Effect of low-power density laser radiation on healing of open skin wounds in rats.

We performed a study to determine whether laser radiation of low-power density would affect the healing of open skin wounds in rats. The wounds were irradiated daily with a helium-neon laser (wavelength, 632.8 nm) and an argon laser (wave-length, 514.5 nm) at a constant power density of 45 mW/sq cm. The rate of wound closure was followed by photographing the wounds in a standardized way. The collagen hydroxyproline concentration in the scar tissue was determined on the 18th postoperative day. Helium-neon laser radiation had a statistically significant stimulating effect on collagen synthesis in the wound, with a maximum effect at an energy density of 4 joules/sq cm. The rate of wound closure was enhanced significantly between the third and 12th postoperative days. The argon laser exposure produced a significant increase in collagen concentration both in irradiated and nonirradiated contralateral wounds. However, an acceleration of the healing rate was not registered in this case. The wound contraction up to the fourth day of the experiment was inhibited under helium-neon and argon laser exposure to 20 joules/sq cm. The described effects were not specific for the laser light. There may be a wavelength-selective influence of coherent light on the metabolic and proliferation processes in wound healing, with the associated problem of the possible carcinogenic effects of laser radiation.

[Effects of direct laser radiation on human lymphocytes (author's transl)]. / Auswirkungen direkter Laserbestrahlung auf menschliche Lymphocyten.

In vitro experiments with human lymphocytes showed that if irradiations with coherent light of a He-Ne-laser were performed an immune suppressor effect is obtained. Using incoherent light of the same wavelength, effects only occur (80% compared to the laser) if the light is linear polarized.

Laser therapy of venous lakes (Bean-Walsh) and telangiectasias.

In 18 patients, venous lakes, and in 77 patients, telangiectasias were successfully treated with the argon laser. Because treatments were easy to perform and patients were not impaired by therapy, the argon laser is the treatment of choice for these conditions in our experience.

Argon laser therapy of verrucous nevi.

In one patient afflicted with a systemic verrucous nevus, a marked improvement was obtained by repeated treatments with an argon laser. In two patients it was possible to remove localized verrucous nevus completely. There was no recurrence in the follow-up of 8 and 14 months, respectively.

Fundamentals of laser light interaction with human tissue, especially in the cardiovascular system.

The absorption of single photons in the molecules of biological tissue can induce various reactions. For the most medical laser applications the transformation from radiation energy into heat is relevant. The laser beam is used for coagulation or vaporization of tissue. The changes in tissue, which are created by light of different wavelengths depends on the thermal and optical properties (absorption and scatting) of tissue but also on the parameters of irradiation. As an example measurements from human skin are discussed. In the cardiovascular system laser light must have a clearly defined effect. Atherosclerotic plaques of different consistence have to be vaporized without damage of the vessel walls. From different reasons the usual medical CW-lasers, Argon-laser, CO2-laser and Nd:YAG-laser, are not optimal for direct ablation of arterial occlusions. In order to mimize reocclusion the walls of the channels have to be completely smooth and free of coagulation necrosis. This can be obtained by short laser pulses. Selection of a light wavelength, which is stronger absorbed in atherosclerotic plaques than in vessel walls and additional selective staining are two ways to reduce the risk of damaging the vessel walls.

[Treatment of zoster, post-zoster pain and herpes simplex recidivans in loco with laser light]. / Behandlung von Zoster, postzosterischen Schmerzen und Herpes simplex recidivans in loco mit Laser-Licht.

Red light of a krypton laser (lambda = 647 nm) was used for treatment of patients suffering from herpes zoster (n = 4), postherpetic neuralgias (n = 8) and herpes simplex recidivans in loco (n = 13). The afflicted skin was irradiated daily for ten days (laserpower 50 mw, exposure time 90 sec). Improvement was observed in 7 out of the 12 patients suffering from herpes zoster and postherpetic neuralgias respectively, and in 8 out of 13 patients afflicted with recurrent herpes simplex.

[Physical and biological principles of the use of lasers in dermatology (author's transl)]. / Physikalische und biologische Grundlagen der Laseranwendung in der Dermatologie.

A description of the principle of laser is followed by indicating the specific characteristics of laser light. The biological and physical influences of light are mentioned slightly. Using the laser in medicine primarily means to utilize the thermcal effect of radiation. This effect results both from the parameters of irradiation and thermcal and optical characteristics (absorption and diffraction) of the tissue. The possibilities of employing different systems of laser in dermatology - surgical operations, treatment of skin lesions and light-induced wound healing - are discussed.

Nd:YAG laser therapy of an oral verrucous leukoplakia.

