Wolfgang Jaschinski

Wolfgang Jaschinski
Technische Universität Dortmund | TUD · Leibniz Research Centre for Working Environment and Human Factors

Dr.-Ing.

About

122
Publications
27,189
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2,112
Citations
Citations since 2017
14 Research Items
604 Citations
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100

Publications

Publications (122)
Article
Purpose. This review article describes recent findings of eye movement research of ocular vergence and provides an in- terpretation regarding those aspects of binocular vision that are assessed by clinical nonius tests. Material and Methods. In the clinical practice of binocular testing, different types of nonius tests are traditionally used for th...
Article
Full-text available
The abstract book of the last European Conference on Eye Movements (Martinez-Conde, Martinez-Otero, Compte, & Groner, 2019) lists abstracts of 373 presentations, but less than five percent investigate vergence eye movements, i.e. the coordination of the right and left eye. Why then a special issue on this neglected issue? Human vision under natural...
Article
Full-text available
Fixation disparity (FD) refers to a suboptimal condition of binocular vision. The oculomotor aspect of FD refers to a misadjustment in the vergence angle between the two visual axes that is measured in research with eye trackers (objective fixation disparity, oFD). The sensory aspect is psychophysically tested using dichoptic nonius lines (subjecti...
Conference Paper
Full-text available
Eye care professionals first identified computer vision syndrome (CVS) more than 30 years ago, when computers emerged in the 1980s. CVS refers to the physical discomfort and vision-related problems experienced during and after prolonged computer use. These include eye fatigue, ocular discomfort, dry eye, blurred vision, tearing, headaches, neck pai...
Article
Full-text available
Inaccuracy in the vergence eye position (“fixation disparity”) can occur despite a fusion stimulus. When measured with eye trackers, this inaccuracy is referred to as “objective fixation disparity”. It is a matter of debate whether objective fixation disparity can be estimated with a technically simple psycho-physical procedure, i.e. the perceived...
Data
The individual linear fixation disparity curves of all participants. (PDF)
Data
Data for group analyses. (XLSX)
Data
Data for individual analyses. (XLSX)
Article
Full-text available
Binocular vision refers to the integration of images in the two eyes for improved visual performance and depth perception. One aspect of binocular vision is the fixation disparity, which is a suboptimal condition in individuals with respect to binocular eye movement control and subsequent neural processing. The objective fixation disparity refers t...
Data
Complete dataset of the individual subjects. For each participant it is displayed the robust regression line of subjective and objective fixation disparity as a function of the vergence stimulus (1/meter). For each vergence stimulus, each data point refers to one of the 8 single runs of both sessions (see Fig 4). (TIF)
Data
Data analyses and mixed-effects models. (PDF)
Data
Accuracy of objective fixation disparity. (PDF)
Article
Full-text available
Video eye trackers rely on the position of the pupil centre. However, the pupil centre can shift when the pupil size changes. This pupillary artifact is investigated for binocular vergence accuracy (i.e. fixation disparity) in near vision where the pupil is smaller in the binocular test phase than in the monocular calibration. A regression between...
Article
Video eye trackers rely on the position of the pupil centre. However, the pupil centre can shift when the pupil size changes. This pupillary artefact is investigated for binocular vergence accuracy (i.e. fixation disparity) in near vision where the pupil is smaller in the binocular test phase than in the monocular calibration. A regression between...
Chapter
At office computer work, musculoskeletal complaints can occur when workplace conditions are not designed according to physiological dispositions of the office worker. Regarding neck pain, the vertical position of the monitor should be adjusted in a way that the head adopts a comfortable posture. For investigating this physiological condition, this...
Chapter
The present paper provides a summary of three studies concerning the influence of glasses on the physiology and ergonomics in presbyopic computer users. The first study was a survey of 175 VDU (visual display unit) workstation users wearing glasses, age 35 and older. In the second study 23 subjects of the survey study (first study) tested a progres...
