Avi Caspi

• Jerusalem College of Technology

Visual prostheses such as the Argus II provide partial vision for individuals with limited or no light perception. However, their effectiveness in daily life situations is limited by scene complexity and variability. We investigated whether additional image processing techniques could improve mobility performance in everyday indoor environments. A...

To date, retinal implants are the only available treatment for blind individuals with retinal degenerations such as retinitis pigmentosa. Argus II is the only visual implant with FDA approval, with more than 300 users worldwide. Argus II stimulation is based on a grayscale image coming from a head-mounted visible-light camera. Normally, the 11°×19°...

Background Restoring sight for the blind using electrical stimulation of the visual pathways is feasible but demands an understanding of the spatial mapping of the visual world at the site of targeted stimulation, whether in the retina, thalamus, or cortex. While a visual cortex stimulator can bypass the eye and create visual percepts, there is an...

Purpose: At present, Argus II is the only retinal prosthesis approved by the US Food and Drug Administration that induces visual percepts in people who are blind from end-stage outer retinal degenerations such as retinitis pigmentosa. It has been shown to work well in sparse, high-contrast settings, but in daily practice visual performance with th...

Objective. To evaluate the benefit of integrating thermal imaging into an artificial vision therapy system, the Argus II retinal prosthesis, in simplifying a complex scene and improving mobility performance in the presence of other persons. Approach. Four Argus II retinal implant users were evaluated on two tasks: to locate and approach target pers...

Tracking the eye of a blind patient can enhance the usability of an artificial vision system. In systems where the sensing element, i.e. the scene camera that captures the visual information, is mounted on the patient's head, the user must use head scanning in order to steer the line of sight of the implant to the region of interest. Integrating an...

Purpose: Heterophoria describes the deviation of the optical axes in the absence of binocular fusion. Eye trackers (ET) can provide an objective assessment but are not broadly used clinically. We examined the feasibility of combining an infrared (IR) pass-filter, IR detector, and an off-the-shelf ET. The proposed setup was validated against the br...

The imaging depth of field (DOF) of white-light illuminated objects is extended by carefully integrating two image-processing techniques, one optical and one digital. The optical technique makes use of a tailored phase mask positioned at the pupil of the imaging system to cause different color channels to have different focal lengths; accordingly,...

Aim To demonstrate the potential clinically meaningful benefits of a thermal camera integrated with the Argus II, an artificial vision therapy system, for assisting Argus II users in localising and discriminating heat-emitting objects. Methods Seven blind patients implanted with Argus II retinal prosthesis participated in the study. Two tasks were...

Purpose: To investigate the effect of a wider field-of-view (FOV) of a retinal prosthesis on the users' performance in locating objects. Methods: One female and four male subjects who were blind due to end-stage retinitis pigmentosa and had been implanted with the Argus II retinal prosthesis participated (aged 63.4 ± 15.4). Thermal imaging was c...

Purpose To compare enhanced depth imaging in swept-source optical coherence tomography and non–enhanced depth imaging optical coherence tomography in their ability to capture choroidal and scleral details. Methods Averaged foveal B-Scans were obtained from 40 eyes of 20 healthy volunteers by swept-source optical coherence tomography with and witho...

Abstract Purpose : Users of retinal prosthetic systems such as the Argus II have limited beneft from their restored vision due to poor resolution; in many real-world situations the scene is too cluttered to be understandable to the prosthesis user. We have previously shown benefit of thermal imaging as an input modality for Argus II retinal implant...

Purpose: Visual scanning by sighted individuals is done using eye and head movements. In contrast, scanning using the Argus II is solely done by head movement, since eye movements can introduce localization errors. Here, we tested if a scanning mode utilizing eye movements increases visual stability and reduces head movements in Argus II users. M...

Purpose: To quantify the precision of mapping from retinotopic (retina-centered) to spatiotopic (world-centered) coordinates in blind humans implanted with a retinal prosthesis device. Additionally, to demonstrate that an eye tracker can be calibrated on sightless patients based on the percept from a visual implant. Methods: We directly activate...

