Laser skin resurfacing is usually performed with CO₂ or Er:YAG lasers. Since frequency doubled Nd:YAG laser (532 nm) is already used in dermatology for angiodysplasias treatment, a new laser resurfacing method was investigated. In this study, we evaluated the possibility to achieve skin resurfacing using a 532 nm laser after topical application of an exogenous chromophore. This exogenous chromophore consisted in carbon dispersed and mixed with film-forming polymers and water. The resultant solution was applied to the skin surface using an air brush. Validation was performed in vivo on rat skin using the following laser parameters (532 nm, 2.7 W, 1 mm, 50 - 200 ms). Skin biopsies were taken to evaluate histological changes and to quantify epidermis ablation and dermis coagulation. Wound healing was followed up. The results showed that dermis coagulation depth increased as a function of exposure time. In conclusion, the concept of applying a carbon-based solution onto skin in order to obtain firstly laser light conversion into heat and secondly an heat transfer to the tissue is valid for laser skin resurfacing. By selecting exposure time, dermis coagulation depth can be either the one observed with Er:YAG laser or the one obtained with CO₂ laser.

This study aimed to evaluate a new skin laser resurfacing technique using a 532 nm laser after previous application of a chromophore on the skin. For this study, a film (Chromofilm), based on transfer process was developed. This 4 layers film allows the control of all parameters (thickness, chromophore concentration, chromophore distribution) before its application on skin surface. The new laser skin resurfacing technique was evaluated on human skin before a surgical face lift procedure. The film was applied on photodamaged skin located in periauricular areas. On both sides four areas were treated. The laser irradiation was performed 15 h prior to undergoing face lift (4 areas), and 1 h before (4 areas). The laser irradiation was performed with a 532 nm Nd:YAG laser (Ophtalas FX2, Alcon Biophysic) connected to a scanner (Hexascan^R, Prein & Partners) with the following parameters: power 2 W, spot diameter 1 mm, hexagonal surface irradiation 7 mm and pulse duration ranging from 50 and 120 ms. Tissue samples were examined histologically to determine the depth injury using nitroblue- tetrazolium chloride (NBTC) staining, haematoxylin-eosin staining, Weigert's staining and Masson's staining. The results showed that the depth of injury was clearly dose- dependent. 50 ms pulse duration induced total epidermis ablation and fine dermal coagulation. 120 ms pulse duration induced dermal coagulation down to 120 micrometers. No residual of carbon film were observed on histologic sections. In conclusion, laser skin resurfacing using a 532 nm laser irradiation after application of carbon film transfer is an effective method for skin resurfacing.

Purpose: To evaluate a method of control of diode laser fluence leading to a reproducible ICG-enhanced selective photocoagulation of blood vessels. This method would use the chromophore clearance, i.e. ICG blood concentration decay to adapt the laser fluence. Materials and Methods: A skin flap window was used on hamsters. After a 15 mg/kg ICG solution injection, photocoagulation of vessels were performed. Results: Selective photocoagulation of blood vessels was obtained only during the first 10 minutes. The fluence required to obtain a selective photocoagulation of vessels (F) was modelized using a one compartment phamacokinetic equation: F equals Of(1-e^-t/(tau )). The best fit was obtained for a time constant (tau) equals 4.8 min and Of equals 300 J/cm² (correlation coefficient r² equals 0.996). During the first 10 minutes, the fluence required for selective photocoagulation of vessels was increased by a factor 4.5. Conclusion: Fluence required for a selective photocoagulation of vessels was correlated to ICG blood concentration decay. The time constant was equivalent to ICG half-life time in human blood. These results demonstrate that diode laser ICG-enhanced photocoagulation can be controlled by monitoring the ICG blood clearance.

This paper is intended to outline the current thinking regarding the process involved in depilation by pulsed ruby laser. The key laser parameters of wavelength, pulse duration, energy density, spot size and spatial profile will be discussed together with their impact on the outcome of the procedure. A parallel series of clinical trials have been carried out in a number of centers on both medical complications of hair growth and the cosmetic use of the technology. The results of these trials detail the efficacy of the treatment as well as the incidence of side-effects or complications.

