Gallium Arsenide Laser Research Articles

The energy density of laser light differentially modulates the skin morphological reorganization in a murine model of healing by secondary intention

This study investigates the influence of gallium-arsenide (GaAs) laser photobiostimulation applied with different energy densities on skin wound healing by secondary intention in rats. Three circular wounds, 10 mm in diameter, were made on the dorsolateral region of 21 Wistar rats weighting 282.12 ± 36.08 g. The animals were equally randomized into three groups: Group SAL, saline solution 0.9%; Group L3, laser GaAs 3 J/cm(2); Group L30, laser GaAs 30 J/cm(2). Analyses of cells, blood vessels, collagen and elastic fibres, glycosaminoglycans and wound contraction were performed on the scar tissue from different wounds every 7 days for 21 days. On day 7, 14 and 21, L3 and L30 showed higher collagen and glycosaminoglycan levels compared to SAL (P < 0.05). At day 21, elastic fibres were predominant in L3 and L30 compared to SAL (P < 0.05). Type-III collagen fibres were predominant at day 7 in both groups. There was gradual reduction in these fibres and accumulation of type-I collagen over time, especially in L3 and L30 compared with SAL. Elevated density of blood vessels was seen in L30 on days 7 and 14 compared to the other groups (P < 0.05). On these same days, there was higher tissue cellularity in L3 compared with SAL (P < 0.05). The progression of wound closure during all time points investigated was higher in the L30 group (P < 0.05). Both energy densities investigated increased the tissue cellularity, vascular density, collagen and elastic fibres, and glycosaminoglycan synthesis, with the greater benefits for wound closure being found at the density of 30 J/cm(2).

Effects of a low-level semiconductor gallium arsenide laser on local pathological alterations induced by Bothrops moojeni snake venom

Antivenom therapy has been ineffective in neutralizing the tissue damage caused by snakebites. Among therapeutic strategies to minimize effects after envenoming, it was hypothesized that a low level laser would reduce complications and reduce the severity of local snake venom effects. In the current study, the effect of a low-level semiconductor gallium arsenide (GaAs) laser on the local pathological alterations induced by B. moojeni snake venom was investigated. The experimental groups consisted of five male mice, each administered either B. moojeni venom (VB), B. moojeni venom + antivenom (VAV), B. moojeni venom + laser (VL), B. moojeni venom + antivenom + laser (VAVL), or sterile saline solution (SSS) alone. Paw oedema was induced by intradermal administration of 0.05 mg kg(-1) of B. moojeni venom and was expressed in mm of directly induced oedema. Mice received by subcutaneous route 0.20 mg kg(-1) of venom for evaluating nociceptive activity and the time (in seconds) spent in licking and biting the injected paw was taken as an indicator of pain response. Inflammatory infiltration was determined by counting the number of leukocytes present in the gastrocnemius muscle after venom injection (0.10 mg kg(-1)). For histological examination of myonecrosis, venom (0.10 mg kg(-1)) was administered intramuscularly. The site of venom injection was irradiated by the GaAs laser and some animals received antivenom intraperitoneally. The results indicated that GaAs laser irradiation can help in reducing some local effects produced by the B. moojeni venom in mice, stimulating phagocytosis, proliferation of myoblasts and the regeneration of muscle fibers.

Effects of Voids in Sintered Silver Joint on Thermal and Optoelectronic Performances of High Power Laser Diode

The thermal and the optoelectronic performance of high power gallium arsenide (GaAs) laser diode die-attached with sintered silver joint were investigated. The thermal and mechanical characteristics of the Laser bar packaging were simulated by finite element analysis (FEA). On the basis of prior experimental observations, voids in the bonding layer were intentionally introduced in the FEA model to examine their effect on the laser diode operating in the continuous-wave (CW) mode under different drive currents. The simulation results indicate that the quality of the bonding layer is very important to the heat dissipation capability of the packaging. Any void in the die-attach material would become a hotspot and thus deteriorate the optoelectronic performance of the laser diode. In addition, because of the coefficient of thermal expansion (CTE) mismatch between the laser bar and the copper heat sink, the interfacial thermomechanical stress will cause a noticeable curvature of the laser diode and a blueshift in the wavelength.

