Utilization of the 1064 nm Wavelength in Photobiomodulation: A Systematic Review and Meta-Analysis

A systematic review and meta-analysis of the effectiveness of high-intensity laser therapy in patients with carpal tunnel syndrome

OBJECTIVES

This systematic review aimed to evaluate the effects of high-intensity laser therapy (HILT) on pain intensity, disability, and electrophysiological parameters in individuals diagnosed with carpal tunnel syndrome (CTS).

DATA SOURCES AND SYNTHESIS

A search of electronic databases, including PubMed, Web of Science, Scopus, CINAHL, Science Direct, Cochrane Library, the PEDro database, and Google Scholar (updated until February 18, 2025), was conducted for randomized controlled trials (RCTs).

DATA EXTRACTION AND QUALITY ASSESSMENT

Data were extracted independently by three researchers. The quality of RCTs was assessed using the Cochrane Risk of Bias (RoB) 2.0 tool, while evidence certainty was evaluated with the GRADE approach. Primary outcomes included pain intensity, with secondary outcomes comprising electrophysiological parameters and disability.

RESULTS

Nine RCTs met inclusion criteria. Most studies exhibited a low risk of bias across RoB2 domains, except for outcome measurement, resulting in an overall RoB of 44%. Meta-analyses demonstrated that HILT, alone or combined with interventions such as splinting, exercise, TENS, vitamin B supplements, or ergonomic modifications, significantly reduced pain (SMD = 0.7 to 1.6) and disability (SMD = 0.68). Electrophysiological improvements included enhanced distal motor latency (SMD = 0.98) and sensory conduction velocity (SMD = 0.8), particularly when combined with median nerve gliding or splinting.

CONCLUSION

This review confirms HILT's effectiveness in reducing pain and disability and improving electrophysiological parameters in CTS. However, evidence certainty remains moderate to low. Future RCTs should standardize outcome measures to evaluate HILT's clinical impact beyond statistical significance, and comparative studies with LLLT are needed to refine laser therapy protocols.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42023470170 (October 17, 2023). CONTRIBUTION OF THE PAPER.

Monitoring photobiomodulation of amyloid-β aggregation in 3D cultured cells using label-free nonlinear optical imaging

The accumulation of beta-amyloid (Aβ) peptide aggregates, commonly known as plaques, is considered a key hallmark in the development of Alzheimer's disease (AD). Recently, low-level light therapy (LLLT), also referred to as photobiomodulation (PBM), has emerged as a promising treatment approach for AD. Previous studies have shown that PBM reduces Aβ load primarily by enhancing the clearance capabilities of glia cells. However, it remains unclear whether PBM can directly reduce the formation of Aβ plaques in neuronal cells independent of the glia cell effect. In this study, we employed three-dimensional (3D) cultured HEK 293 APPsw cells as an AD model to investigate the impact of PBM on Aβ aggregation. We demonstrated that label-free two-photon excited fluorescence (TPEF) imaging and second harmonic generation (SHG) imaging are effective tools for monitoring Aβ aggregation in 3D cell models. The TPEF imaging results and subsequent quantification revealed that PBM, particularly with low-level near-infrared light from an 808 nm laser (compared to 1064, 1210, and 1470 nm lasers), significantly reduced Aβ aggregation, specifically plaques formation, in the 3D cultured cells, with the effect found to be dose-dependent. Moreover, a comprehensive analysis of protein expression in the 3D cultured cells revealed that PBM induces overexpression of the LRP1 receptor, which mediates Aβ degradation and thus leads to the reduction of Aβ aggregation. This study highlights the use of label-free nonlinear optical imaging to monitor Aβ aggregation in AD progression and provides novel insights into the effects of PBM on Aβ plaque formation in AD models.

