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A clinical study explored the use of femtosecond laser treatment to address presbyopia, a condition caused by the stiffening of the crystalline lens due to aging. The study used a specific femtosecond laser to make precise cuts in the lens nucleus, aiming to increase accommodative amplitude (AA). Objective measurements of accommodation were obtained through various tests, and safety was confirmed in a trial involving cataractous eyes. While the study did not meet its target for AA improvement, no cases of lens opacification were observed, and visual acuity remained stable. The findings suggest that femtosecond laser treatment shows promise in increasing AA without inducing cataracts, but further research is needed to optimize the treatment. [Extracted from the article]

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. This work establishes the physical and chemical mechanisms behind the observed effects and describes the influence of process and material parameters onto the creation of step-like structures in hydrogel, Dihydroxyethylmethacrylat (HEMA). By focusing laser pulses in HEMA, reduced pulse separation distance below 50 nm and rise in pulse energy enhances the creation of unintended step-like structures. Spatial resolved Raman-spectroscopy was used to measure the laser induced chemical modification, which results into a reduced breakdown threshold. The reduction in threshold influences the position of optical breakdown for the succeeding laser pulses and consequently leads to the step-like structures. Additionally, the experimental findings were supplemented with numerical simulations of the influence of reduced damage threshold onto the position of optical breakdown. In summary, chemical material change was defined as cause of the step-like structures. Furthermore, the parameters to avoid these structures were identified. [ABSTRACT FROM AUTHOR]

Abstract: Ultrafast laser pulses have become a promising tool for microsurgery of the eye. Due to the low energy threshold, side effects are limited to the micrometer range This precision enables the use of ultrashort laser pulses in a broad field of medical applications. Especially, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue not only on top of a surface but three dimensionally inside the bulk. This mechanism is used in refractive eye surgery, where fs pulses create flaps into the corneal tissue to remodel the curvature of the eye and to improve visual acuity. Moreover, fs pulses could be used to influence the biomechanics of the crystalline lens of the eye and improve accommodation on eyes who suffer from presbyopia. [Copyright &y& Elsevier]

The article by Thomas Asshauer provides a wonderful introduction to the field of femtosecond lasers for eye surgery applications. Cinema projectors, halogen lights and finally laser light followed as light sources to become independent of the weather and to increase precision. The use of light for therapy and diagnosis of the eye is self-evident. [Extracted from the article]

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. The low pulse energy makes it compact and robust, because only an oscillator as a laser source is required. Another important feature of the low energy pulses is the reduced bubble formation during the cutting process. The smaller the bubbles, the more precise the cut can be positioned. However, the compact setup limits the system in its flexibility in cutting geometry. The VisuMax also uses the new generation of femtosecond technology, which should make it more immune to environmental and temperature changes. However, it is a bulky system, and the patient has to be moved to the excimer laser system after the flap is created. The IntraLase is the laser with the most clinical experience by far, which should be an important issue in terms of safety and technical support. On the other hand, it uses older femtosecond laser technology. This technology is sensitive to changes in temperature or humidity, which can be an important factor if the surgical environment is not air conditioned. The 20/10 Perfect Vision FEMTEC system is comparable with the IntraLase with respect to its technical parameters. However, no data are available about the amount of clinical experience. Conclusions: Although the systems are based on the same principle of photodisruption in corneal tissue, differences exist regarding the concept of these devices. [J Refract Surg. 2008;24:S102–S107.] [ABSTRACT FROM AUTHOR]

Unlike corneal inlays, which have wound-healing concerns, small-aperture IOLs (eg, IC-8 IOL, Acufocus, Inc.) that have an embedded annular mask to create the small central aperture, have been more widely accepted for presbyopia correction. Femto-masking can be applied to acrylic and silicone IOLs and can transform standard monofocal IOLs into presbyopia-correcting IOLs. [Extracted from the article]

Purpose: To evaluate a new method for visualizing femtosecond laser pulse–induced microincisions inside crystalline lens tissue. Setting: Laser Zentrum Hannover e.V., Hannover, Germany. Method: Lenses removed from porcine eyes were modified ex vivo by femtosecond laser pulses (wavelength 1040 nm, pulse duration 306 femtoseconds, pulse energy 1.0 to 2.5 μJ, repetition rate 100 kHz) to create defined planes at which lens fibers separate. The femtosecond laser pulses were delivered by a 3-dimension (3-D) scanning unit and transmitted by focusing optics (numerical aperture 0.18) into the lens tissue. Lens fiber orientation and femtosecond laser–induced microincisions were examined using a confocal laser scanning microscope (CLSM) based on a Rostock Cornea Module attached to a Heidelberg Retina Tomograph II. Optical sections were analyzed in 3-D using Amira software (version 4.1.1). Results: Normal lens fibers showed a parallel pattern with diameters between 3 μm and 9 μm, depending on scanning location. Microincision visualization showed different cutting effects depending on pulse energy of the femtosecond laser. The effects ranged from altered tissue-scattering properties with all fibers intact to definite fiber separation by a wide gap. Pulse energies that were too high or overlapped too tightly produced an incomplete cutting plane due to extensive microbubble generation. Conclusions: The 3-D CLSM method permitted visualization and analysis of femtosecond laser pulse–induced microincisions inside crystalline lens tissue. Thus, 3-D CLSM may help optimize femtosecond laser–based procedures in the treatment of presbyopia. [Copyright &y& Elsevier]