Article
Full-text available
In optometry of binocular vision, the question may arise whether prisms should be included in eyeglasses to compensate an oculomotor and/or sensory imbalance between the two eyes. The corresponding measures of objective and subjective fixation disparity may be reduced by the prisms, or the adaptability of the binocular vergence system may diminish...
Article
Full-text available
When measuring fixation disparity (an oculomotor vergence error), the question arises as to whether a monocular or binocular calibration is more precise and physiologically more appropriate. In monocular calibrations, a single eye fixates on a calibration target that is taken as having been projected onto the center of the fovea; the corresponding...
Article
Unlabelled: When presbyopic employees are wearing general-purpose progressive lenses, they have clear vision only with a lower gaze inclination to the computer monitor, given the head assumes a comfortable inclination. Therefore, in the present intervention field study the monitor position was lowered, also with the aim to reduce musculoskeletal s...
Article
Full-text available
This office field study investigated the effects of different types of spectacle lenses habitually worn by computer users with presbyopia and in the beginning stages of presbyopia. Computer vision syndrome was assessed through reported complaints and ergonomic conditions. A questionnaire regarding the type of habitually worn near-vision lenses at t...
Article
Two types of progressive addition lenses (PALs) were compared in an office field study: 1. General purpose PALs with continuous clear vision between infinity and near reading distances and 2. Computer vision PALs with a wider zone of clear vision at the monitor and in near vision but no clear distance vision. Twenty-three presbyopic participants wo...
Article
This study intended to measure the near and far points of clear vision as a function of the inclination of the line of sight with comfortable head posture. Measurements with different lenses for presbyopic correction were made to suggest comfortable positions of the monitor for computer work. An 'inclined optometer' was built, including a concave m...
Article
Full-text available
Progressive addition lenses (PAL) — designed for general use — provide clear vision continuously from distant to near objects (e.g. for car driving and reading printed materials) if presbyopic observers gradually lower the gaze direction of the eyes. We measured the accommodative near point as a function of vertical eye inclination in presbyopic ob...
Article
Full-text available
Zusammenfassung Experiment 1 vergleicht verschiedene Indikatoren der physiologisch günstigen Blickneigung bei individuell komfortabler Kopfneigung: beim Blick auf Sehzeichen wird die Blickneigung minimaler Anstrengung (a) und die bevorzugte Blickneigung (b) bestimmt; weiterhin wird die Ruheblickneigung in Dunkelheit mit einem Eye-tracker gemessen (...
Article
Full-text available
Zusammenfassung Das Sehen am Bildschirm erfordert die abgestimmte Bewegungskoordination der Augen und des Kopfes. Dabei kann die eingenommene Kopfneigung von Bedeutung sein. Diese Studie untersucht horizontale Kopfb ewegungen mithilfe des Trackingverhaltens und weiterer Indikatoren für eine physiologisch günstige Kopfneigung. Die komfortable Kopfne...
Article
The aim of this study was a proof of concept to examine the effects of a web-based office ergonomics intervention on subjects' individual workplace adjustments. An intervention study was conducted with 24 office workers lasting 6 weeks with three consecutive phases (before, 1 and 5 weeks after the intervention). Employees used a purpose-made websit...
Article
Full-text available
Grating patterns can cause discomfort and perceptual distortions. Individuals who experience discomfort and are susceptible to these distortions generally show weaker accommodation than those who are less susceptible. We measured the accommodative response to grating patterns known to differ in the discomfort they evoke because of differences in th...
Article
We evaluated systematically binocular coordination during a reading task by comparing binocular and monocular reading, and considering the potential effects of individual heterophoria and eye dominance. A total of 13 participants (aged 19-29 years, refractive errors -0.5 to 0.125 diopters [D]) read single sentences in a haploscope while eye movemen...
Article
Reading a text requires vergence angle adjustments, so that the images in the two eyes fall on corresponding retinal areas. Vergence adjustments bring the two retinal images into Panum's fusional area and therefore, small remaining errors or regulations do not lead to double vision. The present study evaluated dynamic and static aspects of the bino...