Background: To evaluate the characteristics of retinal vascular shadowing, viewed through en face swept source optical coherence tomography (SS-OCT) imaging in normality and diabetic macular edema (DME). Design: Prospective case series conducted at Shaare Zedek Medical Center. Participants or Samples: 34 eyes of 17 healthy subjects and 30 eyes of...

Spatial mapping, the location in space of a perceived location due to an implanted electrode's electrical stimulation is important in the design of visual prostheses. Generally, a visual prosthesis system consists of an implanted electrode array, an external camera that acquires the image, and a transmitter that sends the information to the implant...

There are presently several ongoing clinical trials to provide usable sight to profoundly visually impaired patients by means of electrical stimulation of the retina. Some of the blind patients implanted with retinal prosthesis reported un-patterned perception and yet benefit from the device in many activities of daily living, seemingly because the...

Vestibulo-Ocular Reflex (VOR) abnormalities in cerebellar ataxias are a matter of renewed interest. We have previously reported vestibular areflexia in a group of Yemenite-Jews with Spinocerebellar Ataxia Type 3 (SCA3) who had clear bilateral pathological horizontal Head Impulse Test (HIT). The objective of this study was to evaluate the VOR of ten...

The Argus II epiretinal prosthesis has been developed to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. Participants were surgically implanted with the system in the United States and Europe in a single arm, prospective, multicenter clinical trial. The purpose of this investigation was to determin...

To investigate the ability of 28 blind subjects implanted with a 60-electrode Argus II (Second Sight Medical Products Inc) retinal prosthesis system to detect the direction of a moving object. Blind subjects (bare light perception or worse in both eyes) with retinitis pigmentosa were implanted with the Argus II prosthesis as part of a phase 1/2 fea...

Purpose: The purpose of the current research is to understand if the different eye movement abnormalities in patients with the same neurologic disease are related to varied disease processes or, alternately, do different patients adopt different strategies to overcome a singular brain deficiency. Methods: Using a magnetic search coil, we measure...

Objective To investigate the ability of 28 blind subjects implanted with a 60-electrode Argus II (Second Sight Medical Products Inc) retinal prosthesis system to detect the direction of a moving object. Methods Blind subjects (bare light perception or worse in both eyes) with retinitis pigmentosa were implanted with the Argus II prosthesis as part...

To determine to what extent subjects implanted with the Argus II retinal prosthesis can improve performance compared with residual native vision in a spatial-motor task. High-contrast square stimuli (5.85 cm sides) were displayed in random locations on a 19″ (48.3 cm) touch screen monitor located 12″ (30.5 cm) in front of the subject. Subjects were...

Terror management theory (TMT) posits that the denial of personal mortality is a central motivation underlying many human behaviors. According to TMT, reminders of death induce proximity-seeking with culturally-similar others. Recent studies have also shown that death reminders lead to emotional withdrawal from others who may remind people of their...

Previous research has suggested that the physical aspects of human nature in general, and physical human frailties in particular become disagreeable and repugnant following death primes. The current research tested this hypothesis in two studies using an eye-tracking methodology. Participants were subliminally primed with death or with a control wo...

The Argus II 60 channel epiretinal prosthesis has been developed in order to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. To date the device has been implanted in 21 subjects as part of a feasibility study. In 6 month post-implantation door finding and line tracking orientation and mobility test...

To demonstrate that an epiretinal prosthesis can produce patterned visual perception in patients blinded by photoreceptor degeneration who have no other treatment options. A totally blind subject with retinitis pigmentosa had a 16-electrode epiretinal prosthesis implanted. The implant is controlled wirelessly by an external computer or a head-mount...

The vestibulo-ocular reflex (VOR) mechanism triggers eye movements as a result of head motion in order to keep gaze stationary relative to the world. However, in order to shift the direction of the gaze along with head motion, the VOR mechanism must be overridden ("cancelled"). Two mechanisms have been proposed to explain this cancellation: a reduc...