Effects of chronic passive smoking on the regeneration of rat femoral defects filled with hydroxyapatite and stimulated by laser therapy

Defects associated with bone mass loss are frequently treated by autogenous bone grafting. However, synthetic biomaterials such as calcium phosphate ceramics can substitute autologous grafts as long as they are biocompatible with bone tissue. In addition, low-level laser therapy (LLLT) is used to enhance bone regeneration by stimulating the local microcirculation and increasing the synthesis of collagen by bone cells. However, bone health is fundamental for osseointegration of the graft and bone repair. In this respect, excessive tobacco consumption can compromise expected outcomes because of its deleterious effects on bone metabolism that predispose to the development of osteoporosis. The objective of this study was to evaluate the regeneration of bone defects implanted with biomaterial and stimulated by LLLT in rats submitted to passive cigarette smoking. Porous hydroxyapatite granules were implanted into critical-size defects induced experimentally in the distal epiphysis of the right femur of 20 female Wistar rats submitted to passive smoking for 8 months in a smoking box. The defect site was irradiated with a gallium-arsenide laser at an intensity of 5.0J/cm2. The animals were divided into four groups: control (non-smoking) rates submitted (G2) or not (G1) to laser irradiation, and smoking rats submitted (G4) or not (G3) to laser irradiation. The animals were sacrificed 8 weeks after biomaterial implantation. The right femurs were removed for photodocumentation, radiographed, and processed for routine histology. The results showed good radiopacity of the implant site and of the hydroxyapatite granules. Histologically, formation of new trabecular bone was observed adjacent to the hydroxyapatite granules in G1 and G2. In G3 and G4, the granules were surrounded mainly by connective tissue. In conclusion, passive smoking compromised bone neoformation in the defects and the LLLT protocol was not adequate to stimulate local osteogenesis.

Stimulatory effects of Gallium-Arsenide laser irradiation on the developing pulp

Stimulatory effects of Gallium-Arsenide laser irradiation on the developing pulp

The immediate effects of 830-nm low-level laser therapy on the myofascial trigger point of the upper trapezius muscle in visual display terminal workers: A randomized, double-blind, clinical trial

The aim of our study was to evaluate the immediate effects of an 830-nm Aluminium gallium arsenide (GaAlAs) laser, by examining the changes, in pressure-pain threshold (PPT) and tenderness at 3 kg of the myofascial trigger point (MTrP) of the upper trapezius muscle in visual display terminal (VDT) workers in comparison with placebo treatment. Thirty VDT workers (13 males, 17 females) with complaints of upper trapezius muscle were recruited. All participants were given either active GaAlAs laser (830 ㎚ wavelength, 450 ㎽, 9 J at point) or placebo GaAlAs laser, according to the double-blinded and placebo-controlled trial. Both active and placebo low-level laser therapy (LLLT) treatments showed no significant effect on PPT and tenderness at 3 kg. These results suggest that a higher dosage may be necessary to produce immediate effects when applying LLLT to the MTrP of relatively large muscles such as the upper trapezius muscle.

