The Experts below are selected from a list of 1956 Experts worldwide ranked by ideXlab platform
Austin Roorda - One of the best experts on this subject based on the ideXlab platform.
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wide vergence multi spectral adaptive optics Scanning Laser Ophthalmoscope with diffraction limited illumination and collection
Biomedical Optics Express, 2020Co-Authors: Sanam Mozaffari, Pavan Tiruveedhula, Francesco Larocca, Volker Jaedicke, Austin RoordaAbstract:Visualizing and assessing the function of microscopic retinal structures in the human eye is a challenging task that has been greatly facilitated by ophthalmic adaptive optics (AO). Yet, as AO imaging systems advance in functionality by employing multiple spectral channels and larger vergence ranges, achieving optimal resolution and signal-to-noise ratios (SNR) becomes difficult and is often compromised. While current-generation AO retinal imaging systems have demonstrated excellent, near diffraction-limited imaging performance over wide vergence and spectral ranges, a full theoretical and experimental analysis of an AOSLO that includes both the light delivery and collection optics has not been done, and neither has the effects of extending wavefront correction from one wavelength to imaging performance in different spectral channels. Here, we report a methodology and system design for simultaneously achieving diffraction-limited performance in both the illumination and collection paths for a wide-vergence, multi-spectral AO Scanning Laser Ophthalmoscope (SLO) over a 1.2 diopter vergence range while correcting the wavefront in a separate wavelength. To validate the design, an AOSLO was constructed to have three imaging channels spanning different wavelength ranges (543 ± 11 nm, 680 ± 11 nm, and 840 ± 6 nm, respectively) and one near-infrared wavefront sensing channel (940 ± 5 nm). The AOSLO optics and their alignment were determined via simulations in optical and optomechanical design software and then experimentally verified by measuring the AOSLO’s illumination and collection point spread functions (PSF) for each channel using a phase retrieval technique. The collection efficiency was then measured for each channel as a function of confocal pinhole size when imaging a model eye achieving near-theoretical performance. Imaging results from healthy human adult volunteers demonstrate the system’s ability to resolve the foveal cone mosaic in all three imaging channels despite a wide spectral separation between the wavefront sensing and imaging channels.
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wide vergence multi spectral adaptive optics Scanning Laser Ophthalmoscope with diffraction limited illumination and collection
bioRxiv, 2020Co-Authors: Sanam Mozaffari, Pavan Tiruveedhula, Francesco Larocca, Volker Jaedicke, Austin RoordaAbstract:Visualizing and assessing the function of microscopic retinal structures in the human eye is a challenging task that has been greatly facilitated by ophthalmic adaptive optics (AO). Yet, as AO imaging systems advance in functionality by employing multiple spectral channels and larger vergence ranges, achieving optimal resolution and signal-to-noise ratios (SNR) becomes difficult and is often compromised. While current-generation AO retinal imaging systems have demonstrated excellent, near diffraction-limited imaging performance over wide vergence and spectral ranges, a full theoretical and experimental analysis of an AOSLO that includes both the light delivery and collection optics has not been done, and neither has the effects of extending wavefront correction from one wavelength to imaging performance in different spectral channels. Here, we report a methodology and system design for simultaneously achieving diffraction-limited performance in both the illumination and collection paths for a wide-vergence, multi-spectral AO Scanning Laser Ophthalmoscope (SLO) over a 1.2 diopter vergence range while correcting the wavefront in a separate wavelength. To validate the design, an AOSLO was constructed to have three imaging channels spanning different wavelength ranges (543 {+/-} 11 nm, 680 {+/-} 11 nm, and 840 {+/-} 6 nm, respectively) and one near-infrared wavefront sensing channel (940 {+/-} 5 nm). The AOSLO optics and their alignment were determined via simulations in optical and optomechanical design software and then experimentally verified by measuring the AOSLOs illumination and collection point spread functions (PSF) for each channel using a phase retrieval technique. The collection efficiency was then measured for each channel as a function of confocal pinhole size when imaging a model eye achieving near-theoretical performance. Imaging results from healthy human adult volunteers demonstrate the systems ability to resolve the foveal cone mosaic in all three imaging channels despite a wide spectral separation between the wavefront sensing and imaging channels. OCIS codes(110.1080) Active or adaptive optics; (170.4460) Ophthalmic optics and devices; (170.4470) Ophthalmology
