Andreas Drauschke

Semi-automatic evaluation of intraocular lenses (IOL) using a mechanical eye model

As cataracts are the most common reason for loss of vision with an age over 55, the implantation of intraocular intraocular lenses is one of the most common surgical interventions. The quality measurement and test instructions for the patients. Therefore more efforts are put into the individualization of IOL in order to achieve better imaging properties. Two examples of typical quality standards for IOL are the modulated transfer function (MTF) and the Strehl ratio which can be measured in vivo or also in mechanical eye models. A mechanical eye model in the scale 1:1 is presented. It has been designed to allow the measurement of the MTF and Strehl ratio and simultaneous evaluation of physiological imaging quality. The eye model allows the automatic analysis of the IOL especially focused on the tolerance for tilting and decentering. Cornea, iris aperture and IOL type are interchangeable, because all these parts are implemented by the use of separated holders. The IOL is mounted on a shift plate. Both are mounted on a tilt plate. This set-up guarantees an independent decentration and tilt of the IOL, both moved by electrical drives. This set–up allows a two–dimensional tolerance analysis of decentration and tilt effects. Different 100×100 point (decentration×tilt) analyzes for various iris apertures, needing only approximately 15 minutes, are presented.

Reproducibility analysis of measurements with a mechanical semiautomatic eye model for evaluation of intraocular lenses

Mechanical eye models are used to validate ex vivo the optical quality of intraocular lenses (IOLs). The quality measurement and test instructions for IOLs are defined in the ISO 11979-2. However, it was mentioned in literature that these test instructions could lead to inaccurate measurements in case of some modern IOL designs. Reproducibility of alignment and measurement processes are presented, performed with a semiautomatic mechanical ex vivo eye model based on optical properties published by Liou and Brennan in the scale 1:1. The cornea, the iris aperture and the IOL itself are separately changeable within the eye model. The adjustment of the IOL can be manipulated by automatic decentration and tilt of the IOL in reference to the optical axis of the whole system, which is defined by the connection line of the central point of the artificial cornea and the iris aperture. With the presented measurement setup two quality criteria are measurable: the modulation transfer function (MTF) and the Strehl ratio. First the reproducibility of the alignment process for definition of initial conditions of the lateral position and tilt in reference to the optical axis of the system is investigated. Furthermore, different IOL holders are tested related to the stable holding of the IOL. The measurement is performed by a before-after comparison of the lens position using a typical decentration and tilt tolerance analysis path. Modulation transfer function MTF and Strehl ratio S before and after this tolerance analysis are compared and requirements for lens holder construction are deduced from the presented results.

Mechanical and Electrical Specifications of the Active Lung Simulator i-Lung – Development of i-Lung 1.0 to i-Lung 2.0

Abstract Lung simulators are important for different application fields like respirator manufacturing processes, teaching purposes as well as environmental and analytical aerosol transport measurements. State-of-the-art lung simulators have a great disadvantage of not taking the internal structure of the human lung into account. Furthermore it is not possible to simulate aerosol exposition to these lung equivalents. To overcome these restrictions and disadvantages, the i-Lung has been developed primarily as an active lung simulator, which can also be used as a passive lung simulator. With the i-Lung it is possible to simulate physiological and pathological breathing patterns with different lung equivalents like latex bags, primed porcine lungs or even fresh porcine lungs. The presented versions 1.0 and 2.0 of the i-Lung are compared in the mechanical and electrical setup. As a development of the i-Lung 1.0, the i-Lung 2.0 provides a refined mechanical construction, more flexible fields of application and an interchangeable dual control unit. The control unit of the lung simulator is either an integrated single based computer (SBC) or the NI cRIO system. With the cRIO control unit, the i-Lung 2.0 is able to perform real time data transmission. Due to the further developments and improvements of the i-Lung system, more physiological and realistic breathing simulation can be executed with the i-Lung 2.0. Thus, the developed lung simulator becomes a real alternative to animal testing. This can be especially interesting for the cosmetic industry, as animal testing has been banned within the EU for the hazardousness and toxicity tests of cosmetic products since March 11 th 2013.

The adolescence of electronic health records: Status and perspectives for large scale implementation

Health informatics started to evolve decades ago with the intention to support healthcare using computers. Since then Electronic health records (EHRs) and personal health records (PHRs) have become available but widespread adoption was limited by lack of interoperability and security issues. This paper discusses the feasibility of interoperable standards based EHRs and PHRs drawing on experience from implementation projects. It outlines challenges and goals in education and implementation for the next years.