LOW LEVEL LASER THERAPY ON EXPERIMENTAL MYOPATHY

The aim of the present work was to study the effect of Helium-Neon (HeNe) and Gallium Arsenide (GaAs) laser upon nitric oxide (NO) plasma levels, an inflammatory biomarker associated with oxidative stress, in rats with experimental myopathy. These were evaluated through histological assessment. The groups studied were: (A) control (intact rats that received LLLT sham exposures), (B) rats with myopathy and sacrificed at 24 h later, (C) rats with myopathy and sacrificed 8 days later, (D) rats with myopathy and treated with HeNe laser, (E) rats with myopathy and treated with GaAs laser, (F) intact rats treated with HeNe laser and (G) intact rats treated with GaAs laser. Myopathy was induced by injecting 50μl of 1% carrageenan λ (type IV) in the left gastrocnemius muscle. Low Level Laser Therapy (LLLT) was applied with 9.5 J.cm(-2) daily for 10 consecutive days with each laser. The determination of the NO was made by spectrophotometry. The muscles were stained with Hematoxylin-Eosin and examined by optic microscopy. Quantitative variables were statistically analyzed by the Fisher test, and categorical by applying Pearson's Chi Squared test at p <0.05 for all cases. In groups B and C, NO was significantly increased compared to groups A, D, E, F and G (p<0.05). In group C, the percentage of area with inflammatory infiltration was significantly increased compared to the other groups (p<0.001). LLLT decreased plasma levels of NO in rats with experimental myopathies and significant muscle recovery.

Investigation of the Effect of GaAs Laser Therapy on Lateral Epicondylitis

There are conflicting reports regarding the efficacy of low energy laser therapy in treatment of lateral epicondylitis (LE). Contradictory results are considered to be due to different joint treatment protocols regarding variables such as dose, duration, and frequency. The aim of this study was to investigate the efficacy of gallium-arsenide (GaAs) laser therapy, which was performed with the dose regimen recommended by the World Association for Laser Therapy, in relieving pain and improving functional activities in patients with LE. Forty-nine patients (50 elbows) evaluated in our outpatient clinic were included in the study. Elbows were randomized into two groups: laser (n = 25) and placebo laser (n = 25). Either laser or placebo laser therapy was applied to patients for 15 sessions (5 d per week for 3 weeks). Main outcome measures were visual analog scale, tenderness, Disability of the Arm Shoulder and Hand (DASH) questionnaire, the Patient-Related Lateral Epicondylitis Evaluation (PRTEE) test, pain-free grip strength, and the Nottingham Health Profile (NHP) questionnaire. Evaluations were performed before treatment, at the end of 3 weeks of treatment, and after the 12th week of treatment ended. Upon post-treatment evaluation, a significant improvement in all parameters was observed for both groups (p < 0.05). No significant difference was found when the laser and placebo groups were compared. At the 12 week evaluation, a significant sustained improvement in all parameters was observed. On intergroup evaluation, a significant improvement was observed in favor of the active treatment group regarding pain with resisted extension of the wrist, tenderness with pressure, and for both the total and subgroup scores of the DASH questionnaire and PRTEE test, as well as for the pain subgroup of the NHP questionnaire (p < 0.05). Although low energy laser therapy had no advantage compared to placebo in patients with LE for the short term, a significant improvement, particularly in functional parameters, was achieved in the long term. Laser, which has relatively no side effects, might be included among long-term treatment options for LE.

Effect of gallium-arsenide laser, gallium-aluminum-arsenide laser and healing ointment on cutaneous wound healing in Wistar rats

This study determined the effects of gallium-aluminum-arsenide laser (GaAlAs), gallium-arsenide laser (GaAs) and Dersani healing ointment on skin wounds in Wistar rats. The parameters analyzed were: type I and III collagen fiber concentrations as well as the rate of wound closure. Five wounds, 12 mm in diameter, were made on the animals' backs. The depth of the surgical incision was controlled by removing the epithelial tissue until the dorsal muscular fascia was exposed. The animals were anesthetized with ketamine and xylazine via intraperitoneal injection. The rats were randomly divided into five groups of 6 animals each, according to the treatment received. Group 1 (L4): GaAs laser (4 J/cm(2)); group 2 (L30): GaAlAs laser (30 J/cm(2)); group 3 (L60): GaAlAs laser (60 J/cm(2)); group 4 (D): Dersani ointment; group 5 (control): 0.9% saline. The applications were made daily over a period of 20 days. Tissue fragments were stained with picrosirius to distinguish type I collagen from type III collagen. The collagen fibers were photo-documented and analyzed using the Quantum software based on the primary color spectrum (red, yellow and blue). Significant results for wound closing rate were obtained for group 1 (L4), 7.37 mm/day. The highest concentration of type III collagen fibers was observed in group 2 (L30; 37.80 + or - 7.10%), which differed from control (29.86 + or - 5.15%) on the 20th day of treatment. The type I collagen fibers of group 1 (L4; 2.67 + or - 2.23%) and group 2 (L30; 2.87 + or - 2.40%) differed significantly from control (1.77 + or - 2.97%) on the 20th day of the experiment.