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binocular eye tracking with the tracking Scanning Laser Ophthalmoscope
Vision Research, 2016Co-Authors: Scott B Stevenson, Austin Roorda, Christy K SheehyAbstract:Abstract The development of high magnification retinal imaging has brought with it the ability to track eye motion with a precision of less than an arc minute. Previously these systems have provided only monocular records. Here we describe a modification to the Tracking Scanning Laser Ophthalmoscope (Sheehy et al., 2012) that splits the optical path in a way that slows the left and right retinas to be scanned almost simultaneously by a single system. A mirror placed at a retinal conjugate point redirects half of each horizontal scan line to the fellow eye. The collected video is a split image with left and right retinas appearing side by side in each frame. Analysis of the retinal motion in the recorded video provides an eye movement trace with very high temporal and spatial resolution. Results are presented from scans of subjects with normal ocular motility that fixated steadily on a green Laser dot. The retinas were scanned at 4° eccentricity with a 2° square field. Eye position was extracted offline from recorded videos with an FFT based image analysis program written in Matlab. The noise level of the tracking was estimated to range from 0.25 to 0.5 arc min SD for three subjects. In the binocular recordings, the left eye/right eye difference was 1–2 arc min SD for vertical motion and 10–15 arc min SD for horizontal motion, in agreement with published values from other tracking techniques.
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active eye tracking for an adaptive optics Scanning Laser Ophthalmoscope
Biomedical Optics Express, 2015Co-Authors: Christy K Sheehy, Pavan Tiruveedhula, Ramkumar Sabesan, Austin RoordaAbstract:We demonstrate a system that combines a tracking Scanning Laser Ophthalmoscope (TSLO) and an adaptive optics Scanning Laser Ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone.
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adaptive optics to study the structure and function of the human visual system
Conference on Lasers and Electro-Optics, 2015Co-Authors: Austin RoordaAbstract:Adaptive optics (AO) corrects the blur caused by the eye’s optical imperfections, enabling optical access to single human retinal cells. An AO Scanning Laser Ophthalmoscope is described for cellular level retinal imaging and vision testing.
William R Freeman - One of the best experts on this subject based on the ideXlab platform.
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Scanning Laser Ophthalmoscope imaging stabilized microperimetry in dry age related macular degeneration
Retina-the Journal of Retinal and Vitreous Diseases, 2011Co-Authors: Kathrin Hartmann, Dirkuwe Bartsch, Lingyun Cheng, Jae S Kim, Maria Laura Gomez, Helaina Klein, William R FreemanAbstract:Purpose To determine the effect of drusen and geographic atrophy (GA) in dry age-related macular degeneration on retinal sensitivity using an eye tracking Scanning Laser Ophthalmoscope microperimetry. Methods A total of 44 eyes from 22 patients with dry age-related macular degeneration and drusen and 11 patients with GA were imaged with Scanning Laser Ophthalmoscope microperimetry (OPKO Health, Miami, FL). A custom microperimetry pattern was used to evaluate retinal sensitivity to a Goldmann III size target (108 μm on the retina). The perimetry used a 4-2 stepladder algorithm to determine maximal sensitivity. Microperimetry and optical coherence tomography were performed using a standardized protocol. Twenty-eight eyes with drusen and 16 eyes with GA were analyzed. Results Retinal sensitivity overlying drusen was significantly reduced compared with the adjacent uninvolved retina. There was a significant correlation between retinal sensitivity and drusen volume, as well as the grading of the photoreceptor inner segment/outer segment junction score. In patients with GA, an absolute scotoma was confirmed. Retinal sensitivity at the margin of GA was significantly decreased compared with the adjacent uninvolved retina. Conclusion Scanning Laser Ophthalmoscope microperimetry is able to detect changes in retinal sensitivity in AMD patients overlying drusen and at the margin of GA. It is a useful device to grade focal retinal sensitivity in patients with dry age-related macular degeneration.
