Differences in the early biomechanical effects of hyperopic and myopic laser in situ keratomileusis

PURPOSE: To compare changes in corneal hysteresis (CH) and the corneal resistance factor (CRF) in myopic and hyperopic laser in situ keratomileusis (LASIK) and evaluate their relationship to the number of photoablative pulses delivered, a surrogate for ablation volume. SETTING: Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, USA. METHODS: Preoperative and 1-week postoperative Ocular Response Analyzer measurements in eyes that had femtosecond-assisted LASIK were studied retrospectively. Changes in CH and CRF were compared and tested for correlation with the number of excimer laser pulses. RESULTS: Thirteen myopic eyes and 11 hyperopic eyes were evaluated. Preoperative corneal thickness, CH, CRF, programmed correction magnitude, flap thickness, and total number of fixed spotsize photoablative pulses were similar in the 2 groups (P>.1). Decreases in CH and CRF were greater after myopic LASIK than after hyperopic LASIK (P<.005), and changes in CRF were correlated with the number of excimer laser pulses in the myopic group only (r = -0.63, P = .02). Regardless of ablation profile, changes in CH were more strongly correlated with preoperative CH values than with attempted ablation volume. CONCLUSIONS: With comparable flap thickness and attempted ablation volumes, myopic photoablation profiles were associated with greater decreases in CRF and CH than hyperopic profiles. Results indicate that preoperative corneal biomechanical status, ablation volume, and the spatial distribution of ablation are important factors that affect corneal resistance and viscous dissipative properties differently. Preferential tissue removal in the natively thicker paracentral cornea in hyperopia may partially account for the rarity of ectasia after hyperopic LASIK.

Novel Treatment Immediately after Myelomeningocele Repair Applying Low-Level Laser Therapy in Newborns: A Pilot Study

Background/Aims: The use of low-level laser therapy (LLLT) in neurosurgery is still hardly disseminated and there are situations in which the effects of this therapeutic tool would be extremely relevant in this medical field. The aim of the present study is to analyze the effect of LLLT on tissue repair after the corrective surgical incision in neonates with myelomeningocele, in an attempt to diminish the incidence of postoperative dehiscences following surgical repair performed immediately after birth. Materials and Methods: Prospective pilot study with 13 patients submitted to surgery at birth who received adjuvant treatment with LLLT (group A). A diode laser CW, lambda = 685 nm, p = 21 mW, was applied punctually along the surgical incision, with 0.19 J delivered per point, accounting for a total of 4-10 J delivered energy per patient, according to the surgical wound area and then compared with the results obtained in 23 patients who underwent surgery without laser therapy (group B). Results: This pilot study disclosed a significant decline in dehiscences of the surgical wounds in neonates who were submitted to LLLT (7.69 vs. 17.39%). Conclusion: This new adjuvant therapeutic modality with LLLT aided the healing of surgical wounds, preventing morbidities, as well as shortening the period of hospital stay, which implies a reduction of costs for patients and for the institution. Copyright (C) 2010 S. Karger AG, Basel

Combined Laser and Intravitreal Triamcinolone for Proliferative Diabetic Retinopathy and Macular Edema: One-year Results of a Randomized Clinical Trial

PURPOSE: To evaluate laser combined with intravitreal triamcinolone acetonide (IVTA) for the management of patients with proliferative diabetic retinopathy (PDR) and clinically significant macular edema (CSME). DESIGN: Randomized clinical trial. METHODS: SETTINGS: Single center. STUDY POPULATION: Twenty-two patients with bilateral treatment,naive moderate PDR and CSME. INTERVENTION: Laser (panretinal and macular) photocoagulation was performed in each eye, followed by IVTA in one randomly assigned eye. Best,corrected visual acuity (BCVA), fundus photography, and optical coherence tomography were performed at baseline and at months 1, 3, 6, 9, and 12. MAIN OUTCOME MEASURES:. Changes in BCVA, central macular thickness (CMT), and total macular volume (TMV). RESULTS: The mean logarithm of the minimal angle of resolution (logMAR) BCVA improved significantly, and mean CMT and TMV were significantly reduced in the IVTA group compared with the laser,only group (controls) at all study follow-up visits (P < .001). The mean logMAR BCVA (Snellen equivalent) was 0.44 (20/50(-2)) for the IVTA group and 0.38 (20/50(+1)) for the controls at baseline, and 0.12 (20/25(-1)) for the IVTA group and 0.32 (20/40(-1)) for the controls at 12 months (P < .001.). The mean CMT and TMV were, respectively, 360 mu m and 8.59 mm(3) for the IVTA group and 331 mu m and 8.44 mm(3) for the controls at baseline, and 236 mu m and 7.32 mm(3) for the IVTA group and 266 mu m and 7.78 mm(3) for the controls at 12 months (P < .001). CONCLUSIONS: The combination of laser photocoagulation with IVTA was associated with improved BCVA and decreased CMT and TMV when compared with laser photocoagulation alone for the treatment of moderate PDR with CSME. (Am J Ophthalmol 2009;147:291-297. (C) 2009 by Elsevier Inc. All rights reserved.)