Assessment of the effectiveness of low-level laser therapy on the hands of patients with rheumatoid arthritis: a randomized double-blind controlled trial

Assess the effectiveness of low-level laser therapy on pain reduction and improvement in function in the hands of patients with rheumatoid arthritis. A randomized double-blind controlled trial was carried out on 82 patients with rheumatoid arthritis. The experimental group was submitted to the application of laser therapy, whereas the control group received a placebo laser. Aluminum gallium arsenide laser was used, at a wavelength of 785 nm, dose of 3 J/cm(2) and mean power of 70 mW. The groups were homogenous at the beginning of the study with regard to the main variables (p > 0.05). There were no statistically significant differences between groups in most of the measurements taken at the end of the intervention including the primary variables; the following variables were the exceptions: favoring the experimental group-inflammation of the interphalangeal joint of the right thumb (p = 0.012) and perimetry of the interphalangeal joint of the left thumb (p = 0.013); and favoring the control group-flexion of the proximal interphalangeal joint of the right fifth finger (p = 0.021), perimetry of the third proximal interphalangeal joint of the right hand (p = 0.044), grip strength in the left hand (p = 0.010), and the work domain of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire (p = 0.010). We conclude that low-level aluminum gallium arsenide laser therapy is not effective at the wavelength, dosage, and power studied for the treatment of hands among patients with rheumatoid arthritis.

Low-Level Laser Therapy in Subacromial Impingement Syndrome

Although previous studies have evaluated the effect of different kinds of physical therapy in subacromial impingement syndrome (SIS), there have been few investigations assessing the effectiveness of low-level laser therapy (LLLT) in shoulder disorders. The goal of this prospective randomized study was to assess whether gallium-arsenide (Ga-As) laser therapy improves the outcome of a comprehensive home exercise program in patients with SIS. Forty-four newly-diagnosed SIS patients were enrolled in this study. Group 1 patients (n = 22) received Ga-As laser therapy combined with a 12-wk comprehensive home exercise program, and group 2 patients (n = 22) received the same 12-wk comprehensive home exercise program alone. Night pain, shoulder pain and disability index (SPADI), and University of California-Los Angeles end-result (UCLA) scores were used as outcome measures. Both groups showed a significant reduction in night pain and SPADI scores at the second and 12th weeks with respect to baseline values, with the exception of the SPADI total score at the second week in group 1. UCLA results improved significantly in both groups at the 12th in comparison to the second week. There were no significant differences between groups in mean actual changes in night pain and SPADI scores at the second week from baseline. When values at the 12th week were compared to baseline, mean actual changes in night pain differed significantly between the groups, with a larger change in group 1, but there was no difference between groups in mean actual change in SPADI scores. Second- and 12th-week UCLA scores did not differ between the two groups. Our study was unable to demonstrate any distinct advantage of low-level laser therapy over exercise alone. Comprehensive home exercise programs should be the primary therapeutic option in the rehabilitation process in SIS.