Conference Paper
Today, electronic reading is not limited to the classical computer screen put on the desk. It is possible to process electronic documents from screens that can be held in the hands. Several studies already showed that visual processing can be modified when participants direct the hands toward the visual display. Using an experimental approach we te...
Article
Full-text available
This study was undertaken to investigate how subjectively measured fixation disparity can be explained by (1) the convergent-divergent asymmetry of vergence dynamics (called dynamic asymmetry) for a disparity vergence step stimulus of 1° (60 arc min), (2) the dark vergence, and (3) the nonius bias. Fixation disparity, dark vergence, and nonius bias...
Article
Full-text available
We investigated the way in which binocular coordination in reading is affected by the spatial structure of text. Vergence eye movements were measured (EyeLink II) in 32 observers while they read 120 single German sentences (Potsdam Sentence Corpus) silently for comprehension. The similarity in shape between the neighboring strokes of component lett...
Article
The present study was based on the physiologically reasonable assumption that the binocular system aims for a reduction of fixation disparity during fixation and that the minimum amount of fixation disparity reflects the optimal binocular status. We measured eye movements (EyeLink II) of 18 participants, while they read 60 sentences from the Potsda...
Article
Fixation disparity, i.e. the vergence error for stationary fusion stimuli, can be measured objectively with eye trackers and subjectively with nonius lines. Between these two measures, previous studies found differences that tended to be proportional to the amount of forced vergence, i.e. the discrepancy between vergence and accommodative stimulus....
Article
Full-text available
In our study, 14 subjects read 60 sentences from the Potsdam Sentence Corpus twice (viewing distance: 60 cm), while eye movements were measured with the EyeLink II. We analyzed fixation disparities for complete sentence replications (N=388). After subtracting the average fixation disparity of each sentence from each observation (which gave the "sta...
Article
Full-text available
Among the eye movements during fixation, the function of small saccades occuring quite commonly at fixation is still unclear. It has been reported that a substantial number of these microsaccades seem to occur in only one of the eyes. The aim of the present study is to investigate microsaccades in monocular stimulation conditions. Although this is...
Article
Measuring vergence eye movements with dichoptic nonius lines (subjectively) usually leads to an overestimation of the vergence state after a step response: a subjective vergence overestimation (SVO). We tried to reduce this SVO by presenting a vergence stimulus that decoupled vergence and accommodation during the step response, i.e. reduced the deg...
Article
Full-text available
The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows fo...
Article
Many observers perceive a horizontal offset between a stereoscopically viewed object and a reference object in the fixation plane, although both objects are presented along a single line that projects through the midpoint between both eyes. These observers weigh one eye more than the other when determining the visual directions of stereo objects. T...
Article
The neural network model of Patel et al. [Patel, S. S., Jiang, B. C., & Ogmen, H. (2001). Vergence dynamics predict fixation disparity. Neural Computation, 13(7), 1495-1525] predicts that fixation disparity, the vergence error for a stationary fusion stimulus, is the result of asymmetrical dynamic properties of disparity vergence mechanisms: faster...
Article
Progressive addition lenses (PAL) - designed for general use - provide clear vision continuously from distant to near objects (e.g. for car driving and reading printed materials) if presbyopic observers gradually lower the gaze direction of the eyes. We measured the accommodative near point as a function of vertical eye inclination in presbyopic ob...
Article
Dichoptic nonius lines are used for subjectively (psychophysically) measuring vergence states, but they have been questioned as valid indicators of vergence eye position. In a mirror-stereoscope, we presented convergent and divergent step-stimuli and estimated the vergence response with nonius lines flashed at fixed delays after the disparity step...
Article
Full-text available
Determine the effects of display viewing distance on both the visual and musculoskeletal systems while the text height is held constant across viewing distances. The distance from the eyes to a computer display may affect visual and neck comfort. If the angular size of the characters remains the same, it is recommended that the display be placed at...