A 75-year-old female patient afflicted with an extensive verrucous oral leukoplakia is reported. With treatment by the Nd:YAG laser under local anesthesia on an outpatient basis, the disease could be kept under control for 4 years.

[Wound healing after laser and red light irradiation]. / Wundheilung nach Laser- und Rotlichtbestrahlung.

Laser irradiation and red light irradiation, daily 2 respectively 4 J/cm2, do not bring any acceleration of wound healing in rats. No significant effect was evident in the cell pattern of wounds during various phases of healing through the irradiation. The tensile strength of cicatrices increased by laser irradiation, but not by red light irradiation (monochromatic lambda = 633 nm).

[Therapeutic use of lasers in dermatology]. / Therapeutische Laseranwendungen in der Dermatologie.

Lasers are used increasingly in dermatology. The use of different laser types for various indications is discussed. Nevi and benign vessel tumors, tattoos, condylomata acuminata, hypertrophic scars, and keloids are indications for laser therapy. The application of lasers in the treatment of malignant tumors, such as malignant melanoma or malignant vessel tumors, is discussed. Finally, the stimulating effects of laser light with low energy density on wound healing is mentioned.

[Treatment of circumscribed lymphangiomas with the argon laser]. / Behandlung zirkumskripter Lymphangiome mit dem Argonlaser.

Six patients suffering from lymphangioma circumscriptum neviforme and two from lymphangioma circumscriptum localisatum were treated with an argon laser. Lymphangiomas regressed in all patients, with some scar formation. In four of the six neviform lymphangiomas there was recurrence of tiny clear pseudovesicles within 3-4 months following the first treatment. Two patients with localized type and two with neviforme type were without recurrence within 1 year following the first irradiation. A cure of extensive lymphangioma circumscriptum is not possible in our experience. Most of the patients were content with the obtained regression and accepted the slight scar formation and repeated treatments. Laser therapy for cosmetical reasons is not indicated.

Comparison of the maximum coagulation depth in human skin for different types of medical lasers.

The values for the maximum coagulation depth (MCD) of various types of lasers which are specified in the literature are not comparable, because often different irradiation times were used. MCD depends not only on the wavelength of laser light, but also on the time of action of the laser beam, because of heat transfer. In excised human skin MCD was determined histologically for irradiation with the argon laser, Nd:YAG laser, and CO2 laser. Extending the irradiation time from 0.2 s to 10 s results in a 4-6-fold increase in MCD. Coagulation experiments performed with a soldering iron have shown results similar to those obtained with the CO2 laser. Enlargement of the laser-beam diameter from 1 to 2 mm leads to a 50% increase in MCD. Additional chilling of the skin with water during laser irradiation protects the skin from evaporation, and the values for MCD increase to 3.5 mm for the argon laser and 5.5 mm for Nd:YAG laser. Detailed knowledge of the MCD is necessary to obtain the desired therapeutic effect, and also to avoid unwanted effects.

The effects of laser light on sperm motility and velocity in vitro.

The effect of Laser light on the motility and the velocity of human spermatozoa were measured by means of multiple exposure photography. Total sperm motility increased after Laser irradiation at 4 J/cm2, 8 J/cm2 and 32 J/cm2 respectively with respect to control. However, no influence on sperm velocity was demonstrated after Laser irradiation. This observation suggests that Laser light stimulates non-motile live spermatozoa.

A three-year experience with the argon laser in dermatotherapy.

Since January 1980, 477 patients were treated with an argon laser, 337 afflicted with vascular lesions and 140 with nonvascular lesions. Laser therapy of portwine stains gave good results in 70% of the adult patients, but it was disappointing in patients younger than 18 years of age. Other vascular lesions, such as telangiectasia, venous lake, angiofibroma, lymphangioma, and cherry angioma, were also treated with success. For the removal of tattoos the argon laser is not an optimal modality. In our experience it should only be used in skin areas, where dermabrasion cannot be performed. Therapy of epidermal nevi, xanthelasma of the eyelids, verrucae, vulgares , and sebaceous gland hyperplasia gave preliminary promising results in some patients.

Neodymium-YAG laser therapy for vascular lesions.