Effect of laser therapy (660 nm) on recovery of the sciatic nerve in rats after injury through neurotmesis followed by epineural anastomosis

The aim of this study was to analyze the influence of aluminum gallium arsenide (AlGaAs) laser (660 nm) on the myelin sheath and functional recovery of the sciatic nerve in rats. The sciatic nerves of 12 Wistar rats were subjected to injury through neurotmesis and epineural anastomosis, and the animals were divided into two groups: group 1 was the control and group 2, underwent low-level laser therapy (LLLT). After the injury, AlGaAs laser at 660 nm, 4 J/cm(2), 26.3 mW and beam area of 0.63 cm(2) was administered to three equidistant points on the injury for 20 consecutive days. In the control group the mean area of the myelin impairment was 0.51 (+/- 0.11) on day 21 after the operation, whereas this value was 1.31 (+/- 0.22) in the LLLT group. Student's t-test revealed a P value = 0.0229 for the mean area values of the myelin sheath between the LLLT and control groups. Comparison of the sciatic functional index (SFI) showed that there was no significant difference between the pre-lesion value in the laser therapy group and the control group. The use of AlGaAs laser (660 nm) provided significant changes to the morphometrically assessed area of the myelin sheath, but it did not culminate in positive results for functional recovery in the sciatic nerve of the rats after injury through neurotmesis.

Focus on lasers and optics

Focus on lasers and optics

Low-level laser therapy modulates cyclo-oxygenase-2 expression during bone repair in rats

The goal of this study was to analyze the role of cyclo-oxygenase-2 following bone repair in rats submitted to low-level laser therapy. A total of 48 rats underwent surgery to inflict bone defects in their tibias having been randomly distributed into two groups: negative control and laser exposed group, i.e., the animals were treated with low-level laser therapy by means of gallium arsenide laser at 16 J/cm(2). The animals were killed after 48 h, 7 days, 14 days, or 21 days. The tibias were removed for morphological, morphometric, and immunohistochemistry analysis for cyclo-oxygenase-2. Statistical significant differences (P < 0.05) were observed in the quality of bone repair and quantity of formed bone between groups 14 days after surgery in the laser exposed group. In the same way, cyclo-oxygenase-2 immunoreactivity was more intense in bone cells for intermediate periods evaluated in this group. Taken together, such results suggest that low-level laser therapy is able to improve bone repair in the tibia of rats after 14 days of surgery as a result of an up-regulation for cyclo-oxygenase-2 expression in bone cells.

Consensus Agreement on the Design and Conduct of Clinical Studies with Low-Level Laser Therapy and Light Therapy for Musculoskeletal Pain and Disorders

Consensus Agreement on the Design and Conduct of Clinical Studies with Low-Level Laser Therapy and Light Therapy for Musculoskeletal Pain and Disorders

Low-Level Laser Therapy for Wound Healing: Mechanism and Efficacy

Given the recent interest in light-emitting diode (LED) photomodulation and minimally invasive nonablative laser therapies, it is timely to investigate reports that low-level laser therapy (LLLT) may have utility in wound healing. To critically evaluate reported in vitro models and in vivo animal and human studies and to assess the qualitative and quantitative sufficiency of evidence for the efficacy of LLLT in promoting wound healing. Literature review, 1965 to 2003. In examining the effects of LLLT on cell cultures in vitro, some articles report an increase in cell proliferation and collagen production using specific and somewhat arbitrary laser settings with the helium neon (HeNe) and gallium arsenide lasers, but none of the available studies address the mechanism, whether photothermal, photochemical, or photomechanical, whereby LLLT may be exerting its effect. Some studies, especially those using HeNe lasers, report improvements in surgical wound healing in a rodent model; however, these results have not been duplicated in animals such as pigs, which have skin that more closely resembles that of humans. In humans, beneficial effects on superficial wound healing found in small case series have not been replicated in larger studies. To better understand the utility of LLLT in cutaneous wound healing, good clinical studies that correlate cellular effects and biologic processes are needed. Future studies should be well-controlled investigations with rational selection of lasers and treatment parameters. In the absence of such studies, the literature does not appear to support widespread use of LLLT in wound healing at this time. Although applications of high-energy (10-100 W) lasers are well established with significant supportive literature and widespread use, conflicting studies in the literature have limited low-level laser therapy (LLLT) use in the United States to investigational use only. Yet LLLT is used clinically in many other areas, including Canada, Europe, and Asia, for the treatment of various neurologic, chiropractic, dental, and dermatologic disorders. To understand this discrepancy, it is useful to review the studies on LLLT that have, to date, precluded Food and Drug Administration approval of many such technologies in the United States. The fundamental question is whether there is sufficient evidence to support the use of LLLT.

