A Hansel & Gretel breadcrumb-style dynamically deployed communication network paradigm using mesh topology for planetary subsurface exploration.

We introduce a dynamically deployed communication network (DDCN) paradigm using mesh topology in support of a distributed robotic multi-agent approach for the autonomous exploration of subsurface environments, i.e., caves, lava tube caves, lakes, and oceans, etc. The DDCN, comprising wireless communication beacons autonomously deployed via a rover or submersible in a Hansel & Gretel-inspired breadcrumb style, allows for the longest and most robust communication link between subterranean robotic agent(s) within, e.g., a lave tube cave or a subsurface ocean, and associated surface-borne robotic agent(s). Moreover, we briefly touch on the development of a robotic testbed and wired/wireless communication beacons in support of such astrobiological surface/subsurface exploration scenarios. Candidate lava tube caves have been identified on the Moon and Mars, raising possibilities for planetary exploration, astrobiology, habitat construction for future astronauts, and potential mining operations. Subterranean caverns, and in particular relatively deep lava tube caves, provide a possible refuge for life under otherwise challenging planetary surface conditions, and, as such, are of prime astrobiological relevance. Lava tube caves or other subsurface environments may also be suitable habitats for astronauts and subsequent human settlement but are yet to be explored in part due to difficulties ensuring continued communication with a robotic probe inside these environments. Moreover, the existence of subsurface oceans on ocean worlds, such as Europa, Enceladus, and Titan, has been backed by varying levels of evidence since the 1980s, though there has been no confirmation, i.e., direct observation, thus far. Such environments are also shielded from radiation, and, in combination with the hypothesized presence of water, are additional candidate environments for finding extant or fossilized life. The DDCN paradigm introduced herein directly addresses NASA's Space Technology Grand Challenges - "All Access Mobility" by enabling the most unconstrained exploration of subsurface environments through a dynamic communication network which ensures transmission of data from and possibly commands to the subsurface robotic probe. 2023 COSPAR. Published by Elsevier B.V. All rights reserved.

VISTATM: Visual Impairment Subtle Touch AidTM - a range detection and feedback system for sightless navigation.

We devised a low-tech, low-cost, robust, and minimally obtrusive navigational travelling aid to be paired with and bolster standard white cane use for people with visual impairments. The device combines ultrasonic range detection with proportional vibrational output. The navigational aid was devised using a sensing belt equipped with independent ultrasonic sensors for distance measurements. Sensors were mounted using adjustable mobile clips to allow for user variability. The sensing belt was connected to a stimulation belt affixed to the ribcage. The stimulation belt used vibrating motors with vibration proportional to the distance between the belt wearer and surrounding obstacles sensed by corresponding ultrasonic sensors. The device was validated through preliminary testing on blindfolded, but fully sighted, persons and one blind person (all authors) in navigating a novel environment without supplemental aid. Testing sessions varied from 45 to 90 min. In preliminary tests, the devised ultrasonic-sensor-belt and vibration-actuator-equipped belt combination was capable of informing users of surrounding obstacles in real-time while navigating a hallway with several turns.

Conceptual design considerations for a wireless intraocular pressure sensor system for effective glaucoma management.

As a leading form of preventable visual impairment, it is imperative to assess glaucoma treatment as a function of intraocular pressure (IOP). IOP can spike throughout the day. This necessitates a device that can (1) monitor IOP outside of clinical visits by providing a memory when IOP exceeds a set threshold indicating the possibility for glaucomatous damage to occur; and (2) accurately assess IOP. Both requirements point ultimately towards the development of an implantable device. The Wireless Intraocular Pressure Sensor System (WIPSS) devised by our team uses optical technologies and may assist an overseeing clinician with assessing glaucoma treatment efficacy and avoiding irreversible glaucomatous visual field loss downstream.

Publisher Correction: Nanobiophotonics: Nature-inspired sensors.

