Frans W Cornelissen

Frans W Cornelissen
University of Groningen | RUG · Department of Ophthalmology

PhD

About

240
Publications
28,702
Reads
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4,542
Citations
Additional affiliations
June 1994 - February 1995
Sensory Research Institute
Position
  • Sensory Research Institute Syracuse
August 1992 - July 1998
University of Freiburg
September 1989 - December 2013
University of Groningen

Publications

Publications (240)
Article
Full-text available
A paper by McCalley, Bouwhuis, and Juola (1995) suggested differences between younger and older adults in the use of visual cues. Furthermore, they reported these differences could largely be attributed to diminished (peripheral) visual processing capacities of elderly adults. Here, we reanalyze the data of McCalley and colleagues emphasizing relat...
Article
It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating t...
Article
We studied the ability of human subjects to memorize the visual information in computer-generated random block patterns defined either by luminance contrast, by color contrast, or by both. Memory performance declines rapidly with increasing inter-stimulus interval, showing a half-life of approximately 3 s. We further show that memory performance de...
Article
BACKGROUNDA critical step in automatic microscopy is focusing. This report describes a robust and fast autofocus approach useful for a wide range of microscopic modalities and preparations.METHODS The focus curve is measured over the complete focal range, reducing the chance that the best focus position is determined by dust or optical artifacts. C...
Conference Paper
Segmentation based on color, instead of intensity only, provides an easier distinction between materials, on the condition that robustness against irrelevant parameters is achieved, such as illumination source, shadows, geometry and camera sensitivities. Modeling the physical process of the image formation provides insight into the effect of Differ...
Article
Characterization of tissues can be based on the topographical relationship between the cells. Such characterization should be insensitive to distortions intrinsic to the acquisition of biological preparation. In this paper, a method for the robust segmentation of tissues based on the spatial distribution of cells is proposed. The neighborhood of ea...
Article
Jenness and Shevell (Vision Res 1995;35:797–805) reported that a red background with white dots scattered on it has a different influence on a target's apparent colour than an equivalent uniform background. We show that this finding depends on what one considers an equivalent background. Jenness and Shevell averaged the chromaticity and luminance o...
Article
We examined search performance throughout the functional visual field. This has been shown to be an important determinant for performance in daily life tasks. We were interested to see how aging affects performance and whether we could find evidence for compensatory strategies in subjects with visual field defects. The task was to localise a target...
Article
On the basis of signal-detection theory, we have formulated a model that accurately explains performance on a visual short-term memory task involving random block patterns. The model assumes that the internal response of an observer for detecting a change in any given element of the block pattern is noisy and has a Gaussian-shaped distribution. On...
Article
Four issues concerning colour constancy and relational colour constancy are briefly considered: (1) the equivalence of colour constancy and relational colour constancy; (2) the dependence of relational colour constancy on ratios of cone excitations due to light from different reflecting surfaces, and the association of such ratios with von Kries' c...
Article
Full-text available
Visual discrimination and short-term recognition memory for computer-generated random patterns were explored in 23 patients with a postsurgical lesion in one of the cortical hemispheres. Their results are compared with those of 23 age-matched volunteers. In a same-different forced-choice discrimination task, d' and log beta (measures of sensitivity...
Article
A binocular pair of fiberscopes relays high-resolution images of CRT displays from an adjacent room to an observer lying in a scanner in functional Magnetic Resonance Imaging (fMRI) studies of visual function. We review the problems that must be overcome by any visual display for use in fMRI, present the specific solution we developed, and discuss...
Article
Purpose: we re-examine Jennes and Sh.'vell's (Vision Res. 35. 1995, 797-805) claim (hat a background scatlered with white or green dots (referred to as the "context") has a different influence on an annul us' apparent colour than an "equivalent" background with the same space averaged chromaticil y and luminance. A critical point, however, is the c...
Article
The apparent colour of a target depends to some extent on the colour of the background. Jennes and Shevell have recently shown that a red background scattered with white or green dots has a different influence on the apparent colour of a target than a uniform background with the same space-averaged chromaticity and luminance (1995 Vision Research 3...
Article
We examined whether matching instructions influenced the eye movements that subjects made during a colour constancy experiment. The instructions changed the average duration of exposure to the spectrally biased surround. We also measured the influence that small changes in exposure duration have on the perceived colour. Eye movement and adaptation...
Article
We investigated the relationship between the illumination level and the ability of visually impaired subjects to detect and recognize objects in a realistic visual environment. Subjects often continued to show substantial improvement at light levels where normal subjects have reached maximum performance. Integrated contrast sensitivity, a summary m...
Article
Full-text available
It has been suggested that density modulated random-dot patterns can be used to study higher order pattern vision [Van Meeteren and Barlow (1981) Vision Research, 21, 765-777]. The high contrast dots of which the pattern is composed, are assumed to be reliably transduced and transmitted by the lower levels of the visual system. Therefore, such dot...
Article
For the rehabilitation of people with impaired vision, it is essential to have adequate (preferably quantitative) information about their residual visual functions. Special attention is given to the extra information provided by the results of measurement of the contrast sensitivity, especially in combination with the results of other measurements,...
Article
Kittens do not learn to use visual information to guide their behaviour if they are deprived of the optic flow that accompanies their own movements. We show that the optic flow that is required for developing visually guided behaviour is derived from changes in contour orientations, rather than from velocity patterns. We used several tests to asses...
Article
Full-text available
In this paper we describe a method for the preliminary assessment of the illumination needs of partially sighted individuals. The method is based on determining the smallest readable lettersize under different levels of illumination. Half of the partially sighted in our population had a performance that was dependent upon the level of illumination....
Article
A monkey (Macaca fascicularis) spent its first three months under far red illumination that made color vision impossible. It developed normal spectral sensitivity. In the present study we examined two aspects of color vision that presumably reflect cortical connectivity. In the first part of this article we show that chromatic induction was also un...

