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At least 1,423 records · Page 79Linked to original sources
PubMed1996

Images, words, and questions: variables that influence beliefs about vision in children and adults.

In three studies we used animated computer graphics to examine beliefs among children and adults that vision involved input to the eyes (the intromission theory) or emissions from the eye (the extramission theory). Results supported previous findings which showed a decrease in extramission and an increase in intromission responses across age. The findings also indicated that there were more extramission interpretations when subjects were tested with graphic images, and more intromission interpretations when the questioning was purely verbal. However, the magnitude of the effect was highly dependent upon question format. The differences between graphic and verbal question presentations (A) are consistent with our theory on the origins of extramission beliefs, (B) suggest that beliefs can vary as a function of form of symbolization, and (C) are contrary to long-standing beliefs of educators and psychologists that emphasize the importance of concrete, pictorial representation.

Adolescent↗
PubMed2006

Vehicle detection by means of stereo vision-based obstacles features extraction and monocular pattern analysis.

This paper presents a stereo vision system for the detection and distance computation of a preceding vehicle. It is divided in two major steps. Initially, a stereo vision-based algorithm is used to extract relevant three-dimensional (3-D) features in the scene, these features are investigated further in order to select the ones that belong to vertical objects only and not to the road or background. These 3-D vertical features are then used as a starting point for preceding vehicle detection; by using a symmetry operator, a match against a simplified model of a rear vehicle's shape is performed using a monocular vision-based approach that allows the identification of a preceding vehicle. In addition, using the 3-D information previously extracted, an accurate distance computation is performed.

Algorithms↗
PubMed1997

[Computer-based assessment of visual acuity--technical realization].

Testing of visual acuity for distant vision can be computerized by using monitor screens to present optotypes. Because of the limited spatial resolution of conventional monitors, measurement of visual acuity for near vision is not possible. This paper describes a new computer-aided method for the measurement of both near and distant visual acuity. Our approach to the assessment of visual acuity for near vision is based on a recently developed liquid crystal display (a screen, LCD) measuring 10.5 mm x 15 mm. The LCD permits the presentation of optotypes for the measurement of visual acuity between 0.063 and 1.25 at a viewing distance of 40 cm (near/distant). The presentation of optotypes for the assessment of the acuity of distant vision uses a standard 17" monitor that permits visual acuity figures of between 0.032 and 1.6 to be assessed.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

Managing low vision patients.

1. The ophthalmologist and staff are ultimately responsible for identifying low vision patients. 2. Most low vision patients who have a professional low vision evaluation are able to use vision enhancing devices. 3. In addition to optical magnifyers, new computer and television technology enhances use of residual vision.

Communication Devices for People with Disabilities↗
PubMed1997

Orbital granulocytic sarcoma in an elderly patient.

PURPOSE: To report a 71-year-old woman with acute myelogenous leukemia in remission who developed orbital granulocytic sarcoma. METHODS: The patient was referred for acute proptosis and decreased vision of the right eye. Computed tomography of the orbits demonstrated a right extraconal mass compressing the optic nerve. A right lateral orbitotomy was performed, and a portion of the mass was excised for diagnostic purposes and orbital decompression. RESULTS: Histopathologic and immunohistochemical evaluation disclosed orbital granulocytic sarcoma. With chemotherapy and radiation, vision remained stable and right proptosis resolved. CONCLUSIONS: Orbital granulocytic sarcoma is usually diagnosed in children with a history of acute myelogenous leukemia. This case demonstrated that this entity may also occur rarely in older patients with a history of acute myelogenous leukemia.

Aged↗
PubMedDate not supplied

Multiple visual hallucinations and pseudohallucinations in one individual patient: when the world is turning upside down and the television keeps falling to the ground while dwarfs are parading on the ceiling.

We report on a patient who experienced visual hallucinations and pseudohallucinations comprising palinopsia, peduncular hallucinosis, and oblique vision. The most probable etiologies of these phenomena are discussed with respect to clinical presentation and findings on computed tomography and magnetic resonance imaging.

Aged↗
PubMed1979

The importance of early diagnosis and treatment of the meningiomas of the planum sphenoidale and tuberculum sellae: a retrospective study of 105 cases.

Delay in the diagnosis of meningiomas of the tuberculum sellae and planum sphenoidale is detrimental to the patient in terms of visual recovery, morbidity and mortality. Early accurate diagnosis of these tumors is possible through the use of computed tomography which is recommended for all patients with unexplained impairment of vision. In this article 105 cases of meningiomas of the planum sphenoidale and tuberculum sellae are reviewed. In only five cases was the diagnosis made within three months of the onset of the symptoms.

Cerebral Angiography↗
PubMed1993

Properties of curvilinear vection.

Approximately linear relationships were observed between contrast, spatial frequency, temporal frequency, or velocity of stimulation and perceived velocity of curvilinear vection--that is, a visually induced self-motion in a curved path. Similarly, linear relationships were also found between the perceived degree of curvature of curvilinear vection and spatial frequency or velocity of stimulation. Since the perceived velocity of curvilinear vection varies with contrast, spatial frequency, temporal frequency, and angular velocity, and the perceived degree of curvature of curvilinear vection varies only with spatial frequency and angular velocity, peripheral vision is not sufficient for computing accurately the curvilinear component of induced self-motion in a curved path. Concurrently, it was shown that the perceived direction of curvilinear vection is not always unambiguously perceived (Sauvan & Bonnet, 1989). Consequently, it is suggested that two different types of visual processing, which involve the peripheral or the central vision, underlie the processing of curvilinear vection.

Adult↗
PubMed2001

Visual indexes, preconceptual objects, and situated vision.

