Effect of red-light therapy on retinal and choroidal blood perfusion in myopic children

Axial Shortening Effects of Repeated Low-level Red-light Therapy in Children With High Myopia: A Multicenter Randomized Controlled Trial

PURPOSE

To evaluate the effectiveness and safety of repeated low-level red-light (RLRL) in delaying the progression of high myopes with -6.00 diopters (D) or worse.

DESIGN

Multicenter, randomized, parallel-group, single-blind clinical trial. A total of 202 high myopic children aged 7 to 12 years with cycloplegia spherical equivalent (SE) refraction ≤-6.00 D, astigmatism less than 2.50 D, and anisometropia of 1.50 D or less were enrolled from March 2022 to December 2022. Follow-up was completed in December 2023.

METHODS

Eligible participants were randomly allocated to the intervention (RLRL + single vision spectacle) or the control group (single vision spectacle). The RLRL treatment was administered every day for 3 minutes, twice a day, with an interval of at least 4 hours. The primary outcome was the change in axial length (AL) at 12 months compared with baseline. Secondary outcomes included changes in SE, changes in choroidal thickness (ChT), and changes in retinal thickness (RT) in different circle sectors. Outcomes were analyzed by means of intention-to-treat and per-protocol methods.

RESULTS

After 12 months of treatment, AL and SE changes were -0.11 ± 0.25 mm and 0.18 ± 0.63 D for the RLRL group and 0.32 ± 0.09 mm and -0.80 ± 0.42 D for the control group, respectively. Axial shortening >0.05 mm was 59% in the RLRL and 0% in the control group at 12 months. ChT and RT from a single center were analyzed. In the RLRL group, ChT was thickened in all sectors at 12 months. RT was increased in parafoveal and perifoveal circles. In the control group, all sectors of ChT and only perifoveal RT were significantly thinner at 12 months. The multivariate linear regression model revealed significant correlations between changes in the ChT central foveal circle and RT perifoveal circle at 1 month and AL changes at 12 months. No fundus structure changes, afterimage exceeding 6 minutes, or best-corrected visual acuity decrease were reported.

CONCLUSIONS

RLRL could effectively shorten the AL and inhibit the progression of myopia in high myopic patients with -6.00 D or worse. AL shortening is sustained over 12 months of treatment. These observed changes appeared to be associated with increases in ChT and RT.

Potential guidelines for cataract surgery and rehabilitation in visually impaired patients: Literature analysis

Cataracts can reduce the quality of vision in visually impaired patients who already have a visual impairment. The most common causes of low vision include age-related macular degeneration (AMD), high myopia (HM), diabetic retinopathy (DR), glaucoma (GL), and inherited degenerative ocular diseases. The surgery aims to improve their independence, quality of life, and ability to engage in daily, social, and work activities. Phacoemulsification and intraocular lens (IOL) implantation, combined with visual rehabilitation, can improve visual acuity of visually impaired patients. Therefore, comprehensive guidelines for cataract surgery in patients with low vision would be beneficial to ensure optimal surgical outcomes by improving surgical planning, execution, and postoperative care, along with a well-coordinated rehabilitation process. In cases of reduced metabolism, such as low vision, oxidative stress can be aggravated by light exposure and surgical interventions. Thus, maintaining redox balance is crucial for stabilizing retinal conditions. Patients with visual impairments rely on retinal regions with the greatest residual function, and cataract surgery aims to enhance focus on these areas, improving reading quality and reducing scotoma perception. Thorough informed consent is crucial, ensuring that patients are fully aware of the potential risks, benefits, and limitations of surgery. Close postoperative follow-up in the first 6 months is crucial to detect and manage any complications promptly, such as reactivation of maculopathy. The aim of this work is to establish potential guidelines for optimal rehabilitation outcomes through careful literature analysis.