In the version of this News and Views article originally published, in the author's e-mail address, the domain was incorrectly given as 'e-mail.arizona.edu'; it should have read 'email.arizona.edu'. This has now been corrected in the online versions.

The Argyre Region as a Prime Target for in situ Astrobiological Exploration of Mars.

At the time before ∼3.5 Ga that life originated and began to spread on Earth, Mars was a wetter and more geologically dynamic planet than it is today. The Argyre basin, in the southern cratered highlands of Mars, formed from a giant impact at ∼3.93 Ga, which generated an enormous basin approximately 1800 km in diameter. The early post-impact environment of the Argyre basin possibly contained many of the ingredients that are thought to be necessary for life: abundant and long-lived liquid water, biogenic elements, and energy sources, all of which would have supported a regional environment favorable for the origin and the persistence of life. We discuss the astrobiological significance of some landscape features and terrain types in the Argyre region that are promising and accessible sites for astrobiological exploration. These include (i) deposits related to the hydrothermal activity associated with the Argyre impact event, subsequent impacts, and those associated with the migration of heated water along Argyre-induced basement structures; (ii) constructs along the floor of the basin that could mark venting of volatiles, possibly related to the development of mud volcanoes; (iii) features interpreted as ice-cored mounds (open-system pingos), whose origin and development could be the result of deeply seated groundwater upwelling to the surface; (iv) sedimentary deposits related to the formation of glaciers along the basin's margins, such as evidenced by the ridges interpreted to be eskers on the basin floor; (v) sedimentary deposits related to the formation of lakes in both the primary Argyre basin and other smaller impact-derived basins along the margin, including those in the highly degraded rim materials; and (vi) crater-wall gullies, whose morphology points to a structural origin and discharge of (wet) flows.

Operational challenges of retinal prostheses.

Two computational models for research on retinal implants are presented. In the first model, the electric field produced by a multi-electrode array in a uniform retina is calculated. It is shown how cross talk of activated electrodes and the resulting bunching of field lines in monopole and dipole activation prevent high resolution imaging with retinal implants. Furthermore, it is demonstrated how sequential stimulation and multipolar stimulation may overcome this limitation. In the second model a target volume, i.e., a probe cylinder approximating a bipolar cell, in the retina is chosen, and the passive Heaviside cable equation is solved inside this target volume to calculate the depolarization of the cell membrane. The depolarization as a function of time indicates that shorter signals stimulate better as long as the current does not change sign during stimulation of the retina, i.e., mono-phasic stimulation. Both computational models are equally applicable to epiretinal, subretinal, and suprachoroidal vision implants.

Artificial vision support system (AVS(2)) for improved prosthetic vision.

State-of-the-art and upcoming camera-driven, implanted artificial vision systems provide only tens to hundreds of electrodes, affording only limited visual perception for blind subjects. Therefore, real time image processing is crucial to enhance and optimize this limited perception. Since tens or hundreds of pixels/electrodes allow only for a very crude approximation of the typically megapixel optical resolution of the external camera image feed, the preservation and enhancement of contrast differences and transitions, such as edges, are especially important compared to picture details such as object texture. An Artificial Vision Support System (AVS(2)) is devised that displays the captured video stream in a pixelation conforming to the dimension of the epi-retinal implant electrode array. AVS(2), using efficient image processing modules, modifies the captured video stream in real time, enhancing 'present but hidden' objects to overcome inadequacies or extremes in the camera imagery. As a result, visual prosthesis carriers may now be able to discern such objects in their 'field-of-view', thus enabling mobility in environments that would otherwise be too hazardous to navigate. The image processing modules can be engaged repeatedly in a user-defined order, which is a unique capability. AVS(2) is directly applicable to any artificial vision system that is based on an imaging modality (video, infrared, sound, ultrasound, microwave, radar, etc.) as the first step in the stimulation/processing cascade, such as: retinal implants (i.e. epi-retinal, sub-retinal, suprachoroidal), optic nerve implants, cortical implants, electric tongue stimulators, or tactile stimulators.