Fiberoptical evanescent wave Fourier transform infrared (FEW- FTIR) spectroscopy has been applied in the middle infrared (MIR) wavelength range (3 to 20 micrometer) to the in vivo diagnostics of normal skin tissue, acupuncture points as well as precancerous and cancerous conditions. The FTIR-FEW technique, using nontoxic unclad fibers, is suitable for noninvasive, sensitive investigations of skin tissue for various dermatological studies of skin caner, aging, laser treatment, cosmetics, skin allergies, etc. This method is direct, nondestructive, and fast (seconds). Our optical fibers are nonhygroscopic, flexible, and characterized by extremely low losses. In this study, we have noninvasively investigated more than 300 cases of normal skin, acupuncture points, precancerous and cancerous tissue in the range of 1400 to 1800 cm^-1. The results of our analysis of skin and other tissue are discussed in terms of structural and mathematical similarities and differences on a molecular level. In addition, we have also performed cluster analysis, using principal component scores, to confirm pathological classifications and to discriminate between genders. We have found good agreement with prior pathological classifications for normal skin tissue and melanoma tumors and normal females were distinctly separate from males.

A survey was carried out on sunbeds in the city of Perth, Scotland (56N) and the surrounding area. UV radiation measurements were carried out using a calibrated double- grating spectroradiometer in 38 of the total 41 tanning units in the area. Data were analyzed using the SCUP-h action spectrum which is an estimate of the sensitivity of human skin to cancer induction from UV radiation of different wavelengths. Results showed that high power stand-up tanning units carry approximately the same cancer risk, minute for minute, as sunbathing in Southern Europe in summer.

Reports on adverse drug reactions, as they were recorded at the Norwegian Medicines Control Authority beginning in the year 1970 up to 1994 were analyzed especially with regard to cutaneous reactions and photosensitivity reactions. During the time period, almost 13.000 side effects were reported. Out of these 799 reports involved the skin and appendages, and 64 out of these reports (8%) were classified as photosensitivity reactions. Tetracyclines, diuretics, antihypertensive agents, and urologicals were the drugs which most often caused photosensitivity reactions. In addition, a number of uncommon photosensitizing drugs were reported. The risk for photosensitization is discussed on the background of experimental data and the prescription rates of these substances.

The objective of this study is to compare the ablation sites induced by two different laser and application systems for myocardial laser revascularization. One system used was an 800 W CO₂ laser, which is clinically established for transmyocardial laser revascularization (TMR). The second system was a self-designed Holmium laser emitting single high energy pulses for the minimal invasive approach of endocardial laser revascularization (ELR), whereby the laser light is transmitted via optical fiber into the left ventricle to ablate the myocardial channels from the inside. The laser energy was applied to Polyacrylamide (PAA) as transparent tissue phantom and in water as blood phantom. The ablation dynamics were investigated by high speed flash photography recording a picture series of a single event. Reperfused ex- vivo porcine hearts were treated to quantify differences in the thermal-mechanical damage ranges by polarization light microscopy. Ablation dynamics in water revealed oscillatory changes of the axial length of the steam bubbles between 3 mm and 12 mm during the CO₂ laser pulse. For the Holmium laser pulse a maximal axial and lateral length of 5 mm was observed. The lateral dimensions of the bubbles were maximal 1 mm with the CO₂- and 3.5 mm with the Holmium laser system. In PAA bubbles also collapse during the laser pulse which affects the size of the ablated channels. Using 12 J Holmium laser pulses for ablation of PAA, channel depths around 7 mm were found. Single Holmium laser pulses demonstrate ablations comparable in size and thermal- mechanical collateral damage to those achieved with the standard CO₂ laser. The results are very encouraging for single pulse ELR and demonstrate the potential of a catheter based minimal invasive procedure for laser heart reperfusion.