Neoangiogenetic potential of Nd:YAG 1064 nm photobiomodulation in non-surgical healing of trauma induced periapical bone defects: a clinicalprospective pilot study

To evaluate Nd: YAG 1064 nm photobiomodulation as a therapeutic adjunct for non-surgical management of trauma-induced periapical bone defects. The present study was a parallel-group, double arm, single-centre clinical, prospective, pilot study. Thirty systematically healthy individuals with radiographic evidence of trauma-induced periapical bone defects in anterior teeth were recruited. Twenty-four patients meeting the inclusion criteria were selected and randomly placed in two treatment groups. Group A: Non-surgical endodontic treatment with intracanal calcium hydroxide-iodoform paste (CH-I), and Group B: Non-surgical endodontic treatment with intracanal calcium hydroxide and adjunctive extracanal Nd:YAG 1064 nm photobiomodulation therapy (PBMT). Improvement in vascular perfusion, reduction in size, volume, area and echogenicity of the lesion was assessed with ultrasound and colour Doppler imaging. The peak systolic velocity increased statistically significantly (p < 0.05) from baseline to 3 and 6 months, suggesting PBMT as a facilitator of neoangiogenesis. Compared to the calcium hydroxide group, the PBM group showed a more significant mean reduction in size, volume, and surface area of the periapical lesion and lower post-operative pain scores, though not statistically significant. Also, the PBM group presented with more remarkable hard tissue development, as seen by an improvement in echogenicity from hypoechoic to predominantly hyperechoic or hyperechoic. Results suggest that PBMT with Nd: YAG can accelerate healing, enhance perfusion of periapical lesions, provide analgesia, and reduce the need for pharmacological drugs. Although the sample size is limited, this research offers a foundation for further clinical studies with larger sample sizes to evaluate the additional benefits of laser therapy in periapical healing. The study was submitted to the Clinical Trails Registry-India (CTRI), under reference no/2023/02/063428, with a registration number/2023/09/057848, before the commencement of the study.

Transcranial low-level laser stimulation in the near-infrared-II region (1064 nm) for brain safety in healthy humans

BACKGROUND

The use of near-infrared lasers for transcranial photobiomodulation (tPBM) offers a non-invasive method for influencing brain activity and is beneficial for various neurological conditions. However, comprehensive quantitative studies on its safety are lacking.

OBJECTIVE

This study aims to investigate the safety of 1064-nm laser-based tPBM across brain structure, brain function, neural damage, cognitive ability and tolerance.

METHODS

We employed a multimodal approach, using magnetic resonance imaging (MRI), electroencephalogram (EEG), biochemical analyses, and cognitive testing to quantitatively assess the potential adverse effects of tPBM on brain structure or function, neurons, glial cells, and executive function (EF). Additionally, a detailed questionnaire was used to evaluate subjective tolerance.

RESULTS

At the whole-brain structural level, no significant variations in gray matter, white matter, or cerebrospinal fluid volume or density were observed as a result of tPBM. There was no increase in neuron-specific enolase (NSE) or S100β levels suggesting no neuronal damage, but an unexpected significant reduction in NSE was detected which requires further study to assess its implications. EEG, analyzed through power spectra and expert evaluation, revealed no potential disease-inducing effects. A series of cognitive tests demonstrated no impairment in any of the EF components. Furthermore, the questionnaire data revealed minimal discomfort across fatigue, itching, pain, burning, warmth, dizziness, and drowsiness.

CONCLUSIONS

Our data indicate that 1064 nm laser tPBM does not induce adverse effects on brain structure or function, nor does it impair cognitive abilities. tPBM is safe for specific parameters, highlighting its good tolerability.

Effects of high-intensity laser therapy on subacromial impingement syndrome: a systematic review and meta-analysis