Planetary imaging in powers of ten: a multiscale, multipurpose astrobiological imager.

Contextual, multiscale astrobiological imaging is necessary to discover, map, and image patchy microbial colonization in extreme environments on planetary surfaces. The large difference in scale--several orders of magnitude--between search environment and microorganisms or microbial communities represents a challenge, which to date no single imaging instrument is able to overcome. In support of future planetary reconnaissance missions, we introduce an adapter-based imager, built from an off-the-shelf consumer digital camera, that offers scalable imaging ranging from macroscopic (meters per pixel) to microscopic (micrometers per pixel) imaging, that is, spanning at least 6 orders of magnitude. Magnification in digital cameras is governed by (1) the native resolution of the CCD/CMOS chip of the camera, (2) the distance between camera and object to be imaged (focal length), and (3) the built-in optical and digital zoom. Both telezoom and macro mode alone are usually insufficient for microscopic imaging. Therefore, the focal distance has to be shortened, and the native CCD resolution of the camera has to be increased to attain a microscopic imaging capability. Our adapter-based imager bridges the gap between macroscopic and microscopic imaging, thereby enabling for the first time contextual astrobiological imaging with the same instrument. Real-world applications for astrobiology and planetary geology are discussed, and proof-of-concept imagery taken with our prototype is presented.

Prospective three-dimensional analysis of structure and function in vitreomacular adhesion cured by pharmacologic vitreolysis.

PURPOSE: To prospectively characterize macular structure and function as assessed by combined three-dimensional spectral-domain optical coherence tomography and scanning laser ophthalmoscopy and 3D computer-automated threshold Amsler grid, respectively, in a patient undergoing pharmacologic vitreolysis for vitreomacular adhesion with tractional cysts. METHODS: Combined 3D optical coherence tomography and scanning laser ophthalmoscopy measured macular volume and 3D computer-automated threshold Amsler grid quantified central visual field function by determining the absolute percent magnitude lost (cumulative value of total visual field loss over all tested levels) before and for a period of 6 months after pharmacologic vitreolysis for vitreomacular adhesion with a single intravitreal injection of microplasmin (125 µg; ThromboGenics). RESULTS: Ocriplasmin pharmacologic vitreolysis released vitreomacular adhesion by 2 weeks and decreased macular volume from 0.32 µL to 0.15 µL by 1 year after injection. There was a concomitant 4-fold improvement in visual function as measured by 3D computer-automated threshold Amsler grid (percent of central visual field lost) and Snellen visual acuity improved from 20/200 to 20/40. CONCLUSION: For assessing macular function improvement in conjunction with structural reintegration after pharmacologic vitreolysis for vitreomacular adhesion, 3D computer-automated threshold Amsler grid is a useful tool. Both 3D measurements quantitatively characterized the resolution of this patient's vitreomacular adhesion, suggesting that this is a useful approach to quantifying macular structure and function as indices of the severity of disease and the response to therapy.

Distinguishing wet from dry age-related macular degeneration using three-dimensional computer-automated threshold Amsler grid testing.