Experiments on atherosclerotic plaque diagnosis were carried out using laser induced fluorescence (LIF) spectroscopy on carotid plaque specimens. The excitation laser was a nitrogen laser, emitting pulses at a wavelength of 337 nm. Over 10 samples were examined in vitro and several spectra were obtained from each sample. Results were compared with conventional clinical techniques, such as histopathological diagnosis, which showed three areas of different composition on the pathological samples: fibrous tissue, lipid constituents and calcified plaque. An effort was made to distinguish the composition of the sample from the obtained spectra. Also, the results were compared with our previous work using longer excitation wavelengths. Spectral morphology of UV excited fluorescence reveals multi-peaks lineshapes, as a result of the superposition of different tissue chromophore signals. However, there was no observed specific wavelength where spectra corresponding to fibrous tissue, calcified tissue and lipid constituents have peaks.

We investigated refractive corneal surgery in vivo and in vitro by intrastromal photodisruption using a compact ultrafast femtosecond laser system. Ultrashort-pulsed lasers operating in the femtosecond time regime are associated with significantly smaller and deterministic threshold energies for photodisruption, as well as reduced shock waves and smaller cavitation bubbles than the nanosecond or picosecond lasers. Our reliable all-solid-state laser system was specifically designed for real world medical applications. By scanning the 5 micron focus spot of the laser below the corneal surface, the overlapping small ablation volumes of single pulses resulted in contiguous tissue cutting and vaporization. Pulse energies were typically in the order of a few microjoules. Combination of different scanning patterns enabled us to perform corneal flap cutting, femtosecond-LASIK, and femtosecond intrastromal keratectomy in porcine, rabbit, and primate eyes. The cuts proved to be highly precise and possessed superior dissection and surface quality. Preliminary studies show consistent refractive changes in the in vivo studies. We conclude that the technology is capable to perform a variety of corneal refractive procedures at high precision, offering advantages over current mechanical and laser devices and enabling entirely new approaches for refractive surgery.

The using of KrCl (223 nm) excimer laser in ophthalmic devices for Photorefractive Keratectomy (PRK) and phototherapeutic Keratectomy (PTK) is offered. The structure and functions of a new surgical UV ophthalmic laser systems Medilex using ArF (193 nm) or KrCl (223 nm) excimer laser for corneal surgery are presented. The systems Medilex with the new optical delivery system is used for photoablative reprofiling of the cornea to correct refraction errors (myopia, hyperopia and astigmatism) and to treat a corneal pathologies. The use of the 223 nanometer laser is proposed to have advantages over the 193 nanometer laser. The results of application of the ophthalmic excimer laser systems Medilex for treatment of myopia are presented.

A 3-D finite element model of the human eye is developed to study the heat transfers induced by an argon laser absorbed on the iris tissue. The main objective is to explain the appearance of complications inherent to the iridectomy such as corneal burns and lens opacities. Contraction burn preceding the iris opening by photovaporization is studied. The iris temperature threshold fixed as onset for the tissue removal is 300 degrees Celsius. For closed angle glaucoma, the thermal history on the corneal endothelium and lens due to recurrent laser shots with pulse durations of 0.5 sec, 0.05 sec and 0.04 sec are presented and discussed. Typically, an overheating of the lens and cornea endothelium by the side of the iridectomy site is observed. This phenomena is important on the cornea endothelium where the temperature increases to 70 degrees Celsius in case of two recurrent laser pulses of 0.5 sec in duration, 0.43 W in power and 0.5 sec in relaxation time. For irradiation time of 0.05 sec this overheating is much less important and the temperature on the cornea endothelium doesn't exceed 47 degrees Celsius. These computations confirm that short laser pulses decrease the amount of adverse effects and agree well with experiments reported by ophthalmologists.