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simultaneous indocyanine green and fluorescein angiography using a confocal Scanning Laser Ophthalmoscope
Archives of Ophthalmology, 1998Co-Authors: William R Freeman, Dirkuwe Bartsch, A J Mueller, Alay S Banker, Robert N WeinrebAbstract:Background Fluorescein and indocyanine green (ICG) angiography are both useful in the diagnosis and treatment of many retinal diseases. In some cases, both tests must be performed for diagnosis and treatment; however, performing both is time-consuming and may require multiple injections. Methods We designed a compact digital confocal Scanning Laser Ophthalmoscope to perform true simultaneous fluorescein and ICG angiography. We report our experience using the instrument to perform 169 angiograms in 117 patients. Results There were no unexpected adverse effects from mixing the dyes and administering them in 1 injection. An entire examination, including fundus photography, fluorescein angiography, and ICG angiography, could be performed in 45 minutes. It was possible to study differences in fluorescein patterns by comparing identically timed frames and to find cases in which ICG or fluorescein was optimal in visualizing retinal and subretinal structures. Confocal optical sections in the depth (z) dimension allowed viewing in different planes. It was possible to overlay ICG and fluorescein images or compare them side-by-side using a linked cursor. Digital transmission of the images was also performed. Conclusions Simultaneous ICG and fluorescein angiography can be performed rapidly, safely, and conveniently. The availability of simultaneous angiography will allow critical determination of the relative advantages and disadvantages of both types of angiography.
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confocal Scanning infrared Laser ophthalmoscopy for indocyanine green angiography
American Journal of Ophthalmology, 1995Co-Authors: D Bartsch, Robert N Weinreb, Gerhard Zinser, William R FreemanAbstract:Purpose We used indocyanine green to study wavelength-optimized confocal Scanning infrared Laser angiography in patients with retinal and choroidal disease. Methods A confocal Scanning Laser Ophthalmoscope with an excitation wavelength of 795 nm was operated both in tight and wide confocal imaging modes. We examined 77 subjects with and without retinal and choroidal disease (including diabetic retinopathy, age-related macular degeneration, and subretinal neovascularization). Results The Scanning Laser Ophthalmoscope allowed acquisition of images, in the wide confocal imaging mode, of the retinal circulation and late leakage sites without late injections of dye to outline the retinal vasculature. In the tight confocal imaging mode, optical subtraction of the light contribution of the retinal circulation allowed examination of the choroidal circulation, and vice versa. The wide confocal mode appears equivalent to other Scanning Laser Ophthalmoscopes in recording images from retinal and choroidal layers. Conclusions There are three differences between the confocal Scanning Laser Ophthalmoscope and conventional instruments. First, the late images allow excellent visualization of the retinal circulation without a landmark injection. Second, confocal imaging allows optical subtraction of retinal circulation when focusing on the choroid and vice versa. Third, the instrument acquires and processes all data digitally, is personal computer-based, is compact, operates with a mouse-driven graphical user interface, and allows easy data exchange with conventional software. With further modifications in software and hardware, this device offers the possibility of producing a three-dimensional map of the retinal and choroidal vasculature.
Frank G. Holz - One of the best experts on this subject based on the ideXlab platform.
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atlas of fundus autofluorescence imaging
2007Co-Authors: Frank G. Holz, Richard F Spaide, Steffen SchmitzvalckenbergAbstract:Methodology.- Lipofuscin of the Retinal Pigment Epithelium.- Origin of Fundus Autofluorescence.- Fundus Autofluorescence Imaging with the Confocal Scanning Laser Ophthalmoscope.- How To Obtain the Optimal Fundus Autofluorescence Image with the Confocal Scanning Laser Ophthalmoscope.- Autofluorescence Imaging with the Fundus Camera.- Macular Pigment Measurement-Theoretical Background.- Macular Pigment Measurement -Clinical Applications.- Evaluation of Fundus Autofluorescence Images.- Clinical Application.- Macular and Retinal Dystrophies.- Discrete Lines of Increased Fundus Autofluorescence in Various Forms of Retinal Dystrophies.- Age-Related Macular Degeneration I-Early Manifestation.- Age-Related Macular Degeneration II-Geographic Atrophy.- Age-Related Macular Degeneration III-Pigment Epithelium Detachment.- Age-Related Macular Degeneration IV-Choroidal Neovascularization (CNV).- Idiopathic Macular Telangiectasia.- Chorioretinal Inflammatory Disorders.- Autofluorescence from the Outer Retina and Subretinal Space.- Miscellaneous.- Perspectives in Imaging Technologies.- Perspectives in Imaging Technologies.
