Femtosecond laser induced step-like structures inside transparent hydrogel due to laser induced threshold reduction.

In the area of laser material processing, versatile applications for cutting glasses and transparent polymers exist. However, parasitic effects such as the creation of step-like structures appear when laser cutting inside a transparent material. To date, these structures were only described empirically.

Comparison of two prototypes of a magnetically adjustable glaucoma implant in rabbits.

Glaucoma drainage devices are used in surgical glaucoma therapy. Success of controlling the intraocular pressure is limited due to fibrous implant encapsulation and fibrin coating on the implant which lead to drainage obstructions. An innovative implant with a magnetically adjustable valve was developed.

Measurement of Ex Vivo Porcine Lens Shape During Simulated Accommodation, Before and After fs-Laser Treatment.

Purpose: According to Helmholtz, accommodation is based on the flexibility of the crystalline lens, which decreases with age, causing presbyopia. With femtosecond (fs)-lentotomy treatment, it is possible to restore the flexibility of presbyopic lenses. The efficiency of the treatment can be systematically evaluated using the finite element method based on experimental data.

Effects of cavitation bubble interaction with temporally separated fs-laser pulses.

We present a time-resolved photographic analysis of the pulse-to-pulse interaction. In particular, we studied the influence of the cavitation bubble induced by a fs-pulse on the optical focusing of the consecutive pulse and its cavitation bubble dynamics in dependence on temporal pulse separation in water. As a first result, by decreasing the temporal separation of laser pulses, there is a diminishment of the laser-induced optical breakdown (LIOB) efficiency in terms of energy conversion, caused by disturbed focusing into persisting gas bubbles at the focal volume.

Interaction dynamics of spatially separated cavitation bubbles in water.

We present a high-speed photographic analysis of the interaction of cavitation bubbles generated in two spatially separated regions by femtosecond laser-induced optical breakdown in water. Depending on the relative energies of the femtosecond laser pulses and their spatial separation, different kinds of interactions, such as a flattening and deformation of the bubbles, asymmetric water flows, and jet formation were observed. The results presented have a strong impact on understanding and optimizing the cutting effect of modern femtosecond lasers with high repetition rates (>1 MHz).

Femtosecond lentotomy: generating gliding planes inside the crystalline lens to regain accommodation ability.

Based on Helmholtz Theory for accommodation the increasing sclerosis of lens nucleus and cortex is the main cause for the developments of presbyopia. Existing therapies, however, do not reverse the stiffness of the crystalline lens and thus do not regain real accommodation ability. A new approach to restore the flexibility of the lens could be realized by photodisruption using ultrafast laser pulses.

Control of femtosecond thin-flap LASIK using OCT in human donor eyes.

Purpose: Thin-flap keratomileusis is a procedure that minimizes LASIK flap thickness to preserve both the corneal epithelium and the maximum residual stroma. This study investigated the usefulness of optical coherence tomography (OCT) as a tool in guiding the femtosecond laser in the creation of a thin flap in human eyes in a non-randomized case series.

Methods: In a private research laboratory, an in vitro investigation was performed on human autopsy eyes.

Repetition rate dependency of reactive oxygen species formation during femtosecond laser-based cell surgery.

Femtosecond (fs) laser-based cell surgery is typically done in two different regimes, at kHz or MHz repetition rate. Formation of reactive oxygen species (ROS) is an often predicted effect due to illumination with short laser pulses in biological tissue. We present our study on ROS formation in single cells in response to irradiation with fs laser pulses depending on the repetition rate while focusing into the cell nucleus.

Visualization of femtosecond laser pulse-induced microincisions inside crystalline lens tissue.

Purpose: To evaluate a new method for visualizing femtosecond laser pulse-induced microincisions inside crystalline lens tissue.

Setting: Laser Zentrum Hannover e.V.

Green laser light activates the inner ear.

The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices.

Femtosecond laser induced flexibility change of human donor lenses.

Background: According to the Helmholtz theory of accommodation the loss of accommodation amplitude is caused by the growing sclerosis of the crystalline lens, whereas the ciliary muscle and the lens capsule are mainly uneffected by age. A permanent treatment method for presbyopia which offers a dynamic accommodation ability is a recent field of study. The concept followed in this paper uses femtosecond laser pulses to potentially overcome the loss of deformation ability of the crystalline lens by creating gliding planes inside the lens tissue to improve its flexibility.

Purinergic signalling in rat GFSHR-17 granulosa cells: an in vitro model of granulosa cells in maturing follicles.