Diabetic Retinopathy (DR) is one of the most severe complications of diabetes mellitus. In 1994, in St. Petersburg, a new system of ophthalmologic care for diabetic patients was set up. For Russia, this system represents an example of adequate care for subjects with DM, including screening strategies, documentation and education of patients and general ophthalmologists. According to our data, about one half of examined patients had DR, and about 20% of patients were in need of laser treatment. The aim of present study was to evaluate the effectiveness of panretinal photocoagulation (PRP) in cases of severe DR, including advanced nonproliferative DR (preproliferative DR) and proliferative DR. Data concerning 1073 diabetics are included in this study. PRP was performed in 736 cases (1163 eyes). DR stabilization was estimated after one year follow-up PRP enabled preventing severe visual loss in patients with preproliferative DR and proliferative DR. Our system of specialized ophthalmic care for diabetic patients proved to be effective.

This paper describes a new method to examine the intraocular pressure (IOP) without any contact to the eye. In our new approach the IOP is determined indirectly from the acoustic properties of the eye as the resonance frequencies of the bulbus are shifting with increasing IOP. Simulations with the Finite Element Method were done to explore the coherence between the IOP and the acoustic properties of the bulbus. A three-dimensional model of the eye was developed comprising the elastic cornea and sclera and the vitreous body. The results showed a significant rise of the resonance-frequencies with increasing IOP. This shift is enlarging for higher modes. In parallel measurements were performed on artificial eyes and on enucleated pig eyes to prove this correlation experimentally. A measuring system existing of a transducer to excite the bulbus, a miniaturized laser-vibrometer and PC was built. The eyes were stimulated both contacting the eye with a transducer by a stick and contactless with sonic waves. Several series of measurements were done to examine the pressure dependency of the acoustic behavior. The measurements showed a proportional constant of 1.25 Hz/mmHg in average, which can be detected easily. The standard deviation measuring different pig eyes was 4.5 mmHg.

We present a new method for processing confocal fluorescence angiographies in order to extract the topography of the perfused surface. The topographies extracted for various normal and pathologic conditions agree well with morphological and functional conditions. They allow, for example, the quantification of leakage and the verification of treatment success in photodynamic therapy and provide thus a new valuable tool for analyzing the topography of functional pathologies.

The scanning laser ophthalmoscope (SLO) is a modern tool which is now widely used to image the fundus of the eye, particularly for assessment of the optic nerve head. We describe a modified SLO capable of producing stereo pairs of the optic disk in real time. A pair of toggling mirrors is used to switch between entry positions of the scanned laser beam into the pupil of the eye thereby creating a stereo base for capturing the two different views required for the pair. Our laboratory prototype is constructed from reflective optics only in the bi-directional part of the beam path, including the focusing and beam shaping unit. Thus, we avoid unwanted back reflections and chromatic aberrations. Light from different laser sources (458 to 1100 nm) can be launched into the SLO, also simultaneously. Collimated beams in beam splitting locations allow for easy modifications. Imaging in fluorescence mode or polarization dependent imaging is also possible. High quality multi-wavelengths stereo pairs of both model and real optic disks were obtained. a lateral resolution of up to 6 micrometer and an axial resolution of up to 65 micrometer was established.

Optical Coherence Tomography (OCT) is a new in vivo imaging device in ophthalmology. We investigated the diagnostic potentials of a slitlamp-adapted OCT in the examination of not only the posterior but also the anterior segment in vivo. Patients were examined with a new prototype of a slitlamp- adapted OCT (Fa.Schwind, D-Kleinostheim) in the anterior and posterior segment using 100 - 200 axial scans with 50 Hz scan frequency. The scan length is variable up to 7.5 mm. The software allows to evaluate the images in gray scale or false color. By the slitlamp-adapted OCT all anatomic structures and morphological changes anterior to the attenuating iris pigment epithelium including the anterior chamber angle can be demonstrated and measured precisely. Within the pupillary opening OCT-imaging of cataract, secondary cataract formation as well as the anterior vitreous can be performed. The slitlamp-adapted OCT also allows direct biomicroscopic control of the measured area in examinations of the posterior segment. The slitlamp-adapted OCT provides a new and helpful diagnostic tool, which allows a precise examination of the anterior and posterior segment of the eye. The advantage of this new method lies in the combination of the familiar examination technique and the simultaneous slitlamp view, which provides an exact position control. It is possible to do pachymetric studies of the cornea after photorefractive and phototherapeutic therapy. Of importance is the objective measurement of the chamber angle, which may improve pre- and postoperative evaluation and allow a better follow up documentation of glaucoma patients.

