Austin Roorda - US grants

DESCRIPTION: In healthy normal subjects, the primary resolution limiting factors to retinal fundus imaging are the aberrations caused by the eyes' own optics. The applicant was among a team of investigators at the University of Rochester that first demonstrated that these aberrations could be measured with a Shack Hartman wavefront sensor and cancelled using a deformable mirror in a process called adaptive optics (AO). The applicant has now obtained funding from the NSF, University of Houston and Pharmacia and Upjohn to develop a similar device. This device would be incorporated into a scanning laser ophthalmoscope (SLO) rather than the more conventional fundus camera design used in Rochester. This SLO design has the potential to greatly decrease the effects of scattered light and further increase the resolution of fundus imaging.

DESCRIPTION (provided by applicant): Imagine a technology able to noninvasively identify individual cones in the living human retina and selectively stimulate them to study their contribution to visual perception. This technology could also track retinal functional organization at the border of a visual scotoma to study mechanisms disease and outcomes of treatment regimes. The technology does not yet exist but the current generation of the adaptive optics scanning laser ophthalmoscope (AOSLO), with its unique ability to compensate for retinal motion and image the cone mosaic, comes very close. The remaining obstacle is real time correction of transverse chromatic aberration (TCA) between the infrared beam and a visible light laser beam so that we can repeatedly, continuously and reliably image and stimulate the individual identified cones from day to day. Achieving and validating this capability is the principal goal (Aim 1) of this proposal. The validation of TCA error correction includes both physical (image processing) and innovative perceptual (chromatic shifts) techniques of characterizing the accuracy and reliability of stimulating the center of single cones. The method includes rapid identification of L & M cone classes which is itself a significant advance. In Aim 2, after we map out an array of cones identified by class near the fovea, we will stimulate different single L and M cones within the array while observers judge the intensity, hue and saturation of the flash. This single cone stimulation aim focuses on characterizing the stability of percepts within a cone and consistency across cones of the same class. This step will establish the parameters of cone activation and resultant percepts and clarify any constraints it might impose on future research. Along the way we expect to confirm or discredit hypotheses on the consequences of different cone class neighborhoods around the single probed cone. In Aim 3 we examine mechanisms of light adaptation; does it occur within a single cone? With our superior image stabilization, small steady, intense pedestals delivered to the center of a cone are expected to result in rapid Troxler fading. Once faded, the pedestal may not saturate the incremental test response (as in the Westheimer effect) but instead act largely like a uniform field with a constant cone-selective Weber law behavior. What appeared to be cone saturation may result from eye tremor. The proposed single cone studies will demonstrate the capabilities of the AOSLO. Future studies involving simultaneous and independent stimulation of multiple identified cones will be just as easy to perform and be able to address research questions extending from color to spatial vision in general.

DESCRIPTION (provided by applicant): This grant will support the 5th in a series of annual translational conferences at UC Berkeley, to support the NEI-funded K12 training program for clinician scientists. The themes for these conferences represent cutting edge, clinically applicable research, and change annually. The theme for the 2010 conference is innovative solutions involving optical manipulations or targeting optical problems. The following topics will be covered: 1) optical solutions to presbyopia, an age-related loss in ones ability to focus (accommodate) on nearby objects, 2) surgical solutions to optical problems of the eye, including presbyopia, 3) novel optical treatments for ocular diseases including myopia (near-sightedness) and keratoconus, and 4) technological advances in 3D simulations of the natural environment and their applications. The final session of the conference will be a panel discussion, involving all speakers, who will be challenged to think into the future. Targeted speakers include international leaders in their respective research fields, with a poster session providing opportunity for K12 trainees to show case their research. Trainees will also be involved as chairs, speakers and discussants of the paper sessions. In addition to K12 trainees, the conference targets local scientists, clinicians, graduate students and members from industry R&D. Travel grants will be offered to encourage involvement of trainees from interstate K12 programs and interested minority undergraduate students from the SETT program. The conference will serve as forum for sharing ideas, and establishing new collaborations, including industry links. PUBLIC HEALTH RELEVANCE: This grant will support the 5th in a series of annual translational conferences at UC Berkeley covering innovative solutions involving optical manipulations or targeting optical problems. The following topics will be covered: 1) optical solutions to presbyopia, an age-related loss in ones ability to focus (accommodate) on nearby objects, 2) surgical solutions to optical problems of the eye, including presbyopia, 3) novel optical treatments for ocular diseases including myopia (near-sightedness) and keratoconus, and 4) technological advances in 3D simulations of the natural environment and their applications.