Optical and retinal changes influenced by different lighting conditions

Retinal morphology, specifically in its curvature, and ocular aberrations change when the eye adapts to different lighting conditions, including photopic, scotopic, mesopic, blue light, and red light. Sixty healthy young subjects with refractive error less than ±4.00 D of sphere and 3.00 D of cylinder, not suffering from accommodative problems, ocular or systemic pathology, and not having used electronic devices half an hour before or having taken substances that alter the retina during the 2 h prior to the study were included. The subjects adapted to five lighting conditions, each for 5 min, in a controlled environment. Ocular aberrometry and Optical Coherence Tomography (OCT) were taken to capture images of the central and peripheral retina before (baseline measurements) and after adaptation to each lighting condition. The OCT images were exported and processed to analyze retinal curvature, obtaining parameters such as eccentricity, asphericity and shape factor. The results showed that the shape of the retina was hyperbolic prolate, becoming flatter in scotopic and blue light conditions, and more curved in mesopic conditions. Retinal curvature was closest to baseline under red light and photopic conditions. Aberrometric differences, particularly in the C(2,0) polynomial for defocus, showed higher values in mesopic, baseline, and scotopic conditions, and lower values in photopic, blue light, and red light. Significant differences were also observed in spherical aberrations C(4,0) and C(6,0), vertical coma C(3,-1), and trefoil C(3,-3). The spherical equivalent indicated more myopic values in mesopic, baseline, and scotopic conditions, and more hyperopic values in blue, photopic, and red light, suggesting a link between myopia and lower luminosity. This study concludes that illumination affects retinal curvature and ocular refraction, influencing myopia.

Safety of repeated low-level red-light therapy for myopia: A systematic review

PURPOSE

Establishing the safety profile of repeated low-level red-light (RLRL) therapy is necessary prior to its widespread clinical implementation.

METHODS

We conducted a systematic review (International Prospective Register of Systematic Reviews, CRD42024516676) of articles across seven databases from inception through February 10, 2024, with keywords related to myopia and RLRL therapy. Pooled safety outcomes and risk-to-benefit ratios were reported, and incidence of side effects was compared with other antimyopia interventions.

RESULTS

Among 689 screened articles, 20 studies (2.90 %; median duration 9 months, longest 24 months) were analysed, encompassing 2380 participants aged 3-18 years and 1436 individuals undergoing RLRL therapy. Two case reports described an identical patient with reversible decline in visual acuity and optical coherence tomography (OCT) abnormalities, completely resolved 4 months after treatment cessation. No cases of permanent vision loss were reported. Temporary afterimage was the most common ocular symptom following treatment, resolving within 6 minutes in reported studies. The number needed to harm outweighed the number needed to treat by a ratio of 12.7-21.4 for a person with -3D to -8D myopia treated with RLRL therapy. Incidence of side effects from RLRL was 0.088 per 100 patient-years (95 % confidence interval, 0.02-0.50).

CONCLUSIONS

No irreversible visual function loss or ocular structural damage was identified with RLRL. Fundus photography and OCT before and during therapy, alongside home monitoring of visual acuity and duration of afterimages, are necessary to identify side effects. Further adequately powered studies of longer duration are needed to evaluate long-term safety of RLRL.

L. S, Jeong J, Saw SM, Sevdalis N, Najjar RP. Light Therapy for Myopia Prevention and Control: A Systematic Review on Effectiveness, Safety, and Implementation

Purpose

This systematic review focuses on the effectiveness, safety, and implementation outcomes of light therapy as an intervention to prevent or control myopia in children.

Methods

A systematic literature search was performed in PubMed, EMBASE, CINAHL, SCOPUS, and Web of Science up to January 27, 2024. Effectiveness outcomes included myopia incidence, and changes in axial length (AL), spherical equivalent refraction (SER), and choroidal thickness (CT). Safety outcomes relating to retinal health or damage and implementation outcomes including compliance rates and loss to follow-up were extracted. ROBINS-I, ROB 2, and ROB-2 CRT were used to assess risk of bias.

Results

Nineteen interventional studies were included. Increased outdoor time (n = 3), red-light therapy (n = 13), and increased classroom lighting (n = 1) had a significant effect on myopia incidence, and changes in AL, SER, and CT. Violet-light therapy (n = 2) was only effective in children aged 8 to 10 years and children without eyeglasses with less than 180 minutes of near-work time daily. Two studies using red-light therapy reported adverse effects. For all studies, only compliance rates and loss to follow-up were reported on implementation effectiveness.