Purinergic signalling in rat GFSHR-17 granulosa cells was characterised by Ca(2+)-imaging and perforated patch-clamp. We observed a resting intracellular Ca(2+)-concentration ([Ca(2+)](i)) of 100 nM and a membrane potential of -40 mV. This was consistent with high K(+)- and Cl(-) permeability and a high intracellular Cl(-) concentration of 40 mM.

In vivo application and imaging of intralenticular femtosecond laser pulses for the restoration of accommodation.

Purpose: According to the Helmholtz theory of accommodation, one major cause of the development of presbyopia is the increasing sclerosis of the crystalline lens. One concept for regaining the elasticity of the sclerosing lens is intralenticular treatment by femtosecond laser pulses.

Methods: The feasibility of applying and imaging in vivo microincisions by femtosecond laser pulses was evaluated in five rabbit lenses with a new high repetition rate (100 kHz) femtosecond laser unit.

Clinical value of optical coherence tomography in laryngology.

Background: Optical coherence tomography (OCT) is a new, noninvasive imaging technology for the evaluation of superficial lesions. The objective of this study is to evaluate microlaryngoscopy in combination with OCT compared with microlaryngoscopy alone (ie, without OCT) in supplying a specific diagnosis, predicting invasive tumor growth and epithelial dysplasia in the larynx.

Methods: This was a prospective study including 217 laryngeal lesions in a total of 193 patients undergoing surgery.

Real-time optical coherence tomography-guided femtosecond laser sub-Bowman keratomileusis on human donor eyes.

Purpose: To determine the usefulness of optical coherence tomography (OCT) as a tool in guiding the femtosecond (fs) laser in the creation of a sub-Bowman keratomileusis (SBK) flap in human eyes.

Design: A nonrandomized case series.

Methods: In a private research laboratory setting, we performed an in vitro investigation on human autopsy eyes.

Overview of commercially available femtosecond lasers in refractive surgery.

Purpose: To report on four different commercially available femtosecond laser systems used in refractive surgery.

Methods: Four systems were analyzed: Ziemer DaVinci system, Zeiss VisuMax, IntraLase FS laser, and 20/10 Perfect Vision FEMTEC.

Results: The DaVinci system attracts attention with its concept of low laser pulse energy and flexible mirror arm as a beam delivery.

fs-Laser induced elasticity changes to improve presbyopic lens accommodation.

Background: According to the Helmholtz theory of accommodation, one of the major reasons for the development of presbyopia is the progressive sclerosis of the crystalline lens. However, both the ciliary muscle and the lens capsule stay active and elastic. Thus, the concept for regaining the deformation-ability of the crystalline lens is to create microincisions inside lens tissue to achieve gliding planes.

Fs-laser scissors for photobleaching, ablation in fixed samples and living cells, and studies of cell mechanics.

The use of ultrashort laser pulses for microscopy has steadily increased over the past years. In this so-called multiphoton microscopy, laser pulses with pulse duration around 100 femtoseconds (fs) are used to excite fluorescence within the samples. Due to the high peak powers of fs lasers, the absorption mechanism of the laser light is based on nonlinear absorption.

Technique of optical coherence tomography of the larynx during microlaryngoscopy.

Optical coherence tomography (OCT) is a new, noninvasive imaging technology for the evaluation of superficial lesions. Because of a penetrating depth of a few millimeters and an ultrahigh tissue resolution, it qualifies for use in the larynx and might in the near future play an important role in the pre-, intra-, and postoperative investigation of early laryngeal cancer and its precursor lesions. Especially directed to otolaryngologists, this paper describes the technique of in vivo OCT imaging of the larynx in detail during microlaryngoscopy and supplies a number of personal hints.

First safety study of femtosecond laser photodisruption in animal lenses: tissue morphology and cataractogenesis.

Purpose: To determine through safety studies the tissue effects and potential cataractogenesis of laser modification of the crystalline lens (photophaco modulation).

Setting: Laser Zentrum Hannover, Hannover, Germany.

Methods: Six fresh porcine lenses and 6 living rabbit eyes (with the contralateral eye as a control) were radiated with a low-energy femtosecond laser to induce lens fiber disruption.

Intrastromal refractive surgery with ultrashort laser pulses: in vivo study on the rabbit eye.

Background: Femtosecond (fs) laser pulses may offer new possibilities in the field of refractive surgery, especially when using the laser as a microkeratome. By induction of nonlinear absorption processes the laser can be used to perform intrastromal cuts. The conventional microkeratome, associated with numerous potential side effects, can possibly be replaced.

Optoacoustic imaging for optimization of laser cyclophotocoagulation.

Optoacoustic imaging was used for ophthalmic imaging, especially of the ciliary body region, which is of interest in the treatment of glaucoma. The different tissue structures below the sclera of porcine and rabbit eyes in vitro could be differentiated up to a depth of more than 1.5 mm.