Results of high dose-rate brachytherapy boost before 2D or 3D external beam irradiation for prostate cancer

Background and purpose: To evaluate biochemical control and treatment related toxicity of patients with localized adenocarcinoma of the prostate treated with high dose-rate brachytherapy (HDRB) combined with conventional 2D or 3D-conformal external beam irradiation (EBI). Material and methods: Four-hundred and three patients treated between December 2000 and March 2004. HDRB was delivered with three fractions of 5.5-7 Gy with a single implant, followed by 45 Gy delivered with 2D or 3D conformal EBI. Results: The median follow-up was 48.4 months. Biochemical failure (BF) occurred in 9.6% according to both ASTRO and Phoenix consensus criteria. Mean time to relapse was 13 and 26 months, respectively. The 5-year BF free survival using the ASTRO criteria was 94.3%, 86.9% and 86.6% for the low, intermediate and high risk groups, respectively; using Phoenix criteria, 92.4%, 88.0% and 85.3%, respectively. The only predictive factor of BF in the multivariate analysis by both ASTRO and Phoenix criteria was the presence of prostate nodules detected by digital palpation, and patients younger than 60 years presented a higher chance of failure using Phoenix criteria only. Conclusions: Treatment scheme is feasible and safe with good efficacy. (C) 2011 Elsevier Ireland Ltd All rights reserved. Radiotherapy and Oncology 98 (2011) 169-174

Determination of the force constant of a single-beam gradient trap by measurement of backscattered light

A single-beam gradient trap could potentially be used to hold a stylus for scanning force microscopy. With a view to development of this technique, we modeled the optical trap as a harmonic oscillator and therefore characterized it by its force constant. We measured force constants and resonant frequencies for 1-4-mu m-diameter polystyrene spheres in a single-beam gradient trap using measurements of back-scattered light. Force constants were determined with both Gaussian and doughnut laser modes, with powers of 3 and 1 mW, respectively. Typical values for spring constants were measured to be between 10(-6) and 4 x 10(-6) N/m. The resonant frequencies of trapped particles were measured to be between 1 and 10 kHz, and the rms amplitudes of oscillations were estimated to be around 40 nm. Our results confirm that the use of the doughnut mode for single-beam trapping is more efficient in the axial direction. (C) 1996 Optical Society of America.

The intercalated disc of monkey myocardial cells and Purkinje fibers as revealed by scanning electron microscopy

The intercalated discs of working myocardium and Purkinje fibers of the monkey heart were examined by scanning and transmission electron microscopy. The NaOH/ultrasonication technique resulted in the digestion of connective tissue and a separation of the intercellular junctions of intercalated discs, such that these could be visualized three-dimensionally. The intercalated discs of ventricular myocytes, atrial myocytes and Purkinje fibers vary considerably in number and configuration, as do the intercalated discs of the three different layers of the ventricular myocardium. Myocytes in the subepicardial, middle and subendocardial layers of the ventricle have 1-3, 4-5 and 5-6 intercalated discs at the end of these cells, respectively, Those in the endocardial layer are characterized by the presence of small laterally-placed intercalated discs. Atrial myocytes and Purkinje fibers usually only have 1-2 intercalated discs, Individual intercalated discs in ventricular myocytes have complicated stairs with 10-30 steps and corresponding risers, while those of atrial myocytes and Purkinje fibers have simple stairs with 1-3 steps and risers, Steps equivalent to the plicate segments are characterized by densely-packed microplicae and finger-like microprojections which greatly increase surface area in vertricular myocytes, Microprojections in atrial myocytes and Purkinje fibers are sparse by comparison, Risers equivalent to the interplicate segments containing large gap junctional areas are most numerous in left ventricular myocytes, followed by right ventricular myocytes, Purkinje fibers and atrial myocytes in decreasing order. The geometric arrangement of the various types of myocytes may be related with impulse propagation. Large intercalated discs of cell trunks and series branches may participate in longitudinal propagation, while small laterally-placed ones may be the site of transverse propagation.

Supersonic velocimetry in a shock tube using laser enhanced ionisation and planar laser induced fluorescence

A novel flow-tagging technique is presented which was employed to measure gas velocities in the free stream of a shock tube. This method is based on the laser spectroscopic techniques of Laser-Enhanced Ionisation (LEI) and Laser-Induced Fluorescence (LIF). The flow in the shock tube is seeded with small amounts of sodium, and LEI is used to produce a substantial depletion of neutral sodium atom concentration in a well-defined region of the flow, by using two wavelength-resonance excitation and subsequent collisional ionisation. At a specific time delay, single-laser-pulse planar LIF is utilised to produce a two-dimensional (2-D) inverse image of the depleted tagged region downstream of the flow. By measuring the displacement of the tagged region, free stream velocities in a shock tube were determined. Large variations in the concentration of sodium seeded into the flow were observed and even in the presence of these large variations accurate free-stream velocity measurements were obtained. The experimentally determined value for velocity compares very well with the predicted velocity.