Sensor system development for the novel spontaneous active breathing lung simulator, i-Lung

Breathing simulation is an indispensable task not only for respirator manufacturing processes. Using an active lung simulator including an aerosol measurement system at different working environments would provide information about the actual aerosol exposure to the respiratory tract of the employees at their specific working places. For this purpose a sensor system is being developed to enhance the options of use of the novel lung simulator i-Lung. The sensor system is designed to gather environmental and simulation specific parameters. The enhancement of the i-Lung module by integrating a sensor system including sensors for temperature, pressure, flow and humidity enlarges the field of potential applications of the simulator. This development is seen as further step in direction of a certification as alternative to animal models and as an essential pre-commercial development of the i-Lung system.

Enhancements of a mechanical lung simulator for ex vivo measuring of aerosol deposition in lungs

With the current exposure to aerosols, nanoparticles and fine dust the cases of pulmonary diseases increase. Nowadays there is still little information about the distribution of inhaled particles in the lung itself. However, this information is important for pharmaceutical industry providing inhalable diagnostics and therapeutics. The presented lung simulator iLung is an active mechanical lung simulator, which offers the use of different lung equivalents, like a primed porcine lung or latex bags. The i-Lung uses a non destructive aerosol measurement system for measuring the size and amount of inand exhaled particles that were produced beforehand. This lung simulator is a first step into the direction of replacing laboratory animals for inhalation test as ordered by the EU REACH regulation. [2]

Mechanical eye model for the comparison of optical imaging quality and physiology of human vision

The implantation of intraocular lenses (IOL) is one of the most common surgical interventions. This surgery is performed using different types of IOL, like monoand multifocal lenses. The measurement and test instructions for IOL are defined in ISO 11979-2[1]. Even though IOL have a high importance there are only approaches for the actual objective evaluation of the quality of an IOL. The reason is given by a still poorly understood human physiology of vision. A direct comparison between physical imaging properties – for example defined by the modulated transfer function (MTF), point spread function (PSF), spot diagrams, Strehl ratio or the coefficients of Seidelor Zernike polynomials – and physiological perception will allow the development of necessary objective quality standards, also for the development of new intraocular lenses. A mechanic eye model in the scale 1:1 is presented, which has been designed to allow the derivation of the intended quality standards. This is achieved by a simultaneous measurement of physiological and physical imaging properties. Moreover the eye model allows the automatic analysis of the tolerance for tilting and decentrating the IOL perpendicular to the optical axis.

Comparison of different wavefront measurement setups to judge the position tolerance of intraocular lenses in a model eye

To treat cataract intraocular lenses (IOLs) are used to replace the clouded human eye lens. Due to postoperative healing processes the IOL can displace within the eye, which can lead to deteriorated quality of vision. To test and characterize these effect an IOL can be embedded into a model of the humane eye. One informative measure are wavefront aberrations. In this paper three different setups, the typical double-pass configuration (DP), a single-pass (SP1) where the measured light travels in the same direction as in DP and a single-pass (SP2) with reversed direction, are investigated. All three setups correctly measure the aberrations of the eye, where SP1 is found to be the simplest to set up and align. Because of the lowest complexity it is the proposed method for wavefront measurement in model eyes.

Further improvement of an intraocular lens holder for more physiological measurements within a mechanical eye model

To evaluate the performance of intraocular lenses to treat cataract, an optomechanical eye model was developed. One of the most crucial components is the IOL holder, which should guarantee a physiological representation of the capsular bag and a stable position during measurement sequences. Individual holders are required due to the fact that every IOL has different geometric parameters. A method which allows obtaining the correct dimensions for the holder of a special IOL was developed and tested, by verifying the position of the IOL before and after a measurement sequence. Results of telecentric measurements and MTF measurements show that the IOL position does not change during the displacement sequence induced by the stepper motors of the eye model.

Experiments for practical education in process parameter optimization for selective laser sintering to increase workpiece quality

Selective Laser Sintering (SLS) is considered as one of the most important additive manufacturing processes due to component stability and its broad range of usable materials. However the influence of the different process parameters on mechanical workpiece properties is still poorly studied, leading to the fact that further optimization is necessary to increase workpiece quality. In order to investigate the impact of various process parameters, laboratory experiments are implemented to improve the understanding of the SLS limitations and advantages on an educational level. Experiments are based on two different workstations, used to teach students the fundamentals of SLS. First of all a 50 W CO2 laser workstation is used to investigate the interaction of the laser beam with the used material in accordance with varied process parameters to analyze a single-layered test piece. Second of all the FORMIGA P110 laser sintering system from EOS is used to print different 3D test pieces in dependence on various process parameters. Finally quality attributes are tested including warpage, dimension accuracy or tensile strength. For dimension measurements and evaluation of the surface structure a telecentric lens in combination with a camera is used. A tensile test machine allows testing of the tensile strength and the interpreting of stress-strain curves. The developed laboratory experiments are suitable to teach students the influence of processing parameters. In this context they will be able to optimize the input parameters depending on the component which has to be manufactured and to increase the overall quality of the final workpiece.