James Werner

Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combining these imaging modalities. We present an ex vivo OCT microscope combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. The combined instrument will be used to investigate remaining technical challenges to combine these imaging modalities, such as the laser power levels needed to achieve a Raman signal above the noise level without damaging the sample. © 2009.

A design for a high-resolution scanning instrument is presented for in vivo imaging of the human eye at the cellular scale. This system combines adaptive optics technology with a scanning laser ophthalmoscope to image structures with high lateral resolution. In this system, the ocular wavefront aberrations that reduce the resolution of conventional SLOs are detected by a Hartmann-Shack wavefront sensor, and compensated with two deformable mirrors in a closed-loop for dynamic correction and feedback control. A laser beam is scanned across the retina and the reflected light is captured by a photodiode, yielding a two-dimensional image of the retina at any depth. The quantity of back-scattered light from the retina is small and requires the elimination of all parasite reflections. As an in vivo measurement, faint cellular reflections must be detected with a low-energy source, a supraluminescent laser diode, and with brief exposures to avoid artifacts from eye movements. The current design attempts to optimize trade-offs between improved wavefront measurement and compensation of the optical aberrations by fractioning the light coming to the wavefront sensor, better sensitivity by increasing the input light energy or the exposure time and the response speed of the system. This instrument design is expected to provide sufficient resolution for visualizing photoreceptors and ganglion cells, and therefore, may be useful in diagnosing and monitoring the progression of retinal pathologies such as glaucoma or aged-related macular degeneration.

Objectives: To elucidate the visual significance of the foveal pit by measuring foveal architecture and function and to reassess use of the term foveal hypoplasia. Methods: We describe 4 patients who lack a foveal pit. Visual acuities ranged from 20/20 to 20/50. Stratus and Cirrus optical coherence tomographs and multifocal electroretinograms were obtained. High-resolution retinal imaging on 2 of the participants was obtained by using a high-resolution Fourier-domain OCT and an adaptive optics flood-illuminated fundus camera. Results: No participants had a visible foveal pit with conventional OCT. Central widening of the outer nuclear layer and lengthening of cone outer segments were seen with high-resolution Fourier-domain OCT. Adaptive optics imaging showed normal cone diameters in the central 1° to 2°. Central multifocal electroretinogram responses were normal. Conclusions: We show that a foveal pit is not required for foveal cone specialization, anatomically or functionally. This helps to explain the potential for good acuity in the absence of a pit and raises questions about the visual role of the foveal pit. Because the term foveal hypoplasia commonly carries a negative functional implication, it may be more proper to call the anatomic lack of a pit fovea plana. ©2008 American Medical Association. All rights reserved.

We describe results of retinal imaging with a novel instrument that combines adaptive optics - Fourier-domain optical coherence tomography with an adaptive optics scanning laser ophthalmoscope. One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between the two imaging modalities and the potential for correcting lateral and transversal eye motion resulting in motion artifact-free volumetric retinal imaging. Additionally this allows for direct comparison between retinal structures that can be imaged with both modalities. This dual imaging modality could provide insight into some retinal properties that could not be accessed by a single imaging system. Additionally, extension of OCT and SLO beyond structural imaging may open new avenues for diagnostics and testing in ophthalmology. In particular, non-invasive vasculature mapping with these modalities holds promise of replacing fluorescein angiography in vascular identification. Several new improvements of our system are described, including results of testing a novel 97-actuator deformable mirror and AO-SLO light intensity modulation. © 2010 SPIE.

Ultra-high isotropic resolution imaging of retinal structures was made possible with an adaptive optics system using dual deformable mirrors and a Fourier-domain optical coherence tomography system with correction for longitudinal chromatic aberration. This system was used to image microscopic retinal structures of healthy as well as diseased retinas in vivo. The improved resolution and contrast enhanced visualization of morphological structures in the retina can be clearly seen. The benefits of this instrument are apparent from comparison of new images with those acquired using a previous generation AO-OCT instrument. Big change in the appearance of speckle field can be observed as well. Additionally, further improvements in volumetric data acquisition and image representation will be discussed. This includes creation of large Field of View AO-OCT volume from multiple sub-volumes and its visualization. Also techniques and results of reducing speckle contrast by averaging multiple B-scans will be presented.