Electrical stimulation of a grid of retinal electrodes produces localized spots of light that can be used to construct an image of the world with a resolution determined by the spacing between neighboring electrodes.

Dyslexia is a language-based learning disability characterized by difficulties with reading, spelling, and writing. Persons with dyslexia often have deficits in processing rapid temporal sensory information. There is also evidence of sensorimotor deficits in persons with dyslexia. Whether these deficits include ocular motor problems is still an ope...

The study of eye movements in reading is among the earliest field of oculomotor research. During reading, the text is scanned by means of saccades separated by periods of fixation during which the information is acquired. The saccades are several letter-lengths long, and at each fixation several characters are acquired. English is read from left-to...

In nonstationary noisy systems the traditional cross-correlation method may not appropriately detect all cases of interdependencies between coupled systems. The phase-synchronization method was previously found useful in detecting synchronization in several systems. We here applied the phase-synchronization decay to study the synchronization betwee...

Eye movements during fixation of a stationary target prevent the adaptation of the visual system to continuous illumination and inhibit fading of the image. These random, involuntary, small movements are restricted at long time scales so as to keep the target at the center of the field of view. Here we use detrended fluctuation analysis in order to...

Real-life visual tasks such as tracking jumping objects and scanning visual scenes often require a sequence of saccadic eye movements. The ability of the ocular motor system to parallel process saccades has been previously demonstrated. We recorded the monocular eye movements of five normal human subjects using the magnetic search coil technique in...

Saccadic eye movements are the result of neural decisions about where to move the eyes. These decisions are based on visual information accumulated before the saccade; however, during an approximately 100-ms interval immediately before the initiation of an eye movement, new visual information cannot influence the decision. Does the brain simply ign...

We study the motion of a probe driven by microtubule-associated motors within a living eukaryotic cell. The measured mean square displacement, <x(t)2> of engulfed 2 and 3 microm diameter microspheres shows enhanced diffusion scaling as t(3/2) at short times, with a clear crossover to ordinary or subdiffusive scaling, i.e., t(gamma) with gamma less...

Centripetal motion of surface-adherent particles is a classic experimental system for studying surface dynamics on a eukaryotic cell. To investigate bead migration over the entire cell surface, we have developed an experimental assay using multinuclear giant fibroblasts, which provide expanded length scales and an unambiguous frame of reference. Be...

Motor proteins associate with filaments of the cellular cytoskeleton to generate directed forces. These interactions have been studied extensively in vitro. Here we present measurements on beads engulfed into living cells, where near the cell center the bead performs a direction-less wandering motion due to collective activity of microtubule-associ...

We show that within a living eukaryotic cell, mean square displacement of an engulfed microsphere shows enhanced diffusion scaling as t(3/2) at short times, with a clear crossover to subdiffusive or ordinary diffusion scaling at longer times. The motion, observed nearby the nucleus, is due to interactions with microtubule-associated motor proteins...

The dynamic movements of tracer particles have been used to characterize their local environment in dilute networks of microtubules, and within living cells. In the former case, 300 nm diameter beads are fixed to individual microtubules, so that the movements of the bead reveal undulatory modes of the polymer. The mean square displacement shows a s...

The thermally driven dynamics of a polymer network are studied by direct view observation of the motion of a single point within a single polymer. Taking advantage of rather rigid biological microtubules as a case study, we expand the space and time scales of the system to those accessible by optical microscopy and standard video tools. Tracking is...

The dynamics of a polymer network are studied by direct view observation of the motion of a single point within a single polymer. Taking advantage of rather rigid biological microtubules as a case study, we expand the space and time scales of the system to those accessible by optical microscopy and standard video tools. Tracking is achieved by chem...

Optical tweezers are used to apply picoNewton forces on micron-sized objects in liquid media, and to measure forces on that order in colloidal, biological, and biomolecular systems. Forces may be applied directly on an element naturally present within the system under observations, such as bacteria, sperm, or specific organelles in a living eukaryo...