This systematic review and meta-analysis aims to identify, critically appraise, and summarize the effects of high-intensity laser therapy on subacromial impingement syndrome. Three databases, PubMed, Embase, and Scopus were searched from inception to March 1, 2024. Clinical trials comparing the effects of high-intensity laser therapy to conventional therapy are eligible for inclusion. Two independent reviewers conducted study selection, data extraction, and quality assessment. Methodological quality was assessed using the Physiotherapy Evidence Database scale. Meta-analyses were performed to determine the effects of high-intensity laser therapy. Five randomized controlled trials and one controlled clinical trial were included, with a total of 284 patients with subacromial impingement syndrome. All included studies were evaluated as good or above for quality assessment. Compared to conventional therapy, high-intensity laser therapy demonstrated significantly better outcomes for pain at both post-intervention (SMD = -1.01, 95%CI = -1.85 to -0.17) and three-month post-intervention (SMD = -0.51, 95%CI = -0.90 to -0.13); shoulder and arm function at both post-intervention (SMD = 0.40, 95%CI = 0.14 to 0.66) and three-month post-intervention (SMD = 0.45, 95%CI = 0.06 to 0.84); shoulder abduction active range of motion (SMD = 3.26, 95%CI = 0.49 to 6.03). No significant difference was found for shoulder flexion and external rotation range of motion. This review highlights the promising effects of high-intensity laser therapy for the rehabilitation of subacromial impingement syndrome. Rehabilitation professionals and policymakers should increase their awareness of high-intensity laser therapy as an emerging technology that may facilitate greater outcomes than current widespread standards.

Can infrared light really be doing what we claim it is doing? Infrared light penetration principles, practices, and limitations

Near infrared (NIR) light has been shown to provide beneficial treatment of traumatic brain injury (TBI) and other neurological problems. This concept has spawned a plethora of commercial entities and practitioners utilizing panels of light emitting diodes (LEDs) and promising to treat patients with TBI and other disorders, who are desperate for some treatment for their untreatable conditions. Unfortunately, an LED intended to deliver photonic energy to the human brain does not necessarily do what an LED pointed at a mouse brain does. There is a problem of scale. Extensive prior research has shown that infrared light from a 0.5-watt LED will not penetrate the scalp and skull of a human. Both the properties of NIR light and the manner in which it interacts with tissue are examined. Based on these principles, the shortcomings of current approaches to treating neurological disorders with NIR light are explored. Claims of clinical benefit from low-level LED-based devices are explored and the proof of concept challenged. To date, that proof is thin with marginal benefits which are largely transient. Extensive research has shown fluence at the level of the target tissue which falls within the range of 0.9 J/cm2 to 15 J/cm2 is most effective in activating the biological processes at the cellular level which underlie direct photobiomodulation. If low-level infrared light from LED devices is not penetrating the scalp and skull, then these devices certainly are not delivering that level of fluence to the neurons of the subjacent brain. Alternative mechanisms, such as remote photobiomodulation, which may underlie the small and transient benefits for TBI symptoms reported for low-power LED-based NIR studies are presented. Actionable recommendations for the field are offered.

Enhancing thermal stability of Nd:GGG WGM microdisk lasers via silica integration

Whispering gallery mode (WGM) resonators, as an integral component of integrated photonics, have attracted considerable attention due to their high Q factor, small footprint, and small mode volume, making them widely applied as microlasers. In this work, Nd:GGG crystal was prepared into a Nd:GGG film with thickness of 1.8 μm through ion implantation-enhanced etching (IIEE) technique, and subsequently, the Nd:GGG film was partened by focused ion beam (FIB) technology to generate a microdisk with diameter of 20 μm. For high-power microcavity lasers, heat generation during laser operation was inevitable. We placed the microdisk on a silica holder and a silica wafer, respectively. The microdisk placed on the silica holder and silica wafer exhibited laser thresholds of 32 μW and 17 μW, respectively. Moreover, due to different heat dissipation conditions, the microdisk placed on the silica holder exhibited a mode shift of 0.13 nm/mW, while the microdisk placed on the silica wafer showed a more stable laser output state with a mode shift of 0.02626 nm/mW.

