Siegfried Wahl

Siegfried Wahl
University of Tuebingen | EKU Tübingen · Institute for Ophthalmic Research

PhD

About

165
Publications
29,219
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1,753
Citations
Additional affiliations
October 1997 - July 2000
Max Planck Institute for Developmental Biology
Position
  • PhD Student

Publications

Publications (165)
Article
Full-text available
When considering external assistive systems for people with motor impairments, gaze has been shown to be a powerful tool as it is anticipatory to motor actions and is promising for understanding intentions of an individual even before the action. Up until now, the vast majority of studies investigating the coordinated eye and hand movement in a gra...
Article
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The present study investigates the effects of peripheral spatial cues and optically distorting augmentations over eccentric vision mechanisms in normally sighted participants with simulated scotoma. Five different augmentations were tested inside a virtual reality (VR)-gaming environment. Three were monocular spatial cues, and two were binocular op...
Preprint
Full-text available
For decades, manufacturers have attempted to reduce or eliminate the optical aberrations that appear on the progressive addition lens' surfaces during manufacturing. Besides every effort made, some of these distortions are inevitable given how lenses are fabricated, where in fact, astigmatism appears on the surface and cannot be entirely removed or...
Preprint
The blind spot is both a necessity and a nuisance for seeing. It is the portion of the visual field projecting to where the optic nerve crosses the retina, a region devoid of photoreceptors and hence visual input. The precise way in which vision transitions into blindness at the blind spot border is to date unknown. A chief challenge to map this tr...
Article
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Purpose: This study proposes a novel approach for objective and automated peripheral contrast sensitivity (CS) testing using reflexive saccades. Here the CS was examined in various areas the of visual field (VF) using a live analysis of gaze data. For validation of the new test, we examined CS with an established procedure of identifying the orien...
Article
We had previously found that chicken eyes with normal visual experience grow larger when they have more L cones, relative to M cones. It is not known whether also S cone abundancies may affect eye size, whether cone abundancy ratios can also affect the amount of deprivation myopia that is induced by diffusers in front of the eyes, and whether broad...
Article
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Understanding the ocular structural changes are fundamental to defining strategies for myopia prevention and management. This study aimed to establish age-gender specific normative LMS parameters for axial length to generate percentile and Z-score growth curves in a population of Chinese schoolchildren. A total of 14,760 individuals aged 6 to 15 ye...
Article
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Perception and action are essential in our day-to-day interactions with the environment. Despite the dual-stream theory of action and perception, it is now accepted that action and perception processes interact with each other. However, little is known about the impact of unpredicted changes of target size during grasping actions on perception. We...
Article
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This paper documents the design, implementation and evaluation of the Unfolding Space Glove – an open source sensory substitution device. It transmits the relative position and distance of nearby objects as vibratory stimuli to the back of the hand and thus enables blind people to haptically explore the depth of their surrounding space, assisting w...
Article
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Peripheral retinal contrast reduction is suggested as a potential myopia control strategy. However, the underlying mechanism is yet unknown. Therefore, this study investigated the influence of peripheral contrast reduction on central chromatic and achromatic contrast sensitivity (CS). A total of 19 participants were included. Peripheral contrast re...
Article
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Purpose: To determine how the position of the centre of rotation of the eyeball is related to axial length and refractive error when horizontal and vertical eye movements are performed. Methods: A custom-built eye tracker was used that determined the centre of rotation of the eye (COR) from lateral displacements of the pupil centre. Horizontal a...
Article
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Virtual reality as a research environment has seen a boost in its popularity during the last decades. Not only the usage fields for this technology have broadened, but also a research niche has appeared as the hardware improved and became more affordable. Experiments in vision research are constructed upon the basis of accurately displaying stimuli...
Article
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Progressive addition lenses (PALs) are ophthalmic lenses to correct presbyopia by providing improvements of near and far vision in different areas of the lens, but distorting the periphery of the wearer’s field of view. Distortion-related difficulties reported by PAL wearers include unnatural self-motion perception. Visual self-motion perception is...
Article
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Objective To investigate whether spectacle lens sales data can be used to estimate the population distribution of refractive error amongst ametropes and hence estimate the current and future risk of vision impairment. Design Cross Sectional Study Subjects A total 141,547,436 spectacle lens sales records from an international European lens manufac...
Article
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Slit lamps are routinely used to examine large numbers of patients every day due to high throughput. Previous, cultivation-based results suggested slit lamps to be contaminated with bacteria, mostly coagulase-negative staphylococci, followed by micrococci, bacilli, but also Staphylococcus aureus. Our study aimed at obtaining a much more comprehensi...
Conference Paper
Colours can induce several psychological effects, conditioning perceptions, cognitive/emotional states and human performances. In this exploratory study we investigated the effect of a yellow light exposure, obtained filtering the ambient light with coloured glasses, on the human's psychological functioning. In particular we wanted to assess if peo...
Article
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Purpose: The aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live- detection of optokinetic nystagmus (OKN) and an adaptive psychometric procedure. In addition, the study sought to replicate the known effect of defocus on CS for the OKN-based measurements in emmetropic participants. Methods...