A new instrument for simultaneous display of an en-face optical coherence tomography (OCT) image and of a confocal image [similar with that produced by the scanning laser ophthalmoscope (SLO)] for the retina in vivo is demonstrated. The system is based on a fiberized OCT configuration, where a separate bulk optical confocal receiver is introduced between the transversal galvanometer scanner and the OCT fiber arm. Criteria for presenting the two images are discussed. These address the resulting impact on the quality of each image as result of differences in the two imaging techniques, low coherence interferometry and confocal imaging. The transversal and depth pixel size are governed by different principles and consequently are generally different. Additionally, the OCT image is disturbed by Doppler shifts introduced by the transversal scanning and speckle.

In an earlier study we showed that precise axial eye length measurement on cataract eyes is possible with the dual beam partial coherence interferometry technique (PCI). A high correlation with the standard ultrasound technique has been obtained. Recently, in a prospective study, partially coherent interferometry and ultrasound biometry were compared in cataract surgery using the SRK II formula based on US applanation biometry. Three months after surgery PCI was repeated and refractive outcome was determined. The use of PCI would have improved refractive outcome by about 30%.

The confocal scanning laser ophthalmoscope, cSLO, can be used for microphotocoagulation of the retina. For this purpose, external and non-scanning therapeutic laser sources are coupled with the instrument. An opto-mechanical coupling device is calibrated to obtain the same Maxwellian view entrance location in the eye for both scanning and external lasers. Two separate but synchronized confocal detection pathways are capable of monitoring the progression of thermal laser applications on the retina. Real-time image processing is further used to indicate the position and size of the aiming beam on the retina. This aiming beam can be pulsed in anti-aliased fashion with regard to its confocal detection, to allow for higher intensities. Its polarization is exploited to sharply reduce corneal reflections. MInimal optical distribution of the therapeutic laser beam, full documentation of application characteristics, simultaneous microperimetry, infra-red and angiographic imaging are useful features to guide microphotocoagulation.

This contribution presents a new OCT technique. In this technique the complex scattered field is detected and used to compute the complex scattering potential of the object. The basic principle is outlined and first experimental measurements on a glass plate and on human skin in vitro are shown.

The evaluation of a cavity profile prepared in hard tissue by the radiation of Er:YAG dental laser with either a fluorocarbon polymer-coated silver hollow glass waveguide or an articulated arm as a delivery system is the objective of present study. Shape of holes in the enamel, dentin and ivory were studied for different energy (from 70 mJ to 450 mJ/pulse) and number of pulses (from 1 to 10). Scanning electron microscopy, photographs and X-ray microtomography were used for analysis of results. Differences between contact and non- contact preparation were studied. As the results it was found that the shape of cavity made by the waveguide delivery system is wider and flatter in comparison with the cavities prepared with the help of mirror arm. Bottom surface of the cavity has a smooth relief, edge of cavity is sharply determined. With the contact preparation the hole could be made with better precision and with comparatively smaller value of energy.

This paper presents the first results of clinical application of YAG:Er laser ('Lasma-1', Laser Center IFMO, Russia) in practical dental procedures performed in Russian clinics. YAG:Er laser operating in free-running mode has been used for in-vivo restorative dentistry. Caries cavities of various types has been treated in contact mode with applied water pulse irrigation of a treatment zone. The paper announces the results of laser treatment of caries cases (426 fillings). 104 patients have been involved in. 396 fillings have been made for non-complicated caries, 30 fillings -- for pulpits and periodontits. In the process of laser treatment it has been observed no pain perception, even in a case of deep caries. The paper reports the results of investigation of patients tooth reaction on several thermal effects immediately after the treatment and 6 months later. Results of electro- odontometry and roentgenography of teeth processed with laser radiation of 2.94 mkm wavelength are demonstrated. Particular attention is given to the quality of filling material adhesion to walls of a laser cavity and conditions of contact points. The last is observed for cavities of III and IV classes.