Effect of phototherapy with low intensity laser on local and systemic immunomodulation following focal brain damage in rat

Brain injury is responsible for significant morbidity and mortality in trauma patients, but controversy still exists over therapeutic management for these patients. The objective of this study was to analyze the effect of phototherapy with low intensity lasers on local and systemic immunomodulation following cryogenic brain injury. Laser phototherapy was applied (or not-controls) immediately after cryogenic brain injury performed in 51 adult male Wistar rats. The animals were irradiated twice (3 h interval), with continuous diode laser (gallium-aluminum-arsenide (GaAlAs), 780 nm, or indium-gallium-aluminum-phosphide (InGaAlP), 660 nm) in two points and contact mode, 40 mW, spot size 0.042 cm(2), 3 J/cm(2) and 5 J/cm(2) (3 s and 5 s, respectively). The experimental groups were: Control (non-irradiated), RL3 (visible red laser/ 3 J/cm(2)), RL5 (visible red laser/5 J/cm(2)), IRL3 (infrared laser/ 3 J/cm(2)), IRL5 (infrared laser/5 J/cm(2)). The production of interleukin-1IL-1 beta (IL-1 beta), interleukin6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-alpha) was analyzed by enzyme immunoassay technique (ELISA) test in brain and blood samples. The IL-1 beta concentration in brain of the control group ;was significantly reduced in 24 h (p < 0.01). This reduction was also observed in the RL5 and IRL3 groups. The TNF-alpha and IL-6 concentrations increased significantly (p < 0.01 and p < 0.05, respectively) in the blood of all groups, except by the IRL3 group. The IL-6 levels in RL3 group were significantly smaller than in control group in both experimental times. IL-10 concentration was maintained stable in all groups in brain and blood. Under the conditions of this study, it is possible to conclude that the laser phototherapy can affect TNF-alpha, IL-1 beta and IL-6 levels in the brain and in circulation in the first 24 h following cryogenic brain injury. (C) 2009 Elsevier B.V. All rights reserved.

Measurements of neutral atom diffusion and electron-ion recombination by laser enhanced ionisation and planar laser induced fluorescence in an air-acetylene flame

The spatial and temporal evolution of a depleted atomic distribution created by laser enhanced ionisation (LEI) was employed to determine both a diffusion coefficient for sodium (Na) and an electron (e(-)) and sodium ion recombination rate coefficient in an analytical air-C2H2 flame. A depleted distribution of neutral sodium atoms was produced in a flame by ionising approximately 80% of the irradiated sodium atoms in a well defined region using a two step LEI excitation scheme. Following depletion by ionisation, planar laser induced fluorescence (PLIF) images of the depleted region recorded the diffusion and decay of the depleted Na distribution for different depletion-probe delays. From measurements of the diffused width of the distribution, an accurate diffusion coefficient D = (1.19 +/- 0.03) x 10(-3) m(2) s(-1) for Na was determined in teh burnt gases of the flame. Measurements of the integrated fluorescence intensity in the depleted region for different depletion-probe delays were related to an increase in atomic sodium concentration caused by electron-ion recombination. At high concentrations (greater than or equal to 50 mu g ml(-1)), where the electron and ion concentrations in the depleted region were assumed equal, a recombination rate coefficient of 4.2 x 10(-9) cm(3) s(-1) was calculated. (C) 1997 Elsevier Science B.V.