Effects of Photobiomodulation on Pain and Return to Play of Injured Athletes: A Systematic Review and Meta-analysis

ABSTRACT

Morgan, RM, Wheeler, TD, Poolman, MA, Haugen, ENJ, LeMire, SD, and Fitzgerald, JS. Effects of photobiomodulation on pain and return to play of injured athletes: A systematic review and meta-analysis. J Strength Cond Res 38(6): e310-e319, 2024-The aims of this systematic review and meta-analysis were to evaluate the effect of photobiomodulation (PBM) on musculoskeletal pain in injured athletes and to determine if the effects of PBM allowed injured athletes to return to play faster. Electronic databases (MEDLINE Complete, CINAHL, and SPORTDiscus, PubMed, Web of Science, and Embase) were systematically searched (up to and including November 7, 2023) for peer-reviewed randomized controlled trials (RCTs) meeting criteria. Six RCTs, representing 205 competitive and recreational athletes with a mean age of 24 years, were included in the analysis. There were 6 intervention groups using standard physical therapy (n = 1), placebo PBM (n = 4), and aloe gel (n = 1) lasting between 10 minutes and 8 weeks in duration. The level of significance set for the study was p < 0.05. Overall, the use of PBM indicated a positive effect on pain reduction for PBM vs. control groups, standardized mean differences = 1.03, SE = 0.22, 95% confidence intervals = [0.43-1.63], p = 0.0089, but the 2 RCTs found evaluating the effect of PBM on time to return to play after injury in athletes do not support a benefit. Allied healthcare professionals may use PBM to reduce pain, thus allowing an athlete to return to their normal biomechanical movement faster; however, limited evidence suggests that PBM does not reduce time to return to play after an injury.

A Preliminary Study on Quantitative Analysis of Collagen and Apoptosis Related Protein on 1064 nm Laser-Induced Skin Injury

To investigate the associated factors concerning collagen and the expression of apoptosis-related proteins in porcine skin injuries induced by laser exposure, live pig skin was irradiated at multiple spots one time, using a grid-array method with a 1064 nm laser at different power outputs. The healing process of the laser-treated areas, alterations in collagen structure, and changes in apoptosis were continuously observed and analyzed from 6 h to 28 days post-irradiation. On the 28th day following exposure, wound contraction and recovery were notably sluggish in the medium-high dose group, displaying more premature and delicate type III collagen within the newly regenerated tissues. The collagen density in these groups was roughly 37-58% of that in the normal group. Between days 14 and 28 after irradiation, there was a substantial rise in apoptotic cell count in the forming epidermis and granulation tissue of the medium-high dose group, in contrast to the normal group. Notably, the expression of proapoptotic proteins Bax, caspase-3, and caspase-9 surged significantly 14 days after irradiation in the medium-high dose group and persisted at elevated levels on the 28th day. During the later stage of wound healing, augmented apoptotic cell population and insufficient collagen generation in the newly generated skin tissue of the medium-high dose group were closely associated with delayed wound recovery.

1064nm Nd:YAG laser promotes chondrocytes regeneration and cartilage reshaping by upregulating local estrogen levels

Cartilage is frequently used as a scaffolds for repairing and reconstructing body surface organs. However, after successful plastic surgery, transplanted cartilage scaffolds often exhibit deformation and absorption over time. To enhance the shaping stability of cartilage scaffolds and improve patients' satisfaction after reconstructions, we employed the ear folding models in New Zealand rabbits to confirm whether the 1064nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser could promote cartilage reshaping. There was an increase in collagen and aromatase (Cyp19) expression within the ear cartilage after laser treatment. Moreover, we have found that the Cyp19 inhibitor can inhibit the laser's effect on cartilage shaping and reduce collagen and Cyp19 expression. The overall findings suggest that treatment with 1064nm Nd:YAG laser irradiation can enhance estrogen levels in local cartilage tissues by upregulating Cyp19 expression in chondrocytes through photobiomodulation, thereby promoting the proliferation and collagen secretion of chondrocytes to improve cartilage reshaping and stability.

