The use of non-coherent light diodes is becoming more popular as a stand-alone therapy as well as in combination with laser diodes in the same emitter. The North American Association of Laser Therapy (NAALT) places both laser and non-laser light therapies under the umbrella term ‘phototherapy.’
Phototherapy includes:
Low level laser
Non-coherent, narrow band light diodes
Non-coherent, broad band light diodes
Polarized light
Photodynamic therapy.
In this article, we will be concentrating on the first three and discuss some of the similarities and differences between non-coherent light therapy and coherent laser light therapy.
Studies of Non-coherent Light Combined With Laser
A number of interesting research studies have been published comparing these two modalities.
Bihari treated three groups of patients with chronic crural ulcers with HeNe laser, HeNe/GaAs laser, and non-coherent unpolarized red light. The two laser groups demonstrated excellent healing with the GaAs group performing slightly better. The red light group had a low effectiveness percentage.¹
Kubola found that an 830 nm GaAlAs laser increased flap survival area in a rat model. Flaps treated with the laser had better perfusion, a greater number of larger blood vessels, and significantly enhanced flow rates. A second group was treated with an 840 nm IR LED. This group showed no difference from the control group.²
Berki used a HeNe laser to stimulate cell activation in vitro. Phagocytic activity was increased along with immunoglobulin secretion. These effects were not seen after irradiation of the cell cultures with normal monochromatic light of the same wavelength and doses.³
Mul’diiarov performed a study utilizing a HeNe laser on arthritis in rats. He found that the laser exerted a therapeutic effect. The rats treated with ordinary red light revealed no statistical differences from the control group.⁴
Haina performed a study in which he compared the effects of HeNe laser with non-coherent light of the same wavelength. Experimental wounds were punched out in the muscle fascia of 249 Wister rats. The granulation tissue increased by 13% at 0.5 J/cm2 and 22% at 1.5 J/cm2 in the HeNe group. The increase of granulation tissue in the non-coherent light therapy group was less than 10%.⁵
Rockhind performed a study comparing five different wavelengths. He gave a single transcutaneous irradiation dose to injured peripheral nerves. HeNe laser prevented the drop in functional activity following crush injury. The 830 nm IR laser was less effective. The 660 nm non-coherent light was even less effective, and the 880 nm and 950 nm non-coherent lights were completely ineffective.⁶
Laasko studied the relationship between laser therapy and opioids. He treated 56 patients with chronic pain in a double blind study. Patients were treated with an 820 nm IR laser at 25 mW, a 670 nm laser at 10mW, or a 660 nm red light LED. ACTH and beta endorphin levels were significantly elevated in the laser therapy groups but not in the LED group.⁷
Pontinen performed a study comparing 633 nm red laser and 670 nm red laser with non-coherent 660 nm LED. Head dermal blood flow was monitored in ten healthy men utilizing laser Doppler technology. Doses were 0.1 to 1.36 J/cm2. Skin blood flow was measured before, immediately after, and 30 minutes after each treatment session at four sites on the scalp. The study demonstrated that the 670 nm laser induced a temporary vasodilitation and increased blood flow with a dose ranging from 0.12 J/cm2 to 0.36 J/cm2. The non-coherent LED, in doses of 0.68 J/cm2 to 1.36 J/cm2, decreased blood flow for at least 30 minutes after treatment.⁸
Lederer found that irradiation with HeNe laser light affected leukocytes in migration inhibition assays. Non-coherent light of the same wavelength and power density showed no influence.⁹
Rosner performed a study in which he evaluated the ability of HeNe laser to delay posttraumatic optical nerve degeneration in rats. The optic nerve was crushed and irradiated through the eye. It is interesting to note that irradiation immediately before the injury was as effective as irradiation soon after the injury. Non-coherent light was ineffective or had an adverse effect. The non-coherent light device had a wavelength of 904 nm however, which makes comparison difficult.¹⁰
Nicola developed a technique for causing highly reproducible inflammatory lesions on the skin of rats. HeNe lasers with a dose of 1J/cm2 produced an acceleration of the healing process. Non-coherent light of the same wavelength and dose was less favorable.¹¹
Onac compared the effect of HeNe laser and monochromatic light at 618 nm. The intact skin of guinea pigs was irradiated with different doses. He irradiated the guinea pigs comparing the two light sources at different dose ranging from 0.63 J/cm2 to 38.1 J/cm2. He concluded that non-coherent light irradiation leads to tegument trophicity at 4.96 J/cm2 (less than a HeNe laser). Lower doses have no effect except with the HeNe laser, whereas higher doses cause focal epidermal hypertrophy. Thus, the therapeutic window was narrower for non-coherent light.¹²
Nicola, in another study, investigated the role of polarization and coherence of laser light on wound healing in rats. There were four groups of wounds:
Treated with HeNe laser at 633 nm (coherent and polarized).
Treated with HeNe laser at 633 nm (coherent and non-polarized).
Treated with polarized, low coherent light at 633 nm.
Untreated control group.
The lesions in group #1 were healed completely after the fourth treatment.
The lesions in group #2 were not healed completely but showed more advanced healing than group #3.
The lesions in group #4 showed a poor degree of healing when compared to groups 1, 2, and 3.¹³
Paolini performed a study on 99 patients with shoulder tendonitis which he divided into three groups. One receive HeNe laser irradiation, one LED 660 nm irradiation, and one anti-inflammatory medication. Twenty-five sessions with either the laser or LED was given. The outcome was better for the laser group than the pharmacological group and much better than the LED group.¹⁴
Tuner and Hode in their comprehensive text, The Laser Therapy Handbook, are quick to point out that these kinds of comparative studies do not prove that non-coherent light is of no value. It is simply showing that laser seems to be more effective by comparison.¹⁵
Monich et al observed that low-intensity luminescent incoherent radiation (LUMIR) exposure on a surgery skin wound, causes the acceleration of wound healing in rats. The influence of LUMIR spectrum on the wound healing processes was found.¹⁵
Neuman and Finkelstein performed a double-blind randomized prospective study, 50 patients with allergic rhinitis and 10 with nasal polyposis received intranasal illumination with red light LED at 660 nm for 4.4 minutes three times a day for 14 days (total dose 6 joules per day). Twenty-nine rhinitis patients and one patient with polyposis received equivalent sham illumination as placebo. Evaluation was based on symptom scores and a clinical assessment that included pre-treatment and post-treatment videotaped rigid and flexible nasendoscopy. Following treatment, improvement of symptoms was reported by 72% of the allergic rhinitis patients and objective improvement was endoscopically demonstrated in 70% of them as compared with 24% and 3%, respectively, in the placebo group. These differences were significant. No improvement was obtained in any of the patients with polyposis. Allergic rhinitis, if uncomplicated by polyps or chronic sinusitis, can be effectively treated by narrow-band red light illumination of the nasal mucosa at 660 nm, with marked alleviation of clinical symptoms. When-ever possible, candidates for phototherapy should be selected by endoscopic examination.¹⁷
Discussion
Even though these studies demonstrate that laser is more effective than non-coherent light such as LED, the latter definitely have an effect on tissues, especially more superficially. For this reason, many laser therapy equipment manufacturers are designing and selling emitters or probes that contain both laser and non-coherent light diodes together in a hybrid emitter (as illustrated in Figures 1–3).
There have been many more studies done on laser therapies compared to non-coherent light therapies. However, more studies are beginning to appear about non-coherent light therapies and the enhanced effect that can be obtained when both laser and non-coherent light are applied simulataneously.