Three patients with port-wine stains with a nodular surface, one patient with macrocheilia resulting from a port-wine stain, and one patient with a capillary hemangioma were treated with a Nd-YAG laser (mediLas, MBB-AT, Munich). Irradiance was between 800 and 1,600 watts/cm2, with energy fluence between 400 and 1,600 joules/cm2. Treatments were performed with local anesthesia on an outpatient basis. In all patients, marked improvements could be obtained after only a few treatments. Histologically there was necrosis of epidermis and dermis immediately after laser application, and ectatic vessels contained coagulated erythrocytes. Depth of coagulation was up to 3.5 mm. Quick restoration of epidermis was observed. After some days, macrophages, fibroblasts, and capillary blood vessels grew into the agglutination thrombi and ectatic vessels were replaced by granulation tissue and, later, by fibrous tissue. In comparison with the argon laser, the Nd-YAG laser coagulates at a much deeper level, but processes of tissue repair take longer and fibrosis is more pronounced after Nd-YAG laser application. Clinically, therefore, scar formation is more likely. Chilling the skin surface during irradiation and shorter exposure times may be effective in reducing the risk of scar formation in the future.

Laser therapy of bowenoid papulosis and Bowen's disease.

Six patients with bowenoid papulosis and two patients with Bowen's disease of the genital area were treated by means of an argon, Nd:YAG, and CO2 laser. In all of the patients, complete resolution of the lesions was achieved. Due to a superficial coagulating effect, application of the argon laser should be restricted to macular and papular pigmented lesions. In contrast, Nd:YAG and CO2 lasers could be used even for treatment of extensive leukoplakia-like and verrucous lesions. Advantages and disadvantages of these two lasers are discussed.

[Morphologic studies in the treatment of nevus flammeus with argon laser]. / Morphologische Untersuchungen zur Behandlung von Naevi flammei mit dem Argonlaser.

Immediately after the argon laser impact one finds necrosis of epidermis and superficial dermis. Dilated vessels down to a depth of 0.8 mm are filled with coagulated erythrocytes. After 2 days there is initial restoration of epidermis, and dilated vessels are filled with agglutination thrombi. With and after the 6th day fibroblasts and capillary blood vessels grow into the thrombi, and later on vessels are completely replaced by granulation tissue and after 2-4 weeks by newly formed fibrous tissue.

Effects of argon, dye, and Nd:YAG lasers on epidermis, dermis, and venous vessels.

The aim of the present study, which was performed at the dorsal aspects of the ears of guinea pigs, was to compare effects of different lasers on epidermis, dermis, and small venous vessels. Irradiations were performed with argon, dye, and Nd:YAG lasers. In the first series tissue repair processes were studied after argon laser application. Laser defects were excised after 1, 4, 8, and 14 days and were prepared for routine histological examination. The breadth of epidermal defect and extent of dermal coagulation and occlusion of vessels by thrombus formation were examined histologically. In a second series parameters of irradiation (ie, exposure time, laser power) of the three different lasers were changed systematically. Laser-induced morphological tissue changes could be best observed 24 hours after irradiation. Each of the lasers led to occlusion of vessels by thrombus formation and also coagulated epidermis and dermis. The extent of dermal and epidermal coagulation was less pronounced after dye laser application. Using short exposure times it was possible to reduce the extent of epidermal damage caused by argon and Nd:YAG lasers. Only 50-msec dye laser pulses led to intravascular thrombus formation without epidermal and dermal damage.

[Condylomata acuminata gigantea (Buschke-Löwenstein tumor). Treatment with the CO2 laser and interferon]. / Condylomata acuminata gigantea (Buschke-Löwenstein-Tumor). Behandlung mit dem CO2-Laser und Interferon.

CO2 laser resection of giant condylomata acuminata of the penis, histologically confirmed, was successfully achieved with excellent cosmetic results in a 58-year-old man, penis amputation having previously been advised. Postoperative recurrence has been prevented, for six months so far, with low-dose, systemic administration of alpha-2b interferon.

[The CO2 laser in dermatotherapy--use and indications]. / Der CO2-Laser in der Dermatotherapie--Anwendung und Indikation.

Due to the high absorption of infrared light in water the CO2 laser (lambda = 10,600 nm) is suitable for cutting and vaporizing tissue. The ablation of pathological tissue by means of the CO2 laser can be exactly controlled. The treated area is usually dry and clear since blood and lymph vessels up to a diameter of 1 mm are sealed. Postoperative swelling and pain are reduced compared with electrosurgery. Important and frequent indications for CO2 laser application are HPV papillomas (condylomata acuminata, common warts, bowenoid papules) and the removal of tattoos. The CO2 laser is also suitable for the removal of benign and disseminated lesions such as angiofibromas, syringomas, trichoepitheliomas, epidermal nevi etc. Lesions of the oral mucosa (leukoplakias, mucosal warts) can be removed by means of the CO2 laser. Additionally, the treatment of vascular lesions (nevi flammei, lymphangiomas, telangiectasias) has been described, although the CO2 laser does not operate in a vessel-specific manner. As this review article demonstrates, the CO2 laser has a broad range of applications and represents an enrichment of dermatotherapy.