Wolfgang Fink

Snapshot hyperspectral imaging in ophthalmology

Retinal imaging spectroscopy can provide functional maps using chromophore spectra. For example, oxygen saturation maps show ischemic areas from diabetes and venous occlusions. Obtaining retinal spatial-spectral data has been difficult due to saccades and long data acquisition times (>5 s). We present a snapshot imaging spectrometer with far-reaching applicability that acquires a complete spatial-spectral image cube in approximately 3 ms from 450 to 700 nm with 50 bands, eliminating motion artifacts and pixel misregistration. Current retinal spectral imaging approaches are incapable of true snapshot operation over a wide spectral range with a large number of spectral bands. Coupled to a fundus camera, the instrument returns true color retinal images for comparison to standard fundus images and for image validation while the patient is still dilated. Oxygen saturation maps were obtained with a three-wavelength algorithm: for healthy subjects arteries were approximately 95% and veins 30 to 35% less. The instrument is now undergoing clinical trials.

Tier-Scalable Reconnaissance Missions For The Autonomous Exploration Of Planetary Bodies

A fundamentally new (scientific) reconnaissance mission concept, termed tier-scalable reconnaissance, for remote planetary (including Earth) atmospheric, surface and subsurface exploration recently has been devised that soon will replace the engineering and safety constrained mission designs of the past, allowing for optimal acquisition of geologic, paleohydrologic, paleoclimatic, and possible astrobiologic information of Venus, Mars, Europa, Ganymede, Titan, Enceladus, Triton, and other extraterrestrial targets. This paradigm is equally applicable to potentially hazardous or inaccessible operational areas on Earth such as those related to military or terrorist activities, or areas that have been exposed to biochemical agents, radiation, or natural disasters. Traditional missions have performed local, ground-level reconnaissance through rovers and immobile landers, or global mapping performed by an orbiter. The former is safety and engineering constrained, affording limited detailed reconnaissance of a single site at the expense of a regional understanding, while the latter returns immense datasets, often overlooking detailed information of local and regional significance.

Three-dimensional computer-automated threshold Amsler grid test

We describe a novel method for testing a visual field that employs a computer monitor with displays of varying contrast that permits unprecedented resolution and characterization of the structure of scotomas in three dimensions. Patients are placed in front of a touch-sensitive computer screen at a fixed distance. With one eye covered, they focus on a central fixation marker and trace with their finger the areas on an Amsler grid that are missing from their field of vision. Increasing degrees of contrast of the Amsler grid are simulated by repeating the test at different gray-scale levels. The results are recorded and then displayed as topographical contour rings by the computer test program. The results can also be rendered as an immediate 3-D depiction of the central hill-of-vision. Several clinical pilot studies have been conducted at the Doheny Eye Institute and more than 200 patients have been examined with this system so far. Conditions such as optic neuritis, anterior ischemic optic neuropathy (AION), age-related macular degeneration (AMD), glaucoma, and ocular hypertension have been successfully assessed by this test. Each condition provides unique patterns that are most evident in 3-D. The 3-D computer-automated threshold Amsler grid test is an innovative and noninvasive visual field test. It provides several advantages over state-of-the-art standard automated perimetry, including: (1) additional information through 3-D depiction of scotomas, such as location, extent, slope, depth, and shape; (2) high angular resolution (1 deg compared with typically 6 deg); (3) a simple test setup (merely a touch-sensitive computer monitor and the test software); (4) excellent patient compliance (spending 4 to 5 min per eye). In light of its promising initial tests, the 3-D visual field test appears to have the potential for the early detection and monitoring of various diseases over time.

Generic Prioritization Framework for Target Selection and Instrument Usage for Reconnaissance Mission Autonomy

A generic prioritization framework is introduced for addressing the problem of automated prioritization of target selection and instrument usage, applicable to Earth and space reconnaissance missions. The framework is based on the assumptions that clustering of preliminary data for identified targets within an operational area has occurred and that the clustering quality can be expressed as an objective function. Target prioritization then means to rank targets according to their probability of changing the objective function value upon close reexamination. The formalism for calculating these probabilities and the probabilities for instruments aboard a science craft to contribute to this change of the objective function value is introduced.

Evolutionary computation technologies for space systems

The Evolvable Computation Group, at NASAs Jet Propulsion Laboratory, is tasked with demonstrating the utility of computational engineering and computer optimized design for complex space systems. The group is comprised of researchers over a broad range of disciplines including biology, genetics, robotics, physics, computer science and system design, and employs biologically inspired evolutionary computational techniques to design and optimize complex systems. Over the past two years we have developed tools using genetic algorithms, simulated annealing and other optimizers to improve on human design of space systems. We have further demonstrated that the same tools used for computer-aided design and design evaluation can be used for automated innovation and design. These powerful techniques also serve to reduce redesign costs and schedules

Scotomas Of Age-related Macular Degeneration Detected And Characterized By Means Of A Novel Three-dimensional Computer-automated Visual Field Test

Purpose: We used the recently devised three-dimensional computer-based threshold Amsler grid test to acquire and identify typical patterns of visual field defects (scotomas) caused by age-related macular degeneration (AMD). Methods: Patients with AMD traced on a computer touch screen the borders of those areas on an Amsler grid that were missing from their field of vision. Scotomas were repeatedly outlined and recorded at different grid contrast levels. The resulting three-dimensional “hole” in the central 25° of the visual field was further characterized by its slope, location, shape, and depth. The results were compared with fundus photographs and fluorescein angiograms. Results: Twenty-five patients and 41 eyes were examined. The three-dimensional depictions consistently demonstrated central scotomas with “scallop”-shaped borders and steplike patterns, with either steep slopes or a combination of steep and shallow slopes. The steep slopes corresponded to nonexudative AMD, while the shallow slopes indicated exudative AMD. Conclusion: The three-dimensional computer-automated threshold Amsler grid test may demonstrate characteristic scotoma patterns in patients with AMD that conform to the respective fluorescein angiograms. The test shows promise as an effective tool in accurately evaluating, characterizing, and monitoring scotomas in patients with AMD. It may have the potential as a screening tool for the early diagnosis of AMD.