In an in vitro study the bond strength of composite materials on Er:YAG and Er,Cr:YSGG laser-radiated enamel was examined. The results achieved on enamel surfaces conditioned conventionally using the acid etching method served as a control. On 80 extracted cariesfree third molars an enamel area of 4 X 4 mm was conditioned with three different systems. The Er:YAG laser was used at pulse frequencies of 8 Hz, 10 Hz, 12 Hz and 15 Hz using an energy of 120 mJ at each setting. The Er,Cr:YSGG laser was used at the settings of 20 Hz/50 mJ, 20 Hz/100 mJ and 20 Hz/150 mJ. The repetition rate for this device is constantly 20 Hz. In the reference group 10 teeth were etched with 37% phosphoric acid. In order to be able to perform the tensile tests under standard conditions metal brackets were placed on the conditioned surfaces. The 'Orthodontic-Bonding-System' was used as an adhesive system. The brackets were pulled off from the etched surfaces vertically to the tooth using a tensile testing machine. The results confirmed the highest bond strengths in the group of enamel surfaces which have been conditioned with acid etching gel. The bond strength of the Er:YAG laser (8, 10 and 12 Hz)- and Er,Cr:YSGG laser (20 Hz/150 mJ)-conditioned enamel surfaces was not significantly lower.

The first results of the investigation of influence of the parameters of pulsed NIR laser radiation on the marginal adaptation of light-cured composite restorations are represented.

Based on the bactericidal effect of subablative irradiation the Er:YAG laser can be used for root canal sterilization in endodontics. For this, an optical fiber will be inserted into the root canal down to a depth of about 1 mm in front of the apex, and then removed while activating the laser. In order to avoid heat accumulation which could be harmful to the desmodont or periodont, repetition rate and fiber withdrawal velocity must be kept within certain limits. These limits were determined by calculations based on a 1-dim, cylindrical model and related temperature measurements on half cutted teeth. The calculations agree well to the control measurements and are used to derive a complete set of application parameters in dependence on the expected root thickness.

Oral cavernous haemangiomas are common lesions which may require treatment due to episodes of bleeding when bitten or deformity particularly when involving the lips and/or cheeks. Surgery can be hazardous due to haemorrhage while cryosurgery tends to be tedious for large lesions and be accompanied by major oedema. Sclerosants produce hard bulky masses. Embolization is seldom helpful due to lack of arterial feeders. The Nd:YAG laser is proving a useful modality in the oro-facial region and appeared worth investigating for these lesions in a laboratory animal model, by thermography and in the clinical situation.

The authors report on the effects of LLLT in the treatment of TMJ pain. This paper reports the results of the use of LLLT on the treatment of TMJ pain and presents LLLT as an effective method of treating such problem. One hundred forty six female and 24 male patients aged between 7 and 81 years old (average 38.6 years old) suffering TMJ pain were treated with 632.8, 670, and 830 nm diodes Lasers at the Laser Center of the UFPE. The treatment consisted of a series of 12 applications twice a week. Patients were treated with an average dose of 2.4 J/cm². One hundred twenty eight out of 180 patients were asymptomatic at the end of the treatment, 26 improved considerably and 26 were symptomatic. These results show although LLLT does not cure TMJ disorders it is effective in reducing TMJ pain.

Pulsed laser deposition technique allow to 'tailor' bioceramic coat for metal implants by the change of deposition conditions. Each attribute is influenced by the several deposition parameters and each parameter change several various properties. Problem caused that many parameters has an opposite function and improvement of one property is followed by deterioration of other attribute. This study monitor influence of each single deposition parameter and evaluate its importance form the point of view of coat properties. For deposition KrF excimer laser in stainless-steel deposition chamber was used. Deposition conditions (ambient composition and pressures, metallic substrate temperature, energy density and target-substrate distance) were changed according to the film properties. A non-coated titanium implant was used as a control. Films with promising mechanical quality underwent an in vitro biological tests -- measurement of proliferation activity, observing cell interactions with macrophages, fibroblasts, testing toxicity of percolates, observing a solubility of hydroxyapatite (HA) coat. Deposition conditions corresponding with the optimal mechanical and biochemical properties are: metal temperature 490 degrees Celsius, ambient-mixture of argon and water vapor, energy density 3 Jcm^-2, target-substrate distance 7.5 cm.