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digital simultaneous fluorescein and indocyanine green angiography autofluorescence and red free imaging with a solid state Laser based confocal Scanning Laser Ophthalmoscope
Retina-the Journal of Retinal and Vitreous Diseases, 2005Co-Authors: J J Jorzik, A Bindewald, Stefan Dithmar, Frank G. HolzAbstract:Purpose: To describe and to evaluate a novel confocal Scanning Laser Ophthalmoscope (cSLO) for fluorescence angiography, fundus autofluorescence (FAF), and red-free imaging. Methods: Digital infrared, red-free, FAF, fluorescein, and indocyanine green (ICG) angiography images were obtained with a cSLO in 766 patients. An optically pumped solid-state Laser generates the excitation wavelength (488 nm) required for red-free, FAF, and fluorescein angiography images. For ICG angiography and infrared imaging, diode Laser sources at 790 and 820 nm are used. Further features include an internal fixation control and a focus range of −24 to +30 diopters. Results: High-image quality is achieved with a resolution of up to 5 μm per pixel in 30- x 30-degree images and allows for accurate delineation of normal and pathologic features. Simultaneous angiography offers high-contrast images. Corresponding display of quasi-simultaneous frames facilitates interpretation. A small focus difference between fluorescein and ICG scans occurs because of chromatic aberrations. Automated alignment and generation of mean images from several single frames allow for acquisition of high-resolution FAF images. Conclusion: Various Laser-source related, optical, and electronic innovations improve cSLO fundus imaging for routine clinical application. A solid-state Laser has advantages compared to argon gas Laser sources, including less space occupation, heat emission, and noise production.
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visualization of retinal pigment epithelial cells in vivo using digital high resolution confocal Scanning Laser ophthalmoscopy
American Journal of Ophthalmology, 2004Co-Authors: A Bindewald, J J Jorzik, Annette Loesch, F Schutt, Frank G. HolzAbstract:Abstract Purpose To visualize retinal pigment epithelial cells in vivo by fundus autofluorescence imaging using a confocal Scanning Laser Ophthalmoscope. Design Experimental study and observational case report. Methods Digital in vivo autofluorescence images were recorded with a confocal Scanning Laser Ophthalmoscope (excitation, 488 nm; emission, >500 nm) and compared with confocal Scanning Laser Ophthalmoscope and fluorescence microscopic recordings from human donor eyes. Results A uniform pattern of the polygonal retinal pigment epithelial cell layer was visualized in vivo outside of absorbing retinal vessels and macular pigment. Autofluorescence intensities of individual cells showed marked variation. The pattern corresponded to in vitro findings. Visualization is based on the topographic distribution of autofluorescent lipofuscin granules and melanin granules in apical retinal pigment epithelium cytoplasm. Conclusions High-resolution autofluorescence imaging may be useful to determine morphologic and lipofuscin-dependent alterations in retinal diseases and may be applicable for monitoring effects of therapeutic interventions targeting the retinal pigment epithelium.
Robert N Weinreb - One of the best experts on this subject based on the ideXlab platform.
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predicting glaucomatous progression in glaucoma suspect eyes using relevance vector machine classifiers for combined structural and functional measurements
Investigative Ophthalmology & Visual Science, 2012Co-Authors: Christopher Bowd, Linda M Zangwill, Christopher A Girkin, Intae Lee, Michael H Goldbaum, Madhusudhanan Balasubramanian, Felipe A Medeiros, Jeffrey M Liebmann, Robert N WeinrebAbstract:Purpose. The goal of this study was to determine if glaucomatous progression in suspect eyes can be predicted from baseline confocal Scanning Laser Ophthalmoscope (CSLO) and standard automated perimetry (SAP) measurements analyzed with relevance vector machine (RVM) classifiers.