Article
For prism correction of associated phoria (at 5-6 m viewing distance), Hans-Joachim Haase developed--among other tests--the prevalence test, which consists of a central fixation target and two triangles that appear stereoscopically about 1.5 m in front of or behind the fixation target; the vertex of each triangle is directed towards the centre of t...
Article
Dark vergence is a resting position of vergence (tonic vergence), measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. The vergence resting position is relevant for measures of phoria and fixation disparity. Dark vergence differs reliably among subjects: the average subject converges at a viewing distance of a...
Article
Full-text available
For calibrating eye movement recordings, a regression between spatially defined calibration points and corresponding measured raw data is performed. Based on this regression, a confidence interval (CI) of the actually measured eye position can be calculated in order to quantify the measurement error introduced by inaccurate calibration coefficients...
Article
Full-text available
Vergence eye movement recordings in response to disparity step stimuli require to present different stimuli to the two eyes. The traditional method is a mirror stereoscope. Shutter glasses are more convenient, but have disadvantages as limited repetition rate, residual cross task, and reduced luminance. Therefore, we compared both techniques measur...
Article
Dark vergence is a resting position of vergence, measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. Dark vergence differs among subjects: the average subject converges to a viewing distance of about 1 m, while the inter-individual range is from infinity to about 40 cm. This paper reviews previous ergonomic s...
Article
We analysed the reliability of individual differences in parameters of binocular saccadic eye movements. During saccades between isovergent targets, the movement of the right and left eye are not exactly symmetrical (conjugate). Typically, the abducting eye has a shorter latency and reaches a higher velocity, so that a transient divergence occurs d...
Article
The visual direction of a continuously presented monocular object is captured by the visual direction of a closely adjacent binocular object, which questions the reliability of nonius lines for measuring vergence. This was shown by Erkelens, C. J., and van Ee, R. (1997a,b) [Capture of the visual direction: An unexpected phenomenon in binocular visi...
Article
With dichoptic nonius lines presented repetitively on a computer monitor for only short moments in time (e.g., 80 ms), temporal aspects of vergence can be assessed: the variability of fixation disparity with a stationary central fusion stimulus and the velocity of convergence or divergence changes. Results and test-retest correlations of these psyc...
Article
An unequal weighting of the eyes in the directional perception of stereodisparate objects, is referred to as ocular prevalence of the right or left eye, respectively. Between 1962 and 1964 H.-J. Haase developed a valence test for the prismatic correction of heterophoria. He suggested that there would be less prevalence for stereo images presented i...
Article
Background: An unequal weighting of the eyes in the directional perception ofstereodisparate objects, is referred to as ocular prevalence of the right or left eye, respectively. Between 1962 and 1964 H.-J. Haase developed a valence test for the prismatic correction of heterophoria. He suggested that there would be less prevalence for stereo images...
Article
It has been reported that changes in visual direction and retinal correspondence may limit the validity of nonius lines as a subjective measure of vergence, at least in particular viewing conditions, e.g., dynamic or forced vergence. Nonius lines may be valid at larger spatial separation between fusion contour and nonius lines. Therefore, we measur...
Article
Full-text available
Eye preference refers to an asymmetric use of the two eyes, but it does not imply a unitary asymmetry between the eyes. Many different methods are used to assess eye preference, including eyedness questionnaires and sighting tasks that require binocular and monocular alignment of a target through a hole in the middle of a card or funnel. The result...
Article
The infrared photorefractor PowerRef II (PR II; PlusoptiX AG, Nurnberg, Germany) uses the principle of eccentric photorefraction. In eight subjects the mean non-cycloplegic refraction measured with the 'Full Scan' mode of the PR II at a far viewing distance (0.2 D) was significantly more hypermetropic by 0.6 D compared with subjective refraction. T...
Article
New computer-controlled psychophysical procedures allow one to measure some temporal aspects of binocular coordination. The present study investigates whether these procedures can be operated by children and whether the tests are useful to detect previously reported impairments in dynamics and stability of vergence in children with disability in re...