PURPOSE. To investigate the use of high-resolution Fourierdomain optical coherence tomography to image choroidal neovascular membranes associated with exudative age-related macular degeneration. METHODS. An Fd-OCT instrument with axial resolution of 4 to 4.5 μm and transverse resolution of 10 to 15 μm was used to image 21 eyes with newly diagnosed eAMD. A raster series of 100 B-scans separated by 60 μm was used to study the growth pattern of CNVM and associated morphologic changes. CNVM size was determined using 250 to 300 serial virtual C-scans of reconstructed three-dimensional macular volume. RESULTS. A highly reflective subretinal and/or subretinal pigment epithelial lesion that co-localized with the CNVM seen on fluorescein angiography was detected in all eyes by Fd-OCT. Although a combined subretinal and sub-RPE growth pattern of various degrees was noted in 15 eyes, a statistically significant difference in the distribution of growth pattern was noted when classic CNVM was compared with occult CNVM. CONCLUSIONS. Fd-OCT is a promising potential alternative modality to visualize CNVM with AMD. Angiographic lesion size and type correlated with growth pattern and size of CNVM on Fd-OCT, with correlation being stronger for classic lesions. © Association for Research in Vision and Ophthalmology.

We describe a novel instrument that combines adaptive optics - Fourier-domain optical coherence tomography with an adaptive optics scanning laser ophthalmoscope. Both systems share a common AO sub-system and vertical scanner to permit simultaneous acquisition of retinal images from both OCT and SLO. One of the benefits of combining OCT with SLO includes automatic co-registration between the two imaging modalities and potential for correcting lateral and transversal eye motion resulting in motion artifact-free volumetric retinal imaging. Results of using this system for eye model imaging are presented. Feasibility for clinical application is briefly discussed as well as potential further improvements of the current system. © 2009 SPIE.

Objective: To evaluate the morphologic changes in the macula of subjects with repaired macula-off retinal detachment using high-resolution Fourier-domain optical coherence tomography and to perform functional correlation in a subset of patients using microperimetry. Design: Prospective observational case series. Participants: Seventeen eyes from 17 subjects who had undergone anatomically successful repair for macula-off, rhegmatogenous RD at least 3 months earlier and without visually significant maculopathy on funduscopy. Methods: FD OCT with axial and transverse resolution of 4.5 μm and 10 to 15 μm, respectively, was used to obtain rapid serial B-scans of the macula, which were compared with that from Stratus OCT. The FD OCT B-scans were used to create a 3-dimensional volume, from which en face C-scans were created. Among 11 patients, MP-1 was performed to correlate morphologic changes with visual function. Main Outcome Measures: Stratus OCT scans, FD OCT scans, and MP-1 data. Results: Stratus OCT and FD OCT images of the macula were obtained 3 to 30 months postoperatively in all eyes. Although Stratus OCT revealed photoreceptor disruption in 2 eyes, FD OCT showed photoreceptor disruption in 13 eyes. This difference was statistically significant. Both imaging modalities revealed persistent subretinal fluid in 2 eyes and lamellar hole in 1 eye. Among 7 subjects who had reliable MP-1 data, areas of abnormal function corresponded to areas of photoreceptor layer disruptions or persistent subretinal fluid in 5 subjects ; one subject had normal FD OCT and MP-1. Conclusions: Photoreceptor disruption after macula-off RD repair is a common abnormality in the macula that is detected better with FD OCT than Stratus OCT. A good correlation between MP-1 abnormality and presence of photoreceptor disruption or subretinal fluid on FD OCT demonstrates that these anatomic abnormalities contribute to decreased visual function after successful repair. Financial Disclosure: The authors have no proprietary or commercial interest in any materials discussed in this article. © 2008 American Academy of Ophthalmology.