Low-Level Laser Therapy in Chronic Autoimmune Thyroiditis: A Pilot Study

Background and Objectives: Chronic autoimmune thyroiditis (CAT) remains the most common cause of acquired hypothyroidism There is currently no therapy that is capable of regenerating CAT-damaged thyroid tissue The objective of this study was to gauge the value of applying low-level laser therapy (LLLT) in CAT patients based on both ultrasound studies (USs) and evaluations of thyroid function and thyroid autoantibodies. Study Design/Materials and Methods: Fifteen patients who had hypothyroidism caused by CAT and were undergoing levothyroxine (LT4) treatment were selected to participate in the study Patients received 10 applications of LLLT (830 nm, output power 50 mW) in continuous mode, twice a week, using either the punctual technique (8 patients) or the sweep technique (7 patients), with fluence in the range of 38-108 J/cm(2) USs were performed prior to and 30 days after LLLT USs included a quantitative analysis of echogenicity through a gray-scale computerized histogram index (El). Following the second ultrasound (30 days after LLLT), LT4 was discontinued in all patients and, if required, reintroduced Truodothyronine, thyroxine (T4), free T4, thyrotropin, thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) antibodies levels were assessed before LLLT and then 1, 2, 3, 6, and 9 months after LT4 withdrawal. Results: We noted all patients` reduced LT4 dosage needs, including 7 (47%) who did not require any LT4 through the 9-month follow-up The LT4 dosage used pre-LLLT (96 +/- 22 mu g/day) decreased in the 9th month of follow-up (38 23 mu g/day; P<0.0001) TPOAb levels also decreased (pre-LLLT = 982 +/- 530 U/ml, post-LLLT = 579 454 U/ml, P = 0 016) TgAb levels were not reduced, though we did observe a post-LLLT increase in the EI (pre-LLLT = 0 99 +/- 0.09, post-LLLT= 1.21 +/- 0.19, P=0.001) Conclusion: The preliminary results indicate that LLLT promotes the improvement of thyroid function, as patients experienced a decreased need for LT4, a reduction in TPOAb levels, and an increase in parenchymal echogenicity Lasers Surg. Med. 42:589-596, 2010. (C) 2010 Wiley-Liss, Inc

INTENSITY-MODULATED AND 3D-CONFORMAL RADIOTHERAPY FOR WHOLE-VENTRICULAR IRRADIATION AS COMPARED WITH CONVENTIONAL WHOLE-BRAIN IRRADIATION IN THE MANAGEMENT OF LOCALIZED CENTRAL NERVOUS SYSTEM GERM CELL TUMORS

Purpose: To compare the sparing potential of cerebral hemispheres with intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) for whole-ventricular irradiation (WVI) and conventional whole-brain irradiation (WBI) in the management of localized central nervous system germ cell tumors (CNSGCTs). Methods and Materials: Ten cases of patients with localized CNSGCTs and submitted to WVI by use of IMRT with or without a ""boost"" to the primary lesion were selected. For comparison purposes, similar treatment plans were produced by use of 3D-CRT (WVI with or without boost) and WBI (opposed lateral fields with or without boost), and cerebral hemisphere sparing was evaluated at dose levels ranging from 2 Gy to 40 Gy. Results: The median prescription dose for WVI was 30.6 Gy (range, 25.2-37.5 Gy), and that for the boost was 16.5 Gy (range, 0-23.4 Gy). Mean irradiated cerebral hemisphere volumes were lower for WVI with IMRT than for 3D-CRT and were lower for WVI with 3D-CRT than for WBI. Intensity-modulated radiotherapy was associated with the lowest irradiated volumes, with reductions of 7.5%, 12.2%, and 9.0% at dose levels., compared with 3D-CRT. Intensity-modulated radiotherapy provided of 20, 30, and 40 Gy, respectively statistically significant reductions of median irradiated volumes at all dose levels (p = 0.002 or less). However, estimated radiation doses to peripheral areas of the body were 1.9 times higher with IMRT than with 3D-CRT. Conclusions: Although IMRT is associated with increased radiation doses to peripheral areas of the body, its use can spare a significant amount of normal central nervous system tissue compared with 3D-CRT or WBI in the setting of CNSGCT treatment. (C) 2010 Elsevier Inc.

Antiphase dynamics of a chaotic multimode laser

Antiphase dynamics of an optically pumped NH3 bidirectional ring laser under the chaotic, phase-sensitive mode coupling is experimentally observed. Our experimental result suggests strongly that the dynamics is a generic behavior of the laser.

Metastable chaos in the ammonia ring laser

We report experimental studies of metastable chaos in the far-infrared ammonia ring: laser. When the laser pump power is switched from above chaos threshold to slightly below, chaotic intensity pulsations continue for a varying time afterward before decaying to either periodic or cw emission. The behavior is in good qualitative agreement with that predicted by the Lorenz equations, previously used to describe this laser. The statistical distribution of the duration of the chaotic transient is measured and shown to be in excellent agreement with the Lorenz equations in showing a modified exponential distribution. We also give a brief numerical analysis and graphical visualization of the Lorenz equations in phase space illustrating the boundary between the metastable chaotic and the stable fixed point basins of attraction. This provides an intuitive understanding of the metastable dynamics of the Lorenz equations and the experimental system.

Homoclinic orbits and chaos in a multimode laser

We show experimentally that under certain conditions the chaotic intensity dynamics of an optically pumped NH3 bidirectional ring laser could be well described in terms of Shil'nikov homoclinic orbits and chaos. We found that the mechanism that resulted in this kind of dynamics of the laser is the competition between effects caused by the mode interaction between the forward and the backward modes of the laser and by the intrinsic single-mode dynamics of the interacting modes. (C) 1997 Optical Society of America.