DESCRIPTION (provided by applicant): This project is to develop and support three state-of-the-art optical instruments that provide microscopic access to the living retina, and use them to obtain a clearer understanding of how the human visual system works. They will be used to answer questions about the most important and the most challenging region in the retina to study, the fovea. The instruments are built upon two key technical strengths - adaptive optics scanning laser ophthalmoscope (AOSLO) systems and accurate, high-speed eye-motion tracking. Adaptive optics (AO) technology corrects the imperfections in the eye and can be used to generate microscopic views of the living retina. AO also enables the delivery of ultra-sharp images to the retina. Eye tracking is used to measure and compensate for ever-present eye motion. Together, these allow for accurate visualization, tracking and delivery of light to retinal features as small as single cone photoreceptors, enabling measurements of properties of spatial and color vision on an unprecedented scale. Although the three systems will be identical and will be used to test vision on a cellular scale, the scope of study for each system will be very different. The AOSLO at the University of Alabama, Birmingham will be used to test vision in primates, the AOSLO at the University of California, Berkeley will be used to perform advanced vision testing on healthy human eyes, and the AOSLO at the University of California, San Francisco will be used to study patients with eye disease. The key advantage of having the BRP manage three identical systems is that it will facilitate hardware innovations plus rapid translation of knowledge and innovative testing from animal models to the clinic. Briefly, the specific aims are: Aim 1: Develop and deploy state-of-the-art AOSLO systems at each site. Demonstrate performance by performing objective densitometry measures in monkeys and humans to map the three classes of cone photoreceptor that subserve color vision. Aim 2: Develop improved eye tracking and stimulus delivery capabilities in each system. Confirm performance by using subjective psychophysical tests to map the same three classes of cone photoreceptor as in Aim 1. Aim 3: Perform a series of experiments in monkeys and humans to map the connections and interactions within and between the retina and the brain and to study how we see the world as stable even though our eyes are in constant motion. Aim 4: Apply advanced vision testing methods in the clinic to discover mechanisms for cone death in different diseases, to monitor changes in cone function and structure during disease progression and to test the efficacy of treatments that aim to stop or slow disease progression. Aim 5: Make eye tracking and targeted stimulus delivery capabilities accessible to a wider audience by providing software, hardware designs and a forum for anyone interesting in building similar advanced systems.