The hypothesis that dichromatic behavior on a clinical anomaloscope can be explained by the complement and arrangement of the long- and middle-wavelength pigment genes was tested. It was predicted that dichromacy is associated with an X-chromosome pigment gene array capable of producing only a single functional pigment type. The simplest case of this is when deletion has left only a single X-chromosome pigment gene. The production of a single L or M pigment type can also result from rearrangements in which multiple genes remain. Often, only the two genes at the 5′ end of the array are expressed; thus, dichromacy is also predicted to occur if one of these is defective or encodes a defective pigment, or if both of them encode pigments with identical spectral sensitivities. Subjects were 128 males who accepted the full range of admixtures of the two primary lights as matching the comparison light on a Neitz or Nagel anomaloscope. Strikingly, examination of the L and M pigment genes revealed a potential cause for a color-vision defect in all 128 dichromats. This indicates that the major component of color-vision deficiency could be attributed to alterations of the pigment genes or their regulatory regions in all cases, and the variety of gene arrangements associated with dichromacy is cataloged here. However, a fraction of the dichromats had genes predicted to encode pigments that would result in two populations of cones with different spectral sensitivities. Nine of the 17 were predicted to have two pigments with slightly different spectral peaks and eight had genes which specified pigments identical in peak absorption, but different in amino acid positions previously associated with optical density differences. In other subjects, reported previously, the same small spectral differences were associated with anomalous trichromacy rather than dichromacy. It appears that when the spectral difference specified by the genes is very small, the amount of residual red-green color vision measured varies; some individuals test as dichromats, others test as anomalous trichromats. The discrepancy is probably partly attributable to testing method differences and partly to a difference in performance not perception, but it seems there must also be cases in which other factors, for example, cone ratio, contribute to a person's ability to extract a color signal from a small spectral difference.

Recent developments in adaptive optics - optical coherence tomography allow for ultra-high isotropic resolution imaging of the in-vivo retina, offering unprecedented insight into its volumetric microscopic and cellular structures. In addition to this promising achievement, the clinical impact and application of this technology still needs to be explored. This includes assessment of limitations and challenges for existing as well as future AO-OCT systems, especially in the context of potential transfer of this technology from an optical bench to a portable imaging system. To address these issues we will describe our current AO-UHR-OCT focusing on its sub-components, as well as application for clinical imaging. Additionally, we describe some directions for future development of our AO-OCT instrument that would improve its clinical utility including: new compact AO-OCT design, new improved AO sub-system, and new generations of Fourier-domain-OCT. © 2008 SPIE.

Purpose: To describe maculopathy diagnosed with high-resolution Fourier-domain optical coherence tomography among eyes with previously unexplained visual loss. Methods: Nine eyes from six patients with previously unexplained vision loss based on funduscopy, fluorescein angiography, and Stratus optical coherence tomography and 32 eyes from 25 asymptomatic age-matched control subjects were imaged with a Fourierdomain optical coherence tomography instrument with axial resolution of 4 mm to 4.5 mm and transverse resolution of 10 mm to 15 mm. Results: Among eyes with unexplained vision loss, visual acuity ranged from 20/20 to 20/80 and central scotoma was noted in all eyes by microperimetry or Amsler grid. Fourierdomain optical coherence tomography showed abnormality in the foveal photoreceptor layer in six eyes from four subjects. These abnormalities include focal loss of the PR layer with microcystoid changes in the macula, focal discontinuity of the PR layer, and focal elevation and blurring of the PR layer associated with a mild epiretinal membrane. Among age-matched control eyes, no foveal PR abnormality was seen. Conclusion: Fourier-domain optical coherence tomography detected subtle changes in the foveal PR layer in some eyes with vision loss and central scotoma unexplained with routine clinical diagnostic tests. © by Ophthalmic Communications Society, Inc.