Therapeutic efficacy and safety of home-based portable laser irradiation on patients with wrist pain: a single-blinded randomized controlled trial

The purpose of this study is to confirm the effect of small, portable low-level laser therapy (light sources in square configuration: 830 nm GaAs diode 3.2 mW at the center, 4 × 650 nm InGaAIP diodes over the corners) treatment in reducing and enhancing hand function in patients with wrist pain. This study was a prospective, randomized, sham-controlled, and home-based self-therapy trial. A total of thirty subjects with wrist pain were enrolled. All participants received low-level laser therapy on painful area at the wrist. The experimental group (n = 15) received laser stimulation, while the control group (n = 15) received sham stimulation using identical equipment that generated only a red light without the laser output. Both groups self-treated for 30 min a day, 5 days per week for 3 weeks, total of 15 sessions. The primary outcome was assessed using a visual analogue scale (VAS) for wrist pain from 0 (painless) to 10 (extreme pain). The secondary outcomes were measured with patient-rated wrist evaluation (PRWE), grip strength, lateral, palmar, and tip pinch strength. Measures were taken before and after treatment. A total of thirty participants provided outcome data. After the intervention, both groups showed a significant decrease in VAS score, from 4.93 to 3.67 in experimental group, from 5.53 to 4.00 in control group (the experiment group: p = 0.020, the control group: p = 0.003). The experimental group showed a significant improvement in function scale score (p = 0.012), the control group did not. Lateral and pinch strength was significantly improved in the experimental group (p = 0.017) and in the control group (p = 0.034) respectively. There were no side effects in the patients. Medical laser irradiation is a portable and easy-to-use laser irradiator without side effects. Clinical Trial Registration number: KCT0006604.

Clinical Efficiency of High-Intensity Laser Therapy in Patients With Cervical Radiculopathy: A 12-Week Follow-up, Randomized, Placebo-Controlled Trial

OBJECTIVE

The purpose of this study was to research the clinical effectiveness of high-intensity laser therapy combined with exercise on pain, quality of life, and disability in patients with cervical radiculopathy and compared it with that of placebo and exercise alone.

DESIGN

Ninety participants with cervical radiculopathy were randomized into the following three groups: high-intensity laser therapy + exercise ( n = 30), placebo + exercise ( n = 30), and exercise only ( n = 30). Pain, cervical range of motion, disability, and quality of life (36-item Short Form Health Survey) were assessed at baseline and weeks 4 and 12.

RESULTS

The mean age of the patients (66.7% female) was 48.9 ± 9.3 yrs. Pain intensity in the arm and neck, neuropathic and radicular pain levels, disability, and several parameters of the 36-item Short Form Health Survey showed an improvement in the short and medium term in all three groups. These improvements were greater in the high-intensity laser therapy + exercise group than in the other two groups.

CONCLUSIONS

High-intensity laser therapy + exercise was much more effective in improving medium-term radicular pain, quality of life, and functionality in patients with cervical radiculopathy. Thus, high-intensity laser therapy should be considered for the management of cervical radiculopathy.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

At the conclusion of this article, readers will be able to: (1) Define cervical radicular pain and its clinical presentation, and explain the main pathomechanism in cervical radiculopathy (CR); (2) Describe the effects of laser administration on neuropathic pain; and (3) Discuss the clinical significance of coadministration of high-intensity laser therapy (HILT) with exercise (HILT + EX) in CR.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s) ™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Case report: use of high-intensity laser therapy for treatment of trigeminal neuralgia

Trigeminal neuralgia represents a form of chronic facial pain that is characterized by its incapacitating nature. The current therapeutic approaches encompass pharmacological agents with carbamazepine or non-pharmacologic options including utilization of percutaneous rhizotomy, Gamma knife radiosurgery or microvascular decompression may be indicated in certain cases. While the interventions may be effective, medications have negative side effects and procedures are invasive which can pose challenges for patients with various comorbidities. High-intensity laser therapy (HILT) has demonstrated safety and efficacy for many types of chronic pain such as musculoskeletal, autoimmune and neuropathic. Herein, we demonstrate the benefits of HILT therapy in the management of trigeminal neuralgia in a 72 year-old patient with a complex history of facial surgery and radiation who had failed pharmacological treatments and denied any invasive procedures.