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simultaneous indocyanine green and fluorescein angiography using a confocal Scanning Laser Ophthalmoscope
Archives of Ophthalmology, 1998Co-Authors: William R Freeman, Dirkuwe Bartsch, A J Mueller, Alay S Banker, Robert N WeinrebAbstract:Background Fluorescein and indocyanine green (ICG) angiography are both useful in the diagnosis and treatment of many retinal diseases. In some cases, both tests must be performed for diagnosis and treatment; however, performing both is time-consuming and may require multiple injections. Methods We designed a compact digital confocal Scanning Laser Ophthalmoscope to perform true simultaneous fluorescein and ICG angiography. We report our experience using the instrument to perform 169 angiograms in 117 patients. Results There were no unexpected adverse effects from mixing the dyes and administering them in 1 injection. An entire examination, including fundus photography, fluorescein angiography, and ICG angiography, could be performed in 45 minutes. It was possible to study differences in fluorescein patterns by comparing identically timed frames and to find cases in which ICG or fluorescein was optimal in visualizing retinal and subretinal structures. Confocal optical sections in the depth (z) dimension allowed viewing in different planes. It was possible to overlay ICG and fluorescein images or compare them side-by-side using a linked cursor. Digital transmission of the images was also performed. Conclusions Simultaneous ICG and fluorescein angiography can be performed rapidly, safely, and conveniently. The availability of simultaneous angiography will allow critical determination of the relative advantages and disadvantages of both types of angiography.
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confocal Scanning infrared Laser ophthalmoscopy for indocyanine green angiography
American Journal of Ophthalmology, 1995Co-Authors: D Bartsch, Robert N Weinreb, Gerhard Zinser, William R FreemanAbstract:Purpose We used indocyanine green to study wavelength-optimized confocal Scanning infrared Laser angiography in patients with retinal and choroidal disease. Methods A confocal Scanning Laser Ophthalmoscope with an excitation wavelength of 795 nm was operated both in tight and wide confocal imaging modes. We examined 77 subjects with and without retinal and choroidal disease (including diabetic retinopathy, age-related macular degeneration, and subretinal neovascularization). Results The Scanning Laser Ophthalmoscope allowed acquisition of images, in the wide confocal imaging mode, of the retinal circulation and late leakage sites without late injections of dye to outline the retinal vasculature. In the tight confocal imaging mode, optical subtraction of the light contribution of the retinal circulation allowed examination of the choroidal circulation, and vice versa. The wide confocal mode appears equivalent to other Scanning Laser Ophthalmoscopes in recording images from retinal and choroidal layers. Conclusions There are three differences between the confocal Scanning Laser Ophthalmoscope and conventional instruments. First, the late images allow excellent visualization of the retinal circulation without a landmark injection. Second, confocal imaging allows optical subtraction of retinal circulation when focusing on the choroid and vice versa. Third, the instrument acquires and processes all data digitally, is personal computer-based, is compact, operates with a mouse-driven graphical user interface, and allows easy data exchange with conventional software. With further modifications in software and hardware, this device offers the possibility of producing a three-dimensional map of the retinal and choroidal vasculature.
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agreement between clinicians and a confocal Scanning Laser Ophthalmoscope in estimating cup disk ratios
American Journal of Ophthalmology, 1995Co-Authors: Linda M Zangwill, Sima Shakiba, Joseph Caprioli, Robert N WeinrebAbstract:Purpose We assessed agreement between cup/disk ratio measurements obtained by glaucoma expert evaluation of stereoscopic photographs of the optic disk and those obtained with a confocal Scanning Laser Ophthalmoscope. Methods Three glaucoma experts estimated vertical and horizontal cup/disk ratios from stereoscopic photographs of 15 normal subjects and 15 patients with glaucoma. These estimates were compared to vertical, horizontal, and area cup/disk ratios measured with a confocal Scanning Laser Ophthalmoscope. Intraobserver and interobserver agreements were also estimated. Results Agreement between clinicians and the confocal Scanning Laser Ophthalmoscope varied by clinician. Agreement was moderate to substantial for vertical cup/disk ratio and fair to moderate for horizontal cup/disk ratio; kappas ranged from 0.57 to 0.72 and from 0.21 to 0.55, respectively. The mean confocal Scanning Laser Ophthalmoscope area cup/disk ratio measurements were smaller than each clinician's mean vertical and horizontal cup/disk ratio estimates; differences ranged from 0.10 to 0.24 and from 0.06 to 0.16, respectively. Differences were smaller between clinician estimates and instrument measurements of horizontal and vertical cup/disk ratios of patients with glaucoma than normal subjects. Conclusions These results demonstrate good agreement between confocal Scanning Laser Ophthalmoscope measurements and clinician estimates of the vertical cup/disk ratios from stereoscopic photographs, particularly of patients with glaucoma. However, as differences between clinician and instrument estimates of cup/disk ratios were found, new quantitative criteria must be established for characterizing a disk as glaucomatous using confocal Scanning Laser ophthalmoscopy.