Conclusions

Evidence is compelling for the effectiveness of red-light therapy and outdoors time; more data are needed to confirm safety. Robust data are still needed to prove the effectiveness of violet-light and increased classroom lighting. Clearer implementation strategies are needed for all light therapies.

Translational Relevance

Light therapy has emerged as effective for myopia prevention and control. This systematic review summarizes the state of knowledge and highlights gaps in safety and implementation for these strategies.

Safety of repeated low-level red-light therapy for children with myopia

BACKGROUD

To investigate the safety of repetitive low-level red-light therapy (RLRLT) in children with myopia.

METHODS

Children with myopia were assigned to the RLRL and control groups. Axial length (AL) and spherical equivalent refraction (SER) were followed up at 3-, 6-, and 12-month. To evaluate the safety of RLRLT, at 6 and 12 months in the RLRL group, multifocal electroretinography (mfERG) and contrast sensitivity were recorded. Furthermore, optical coherence tomography was used to measure the relative reflectance of the ellipsoid zone (rEZR), photoreceptor outer segment (rPOSR), and retinal pigment epithelium (rRPER).

RESULTS

A total of 108 children completed the trial (55 in the RLRL group and 53 in the control group). After 3, 6, and 12 months, AL was shorter and SER less myopic in the RLRL group than in the control group. Regarding the safety of the RLRLT, the response density and amplitude of the P1 wave of the first ring of the mfERG increased significantly at 6 months (P = 0.001 and P = 0.017, respectively). At 6 and 12 months, contrast sensitivity at the high spatial frequency increased. Moreover, the rEZR increased significantly at 6 months (P = 0.029), the rPOSR increased significantly at 6 and 12 months (both P < 0.001), and the increase in rPOSR was greater with greater AL regression.

CONCLUSIONS

Based on retinal function and structure follow-up, RLRLT was safe within 12 months. However, rEZR and rPOSR increased, the effects of this phenomenon requires further observation.

Red light instruments for myopia exceed safety limits

PURPOSE

Low-level red light (LLRL) therapy has recently emerged as a myopia treatment in children, with several studies reporting significant reduction in axial elongation and myopia progression. The goal of this study was to characterise the output and determine the thermal and photochemical maximum permissible exposure (MPE) of LLRL devices for myopia control.

METHODS

Two LLRL devices, a Sky-n1201a and a Future Vision, were examined. Optical power measurements were made using an integrating sphere radiometer through a 7-mm diameter aperture, in accordance with ANSI Z136.1-2014, sections 3.2.3-3.2.4. Retinal spot sizes of the devices were obtained using a model eye and high-resolution beam profiler. Corneal irradiance, retinal irradiance and MPE were calculated for an eye positioned at the oculars of each device.

RESULTS

Both devices were confirmed to be Class 1 laser products. Findings showed that the Sky-n1201a delivers laser light as a point source with a 654-nm wavelength, 0.2 mW power (Ø 7 mm aperture, 10-cm distance), 1.17 mW/cm2 corneal irradiance and 7.2 W/cm2 retinal irradiance (Ø 2 mm pupil). The MPE for photochemical damage is 0.55-7.0 s for 2-7 mm pupils and for thermal damage is 0.41-10 s for 4.25-7 mm pupils. Future Vision delivers the laser as an extended source subtending 0.75 × 0.325°. It has a 652-nm wavelength, 0.06 mW power (Ø 7 mm aperture, 10 cm distance), 0.624 mW/cm2 corneal irradiance and 0.08 W/cm2 retinal irradiance (Ø 2 mm pupil). MPE for photochemical damage is 50-625 s for 2-7 mm pupils.

DISCUSSION

For both of the LLRL devices evaluated here, 3 min of continuous viewing approached or surpassed the MPE, putting the retina at risk of photochemical and thermal damage. Clinicians should be cautious with the use of LLRL therapy for myopia in children until safety standards can be confirmed.