The investigation was performed on extracted teeth which were in wet and dry condition. Firstly the intensity of HeNe-laser light backscattered on enamel facial surface was measured. Then plano-parallel longitudinal facio-lingual slice has been made from each tooth. The spatial distribution of side- scattered HeNe-laser radiation has been detected by CCD camera while the laser beam was aimed on to enamel surface (formed facet) of slice. The obtained data demonstrated the dependence between backscattered intensity, distribution of light scattered inside dental tissues and tissue status. The last one included the degree of enamel maturation and demineralization, degree of enamel hydration, enamel thickness, existence of sclerosed dentin.

Transmyocardial Laser Revascularization (TMLR) is a new experimental method for relief of angina pectoris in patients with severe coronary artery disease. TMLR aims at revascularizing chronic hibernating myocardium by creating transmural channels. One of the working mechanism hypotheses is that the endocardial side of the channels remains open, enabling perfusion of the hibernating myocardium directly from the left ventricle. Although the working mechanism of TMLR is still unknown (perfusion through patent channels, induction of angiogenesis, relief of angina through destruction of sympatic innervation, others?), first clinical studies are successful. Currently, the Heart Laser^TM and other CO₂ lasers, XeCl Excimer laser and Ho:YAG laser are under investigation for TMLR. The initial attempts of TMR with needles were soon replaced by laser induced channels. Efforts were focused on developing a CO₂ laser that could penetrate a beating heart during its relaxation phase. Later, the position of the beam could be fixed in the myocardial wall using lasers with fiber delivery systems and perforation was achieved within multiple cycles. Various researchers reported on both patent and non-patent channels after TMLR. Our belief is that the extent of laser induced thermal damage is one of the factors that determine the clinical outcome and the extent of angiogenesis (and, possibly, the patency of the channel). The purpose of this study is to present a simple theoretical model to predict the extent of thermal damage around a transmyocardial channel. In vitro experiments were performed on myocardial bovine tissue and damage was assessed. The results were used to determine the final parameters of the approximating theoretical equation. To evaluate our results, we compared our results to in vitro data using the Heart Laser^TM from the literature. Ablation velocities were also measured and the results were compared to ablation velocity calculations using a model described by Ostegar et al.

The comparative study of Hunter-Schreger bands patterns has been done in reflected light and under the illumination of enamel surface by HeNe-laser beam. In the absence of laser illumination the exterior of bands depends on direction of incident light. Under enamel surface laser illumination the exterior of bands may coincide or not with the patterns revealed in reflected light. The present paper gives the explanation of this phenomenon on base of waveguide theory of light propagation in enamel prisms. No Hunter-Schreger bands were observed in hypermineralized enamel because the hypermineralization results in homogenization of structure and probably in disappearance of difference between values of refraction indices of prism and interprism spaces.

A fast and accurate fiberoptic-based interferometer for non- contact measurements of the axial length of the eye was constructed and tested. A novelty of the interferometer design is the use of a diffractive, bifocal lens, which simultaneously focuses on the cornea and on the retina. A superluminescent light emitting diode with a coherence length of 30 micrometers is used as light source. The axial length of the eye is measured by rapidly translating a reference mirror a distance covering the axial length. The estimated accuracy of a measurement is about 100 micrometer, a number which compares well with those of conventional ultrasonic-based measurements.

Optical model of a human tooth enamel surface and results of numerical calculations of a coherent Gaussian beam scattering on enamel surface are represented. The experimental set-up for complex investigations of optical properties of hard tooth tissues is described and tested.