Low-Power Laser Treatment for Shoulder Pain

The objective of this study is to investigate the effect of low-power gallium-arsenide laser treatment on the patients with shoulder pain. Low-energy laser therapy has recently been popularized in the treatment of various rheumatologic, neurologic, and musculoskeletal disorders such as osteoarthritis, rheumatoid arthritis, fibromyalgia, carpal tunnel syndrome, rotator cuff tendinitis, and chronic back pain syndromes. A total of 40 patients who applied to our clinic with shoulder pain and complied with the selection criteria were included in the study. The patients were randomly assigned into Group I (n = 20, laser treatment) and Group II (n = 20, control). In Group I, patients were given laser treatment and an exercise protocol for 10 sessions during a period of 2 weeks. Laser was applied over tuberculum majus and minus, bicipital groove, and anterior and posterior faces of the capsule, regardless of the existence of sensitivity, for 1 min at each location at each session with a frequency of 2000 Hz using a GaAs diode laser instrument (Roland Serie Elettronica Pagani, wavelength 904 nm, frequency range of 5-7000 Hz, and maximum peak power of 27 W, 50 W, or 27 x 4 W). In Group II, placebo laser and the same exercise protocol was given for the same period. Patients were evaluated according to the parameters of pain, palpation sensitivity, algometric sensitivity, and shoulder joint range of motion before and after treatment. Analysis of measurement results within each group showed a significant posttreatment improvement for some active and passive movements in both groups, and also for algometric sensitivity in Group I (p < 0.05-0.01). Posttreatment palpation sensitivity values showed improvement in 17 patients (85%) for Group I and six patients (30%) for Group II. Comparison between two groups showed superior results (p < 0.01 and p < 0.001) in Group I for the parameters of passive extension and palpation sensitivity but no significant difference for other parameters. The results of our study have shown better results in palpation sensitivity and passive extension, but no significant improvement in pain, active range, and algometric sensitivity in laser treatment group compared to the control group in the patients with shoulder pain.

A comparative study of the effects of electrical stimulation and laser treatment on experimental wound healing in rats

We investigated the effects of electrical stimulation (ES) and laser treatment on wound healing in rats. A randomized-controlled trial, conducted at the Experimental and Clinical Research Centre of Erciyes University (Kayseri, Turkey), divided 124 healthy female Swiss-Albino rats into four groups. A 6 cm linear incision was made at the dorsal skin of all rats. Group 1 was given a constant direct current of 300 microA for 30 min per day. The current was applied in negative polarity for the first 3 days and in positive polarity for the next 7 days. Group 3 received a full-contact, continuous gallium-arsenide (GaAs) laser therapy, with a wavelength of 904 nm, an energy density of 1 J/cm2, and an average power of 6 mW for 10 min per day. The remaining two groups (Groups 2 and 4) were considered the control groups and received sham treatment. All groups were treated for 10 days. Histopathologic and biochemical evaluations were conducted on 10 rats from each group on the 4th and 10th days, and wound breaking strength was measured for biomechanical evaluation on the 25th day of the study. Both ES and laser treatment proved significantly effective in the inflammatory phase compared with control groups (p < 0.05); however, the ES was even more effective than laser treatment, with more significant results (p < 0.05). In the proliferation and maturation phases, while ES and laser treatment were both found to be significantly effective treatment methods compared with the control groups, no statistically significant difference was observed between the two treatment groups (p > 0.05). Although ES and laser treatment both were effective in the maturation phase, increasing wound breaking strength compared with their control groups (p < 0.05), there was no statistically significant difference between the two treatment groups (p > 0.05). We conclude that ES and laser treatment both have beneficial effects during the inflammatory, proliferation, and maturation phases of a wound. Both ES and laser treatment can be used successfully in decubitis ulcers and chronic wounds, in combination with conventional therapies such as daily care and debridement of wounds; however, ES has more beneficial effects during the inflammatory phase in some parameters than laser treatment.

