This research project is a prospective, randomized controlled trial designed to assess the short-term effects of varied red light therapies on the choroidal and retinal structures in adult myopes. The primary objective is to determine which specific retinal regions or cells are primarily affected by short-term repeated low-level red-light (RLRL) therapy, potentially inducing choroidal thickening. The secondary objective is to assess the safety of different types of red light therapy in adult myopes. The study will enroll 45 myopic adults aged 18-40 years old as participates. They will be randomly assigned into three RLRL groups: small circle (d=0.30mm), medium circle (d=0.50mm), and annular groups (an inner diameter of 0.50 mm and an outer diameter of 0.70mm) without disclosure of their specific group to maintain study blinding. The groups are differentiated by the size and shape of the light spots formed on the retina but with the same power (0.15 mW with a 4 mm pupil size). The Eyerising Myopia Management Device, modified for this study, will be used to administer RLRL with three different spot patterns, adhering to safety standards to minimize risk and ensure participant safety. Before the treatment, baseline data will be collected from each participant. Baseline assessments will consist of demographics information, visual acuity checks, axial length measurements, subjective refraction, slit-lamp examinations, adaptive optics imaging, optical coherence tomography and angiography (OCT \& OCTA), posterior blood flowgraphy, electroretinography (ERG), and the Flicker-plus test. Then participants will undergo daily treatments for 14 days, using the therapy settings of the group to which they have been assigned. The treatment will last for 3 minutes twice a day, with a minimal interval of 4 hours. During the 14-day study period, participants will undergo daily assessments by a series of ophthalmic examinations. Outcomes measured will track changes in choroidal thickness, electrical activity of the retina, axial length, and best corrected visual acuity, alongside other image reports such as adaptive optics imaging, posterior blood flowgraphy and OCT \& OCTA scans. This study addresses the gaps in understanding how RLRL therapy affects myopia and aims to identify the retina's high-response areas to red light. By doing so, it hopes to minimize unnecessary exposure and potential damage, enhancing the safety and effectiveness of the therapy.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
60
All participants will receive a video guide of the Repeated Low-Level Red-Light device. Eligible subjects will receive daily treatment for 14 days, with each treatment lasting for 3 minutes twice a day, with a minimal interval of 4 hours.
The Hong Kong Polytechnic University
Hong Kong, Hong Kong
RECRUITINGChange in choroidal thickness measured by OCT
The change in choroidal thickness (ChT) after 14-day of repeated low-level red-light therapy in adult myopes. OCT and OCTA imaging will be performed using the ultra-wide field swept-source OCT/A system (VG200). The macula was scanned using the 12-line radial scan pattern with a resolution of 1024 × 12. Each image will cover an area of 12 × 9 mm centered on the fovea with an average of 4 consecutive scan overlaps. ChT is defined as the perpendicular distance between the outer choroid-sclera margin and the retinal pigment epithelium-Bruch's complex. The average ChT of the whole ETDRS 9 grid and central ChT (an area centered on the fovea with a diameter of 1 mm) was calculated with the built-in software. The VG200 device has been acquired by our team and is available for use.
Time frame: Choroidal thickness will be measured every day from enrollment to the end of treatment at 2 weeks.
Change in electrical activity of the retina measured by ERG
A standard full-field ERG and mfREG will be conducted. The full-field ERG includes Dark-adapted 0.01 ERG, Dark-adapted 3.0 ERG, Light-adapted 3.0 ERG, and 30 Hz Flicker ERG. Prior to testing, patients will undergo appropriate dark adaptation for 20 minutes to ensure accurate results for the dark-adapted tests.
Time frame: ERG will be carried out on the 7th and 14th days of the study
Change in axial length (AL) measured by IOL Master
IOL Master will be used to measure the AL of both eyes. Five measurements will be taken for each eye. The AL measurement will be based on the mean of these five values if the desired precision (≤0.05 mm) is achieved.
Time frame: AL will be taken every day from enrollment to the end of treatment at 2 weeks.
Change in best corrected visual acuity (BCVA)
An Early Treatment Diabetic Retinopathy Study (ETDRS) chart (Precision Vision, Villa Park, Illinois, USA) with standard illumination will be used to measure distance visual acuity. Visual acuity measurement is performed at a distance of 4 meters. BCVA will be measured.
Time frame: BCVA will be taken every day from enrollment to the end of treatment at 2 weeks.
Change in adaptive optics imaging
The adaptive optics retinal camera rtx1 system (Imagine Eyes) will be employed for high-resolution imaging of cones and rods cells.
Time frame: Adaptive optics imaging assessment will be carried out on the 7th and 14th days of the study.
Change in optical coherence tomography angiography (OCTA) scan
OCT and OCTA imaging will be performed using the ultra-wide field swept-source OCT/A system (VG200). The macula was scanned using the 12-line radial scan pattern with a resolution of 1024 × 12. Each image will cover an area of 12 × 9 mm centered on the fovea with an average of 4 consecutive scan overlaps.
Time frame: OCTA assessment will be taken every day from enrollment to the end of treatment at 2 weeks.
Change in posterior blood flowgraphy
The Laser Speckle Flowgraphy system (LSFG-NAVI) will be utilized to assess blood flow in the posterior segment of the eye. This method involves capturing and analyzing dynamic changes in speckle patterns created by laser light reflecting off moving blood cells, specifically targeting the retinal and choroidal blood flow. The LSFG-NAVI device has been acquired by our team and is available for use.
Time frame: The posterior blood flowgraphy will be taken every day from enrollment to the end of treatment at 2 weeks.
Change in flicker-plus test
The Flicker-plus test, part of the AVOT system, quickly identifies losses in rod and cone photoreceptors without extensive dark adaptation by measuring flicker modulation thresholds (FMTs) at five key central vision points. Adaptation times are minimal-15 seconds for cones and 90 seconds for rods. The test protocol follows the methodologies established by Amithavikram et al.
Time frame: Flicker-plus test will be carried out on the 7th and 14th days of the study
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