Background: Our lab has previously demonstrated losses in contrast sensitivity to low spatial frequencies under scotopic conditions with older adults. It is not clear, however, whether the temporal frequency of a stimulus alters the relation between age and the spatial contrast sensitivity function under scotopic conditions. Methods: A maximum-likelihood, two-alternative, temporal forced-choice QUEST procedure was used to measure threshold to spatially and temporally modulated stimuli in both young and old adults. Results: In general, the shapes of the spatial and temporal CSFs were low-pass for both young and old observers; contrast sensitivity decreased at approximately the same rate with increasing spatial frequency and temporal frequency for both age groups, although the overall sensitivity of the old group was lower than that of the young group. The high-frequency resolution limit was lower for the old group compared to the young group. Conclusions: The differences in contrast sensitivity between the young and old groups suggest a uniform loss in sensitivity of the channels mediating spatial and temporal vision. Because of this loss, the spatial and temporal window of visibility for the older adults is compromised relative to the younger adults. © 2010 The Authors. Journal compilation © 2010 The College of Optometrists.

The purpose of this study was to evaluate the performance of a bimorph deformable mirror from AOptix, inserted into an adaptive optics system designed for in-vivo retinal imaging at high resolution. We wanted to determine its suitability as a wavefront corrector for vision science and ophthalmological instrumentation. We presented results obtained in a closed-loop system, and compared them with previous open-loop performance measurements. Our goal was to obtain precise wavefront reconstruction with rapid convergence of the control algorithm. The quality of the reconstruction was expressed in terms of root-mean-squared wavefront residual error, and number of frames required to perform compensation. Our instrument used a Hartmann-Shack sensor for the wavefront measurements. We also determined the precision and ability of the deformable mirror to compensate the most common types of aberrations present in the human eye, and the quality of its correction, in terms of maximum amplitude of the corrected wavefront. In addition to wavefront correction, we had also used the closed-loop system to generate an arbitrary aberration pattern by entering the desired Hartmann-Shack centroid locations as input to the AO controller. These centroid locations were computed in Matlab for a user-defined aberration pattern, allowing us to test the ability of the DM to generate and compensate for various aberrations. We conclude that this device, in combination with another DM based on Micro-Electro Mechanical Systems technology, may provide better compensation of the higher-order ocular wavefront aberrations of the human eye.

The static and dynamic characteristics of a bimorph deformable mirror for use in an adaptive optics system are described. The DM is a 35-actuator device composed of two disks of lead magnesium niobate, an electrostrictive ceramic that produces a mechanical strain in response to an imposed electric field. A custom stroboscopic phase-shifting interferometer was developed to measure the deformation of the mirror in response to applied voltage. The ability of the mirror to replicate optical aberrations described by the Zernike polynomials was tested as a measure of the mirror's static performance. The natural frequencies of the DM were measured up to 20 kHz using both stroboscopic interferometry as well as a commercial laser Doppler vibrometer. Interferometric measurements of the DM surface profile were analyzed by fitting the surface with mode-shapes predicted using classical plate theory for an elastically supported disk. The measured natural frequencies were found to be in good agreement with the predictions of the theoretical model. © 2006 Elsevier B.V. All rights reserved.

This paper reports the results of interferometric characterization of a bimorph deformable mirror designed for use in an adaptive optics system. The natural frequencies of this DM were measured up to 20 kHz using both a custom stroboscopic phase-shifting interferometer as well as a commercial Laser Doppler Vibrometer. Interferometric measurements of the DM surface profile were analyzed by fitting the surface with mode-shapes predicted using classical plate theory for an elastically-supported disk. The measured natural frequencies were found to be in good agreement with the predictions of the theoretical model. Copyright © 2005 by ASME.