BACKGROUND/AIMS: With the increased efficacy of current therapy for wet age-related macular degeneration (AMD), better ways to detect wet AMD are needed. This study was designed to test the ability of three-dimensional contrast threshold Amsler grid (3D-CTAG) testing to distinguish wet AMD from dry AMD. METHODS: Conventional paper Amsler grid and 3D-CTAG tests were performed in 90 eyes: 63 with AMD (34 dry, 29 wet) and 27 controls. Qualitative comparisons were based upon the three-dimensional shapes of central visual field (VF) defects. Quantitative analyses considered the number and volume of the three-dimensional defects. RESULTS: 25/34 (74%) dry AMD and 6/29 (21%) wet AMD eyes had no distortions on paper Amsler grid. Of these, 5/25 (20%) dry and 6/6 (100%) wet (p=0.03) AMD eyes exhibited central VF defects with 3D-CTAG. Wet AMD displayed stepped defects in 16/28 (57%) eyes, compared with only 2/34 (6%) of dry AMD eyes (p=0.002). All three volumetric indices of VF defects were two- to four-fold greater in wet than dry AMD (p<0.006). 3D-CTAG had 83.9% positive and 90.6% negative predictive values for wet AMD. CONCLUSIONS: 3D-CTAG has a higher likelihood of detecting central VF defects than conventional Amsler grid, especially in wet AMD. Wet AMD can be distinguished from dry AMD by qualitative and quantitative 3D-CTAG criteria. Thus, 3D-CTAG may be useful in screening for wet AMD, quantitating disease severity, and providing a quantitative outcome measure of therapy.

Microcomputer-based artificial vision support system for real-time image processing for camera-driven visual prostheses.

It is difficult to predict exactly what blind subjects with camera-driven visual prostheses (e.g., retinal implants) can perceive. Thus, it is prudent to offer them a wide variety of image processing filters and the capability to engage these filters repeatedly in any user-defined order to enhance their visual perception. To attain true portability, we employ a commercial off-the-shelf battery-powered general purpose Linux microprocessor platform to create the microcomputer-based artificial vision support system (microAVS(2)) for real-time image processing. Truly standalone, microAVS(2) is smaller than a deck of playing cards, lightweight, fast, and equipped with USB, RS-232 and Ethernet interfaces. Image processing filters on microAVS(2) operate in a user-defined linear sequential-loop fashion, resulting in vastly reduced memory and CPU requirements during execution. MiccroAVS(2) imports raw video frames from a USB or IP camera, performs image processing, and issues the processed data over an outbound Internet TCP/IP or RS-232 connection to the visual prosthesis system. Hence, microAVS(2) affords users of current and future visual prostheses independent mobility and the capability to customize the visual perception generated. Additionally, microAVS(2) can easily be reconfigured for other prosthetic systems. Testing of microAVS(2) with actual retinal implant carriers is envisioned in the near future.

Novel 3D computer-automated threshold Amsler grid visual field testing of scotomas in patients with glaucoma.

PURPOSE: Three-dimensional (3D) computer-automated threshold Amsler grid testing was used to identify and characterize scotomas typical of glaucoma. METHODS: The 3D test exhibits a grid on a computer screen at a preselected grayscale and angular resolution, and allows patients to trace those areas on the grid that are missing in their visual field using a touch screen. Eleven eyes in patients with an established diagnosis of glaucoma were examined according to the above protocol. A total of 23 eyes from normal subjects were used as controls. The 5-minute test required that patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterized by the location, shape, extent, depth, and slope of the scotomas. RESULTS: In this pilot study, the 3D depiction of visual field loss demonstrated paracentral, superior and inferior altitudinal, and nasal step defects consistent with glaucomatous damage. The 3D depiction showed a shape, extent, depth, and slope that are consistent with the severity of damage. CONCLUSIONS: The 3D test identified and characterized scotomas typical of glaucoma. The test provides several advantages over conventional perimetry including additional information through 3D depiction of scotomas with the addition of contrast sensitivity and a higher angular/spatial resolution. Improved patient compliance and reliability through shorter testing time and potential interactive accessibility and distribution over the Internet further characterize the test.

CYCLOPS: A mobile robotic platform for testing and validating image processing and autonomous navigation algorithms in support of artificial vision prostheses.

