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Mechanical Eye Model for Evaluating Intraocular Pressure Measurements
Kutaiba Saleh,Volkmar Unger,Alexander Dietzel,Detlef Heydenreich,Rico Großjohann,Clemens Jürgens,Frank Tost,Jens Haueisen 대한의용생체공학회 2014 Biomedical Engineering Letters (BMEL) Vol.4 No.4
Purpose For the development of new intraocular pressure(IOP) measurement devices, as well as for comparison withexisting devices it is important to consider the variousbiomechanical properties of the eye in test setups. Therefore,a controllable physical phantom with flexibility in theadjustment of biomechanical parameters and geometries isbeing proposed and analyzed. Methods Different configurations of a mechanical eyemodel are simulated together with the applanation process,based on the finite element method (FEM). Forming toolsare designed to produce artificial corneas with variablethicknesses and stiffness’s using injection molding. Anapparatus is assembled for controlling and evaluating thephantom eye in connection with a piezoelectric IOP testsensor. Measurements are also performed using thecommercially available non-contact tonometer NCT-800. Results Simulation results for surface pressure and stressdistribution at the cornea together with the pressure in thecentral part of the applanation body show that the pressurereaches a maximum when the local stress is centrallyconcentrated and decreases to a stable level afterwards. Morerigid corneas result in higher maximum values for thepressure. The measurements with the piezoelectric IOP testsensor are in good agreement with the simulation results. The NCT-800 measurements show a significant influence of the biomechanical properties of the cornea on measured IOPs. Conclusion Our phantom is suitable for describing the effectof biomechanical characteristics of the human eye ontonometric measurements and will facilitate the evaluation ofnew tonometry systems.
Lee, Sejin,Ha, Woosung,Kobelke, Jens,Schuster, Kay,Unger, Sonja,Oh, Kyunghwan Optical Society of America 2012 Optics letters Vol.37 No.22
<P>A unique multicorelike guidance was achieved in a microstructured optical fiber composed of a circular air hole at the center surrounded by a high-index triangular core. Unique spectral evolution of the degeneracy was theoretically investigated using a vectorial finite element method to find a threefold degeneracy in both the fundamental and the first excited modes in the visible range, which evolved to twofold degeneracy as the wavelength increased to IR. Experimental measurements also confirmed evolution of the modal intensity from three spatially isolated patterns confined to individual corners into a supermode combining the three corners.</P>
A micro-structured aperture made of a hollow triangular-core fiber for novel beam shaping
Ha, Woosung,Lee, Sejin,Kim, Jongki,Jeong, Yoonseob,Oh, Kyunghwan,Kobelke, Jens,Schuster, Kay,Unger, Sonja,Schwuchow, Anka,Kim, Jun Ki The Optical Society 2010 Optics express Vol.18 No.20
<P>We demonstrate a micro-structured aperture made of a unique hollow triangular-core fiber (HTCF) that consists of a central air hole, a high-index hollow triangular core, and silica cladding for all-fiber novel beam shaping. Detailed fabrication processes to embed a hollow triangular structure into a cylindrical optical fiber are described and unique diffraction patterns out of the HTCF for monochromatic light are analyzed both experimentally and theoretically. Fourier-optic analysis combined with guided mode calculation was pursued to interpret experimental patterns in terms of the beam propagation distance.</P>