Image processing and interface for retinal visual prostheses

Controlled electrical stimulation of the retina can result in visual perception in blind patients. In contrast to the over 100,000,000 photoreceptors in a healthy retina, even hundreds of pixels/electrodes of a retinal implant may restore low-resolution vision for unaided mobility and large print reading. We describe the real-time application of image processing techniques, such as contrast and brightness enhancement, grayscale histogram equalization, edge detection, and grayscale reduction, to enhance the visual perception provided by a retinal implant. We discuss schemes for reducing the amount of data transmitted wirelessly to the implant, as well as the interface between the external imaging unit and retinal implant.

Robotic test bed for autonomous surface exploration of Titan, Mars, and other planetary bodies

Tier-scalable robotic reconnaissance missions are called for in extreme space environments, including planetary atmospheres, surfaces (both solid and liquid), and subsurfaces (e.g., oceans), as well as in potentially hazardous or inaccessible operational areas on Earth. Such future missions will require increasing degrees of operational autonomy: (1) Automatic mapping of an operational area from different vantages (i.e., spaceborne, airborne, surface, subsurface); (2) automatic sensor deployment and sensor data gathering; (3) automatic feature extraction and target/region-of-interest/anomaly identification within the mapped operational area; (4) automatic target prioritization for follow-up or close-up (in-situ) examination; and (5) subsequent automatic, targeted deployment and navigation/relocation of agents/sensors (e.g., to follow up on transient events). We report on recent progress in developing an Earth-based (outdoors) robotic test bed for Tier-scalable Reconnaissance at the University of Arizona and Caltech for distributed, science-driven, and significantly less constrained (compared to state-of-the-art) reconnaissance of prime locations on a variety of planetary bodies, with particular focus on Saturns moon Titan with its methane/hydrocarbon lakes and Mars. The test bed currently comprises several computer-controlled robotic surface vehicles, i.e., rovers and lake landers/boats equipped with a variety of sensors. To achieve a fully operational Tier-scalable Reconnaissance test bed, aerial platforms will be integrated as a next step. The robotic surface vehicles can be interactively or automatically controlled from anywhere in the world in near real-time via the Internet. The test bed enables the implementation, field-testing, and validation of algorithms and strategies for navigation, exploration, sensor deployment, sensor data gathering, feature extraction, anomaly detection, and science goal prioritization for autonomous planetary exploration. Furthermore, it permits field-testing of novel instruments and sensor technologies, as well as testing of cooperative multi-agent scenarios and distributed scientific exploration of operational areas. As such the robotic test bed enables the development, implementation, field-testing, and validation of software packages for inter-agent communication and coordination to navigate and explore operational areas with greatly reduced reliance on (ultimately without assistance from) ground operators, thus affording the degree of mission autonomy/flexibility necessary to support future missions to Titan, Mars, and other planetary bodies, including asteroids. 1 2

Quantitative analysis of central visual field defects in macular edema using three-dimensional computer-automated threshold Amsler grid testing

PurposeTo evaluate the central visual field (CVF) with specialized Amsler grid testing methods that include contrast sensitivity evaluation, in an attempt to detect abnormalities not identified with standard methods and to define new patterns of CVF deficits in two different diseases.Methods3D computer-automated threshold Amsler grid testing (3D-CTAG) was performed at five levels of contrast in one eye of 37 patients with diabetic macular edema (DME, n = 16) and exudative age-related macular degeneration (AMD, n = 21).Results3D-CTAG abnormalities were detected in six patients (16%) who had no abnormalities with conventional Amsler grid testing. DME patients had more foci of CVF deficits (3.56 ± 2.92 defects/eye), than AMD patients (1.24 ± 0.89 defects/eye; P < 0.0002). The shape of the 3D-CTAG abnormality in DME was an inverted cone, while the deficits in AMD were always cylindrical. All eyes showed significant increases in CVF deficit surface area at minimum contrast levels when compared to maximum contrast (295% greater with DME, P < 0.02 and 150% greater with AMD, P < 0.03).Conclusion3D-CTAG detected CVF abnormalities not identified with conventional Amsler grid testing in 16% of subjects. Low-contrast conditions elicited a larger defect in both DME (3-fold) and AMD (1.5-fold). DME and AMD have unique 3D-CTAG profiles, enabling diagnostic discrimination. Measuring CVF defects with 3D-CTAG can quantitatively index disease severity and may be useful in longitudinal studies of the natural history of disease, as well as providing a quantitative outcome measure of the response to therapy.

Progress Towards A High-Resolution Retinal Prosthesis

Simulations of artificial vision suggest that 1000 electrodes may be required to restore vision to individuals with diseases of the outer retina. In order to achieve such an implant, new technology is needed, since the state-of-the-art implantable neural stimulator has at most 22 contacts with neural tissue. Considerable progress has been made towards that goal with the development of image processing, microelectronics, and polymer based electrodes and interconnects. An image processing system has been realized that is capable of real-time implementation of image decimation and filtering (for example, edge detection). Application specific integrated circuits (ASICs) have been designed and tested to demonstrate closed loop power control and efficient microstimulation. A novel packaging process has been developed that is capable of simultaneously forming a receiver coil, interconnects, and stimulating electrodes