While artificial vision prostheses are quickly becoming a reality, actual testing time with visual prosthesis carriers is at a premium. Moreover, it is helpful to have a more realistic functional approximation of a blind subject. Instead of a normal subject with a healthy retina looking at a low-resolution (pixelated) image on a computer monitor or head-mounted display, a more realistic approximation is achieved by employing a subject-independent mobile robotic platform that uses a pixelated view as its sole visual input for navigation purposes. We introduce CYCLOPS: an AWD, remote controllable, mobile robotic platform that serves as a testbed for real-time image processing and autonomous navigation systems for the purpose of enhancing the visual experience afforded by visual prosthesis carriers. Complete with wireless Internet connectivity and a fully articulated digital camera with wireless video link, CYCLOPS supports both interactive tele-commanding via joystick, and autonomous self-commanding. Due to its onboard computing capabilities and extended battery life, CYCLOPS can perform complex and numerically intensive calculations, such as image processing and autonomous navigation algorithms, in addition to interfacing to additional sensors. Its Internet connectivity renders CYCLOPS a worldwide accessible testbed for researchers in the field of artificial vision systems. CYCLOPS enables subject-independent evaluation and validation of image processing and autonomous navigation systems with respect to the utility and efficiency of supporting and enhancing visual prostheses, while potentially reducing to a necessary minimum the need for valuable testing time with actual visual prosthesis carriers.

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

PURPOSE: To 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. METHODS: 3D 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). RESULTS: 3D-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). CONCLUSION: 3D-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.

Early detection of glaucoma by means of a novel 3D computer-automated visual field test.

PURPOSE: A recently devised 3D computer-automated threshold Amsler grid test was used to identify early and distinctive defects in people with suspected glaucoma. Further, the location, shape and depth of these field defects were characterised. Finally, the visual fields were compared with those obtained by standard automated perimetry. PATIENTS AND METHODS: Glaucoma suspects were defined as those having elevated intraocular pressure (>21 mm Hg) or cup-to-disc ratio of >0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were tested as controls. The recently developed 3D computer-automated threshold Amsler grid test was used. The test exhibits a grid on a computer screen at a preselected greyscale and angular resolution, and allows patients to trace those areas on the grid that are missing in their visual field using a touch screen. The 5-minute test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterised by the location, shape and depth of the scotomas. The exam was repeated three times per eye. The results were compared to Humphrey visual field tests (ie, achromatic standard or SITA standard 30-2 or 24-2). RESULTS: In this pilot study 79% of the eyes tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3D perimetry. The 3D depictions of visual field loss associated with these risk factors were all characteristic of or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group. CONCLUSIONS: The 3D computer-automated threshold Amsler grid test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma suspects with normal achromatic Humphrey visual field testing. This test may be used as a screening tool for the early detection of glaucoma.

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.

simEye: Computer-based simulation of visual perception under various eye defects using Zernike polynomials.

We describe a computer eye model that allows for aspheric surfaces and a three-dimensional computer-based ray-tracing technique to simulate optical properties of the human eye and visual perception under various eye defects. Eye surfaces, such as the cornea, eye lens, and retina, are modeled or approximated by a set of Zernike polynomials that are fitted to input data for the respective surfaces. A ray-tracing procedure propagates light rays using Snell's law of refraction from an input object (e.g., digital image) through the eye under investigation (i.e., eye with defects to be modeled) to form a retinal image that is upside down and left-right inverted. To obtain a first-order realistic visual perception without having to model or simulate the retina and the visual cortex, this retinal image is then back-propagated through an emmetropic eye (e.g., Gullstrand exact schematic eye model with no additional eye defects) to an output screen of the same dimensions and at the same distance from the eye as the input object. Visual perception under instances of emmetropia, regular astigmatism, irregular astigmatism, and (central symmetric) keratoconus is simulated and depicted. In addition to still images, the computer ray-tracing tool presented here (simEye) permits the production of animated movies. These developments may have scientific and educational value. This tool may facilitate the education and training of both the public, for example, patients before undergoing eye surgery, and those in the medical field, such as students and professionals. Moreover, simEye may be used as a scientific research tool to investigate optical lens systems in general and the visual perception under a variety of eye conditions and surgical procedures such as cataract surgery and laser assisted in situ keratomileusis (LASIK) in particular.