Daniel X Hammer - One of the best experts on this subject based on the ideXlab platform.
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Tracking adaptive optics Scanning Laser Ophthalmoscope
2020Co-Authors: Daniel R Ferguson, Daniel X Hammer, Chad E Bigelow, Nicusor Iftimia, Teoman E Ustun, Ann E. Elsner, Stephen A. Burns, David R WilliamsAbstract:ABSTRACT Active image stabilization for an adaptive optics Scanning Laser Ophthalmoscope (AOSLO) was developed and tested in human subjects. The tracking device, a high speed, closed-loop optical servo which uses retinal features as tracking target, is separate from AOSLO optical path. The tracking system and AOSLO beams are combined via a dichroic beam splitter in front of the eye. The primary tracking system galvanometer mirrors follow the motion of the eye. The AOSLO raster is stabilized by a secondary set of galvanometer mirrors in the AOSLO optical train which are "slaved" to the primary mirrors with fixed scaling factors to match the angular gains of the optical systems. The AO system (at 830 nm) uses a MEMS-based deformable mirror (Boston Micromachines Inc.) for wave-front correction. The third generation retinal tracking system achieves a bandwidth of greater than 1 kHz allowing acquisition of stabilized AO images with an accuracy of <10 µm. However, such high tracking bandwidth, required for tracking saccades, results in finite tracking position noise which is evident in AOSLO images. By means of filtering algorithms, the AOSLO raster is made to follow the eye accurately with reduced tracking noise artifacts. The system design includes simultaneous presentation of non-AO, wide-field (~40 deg) live reference image captured with a line Scanning Laser Ophthalmoscope (LSLO) typically operating from 900 to 940 nm. High-magnification (1-2 deg) AOSLO retinal scans easily positioned on the retina in a drag-and-drop manner. Normal adult human volunteers were tested to optimize the tracking instrumentation and to characterize AOSLO imaging performance. Automatic blink detection and tracking re-lock, enabling reacquisition without operator intervention, were also tested. The tracking-enhanced AOSLO may become a useful tool for eye research and for early detection and treatment of retinal diseases
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Tracking Scanning Laser Ophthalmoscope (TSLO)
2020Co-Authors: Daniel X Hammer, Daniel R Ferguson, Ann E. Elsner, John C Magill, Michael A White, R.h. WebbAbstract:ABSTRACT The effectiveness of image stabilization with a retinal tracker in a multi-function, compact Scanning Laser Ophthalmoscope (TSLO) was demonstrated in initial human subject tests. The retinal tracking system uses a confocal reflectometer with a closed loop optical servo system to lock onto features in the fundus. The system is modular to allow configuration for many research and clinical applications, including hyperspectral imaging, multifocal electroretinography (MFERG), perimetry, quantification of macular and photo-pigmentation, imaging of neovascularization and other subretinal structures (drusen, hyper-, and hypo-pigmentation), and endogenous fluorescence imaging. Optical hardware features include dual wavelength imaging and detection, integrated monochromator, higher-order motion control, and a stimulus source. The system software consists of a real-time feedback control algorithm and a user interface. Software enhancements include automatic bias correction, asymmetric feature tracking, image averaging, automatic track re-lock, and acquisition and logging of uncompressed images and video files. Normal adult subjects were tested without mydriasis to optimize the tracking instrumentation and to characterize imaging performance. The retinal tracking system achieves a bandwidth of greater than 1 kHz, which permits tracking at rates that greatly exceed the maximum rate of motion of the human eye. The TSLO stabilized images in all test subjects during ordinary saccades up to 500 deg/sec with an inter-frame accuracy better than 0.05 deg. Feature lock was maintained for minutes despite subject eye blinking. Successful frame averaging allowed image acquisition with decreased noise in low-light applications. The retinal tracking system significantly enhances the imaging capabilities of the Scanning Laser Ophthalmoscope
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adaptive optics Scanning Laser Ophthalmoscope with integrated wide field retinal imaging and tracking
