Dr. Klaus Ehrmann Profile

Dr. Klaus Ehrmann

Director of Technology at nthalmic technologies

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Publications (12)

Proceedings Article | 9 March 2012 Paper

Validation of a quasi real-time global aberrometer: the EyeMapper

C. Fedtke, K. Ehrmann, D. Falk, B. Holden

Proceedings Volume 8209, 82090C (2012) https://doi.org/10.1117/12.906927

KEYWORDS: Eye, Refraction, Visualization, Eye models, Imaging systems, Retina, Wavefront sensors, Mirrors, Wavefronts, Light scattering

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SPIE Journal Paper | 1 May 2011 Open Access

Semiautomated analysis of optical coherence tomography crystalline lens images under simulated accommodation

Eon Kim, Klaus Ehrmann, Jean-Marie Parel, Stephen Uhlhorn, David Borja, Esdras Arrieta-Quintero

JBO, Vol. 16, Issue 05, 056003, (May 2011) https://doi.org/10.1117/12.10.1117/1.3574613

KEYWORDS: Optical coherence tomography, Crystals, Edge detection, Crystal optics, Biological research, Analytical research, Eye, Optical properties, Crystallography, Refractive index

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Proceedings Article | 18 February 2009 Paper

Automated analysis of OCT images of the crystalline lens

Eon Kim, Klaus Ehrmann, Stephen Uhlhorn, David Borja, Jean-Marie Parel

Proceedings Volume 7163, 716313 (2009) https://doi.org/10.1117/12.809986

KEYWORDS: Refractive index, Optical coherence tomography, Crystals, Edge detection, Image analysis, Optical properties, Refraction, Analytical research, Geometrical optics, Eye

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Proceedings Article | 18 February 2009 Paper

Optical power mapping using paraxial laser scanning

Klaus Ehrmann, Darrin Falk

Proceedings Volume 7163, 71631E (2009) https://doi.org/10.1117/12.806765

KEYWORDS: Contact lenses, Sensors, Spherical lenses, Beam splitters, Laser scanners, Wavefronts, Glasses, Error analysis, Monochromatic aberrations, Data conversion

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Proceedings Article | 18 February 2009 Paper

A theoretical design of gradient index multifocal contact lens for correcting presbyopia and an attempt to elicit its performance using ray tracing

Ravi Bakaraju, Klaus Ehrmann, Eric Papas, Arthur Ho

Proceedings Volume 7163, 716319 (2009) https://doi.org/10.1117/12.808653

KEYWORDS: GRIN lenses, Aspheric lenses, Eye models, Contact lenses, Eye, Gradient-index optics, Monochromatic aberrations, Ray tracing, Modulation transfer functions, Lens design

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Proceedings Article | 18 February 2009 Paper

Working sketch of an anatomically and optically equivalent physical model eye

Ravi Chandra Bakaraju, Klaus Ehrmann, Darrin Falk, Eric Papas, Arthur Ho

Proceedings Volume 7163, 716316 (2009) https://doi.org/10.1117/12.808646

KEYWORDS: Eye models, Eye, Visual process modeling, Performance modeling, Contact lenses, Data modeling, Cornea, Cameras, Calibration, Refractive index

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Proceedings Article | 11 February 2008 Paper

Mechanical properties of intra-ocular lenses

Klaus Ehrmann, Eon Kim, Jean-Marie Parel

Proceedings Volume 6844, 68440O (2008) https://doi.org/10.1117/12.787107

KEYWORDS: Haptic technology, Lenses, Eye, Surgery, Resistance, Chemical elements, Crystals, Temperature metrology, Manufacturing, Body temperature

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Proceedings Article | 7 March 2006 Paper

Measurement of ocular parameters under various directions of gaze

Klaus Ehrmann, Fabian Conrad, Eric Papas, Arthur Ho

Proceedings Volume 6138, 61381W (2006) https://doi.org/10.1117/12.674410

KEYWORDS: Eye, Cameras, Contact lenses, Lenses, Image analysis, Edge detection, Error analysis, Head, Lens design, CCD cameras

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Lid angles and aperture size are important factors for fitting and on-eye performance of contact lenses. In particular, toric and translating bifocal lenses rely on predictable interaction with the eyelid for successful positioning and orientation. Traditionally, lid assessment and fitting evaluation is performed under slit lamp observation. Observations are limited to primary gaze and nasal or temporal directions. Quantification of lid parameters and lens positioning is subjective and depended on the skill of the practitioner. No commercial instrument is available off the shelf, which would be suitable to measure objectively ocular parameters and/or contact lens positioning under different directions of gaze. This is the likely reason why only one study has been published in which ocular characteristics for different gaze angles were obtained [1]. However, only a limited number of parameters and gaze directions were investigated. Almost all contact lenses are designed for and assessed under primary gaze. Considering that patients constantly change their gaze while wearing contact lenses, the quantification of contact lens movement and changes in ocular parameters with eye movement can contribute substantially to the understanding of lens performance and thereby lead to improved lens designs. This is of particular importance for toric and translating bifocal lenses. Their complex optical and topographical design requires precise positioning, orientation and movement with changes in gaze direction in order to provide adequate vision. Baron [2] suggested that the lower eyelid is the most important factor for lens movement of translating bifocal lenses, but questions still remained on the complete dynamics of on eye behaviour. For toric contact lenses, the rotational orientation is more important than vertical translation to obtain optimum visual correction. Most toric lenses feature a prism ballast design. Blinking movements, mainly of the upper eyelid, interact with the wedge like shape and squeeze the thick part downwards. It has been observed that the upper eyelid does not move in a straight downward movement, but also twists slightly to close the temporal side first [3]. Precise quantification of this motion and how it affects the contact lens movement have not been reported. A new instrument was designed and constructed to provide objective measurements of ocular parameters.

Proceedings Article | 18 April 2005 Paper

Evaluation of the performance of crystalline lens refilled with polymer gel with an improved ex vivo accommodation simulator

Klaus Ehrmann, Arthur Ho

Proceedings Volume 5688, (2005) https://doi.org/10.1117/12.599223

KEYWORDS: Lenses, Crystals, Eye, Sclera, Plastic lenses, Refractive index, CCD cameras, Motion measurement, Polymers, Silicon

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Proceedings Article | 13 July 2004 Paper

Ex vivo accommodation simulator II: concept and preliminary results

Klaus Ehrmann, Arthur Ho, Jean-Marie Parel

Proceedings Volume 5314, (2004) https://doi.org/10.1117/12.539111

KEYWORDS: Transducers, Eye, Crystals, Motion measurement, Sclera, Calibration, Tissues, Device simulation, Adhesives, Latex

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Proceedings Article | 7 June 2000 Paper

Dacryomeniscometry: an early attempt

Arthur Ho, Eric Papas, Kaykhosrow Keshavarzi, Edward Lum, Klaus Ehrmann

Proceedings Volume 3908, (2000) https://doi.org/10.1117/12.387530

KEYWORDS: Detection and tracking algorithms, Algorithm development, Eye, Cameras, Aspheric lenses, Computer simulations, Imaging systems, Image analysis, Error control coding, Cornea

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Proceedings Article | 7 June 2000 Paper

Knife-edge system for evaluating contact lenses

Arthur Ho, Klaus Ehrmann

Proceedings Volume 3908, (2000) https://doi.org/10.1117/12.387512

KEYWORDS: Contact lenses, Light sources, Objectives, Optical design, Calibration, Visualization, Optics manufacturing, Standards development, Lens design, Aspheric lenses

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Showing 5 of 12 publications

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