Cutaneous effects of photobiomodulation with 1072 nm light

Photobiomodulation, also known as low-level light therapy, has gained popularity in treating a variety of dermatologic and non-dermatologic conditions. The near-infrared (NIR) portion ranging from 700 to 1440 nm has a broad spectrum but most current research focuses on relatively shorter wavelengths. To date, clinical research regarding the application of 1072 NIR is limited to treatments for infections and photorejuvenation treatment in females. However, 1072 NIR light therapy may benefit male patients. This theoretical application is based on the biological properties of this subgroup having increased cutaneous density and thickness and the physical properties of 1072 NIR allowing it to penetrate increased depth. 1072 NIR can reach more cells throughout the epidermis and dermis compared to other parts of the electromagnetic spectrum traditionally used in phototherapy to provide unique and targeted benefits. 1072 NIR light-emitting diodes are commercially available and therefore hold tremendous potential to become accessible, affordable treatment options. Given the increased demand and market size for aesthetics for men that remains untapped, there is opportunity for future research to elucidate the potential for this wavelength as a safe and effective treatment.

Comparison between Low-Level and High-Intensity Laser Therapy as an Adjunctive Treatment for Knee Osteoarthritis: A Randomized, Double-Blind Clinical Trial

BACKGROUND

Low-level (LLLT) and high-intensity laser therapy (HILT) can be beneficial additions to knee osteoarthritis (KOA) rehabilitation exercises; however, it is still being determined which electrophysical agent is more effective.

AIM

To compare the effects of LLLT and HILT as adjuncts to rehabilitation exercises (LL + EX and HL + EX) on clinical outcomes in KOA.

METHODS

Thirty-four adults with mild-to-moderate KOA were randomly allocated to either LL + EX or HL + EX (n = 17 each). Both groups underwent their respective intervention weekly for twelve weeks: LL + EX (400 mW, 830 nm, 10 to 12 J/cm², and 400 J per session) or HL + EX (5 W, 1064 nm, 19 to 150 J/cm², and 3190 J per session). The laser probe was placed vertically in contact with the knee and moved in a slow-scan manner on the antero-medial/lateral sides of the knee joint. Participants' Knee Injury and Osteoarthritis Outcome Score (KOOS), Numerical Pain Rating Scale (NPRS), active knee flexion, and Timed Up-and-Go test (TUG) were assessed.

RESULTS

Post intervention, both groups showed improvements in their KOOS, NPRS, active knee flexion, and TUG scores compared to baseline (p < 0.01). The mean difference of change in KOOS, NPRS, and active knee flexion scores for the HL + EX group surpassed the minimal clinically important difference threshold. In contrast, the LL + EX group only demonstrated clinical significance for the NPRS scores.

CONCLUSIONS

Incorporating HILT as an adjunct to usual KOA rehabilitation led to significantly higher improvements in pain, physical function, and knee-related disability compared to LLLT applied in scanning mode.

Photobiomodulation and nitric oxide signaling

Nitric oxide (NO) is a well-known gaseous mediator that maintains vascular homeostasis. Extensive evidence supports that a hallmark of endothelial dysfunction, which leads to cardiovascular diseases, is endothelial NO deficiency. Thus, restoring endothelial NO represents a promising approach to treating cardiovascular complications. Despite many therapeutic agents having been shown to augment NO bioavailability under various pathological conditions, success in resulting clinical trials has remained elusive. There is solid evidence of diverse beneficial effects of the treatment with low-power near-infrared (NIR) light, defined as photobiomodulation (PBM). Although the precise mechanisms of action of PBM are still elusive, recent studies consistently report that PBM improves endothelial dysfunction via increasing bioavailable NO in a dose-dependent manner and open a feasible path to the use of PBM for treating cardiovascular diseases via augmenting NO bioavailability. In particular, the use of NIR light in the NIR-II window (1000-1700 nm) for PBM, which has reduced scattering and minimal tissue absorption with the largest penetration depth, is emerging as a promising therapy. In this review, we update recent findings on PBM and NO.