In the study by Xiong et al., two intriguing cases involving monozygotic twins were reported(5). These twins shared identical genetic backgrounds, yet they were assigned to different treatment groups. The twin who underwent RLRL therapy experienced a reduction in axial length by 0.2mm, a reversal of myopia progression, and notable choroidal thickening. Conversely, the twin in the control group, who wore single vision spectacles, showed ongoing myopic progression, increased axial length, and choroidal thinning.

Fig 5. Representative cases of a pair of monozygotic twins. They were randomly allocated to the repeated low-level red-light (RLRL) and single-vision spectacle (SVS) groups, respectively. A, OCT images show macular choroidal thickening after 12 months of RLRL therapy. B, OCT images show macular choroidal thinning after 12 months of SVS treatment. Data from the paper Longitudinal Changes and Predictive Value of Choroidal Thickness for Myopia Control after Repeated Low-Level Red-Light Therapy(5).

In one reported case, a 12-year-old children with high myopia experienced a decline in bilateral visual acuity for 2 weeks (from 20/20 to 20/30 OU) after using RLRL therapy for myopia for 5 months. The child had experienced rainbow-like afterimages occasionally lasting for over 8 minutes before, but continued RLRL treatment to maintain myopic control. Ultra-wide-angle fundus imaging revealed a round lesion at the macular fovea. OCT identified discontinuity in the foveal ellipsoid and interdigitation zones with a diameter of 712 μm, which is similar to macular damage caused by laser pens. Subsequent examinations showed that there were significant abnormalities in the visual fields of both eyes. The multifocal electroretinogram (mfERG) showed a reduction in the amplitude density of the first ring in both eyes, with the disappearance of the central response peak. Both eyes had a slight reduction in the amplitudes of both rod and cone response waves. After timely cessation of irradiation and medical intervention for 3 months, her visual acuity improved to 20/25 OU, and after 4 months her retinal structure was intact(21,22).

Fig 6. Optical Coherence Tomography Images of Both Eyes After 5 Months of Repeated Low-Level Red-Light Laser Exposure. Image from the paper Retinal Damage After Repeated Low-level Red-Light Laser Exposure(21).

One possible explanation is that the patient in this case was probably a super responder to light therapy, as indicated by the remarkable 2.00D myopic regression after the first month of treatment. These authors cited that some children may be more sensitive to retinal phototoxicity, but that how to identify these cases is unknown. It’s important for treatments to be conducted under appropriate supervision to ensure safety and efficacy. According to the expert consensus, if the afterimage lasts longer than 6 minutes, it is crucial to stop using the device and seek advice from an eye care professional. If the irradiated eye repeatedly presents prolonged after-images, the duration of the after-image should be recorded, and a retinal function and structure examination should be performed under the guidance of a professional doctor. Additionally, to ensure the safety and efficacy of RLRL therapy, clinic appointments should be scheduled at 1 month, 3 months, 6 months, and then every 6 months thereafter. These visits will allow doctors to monitor the progression of myopia and patients’ response to the therapy.

Professor Ohno-Matsui also commented on the case from another perspective. She speculated that the patient might have had pre-clinical Stargardt disease, evidenced by a dark choroid and unusual high fundus autofluorescence, which is atypical for children. This condition could be causing secondary myopia, and RLRL may not be an appropriate treatment for this patient. Genetic testing is important to confirm this hypothesis about the underlying condition.

Reference

5. Xiong R, Zhu Z, Jiang Y, Wang W, Zhang J, Chen Y, et al. Longitudinal Changes and Predictive Value of Choroidal Thickness for Myopia Control after Repeated Low-Level Red-Light Therapy. Ophthalmology. 2023 Mar;130(3):286–96.

21. Liu H, Yang Y, Guo J, Peng J, Zhao P. Retinal Damage After Repeated Low-level Red-Light Laser Exposure. JAMA Ophthalmol. 2023 Jul 1;141(7):693.

22. Yu T, Zhigang X. Recovery of retinal structural damage after repeated low-intensity red light therapy for high myopia: a case report. 2023;41(9).