Projects

Projects (6)
Project
Homonymous Hemianopia refers to a visual field defect in which the left or right half of the visual field is not perceived, contralateral to the brain damage and where the defect is similar for both eyes. People with hemianopia experience difficulties in daily life, mainly with regards to reading, searching and mobility. They benefit from training aimed to decrease the impact of the visual field deficit through optimizing visual scanning. Therefore, it is of utmost importance to inform patients about how their (lack of) scanning behavior relates to difficulties they experience in daily life and how they can improve it to overcome these difficulties. Knowledge about which scanning behavior is optimal, however, is mostly based on experiences and assumptions of professionals, and not supported by scientific literature and empirical data. Innovative techniques such as mobile eye-tracking and Virtual Reality allow us to examine scanning behavior in a standardized manner. In the current project, existing prototypes using these techniques are being developed into measures that can be used in clinical practice. The aim of this project is to use these innovative techniques to examine the relationship between scanning behavior and various behaviors (mobility, searching) in patients with hemianopia, people with simulated hemianopia and a control group with normal vision. Insight into efficient scanning behavior will contribute to an improvement of the clinical practice of people with hemianopia. The project will take place from 2019 to 2023 at Royal Dutch Visio, center of expertise for blind and partially sighted people, in collaboration with the University of Groningen (UG) and the University Medical Center Groningen (UMCG). Josephien Jansen, PhD student at the UG will conduct the research. The project leaders are dr. G.A. de Haan, dr. J.H.C. Heutink (UG, Royal Dutch Visio) and prof. dr. F.W. Cornelissen (UMCG).
Project
EGRET is the training environment for 15 highly talented Early Stage Researchers. The individual and collaborative outputs of their work contribute to the following aims: a) acquiring new, quantitative knowledge on glaucoma and the ageing visual system; and b) applying this new knowledge to boost innovation in glaucoma care in both the public and private sectors.
Project
EGRET-plus is the training environment for 15 highly talented Early Stage Researchers. The individual and collaborative outputs of their work contribute to the following aims: a) acquiring new, quantitative knowledge on glaucoma and the ageing visual system; and b) applying this new knowledge to boost innovation in glaucoma care in both the public and private sectors. For more information about EGRET+ and its fellows, please visit www.egret-plus.eu