Article
Background: New computer-controlled psychophysical procedures allow one to measure some temporal aspects of binocular coordination. The present study investigates whether these procedures can be operated by children and whether the tests are useful to detect previously reported impairments in dynamics and stability of vergence in children with disa...
Article
The psychophysical technique for measuring vergence with dichoptic nonius lines was used to investigate dynamic responses to step vergence stimuli. Liquid crystal shutter glasses were operated with a cathode ray tube monitor to present convergent or divergent step stimuli of 32 min arc at t = 0. The resulting initial vergence response was estimated...
Article
Full-text available
Despite previous studies it remains unclear, whether saccadic eye movements across computer screens may be adversely affected by the intermittency of light of cathode ray tubes (CRT). We measured the latency of simple saccades to peripheral targets presented on a CRT-screen, operated at refresh rates of 50, 100 and 150 Hz, compared with a special f...
Article
The present paper summarizes a series of ergonomic studies on the relation between asthenopic complaints and binocular vision at the computer workstation. In particular, the paper reports on measurements of the accuracy of ocular convergence during fixation of central fusion stimuli (i. e. fixation disparity) as a function of viewing distance. Diff...
Article
Background: The present paper summarizes a series of ergonomic studies on the relation between asthenopic complaints and binocular vision at the computer workstation. In particular, the paper reports on measurements of the accuracy of ocular convergence during fixation of central fusion stimuli (i.e. fixation disparity) as a function of viewing dis...
Chapter
This chapter addresses the question of whether vergence - an oculomotor component of binocular vision - is related to the variation of chromatic information in stimuli, thereby contributing to binocular 'colour-and-depth' perception. In particular, the chapter examined whether a near-vergence response elicited by a fusion stimulus would change when...
Article
This laboratory study investigates the relation between measures of fixation disparity (FD) (and other optometric measures) and near vision fatigue at a computer workstation. Young adult subjects with normal binocular vision performed three blocks of a visual task of 30 min each. In Block A, the viewing distance was 100 cm, as a reference without n...
Article
Some observers do not fixate accurately at the point of regard: Their vergence angle (between the visual axes of the two eyes) may correspond to points slightly nearer or farther away. This vergence error, or fixation disparity, was measured with nonius (vernier) lines at six positions of a visual display relative to the eyes. At viewing distances...
Article
Full-text available
We investigated saccades from central fixation to targets at 5 degrees to the left or right. These targets were red laser points of light with an intensity unmodulated in time (referred to as steady), while a bright background (76 cd/m(2)) was illuminated by a special fluorescent lamp, the output of which were series of light pulses (at frequencies...
Article
The reliability and validity of new tests of fixation disparity were investigated as a function of viewing distance (100, 60, 40, and 30 cm). The 'nonius offset card' presents a set of paired dichoptic nonius (vernier) lines with different offset simultaneously: the subject has to indicate the coinciding lines. The 'computer test' uses a psychophys...
Article
Both the vergence and the accommodative system have individual tonic positions (also referred to as dark vergence and dark focus, respectively) where the static response may be expected to be most accurate. This was confirmed by measuring fixation disparity with nonius lines and accommodation with an autorefractometer for foveal stimuli at viewing...
Article
The present study assumed that whole-body vibration, transmitted through the seat, impairs spatial retinal resolution and oculomotor alignment parallel to the vibration axis. More specifically, that the decrement increases gradually from single-axis lateral via single-axis vertical and dual-axis linear to dual-axis circular motion. Twenty participa...
Article
Full-text available
In an intervention phase, 38 operators used four different imposed screen positions (near versus distant, high versus low) for a full working day to experience the advantages and disadvantages. Screens at about 66 cm induced more reported strain than screens at about 98 cm. When operators later freely selected their individually most comfortable sc...