Journal of The Optical Society of America A-optics Image Science and Vision, 2010Co-Authors: Daniel R Ferguson, Daniel X Hammer, Mircea Mujat, Zhangyi Zhong, Ankit H Patel, Cong Deng, Stephen A. BurnsAbstract:We have developed a new, unified implementation of the adaptive optics Scanning Laser Ophthalmoscope (AOSLO) incorporating a wide-field line-Scanning Ophthalmoscope (LSO) and a closed-loop optical retinal tracker. AOSLO raster scans are deflected by the integrated tracking mirrors so that direct AOSLO stabilization is automatic during tracking. The wide-field imager and large-spherical-mirror optical interface design, as well as a large-stroke deformable mirror (DM), enable the AOSLO image field to be corrected at any retinal coordinates of interest in a field of >25 deg. AO performance was assessed by imaging individuals with a range of refractive errors. In most subjects, image contrast was measurable at spatial frequencies close to the diffraction limit. Closed-loop optical (hardware) tracking performance was assessed by comparing sequential image series with and without stabilization. Though usually better than 10 μm rms, or 0.03 deg, tracking does not yet stabilize to single cone precision but significantly improves average image quality and increases the number of frames that can be successfully aligned by software-based post-processing methods. The new optical interface allows the high-resolution imaging field to be placed anywhere within the wide field without requiring the subject to re-fixate, enabling easier retinal navigation and faster, more efficient AOSLO montage capture and stitching.
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compact adaptive optics line Scanning Laser Ophthalmoscope
Progress in biomedical optics and imaging, 2009Co-Authors: Daniel X Hammer, Nicusor Iftimia, Mircea Mujat, Daniel R FergusonAbstract:We have developed a compact retinal imager that integrates adaptive optics (AO) into a line Scanning Laser Ophthalmoscope (LSLO). The bench-top AO-LSLO instrument significantly reduces the size, complexity, and cost of research AOSLOs, for the purpose of moving adaptive optics imaging more rapidly into routine clinical use. The AO-LSLO produces high resolution retinal images with only one moving part and a significantly reduced instrument footprint and number of optical components. The AO-LSLO has a moderate field of view (5.5 deg), which allows montages of the macula or other targets to be obtained more quickly and efficiently. In a preliminary human subjects investigation, photoreceptors could be resolved and counted within ~0.5 mm of the fovea. Photoreceptor counts matched closely to previously reported histology. The capillaries surrounding the foveal avascular zone could be resolved, as well as cells flowing within them. Individual nerve fiber bundles could be resolved, especially near the optic nerve head, as well as other structures such as the lamina cribrosa. In addition to instrument design, fabrication, and testing, software algorithms were developed for automated image registration, cone counting, and montage stitching.
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line Scanning Laser Ophthalmoscope
Journal of Biomedical Optics, 2006Co-Authors: Daniel X Hammer, Daniel R Ferguson, Chad E Bigelow, Nicusor Iftimia, Teoman E Ustun, R.h. WebbAbstract:Scanning Laser ophthalmoscopy (SLO) is a powerful imaging tool with specialized applications limited to research and ophthalmology clinics due in part to instrument size, cost, and complexity. Conversely, low-cost retinal imaging devices have limited capabilities in screening, detection, and diagnosis of diseases. To fill the niche between these two, a hand-held, nonmydriatic line-Scanning Laser Ophthalmoscope (LSLO) is designed, constructed, and tested on normal human subjects. The LSLO has only one moving part and uses a novel optical approach to produce wide-field confocal fundus images. Imaging modes include multiwavelength illumination and live stereoscopic imaging with a split aperture. Image processing and display functions are controlled with two stacked prototype compact printed circuit boards. With near shot-noise limited performance, the digital LSLO camera requires low illumination power (<500 microW) at near-infrared wavelengths. The line-Scanning principle of operation is examined in comparison to SLO and other imaging modes. The line-Scanning approach produces high-contrast confocal images with nearly the same performance as a flying-spot SLO. The LSLO may significantly enhance SLO utility for routine use by ophthalmologists, optometrists, general practitioners, and also emergency medical personnel and technicians in the field for retinal disease detection and other diverse applications.
