Low-coherence interferometry was first demonstrated, in the early 1990s, in imaging the eye due i... more Low-coherence interferometry was first demonstrated, in the early 1990s, in imaging the eye due its tissue transparency and minimal attenuation of the input light. For this reason, ophthalmic imaging is the most successful application of optical coherence tomography (OCT). Since its first demonstration, advancements in technology and OCT designs have resulted in higher resolution images of the retinal layers including retinal photoreceptors, retinal pigment epithelium (RPE), and retinal nerve fiber layer (RNFL) thus improving the potential for early diagnosis, the understanding of disease pathology, as well as the assessment of therapeutic response. This chapter will mainly discuss improvements in OCT systems over time, particularly developments towards cellular level imaging and their clinical applications in ophthalmology in the present and in the future.
ABSTRACT The performance of an adaptive optics (AO) system is typically measured using the wavefr... more ABSTRACT The performance of an adaptive optics (AO) system is typically measured using the wavefront sensor (WFS). However, another method is to use the point spread function (PSF), which is sensitive to scatter, does not act as a low pass filter and is not dependent on the WFS calibration. We decided to examine the performance of an AO system built for vision science that employed a micromechanical systems (MEMS) based deformable mirror (DM). Specifically, the MEMS DM consists of 489 actuators, resulting in 163 segments each with individual piston/tip/tilt control. Initial evaluation of the DM with a model eye included determining the ability of the DM to generate individual Zernike polynomials and evaluating the far field PSF to measure wavefront correction performance. For individual Zernike polynomial terms, the DM was found to be capable of correcting the aberration magnitudes expected from previously published human population studies.1, 2 Finally, the DM was used in an AO fundus camera to successfully acquire images of cone photoreceptors in a living human eye. This is part of ongoing work which will incorporate the MEMS DM into both an AO scanning laser ophthalmoscope (SLO) and an AO optical coherence tomography (OCT) system where the form of the PSF at the confocal pinhole/optical fiber is important for optimal imaging.
This article presents a simple and novel method for the fabrication of cylindrical microchannels ... more This article presents a simple and novel method for the fabrication of cylindrical microchannels in polymer or biopolymer substrates. This process results in highly regular, cylindrical microchannels, suitable both to the transport of liquid and the transmission of light. This method eliminates issues associated with positioning tolerances characteristic of conventional fabrication techniques, such as soft lithography. Such devices hold great promise in the field of biomedical engineering by providing a true cylindrical profile for microflow studies and vascular modeling, as well as the ability to optically analyze injected biological samples. An evaluation of these devices is performed by real time optical imaging of blood flow.
Low-coherence interferometry was first demonstrated, in the early 1990s, in imaging the eye due i... more Low-coherence interferometry was first demonstrated, in the early 1990s, in imaging the eye due its tissue transparency and minimal attenuation of the input light. For this reason, ophthalmic imaging is the most successful application of optical coherence tomography (OCT). Since its first demonstration, advancements in technology and OCT designs have resulted in higher resolution images of the retinal layers including retinal photoreceptors, retinal pigment epithelium (RPE), and retinal nerve fiber layer (RNFL) thus improving the potential for early diagnosis, the understanding of disease pathology, as well as the assessment of therapeutic response. This chapter will mainly discuss improvements in OCT systems over time, particularly developments towards cellular level imaging and their clinical applications in ophthalmology in the present and in the future.
ABSTRACT The performance of an adaptive optics (AO) system is typically measured using the wavefr... more ABSTRACT The performance of an adaptive optics (AO) system is typically measured using the wavefront sensor (WFS). However, another method is to use the point spread function (PSF), which is sensitive to scatter, does not act as a low pass filter and is not dependent on the WFS calibration. We decided to examine the performance of an AO system built for vision science that employed a micromechanical systems (MEMS) based deformable mirror (DM). Specifically, the MEMS DM consists of 489 actuators, resulting in 163 segments each with individual piston/tip/tilt control. Initial evaluation of the DM with a model eye included determining the ability of the DM to generate individual Zernike polynomials and evaluating the far field PSF to measure wavefront correction performance. For individual Zernike polynomial terms, the DM was found to be capable of correcting the aberration magnitudes expected from previously published human population studies.1, 2 Finally, the DM was used in an AO fundus camera to successfully acquire images of cone photoreceptors in a living human eye. This is part of ongoing work which will incorporate the MEMS DM into both an AO scanning laser ophthalmoscope (SLO) and an AO optical coherence tomography (OCT) system where the form of the PSF at the confocal pinhole/optical fiber is important for optimal imaging.
This article presents a simple and novel method for the fabrication of cylindrical microchannels ... more This article presents a simple and novel method for the fabrication of cylindrical microchannels in polymer or biopolymer substrates. This process results in highly regular, cylindrical microchannels, suitable both to the transport of liquid and the transmission of light. This method eliminates issues associated with positioning tolerances characteristic of conventional fabrication techniques, such as soft lithography. Such devices hold great promise in the field of biomedical engineering by providing a true cylindrical profile for microflow studies and vascular modeling, as well as the ability to optically analyze injected biological samples. An evaluation of these devices is performed by real time optical imaging of blood flow.
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Papers by Cherry Greiner