Article
Fixation disparity, i.e. the vergence error within Panum's area, can be measured psychophysically with two nonius (vernier) lines that are presented dichoptically, i.e. one to each eye. The observer adjusts these nonius lines to subjective alignment; the resulting physical nonius offset indicates the amount of fixation disparity. The present experi...
Article
When requested to place the visual display unit (VDU) at the computer workplace in the most comfortable position, users prefer viewing distances from the eyes to the screen between about 50-100 cm and a vertical inclination of gaze between the horizontal and 25 degrees. Within this range, most individuals prefer the screen at a certain position. Re...
Article
The viewing distance from the eyes to the visual display screen and the vertical inclination of gaze relative to horizontal are two aspects of work with visual display units that may affect visual functions and cause eye strain. The resting position of vergence of the eyes and the accuracy of vergence at near vision suggest that - with inter-indivi...
Article
This paper concerns the hypothesis that whole-body vibrations transmitted through the seat impair oculomotor alignment and degrade spatial retinal resolution. The decrement was assumed to increase gradually from single-axis lateral via single-axis vertical and dual-axis linear to dual-axis circular motions. 14 men and 6 women (19–26 yrs,) with good...
Article
Full-text available
We investigated several oculomotor functions at different angles of vertical inclination of the gaze direction from 15 deg upwards to 45 deg downwards. The mean accommodative resting state (measured in a dark visual field) increased when the eyes or the head were declined from 0 to 45 deg. Fixation disparity (the vergence error in minutes of arc re...
Article
Full-text available
At office workplaces equipped with visual display units (VDU) that were adjustable to various positions relative to the eyes short and long viewing distances from the eyes to the screen were imposed (mean value of about 63 and 92 cm) at two levels of screen height so that the visual target was either at eye level or 18 cm below, on the average. The...
Article
Previous research has shown that subjects with normal binocular vision differ reliably in the extent to which their fixation disparity changes in the exo direction when the viewing distance is shortened from 100 to 20 cm. Since fixation disparity can lead to asthenopic complaints, the present study investigates whether an exo fixation disparity ind...
Article
In binocular vision, fixation disparity is present when a fixation point falls within Panum's area, but not on corresponding retinal points. To investigate the effect of vergence load, fixation disparity was measured at viewing distances of 20, 30, 40, 60, and 100 cm (while the test subtended a constant angular size) by the psychophysical method of...
Article
In a series of experiments we have quantified the spatial and temporal dynamics of binocular coordination. Tasks studied ranged from simple scanning and letter detection to complex visual processing in text reading. In all of these paradigms we found similar eye movement characteristics: in 70% to 90% of the observations, the saccade of the abducti...
Article
Full-text available
Contrast sensitivity to sinusoidal gratings was measured at spatial frequencies of 1.5-16 c/deg in 8 subjects before and after wearing prisms (for at least two weeks) to correct heterophoria, prescribed by the full correction method of H.J. Haase (Binocular testing and distance correction with the Berlin Polatest [trans. W. Baldwin]. J. Am. Optom....
Article
Contrast sensitivity to sinusoidal gratings was measured at spatial frequencies of 1.5–16 c/deg in 8 subjects before and after wearing prisms (for at least two weeks) to correct heterophoria, prescribed by the full correction method of H.-J. Haase (Binocular testing and distance correction with the Berlin Polatest [trans. W. Baldwin]. J. Am. Optom....
Article
A 19-day time series of fluid, flow, and suspended-sediment characteristics in the benthic boundary layer is analyzed to identify major sedimentary processes active over the prodelta region of the Amazon subaqueous delta. Measurements were made by the benthic tripod GEOPROBE placed on the seabed in 65 m depth near the base of the deltaic foreset be...
Article
Full-text available
This study investigates possible effects of temporally modulated light stimulation near critical fusion frequency (CFF) when subjects observe a cathode ray tube (CRT) operated at different refresh rates. Various visual functions were measured in a series of tests of 2.5 min duration. In experiment 1, at a repetition rate of 50 Hz mean pupil size wa...