). A rebound effect was noted in the children who discontinued RLRL after one year, with 0.14mm more axial length growth compared to those who continued in SVS. Again, no adverse events or structural / functional retinal damage was reported.

A case study published from China in May 2023 reported that a 12-year-old girl suffered two weeks of reduced best-corrected visual acuity (from 20/20 normally to 20/30 OU) after 5 months of repeated low-level red-light (RLRL) laser exposure for myopia treatment. Baseline fundus photography and optical coherence tomography (OCT) images were normal; the RLRL damage manifested as bilaterally darkened foveae with hypoautofluoresence of the maculae, and "bilateral foveal ellipsoid zone disruption and interdigitation zone discontinuity". There was no ocular inflammation. Multifocal ERG showed impact to macula and paramacular responses. After 3 months discontinuation of RLRL therapy, there was partial retinal recovery and acuity improved to 20/25 OU.

 The authors stated that solar and laser pointer retinal injuries present similarly, but the patient denied these risk factors. The patient confirmed adhering to the limited exposure schedule of the RLRL device - particular patients could be sensitive to light toxicity, although how to determine this is unknown. While clinical trials have shown this specific RLRL device (Eyerising) had no adverse effects and this laser is classified as safe, the authors cited that more data is needed on treatment protocols, different ethnicities and instrument longevity and maintenance.

POSITIVES: The RLRL clinical trial results are impressive and have been conducted with a robust methodology. The observation of axial length shortening in 20% of study participants after one year is notable, although the mechanism of this is unknown as choroidal thickness accounts for only a small amount of this change. After two years, the results for axial length control are more in line with other optical interventions and 0.05% atropine, being just in excess of 50%.

NEGATIVES: The case report is concerning, especially in view of no adverse events being reported in the clinical trial. These authors cited that some children may be more sensitive to retinal phototoxicity, but that how to identify these cases is unknown. Also, the rebound effect found after one year of treatment and one year of discontinuation is in excess of that which has been observed with 0.05% atropine and optical treatments (see links on Highly Aspherical Lenslet spectacles; DIMS spectacles and dual-focus MiSight 1 day contact lenses).

THE BALANCE: Perhaps proceed with caution at this stage, with close monitoring of patients' visual acuity and retinal health throughout treatment.

NOTE: Read a response to this case study by Eyerising International, manufacturers and distributors of the RLRL device, via this link. 

1. If RLRL is safe and effective for children of a variety of ethnicities, across more studies.
2. What the potential other mechanisms could be for axial length shortening, given that choroidal thickness changes are not the major cause.
3. Whether short-term treatment could be effective to reduce risk of retinal damage, although rebound after 12 months of treatment, as shown in the two-year clinical study, is concerning.

Title: Effect of Repeated Low-Level Red-Light Therapy for Myopia Control in Children: A Multicenter Randomized Controlled Trial

Authors:  Yu Jiang, Zhuoting Zhu, Xingping Tan, Xiangbin Kong, Hui Zhong, Jian Zhang, Ruilin Xiong, Yixiong Yuan, Junwen Zeng, Ian G Morgan, Mingguang He

Purpose: To assess the efficacy and safety of repeated low-level red-light (RLRL) therapy in myopia control in children. 

Design: Multicenter, randomized, parallel-group, single-blind clinical trial.

Participants: Two hundred sixty-four eligible children 8 to 13 years of age with myopia of cycloplegic spherical equivalent refraction (SER) of -1.00 to -5.00 diopters (D), astigmatism of 2.50 D or less, anisometropia of 1.50 D or less, and best-corrected visual acuity (BCVA) of 0.0 logarithm of the minimum angle of resolution or more were enrolled in July and August 2019. Follow-up was completed in September 2020.

Methods: Children were assigned randomly to the intervention group (RLRL treatment plus single-vision spectacle [SVS]) and the control group (SVS). The RLRL treatment was provided by a desktop light therapy device that emits red light of 650-nm wavelength at an illuminance level of approximately 1600 lux and a power of 0.29 mW for a 4-mm pupil (class I classification) and was administered at home under supervision of parents for 3 minutes per session, twice daily with a minimum interval of 4 hours, 5 days per week.

Main outcome measures: The primary outcome and a key secondary outcome were changes in axial length and SER measured at baseline and the 1-, 3-, 6-, and 12-month follow-up visits. Participants who had at least 1 postrandomization follow-up visit were analyzed for treatment efficacy based on a longitudinal mixed model.

Results: Among 264 randomized participants, 246 children (93.2%) were included in the analysis (117 in the RLRL group and 129 in the SVS group). Adjusted 12-month axial elongation and SER progression were 0.13 mm (95% confidence interval [CI], 0.09-0.17mm) and -0.20 D (95% CI, -0.29 to -0.11D) for RLRL treatment and 0.38 mm (95% CI, 0.34-0.42 mm) and -0.79 D (95% CI, -0.88 to -0.69 D) for SVS treatment. The differences in axial elongation and SER progression were 0.26 mm (95% CI, 0.20-0.31 mm) and -0.59D (95% CI, -0.72 to -0.46 D) between the RLRL and SVS groups. No severe adverse events (sudden vision loss ≥2 lines or scotoma), functional visual loss indicated by BCVA, or structural damage seen on OCT scans were observed.

Conclusions: Repeated low-level red-light therapy is a promising alternative treatment for myopia control in children with good user acceptability and no documented functional or structural damage.

[Link to open access paper]

Title: Retinal Damage After Repeated Low-level Red-Light Laser Exposure

Authors: Huanyu Liu, Yuan Yang, Jingli Guo, Jie Peng, Peiquan Zhao

Case report: A 12-year-old female individual presented with bilateral vision loss for 2 weeks after 5-month application of repeated low-level red-light (RLRL) laser exposure (Eyerising [Suzhou Xuanjia Optoelectronics Technology]) for bilateral moderate myopia. One month before her presentation, the patient complained of abnormally bright light and prolonged afterimages after exposure to light. Optical coherence tomography (OCT) images before RLRL therapy were normal. The best-corrected visual acuity declined from 20/20 to 20/30 OU. No inflammation was noted in the anterior or posterior segment. Fundus photographs revealed only bilaterally darkened foveae with a hypoautofluorescent plaque in autofluorescence images (Figure 1A and B). OCT identified bilateral foveal ellipsoid zone disruption and interdigitation zone discontinuity (Figure 2A and B). Magnetic resonance imaging showed no positive optic nerve or central nervous system lesions. The infectious and inflammatory workup was negative. Multifocal electroretinogram revealed moderately and mildly decreased response in the macula and paramacula, respectively (Figure 1C and D). After 3 months without RLRL therapy, the bilateral outer retinal damage partially recovered (Figure 2C and D), and the visual acuity improved to 20/25 OU.

[Link to open access paper]