? DESCRIPTION (provided by applicant): Our goal is to develop a new technology for non-invasive optical monitoring of activity of individual retinal neurons and their light-driven inputs at cellular resolution, in the living human retina. If successful, this technology will provide an entirely new and objective approach to understand and monitor treatment of retinal disease, thereby transforming scientific studies of the eye and vision. This project directly addresses the priorities outlined in the RFA-EY-14-001, the first RFA within the NEI Audacious Goal Initiative. The proposed work relies on combining and validating two new approaches. First, interferometry (including phase-resolved OCT; Park Lab at UC Riverside) can, in principle, be used to measure nanometer-scale distortions in the membranes of cells that occur during membrane depolarization and ion influx. With depth resolution, these measurements will enable us to measure neural activity non-invasively, throughout the layers of the retina, at cellular resolution. Second, adaptive optics scanning laser ophthalmoscopy (Roorda Lab at UC Berkeley) and image-based eye tracking can be used to position stimulating and measurement beams on the retina with cellular precision in the living eye, by overcoming optical aberrations and eye jitter. This technology will allow us to activate individual photoreceptors and groups of photoreceptors with visible light while imaging the resulting electrical activity of individual downstream cells, in vivo. To advance and combine these approaches requires a stepwise aggregation of technology. In a unique collaboration, we will build on simpler wide-field interferometric measurements of electrical activity in isolated retina (Palanker Lab at Stanford University), combined with large-scale multi-electrode physiological measurements in primate retina (Chichilnisky Lab at Stanford University) to validate and tune the optical measurements. Ultimately, the innovation at each step forms a powerful tool, independently or with a combination of other approaches, and finds applicability to optical imaging, retinal physiology, psychophysics and clinical ophthalmology. The specific aims are: Aim 1. Wide-field interferometry for measuring patterns of neural activity in primate retina Depolarization during neural signaling produces nanometer-scale deformations in cells that are detectable with interferometry. The simplest approach is wide-field interferometric microscopy with transmission geometry in isolated retina. We will measure depth-resolved optical phase changes produced by neural activity in primate retina, and use them for physiological characterizations of many retinal ganglion cells (RGCs) and other retinal neurons simultaneously. Aim 2. Phase-resolved OCT for reflectance measurements of patterns of retinal activity. The next step toward human application is phase-resolved OCT; essentially, low-coherence interferometry and a well-established tool for in vivo imaging. We will record optical path length changes associated with neural activity in reflection geometry using point-scanning, near-IR (1060 nm), phase-resolved OCT on isolated primate retina. Aim 3. Adaptive optics, eye tracking and phase-resolved OCT for measuring human retinal function. Deployment in humans requires compensating for optical aberrations in the eye as well as eye movements. We will develop a system that uses AOSLO to image the retina for eye tracking, targeted delivery of stimulation light, and positioning of the OCT probe. We will test this system in humans and demonstrate its potential application in clinical settings.

Project Summary/Abstract The last few decades have seen major inroads into detailing the physiological mechanisms supporting vision as well as therapies aimed at rescue and repair of neurons affected by retinal diseases. For the continued evolution of treatments and their rapid translation to the clinic, it is essential to find a non-invasive, all-optical biomarker to monitor the efficacy of disease and potential therapeutic agents. To this end, we propose to develop the optoretinogram, or ORG, the optical analog to the electroretinogram (ERG) which is the current gold standard for retinal function assessment in humans. The ORG is rooted in classical interferometry and enables a highly sensitive assay of how neurons interact with light. Using this technique, our group has demonstrated the ability to visualize light-driven neural activity across a range of spatiotemporal resolution ? from single cells to a collection of neurons, and from µsecs to ms timescales. Here, we aim to expand the capabilities of the ORG and demonstrate its efficacy for basic science and clinical applications. The proposed technology is built upon a solid foundation of established approaches, and combines them in new and complementary ways to achieve an optimal combination of speed, resolution and sensitivity geared towards overcoming the key challenges faced with imaging cellular structure-function in humans. The core technologies are phase-resolved OCT, an eye-safe, interferometric method to measure nm-scale changes at ms time scales in vivo, adaptive optics (AO) to overcome ocular aberrations, increase the signal-to-noise and allow resolution down to single cells and real-time eye tracking to overcome eye motion and allow targeting, recording and averaging of responses from single and a collection of retinal neurons. These are implemented across three ORG platforms. At the University of Washington, we will refine the line-scan phase-resolved OCT with improvements in optical design and eye-tracking and use it to characterize the basic properties of phototransduction and inner retinal function in healthy human volunteers and patients with retinal degenerations. At Stanford University, we will develop a similar line-scan system for rodents, and together with transgenic models and pharmacology, determine the biophysical mechanisms that underlie the ORG and develop templates for human recordings. At UC Berkeley, we will push the envelope of speed and sensitivity by incorporating a real-time eye-tracking system to drive an AO-OCT interferometric probe, with the aim to measure the tiniest and briefest neuronal changes in the human retina. This bioengineering research partnership will benefit from complementary expertise, research direction and ORG implementation across the three sites, and the use of common approaches for image/data analysis, eye tracking and visual stimulation. Ultimately, the aggregate technology will facilitate a deeper mechanistic understanding of early visual processing and eye disease, and provide entirely new avenues for accelerating therapeutic interventions.