The wave front corrector is one of the three key elements in adaptive optics, along with the wave front sensor and the control computer. Low cost, compact deformable mirrors are increasingly available. We have tested the AOptix bimorph deformable mirror, originally developed for ultra-high bandwidth laser communication systems, to determine its suitability for vision science applications, where cornea and lens introduce optical aberrations. Measurements of the dynamic response of the mirror to a step input were obtained using a commercial Laser Doppler Vibrometer. A computer-controlled Twyman-Green interferometer was constructed to allow the surface height of the deformable mirror to be measured using Phase-Shifting Interferometry as a function of various control voltages. A simple open-loop control method was used to compute the control voltages required to generate aberration mode shapes described by the Zernike polynomials. Using this method, the ability of the deformable mirror to generate each mode shape was characterized by measuring the maximum amplitude and RMS error of each Zernike mode shape up to the fifth radial order. The maximum deformation amplitude was found to diminish with the square of the radial order of the Zernike mode, with a measured deformation of 8 microns and 1.5 microns achieved at the second-order and fifth-order Zernike modes, respectively. This deformation amplitude appears to be sufficient to allow the mirror to correct for aberrations up to the fifth order in the human eye.

When a dark chromatic contour delineating a figure is flanked on the inside by a brighter chromatic contour, the brighter color will spread into the entire enclosed area. This is known as the watercolor effect. Here we quantified the effect of color spreading using both color-matching and hue-cancellation tasks. Over a wide range of stimulus chromaticities, there was a reliable shift in color appearance that closely followed the direction of the inducing contour. When the contours were equated in luminance, the WCE was still present, but weak. The magnitude of the color spreading increased with increases in luminance contrast between the two contours. Additionally, as the luminance contrast between the contours increased, the chromaticity of the induced color more closely resembled that of the inside contour. The results support the hypothesis that the WCE is mediated by luminance-dependent mechanisms of long-range color assimilation. © 2005 Elsevier Ltd. All rights reserved.

A new visual phenomenon that we call flashing anomalous color contrast is described. This phenomenon arises from the interaction between a gray central disk and a chromatic annulus surrounded by black radial lines. In an array of such figures, the central gray disk no longer appears gray, but assumes a color complementary to that of the surrounding annulus. The induced color appears: vivid and saturated; self-luminous, not a surface property; flashing with eye or stimulus movement; floating out of its confines; and stronger in extrafoveal than in foveal vision. The strength of the effect depends on the number, length, width, and luminance contrast of the radial lines. The results suggest that the chromatic ring bounding the inner tips of the black radial lines induces simultaneous color contrast, whereas the radial lines elicit, in conjunction with the gray disk and the ring, the flashing, vividness, and high saturation of the effect. The stimulus properties inducing the illusion suggest that flashing anomalous color contrast may be based on asynchronous interactions among multiple visual pathways.

An impulse response function to a luminous pulse was derived for 70 normal observers ranging in age from 16 to 86 years. Thresholds were measured for two pulses separated by interstimulus intervals from 6.7 to 180 ms. The pulses had a spatial Gaussian shape and were presented as increments on a 10 cd/m2 background, having the same chromaticity as the pulse. A spatial 4-alternative forced-choice method was combined with a staircase procedure. Retinal illuminance was equated individually by heterochromatic flicker photometry and control of pupil area. Each IRF was measured four times, in separate sessions, for each observer. IRFs calculated from the threshold data revealed significant age-related changes in the response amplitude of both excitatory and inhibitory phases. In general, there were no significant changes in the time to the first peak or in the first zero crossing. For 12 of 20 observers over 60 years of age, however, the amplitude of the second phase was reduced relative to the excitatory phase so their IRFs were quite slow and long. Control conditions with three pseudophakic observers and two normal observers with induced blur demonstrated that age-related changes in the IRF under these conditions cannot be ascribed to optical factors. The data suggest that the human visual system generally maintains a stable speed of response to a flash until at least about 80 years of age, even while there are senescent reductions in response signal amplitude. © 2003 Elsevier Science Ltd. All rights reserved.