Article
A novel interferometric instrument for measuring neural transfer function (NTF) of the eye is presented. The device is based on a liquid-crystal-on-silicon spatial light modulator (SLM), which is used to create two laterally separated wavefronts in the pupil plane of the eye that interfere on the retina. The phase mask on the SLM, consisting of two...
Article
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Myopia is increasing worldwide hence it exists a pressing demand to find effective myopia control strategies. Previous studies have shown that light, spectral composition, spatial frequencies, and contrasts play a critical role in refractive development. The effects of light on multiple retinal processes include growth regulation, but also visual p...
Article
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Purpose. Current prevalence rates of myopia in children and adolescents vary all over the world, with especially high prevalence rates in East Asian countries. The objective of this study was to describe the refractive status in children and adolescents growing up in Germany. Material and Methods. Non-cycloplegic refractive status of children of th...
Preprint
Full-text available
Objective: To investigate whether spectacle lens sales data can be used to estimate the population distribution of refractive error amongst ametropes and hence estimate the current and future risk of vision impairment. Design: Cross Sectional Study Subjects: A total 141,547,436 spectacle lens sales records from an international European lens manufa...
Article
Full-text available
Purpose: To examine whether data sourced from electronic medical records (EMR) and a large industrial spectacle lens manufacturing database can estimate refractive error distribution within large populations as an alternative to typical population surveys of refractive error. Subjects: A total of 555,528 patient visits from 28 Irish primary care...
Article
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With rapidly developing technology, visual cues became a powerful tool for deliberate guiding of attention and affecting human performance. Using cues to manipulate attention introduces a trade-off between increased performance in cued, and decreased in not cued, locations. For higher efficacy of visual cues designed to purposely direct user’s atte...
Article
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Purpose To generate continuous growth curves for axial length (AL) in German children. We hypothesise that percentile curves of AL can be used as a predictive measure of myopia. Methods In this longitudinal and cross‐sectional LIFE Child Study, children’s non‐cycloplegic refraction data was collected using the Zeiss i.Profiler plus while AL was me...
Preprint
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Purpose: The purpose of this study is to present a framework to predict visual acuity (VA) based on a convolutional neural network (CNN) and to further to compare PAL designs. Method: A simple two hidden layer CNN was trained to classify the gap orientations of Landolt Cs by combining the feature extraction abilities of a CNN with psychophysical st...
Article
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The prevalence of myopia is increasing extensively worldwide. The number of people with myopia in 2020 is predicted to be 2.6 billion globally, which is expected to rise up to 4.9 billion by 2050, unless preventive actions and interventions are taken. The number of individuals with high myopia is also increasing substantially and pathological myopi...
Article
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Visual search becomes challenging when the time to find the target is limited. Here we focus on how performance in visual search can be improved via a subtle saliency-aware modulation of the scene. Specifically, we investigate whether blurring salient regions of the scene can improve participant’s ability to find the target faster when the target i...
Article
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People living with a degenerative retinal disease such as retinitis pigmentosa are oftentimes faced with difficulties navigating in crowded places and avoiding obstacles due to their severely limited field of view. The study aimed to assess the potential of different patterns of eye movement (scanning patterns) to (i) increase the effective area of...
Article
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A number of virtual reality head-mounted displays (HMDs) with integrated eye trackers have recently become commercially available. If their eye tracking latency is low and reliable enough for gaze-contingent rendering, this may open up many interesting opportunities for researchers. We measured eye tracking latencies for the Fove-0, the Varjo VR-1,...
Article
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Background: A case study is proposed to empirically test and discuss the eye-tracking status-quo hardware capabilities and limitations of an off-the-shelf virtual reality (VR) headset with embedded eye-tracking for at-home ready-to-go online usability in ophthalmology applications. Methods: The eye-tracking status-quo data quality of the HTC Viv...
Article
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Progressive addition lenses introduce distortions in the peripheral visual field that alter both form and motion perception. Here we seek to understand how our peripheral visual field adapts to complex distortions. The adaptation was induced across the visual field by geometrically skewed image sequences, and aftereffects were measured via changes...
Article
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Retinal shape presents a clinical parameter of interest for myopia, and has commonly been inferred indirectly from peripheral refraction (PRX) profiles. Distortion-corrected optical coherence tomography (OCT) scans offer a new and direct possibility for retinal shape estimation. The current study compared retinal curvatures derived from OCT scans v...
Article
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Spatially varying distortions (SVDs) are common artifacts of spectacles like progressive additional lenses (PALs). To habituate to distortions of PALs, the visual system has to adapt to distortion-induced image alterations, termed skew adaptation. But how this visual adjustment is achieved is largely unknown. This study examines the properties of v...
Article
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Optical distortions as a visual disturbance are inherent in many optical devices such as spectacles or virtual reality headsets. In such devices, distortions vary spatially across the visual field. In progressive addition lenses, for example, the left and right regions of the lens skew the peripheral parts of the wearers visual field in opposing di...
Article
