Predictive factors of femtosecond laser flap thickness measured by online optical coherence pachymetry subtraction in sub-Bowman keratomileusis.

PURPOSE: To evaluate possible factors responsible for the difference between predicted and measured parameters during 100 microm flap creation with a femtosecond laser (IntraLase FS30) using online optical coherence pachymetry (OCP). SETTING: AugenVersorgungsZentrum, Weilheim, and the Technical University of Munich, Munich, Germany. METHODS: In this nonrandomized prospective interventional case study, 287 eyes of 146 consecutive patients were monitored by online OCP before and after flap creation with the femtosecond laser. The laser-specific settings were held constant during the study to attempt a 100 microm flap in all eyes. A multiple linear regression model with backward variable selection procedure was applied to evaluate possible multivariable explanatory powers of several covariates. In addition, very thin and very thick flaps (ie, lower and upper quartiles of flap thickness distribution) were analyzed separately in a logistic regression model. RESULTS: Central flap thickness measured with online OCP subtraction varied according to a Gaussian distribution from 57 to 138 microm, with a mean of 100.4 microm +/- 13.6 (SD). Regression analysis between predicted and measured flap thickness showed no predictive power of 11 variables including the keratometry value of the cornea, preoperative corneal thickness, and patient age. CONCLUSION: The plano applanation interface of the IntraLase FS30 femtosecond laser produced ultrathin flaps for sub-Bowman keratomileusis that were independent of some preoperative and surgical factors known to affect outcomes with mechanical microkeratomes

Circuit topology and control principle for a first magnetic stimulator with fully controllable waveform.

Magnetic stimulation pulse sources are very inflexible high-power devices. The incorporated circuit topology is usually limited to a single pulse type. However, experimental and theoretical work shows that more freedom in choosing or even designing waveforms could notably enhance existing methods. Beyond that, it even allows entering new fields of application. We propose a technology that can solve the problem. Even in very high frequency ranges, the circuitry is very flexible and is able generate almost every waveform with unrivaled accuracy. This technology can dynamically change between different pulse shapes without any reconfiguration, recharging or other changes; thus the waveform can be modified also during a high-frequency repetitive pulse train. In addition to the option of online design and generation of still unknown waveforms, it amalgamates all existing device types with their specific pulse shapes, which have been leading an independent existence in the past years. These advantages were achieved by giving up the common basis of all magnetic stimulation devices so far, i.e., the high-voltage oscillator. Distributed electronics handle the high power dividing the high voltage and the required switching rate into small portions

Magnetic stimulation with arbitrary waveform shapes

Device technology for magnetic stimulation is still extremely limited regarding waveform dynamics and flexibility. Existing systems are well-known to be very inefficient from an energy perspective. In addition, neither a noninvasive analysis of different neuron dynamics nor an adjustment of the pulse waveform for a more specific stimulation is possible with existing equipment as a matter of principle. The uncontrollable high power in the Megawatt range obstructs such aims with classical means. This contribution introduces a novel stimulator technology which gives up the traditions from classical pulse-source topologies. The design forgoes any high-voltage devices in the actual pulse circuitry, but is based on mass-produced high-power lowvoltage components instead. It enables the generation of almost arbitrary waveforms, including all classical waveforms in magnetic stimulation, with a single device. For any of these pulses the field energy, except the unavoidable basic ohmic losses, can be retrieved from the stimulation coil and be fed back into the internal energy storages. This also applies to classical monophasic pulses, which converted all their energy into heat in classical systems. The power requirements of this technology are comparably low accordingly. The combination of switching control and big highly flexible energy storages moreover enables even high pulse trains as in theta-burst protocols with one pulse source. © 2013 Springer-Verlag

Inbetriebnahme und Betrieb des Rollpruefstands. T.1.2 Abschlussbericht. Abschlussdatum: 31.12.1980

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