Effects of the Ga-As laser irradiation on myonecrosis caused by Bothrops Moojeni snake venom.

Viper snake envenoming induces in the victims systemic coagulopathy, and severe local tissue damage such as edema, hemorrhage, intense pain, and myonecrosis. Serumtherapy and other first-aid managements are ineffective in neutralizing these local effects. The effects of the gallium-arsenide (Ga-As) laser irradiation on mice gastrocnemius injected intramuscularly (i.m.) with Bothrops moojeni snake venom were investigated. Macroscopical, histopatological, and myonecrosis quantification through serum creatine kinase (CK) evaluation was done at 3, 12, and 24 hours (two, five, and eight irradiation sessions, 4 J/cm(2), 1 minute 32 seconds per period, respectively), were done after the venom or saline injection, and in venom-unirradiated mice. In unirradiated gastrocnemius, the venom induced massive hemorrhage, vascular congestion, time-progressing myonecrosis, edema, abundant inflammatory infiltrate, and high CK serum levels. Ga-As irradiation significantly decreased the amount of myonecrosis in all the periods tested (P < 0.05). The laser treatment significantly inhibited the ability of B. moojeni venom to rapidly disrupt the integrity of the plasma membrane.

No effect of GA-AS (904 nm) laser irradiation on the intact skin of the injured rat sciatic nerve.

We evaluated the electrophysiological and histopathological effects of low-energy gallium arsenide (904 nm) laser irradiation on the intact skin injured rat sciatic nerve. Twenty-four male Wistar rats were divided into three groups ( n=8 each). At the level of proximal third of the femur the sciatic nerve was crushed bilaterally with an aneurysm clip (Aesculap FE 751, Tuttingen, Germany) for half a second. A gallium arsenide laser (wavelength 904 nm, pulse duration 220 ns, peak power per pulse 27 W, spot size 0.28 cm2, pulse repetition rate 16, 128 and 1000 Hz; total applied energy density 0.31, 2.48 and 19 J/cm2) was applied to the right sciatic nerve for 15 min daily at the same time on 7 consecutive days. The same procedure was performed on the left sciatic nerve of same animal, but without radiation emission, and this was accepted as control. Compound muscle action potentials were recorded from right and left sides in all three groups before surgery, just at the end of injury, at the 24th hour and on the 14th and 21st days of injury in all rats using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara, USA). BIOPAC Acknowledge Analysis Software (ACK 100 W) was used to measure CMAP amplitude, area, proximal and distal latency, total duration and conduction velocity. Twenty-one days after injury, the rats were sacrificed. The sciatic nerves of the operated parts were harvested from the right and left sides. Histopathological evaluation was performed by light microscopy. Statistical evaluation was done using analysis of variance for two factors (right and left sides) repeated-measures (CMAP variables within groups) and the Tukey-Kramer Honestly Significant Difference test (CMAP variables between laser groups). The significance was set at p < 0.05. No statistically significant difference (p > 0.05) was found regarding the amplitude, area, duration and conduction velocity of CMAP for each applied dose (0.31, 2.48 and 19 J/cm2) on the irradiated (right) side and the control (left) side, or between irradiated groups. Twenty-one days after injury there were no qualitative differences in the morphological pattern of the regenerated nerve fibres in either irradiated (0.31, 2.48 and 19 J/cm2) or control nerves when evaluated by light microscopy. This study showed that low-energy GaAs irradiation did not have any effect on the injured rat sciatic nerve.