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Lasers with wavelengths in the visible and near infrared region, pose a potential hazard to vision as the radiation can be focused on the retina. The laser safety standard IEC 60825‐1:2014 provides limits and evaluation methods to performa classification for such systems. An important parameter is the retinal spot size which is described by the ang...
Preprint
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To report eye examinations findings and cost-efficiency of mobile eye and vision care screening in underserved areas in north India. The Aloka Vision Program combines optometrical and ophthalmological screening as mobile eye camps with organized referrals to local eye hospitals. 402 people from urban (N = 191) and rural (N = 211) areas in the distr...
Article
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Purpose This study describes the prevalence of visual impairment caused by uncorrected distance refractive error and the spectacle coverage in a large cohort of German children and adolescents. Furthermore, we determined the prevalence of amblyopia and amblyopia treatment. Methods Optometrists carried out visual acuity (VA) testing, non‐cycloplegi...
Article
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Purpose: Choroidal thickness (ChT) and choroidal vascularity index (CVI) represent two important metrics in health-, disease-, and myopia-related studies. Wide-field swept-source optical coherence tomography (OCT) provides improved and extended imaging and extraction of choroidal variables. This study characterizes the topography and repeatability...
Article
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Eccentric photorefraction is an objective technique to determine the refractive errors of the eye. To address the rise in prevalence of visual impairment, especially in rural areas, a minicomputer-based low-cost infrared photorefractor was developed using off-the-shelf hardware components. Clinical validation revealed that the developed infrared ph...
Article
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Purpose In this study, we investigate to what degree augmented reality technology can be used to create and evaluate a visual-to-auditory sensory substitution device to improve the performance of blind persons in navigation and recognition tasks. Methods A sensory substitution algorithm that translates 3D visual information into audio feedback was...
Article
We had previously found that M to L cone abundancy ratios in the chicken retina are correlated with vitreous chamber depth and refractive state in chickens eyes, when they have normal visual exposure but not when they develop deprivation myopia. The finding suggests an interaction between cone abundancies and emmetropization. In the current study,...
Preprint
Full-text available
Background: Adding an eye tracker inside a head-mounted display (HMD) can offer a variety of novel functions in virtual reality (VR). Promising results point towards its usability as a flexible and interactive tool for low vision assessments and research of low vision functional impairment. Visual field (VF) perimetry performed using VR methodologi...
Article
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Systematic shortening or lengthening of target objects during saccades modifies saccade amplitudes and perceived size of the objects. These two events are concomitant when size change during the saccade occurs asymmetrically, thereby shifting the center of mass of the object. In the present study, we asked whether or not the two are necessarily lin...
Article
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Advancements in clinical measurement of refractive errors should lead to faster and more reliable measurements of such errors. The study investigated different aspects of advancements and the agreement of the spherocylindrical prescriptions obtained with an objective method of measurement (“Aberrometry” (AR)) and two methods of subjective refinemen...
Article
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Myopic axial eye growth has mechanical implications on ocular structures, such as the retinal and foveal shape integrity or choroidal thickness. The current study investigated myopia-related changes of retinal radius of curvature, foveal width, depth, slope and choroidal thickness. Wide-field swept-source OCT line and volume scans were performed on...
Article
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Clinical studies and basic research have attempted to establish a relationship between myopia progression and single vision spectacle wear, albeit with unclear results. Single vision spectacle lenses are continuously used as the control group in myopia control trials. Hence, it is a matter of high relevance to investigate further whether they yield...
Article
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Microsaccades are involuntary eye movements occurring naturally during fixation. In this study, microsaccades were investigated under monocularly and binocularly stimulated conditions with respect to their directional distribution and rate signature, that refers to a curve reporting the frequency modulation of microsaccades over time. For monocular...
Article
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Microscopes are used in virtually every biological and medical laboratory. Previous cultivation-based studies have suggested that direct contact with microscope eyepieces increases the risk of eye infections. To obtain a deeper insight into the microbiota on oculars, we analysed 10 recently used university microscopes. Their left oculars were used...
Preprint
Laser systems emitting radiation in the visible and near infrared region are potentially hazardous for the retina of the human eye. This can result in irreparable injuries due to photomechanical, photothermal or photochemical light-tissue interactions. This investigation focuses on the photothermal interaction for which a computer model is used to...
Article
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The current study explored the effects of contrast adaptation on the accommodation response (AR), using low- and high-pass filtered video clips as stimuli. Ten young myopic (mean ± standard deviation: −2.91 ± 1.36D) and 10 near emmetropic subjects (−0.19 ± 0.14D) participated in the study. The AR was monitored under monocular viewing conditions usi...
Article
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Regularly touched surfaces are usually contaminated with microorganisms and might be considered as fomites. The same applies for spectacles, but only little is known about their microbial colonization. Previous cultivation-based analyses from our group revealed a bacterial load strongly dominated by staphylococci. To better account for aerotolerant...
Article
Background: In low vision patients, the assessment of contrast sensitivity is an essential tool to determine the stage of visual impairment. However, traditional contrast sensitivity tests rely on verbal feedback, and the expertise of the examiner. Objective: In the current study, a fast, OKN-based virtual diagnosis tool was developed estimating...