This paper argues that a theory of situated vision, suited for the dual purposes of object recognition and the control of action, will have to provide something more than a system that constructs a conceptual representation from visual stimuli: it will also need to provide a special kind of direct (preconceptual, unmediated) connection between elements of a visual representation and certain elements in the world. Like natural language demonstratives (such as 'this' or 'that') this direct connection allows entities to be referred to without being categorized or conceptualized. Several reasons are given for why we need such a preconceptual mechanism which individuates and keeps track of several individual objects in the world. One is that early vision must pick out and compute the relation among several individual objects while ignoring their properties. Another is that incrementally computing and updating representations of a dynamic scene requires keeping track of token individuals despite changes in their properties or locations. It is then noted that a mechanism meeting these requirements has already been proposed in order to account for a number of disparate empirical phenomena, including subitizing, search-subset selection and multiple object tracking (Pylyshyn et al., Canadian Journal of Experimental Psychology 48(2) (1994) 260). This mechanism, called a visual index or FINST, is briefly discussed and it is argued that viewing it as performing a demonstrative or preconceptual reference function has far-reaching implications not only for a theory of situated vision, but also for suggesting a new way to look at why the primitive individuation of visual objects, or proto-objects, is so central in computing visual representations. Indexing visual objects is also, according to this view, the primary means for grounding visual concepts and is a potentially fruitful way to look at the problem of visual integration across time and across saccades, as well as to explain how infants' numerical capacity might arise.

Cognitive Science↗
PubMed1994

Representation of the visual field in the occipital striate cortex.

The representation of the field of vision in the human striate cortex is based on the Holmes map in which about 25% of the surface area of the striate cortex is allocated to the central 15 degrees of vision. Following the introduction of computed tomography of the brain, the accuracy of the Holmes map was apparently confirmed by clinical/radiological correlation, but a revision has been proposed by Horton and Hoyt based on a magnetic resonance imaging study of three patients with visual field defects due to striate lesions. They propose that the central cortical representation of vision occupies a much larger area. This study reviews the perimetric and imaging findings in a larger series of patients with striate cortical disease and provides support for the revised representation. The clinical phenomenon of macular sparing and its relation to representation of the macula at the occipital pole is also discussed.

Adult↗
PubMed2002

Introduction to the special issue on virtual reality environments in behavioral sciences.

Virtual reality (VR) is usually described in biology and in medicine as a collection of technologies that allow people to interact efficiently with three-dimensional (3-D) computerized databases in real time using their natural senses. This definition lacks any reference to head-mounted displays (HMDs) and instrumented clothing such as gloves or suits. In fact, less than 10% of VR healthcare applications in medicine are actually using any immersive equipment. However, if we focus our attention on behavioral sciences, where immersion is used by more than 50% of the applications, VR is described as an advanced form of human- computer interface that allows the user to interact with and become immersed in a computer-generated environment. This difference outlines a different vision of VR shared by psychologists, psychotherapists, and neuropsychologists: VR provides a new human-computer interaction paradigm in which users are no longer simply external observers of images on a computer screen but are active participants within a computer-generated 3-D virtual world. This special issue investigates this vision, presenting some of the most interesting applications actually developed in the area. Moreover, it discusses the clinical principles, human factors, and technological issues associated with the use of VR in the behavioral sciences.

Behavioral Sciences↗
PubMed1996

The necessary field of view to read with an optimal stand magnifier.

BACKGROUND: For most people with low vision, some form of magnification is necessary to read. Using a magnifier reduces the number of letters that can be seen simultaneously (field of view), which has been shown to decrease reading rates. This study sought to determine how many letters are necessary to attain maximal reading rates with a stand magnifier. METHODS: Younger and older normally-sighted and visually-impaired observers read short passages using a fiber optic stand magnifier (taper). The optical properties of this magnifier allowed the field of view to be precisely varied. Each subject read using at least four field sizes (3, 5, 9 and 13 characters visible) while reading speed was measured. RESULTS: Reading rates continued to increase with as many as 13 characters visible, regardless of age or vision status. In addition, reading with the taper was slower for all subject groups than reading without the magnifier. CONCLUSIONS: This study confirms reports that reading rates increase as the field of view increases when reading from a page of text. The need for this large field of view relative to other low vision reading aids (i.e., computer-generated scroll displays) is likely the result of the readers' need to actively navigate across the page of text.

Adolescent↗
PubMed1980

Visual information processing: the structure and creation of visual representations.

For human vision to be explained by a computational theory, the first question is plain: What are the problems that the brain solves when we see? It is argued that vision is the construction of efficient symbolic descriptions from images of the world. An important aspect of vision is therefore the choice of representations for the different kinds of information in a visual scene. An overall framework is suggested for extracting shape information from images, in which the analysis proceeds through three representations: (1) the primal sketch, which makes explicit the intensity changes and local two-dimensional geometry of an image; (2) 2 1/2-D sketch, which is a viewer-centred representation of the deplth, orientation and discontinuities of the visible surfaces; and (3) the 3-D model representation, which allows an object-centred description of the three-dimensional structure and organization of a viewed shape. The critical act in formulating computational theories for process capable of constructing these representations is the discovery of valid constraints on the way the world behaves, that provide sufficient additional information to allow recovery of the desired characteristic. Finally, once a computational theory for a process has been formulated, algorithms for implementing it may be designed, and their performance compared with that of the human visual processor.

Depth Perception↗
PubMed2005

Mathematical modeling of cancer: the future of prognosis and treatment.

BACKGROUND: Cancer research has undergone radical changes in the past few years. Producing information both at the basic and clinical levels is no longer the issue. Rather, how to handle this information has become the major obstacle to progress. Intuitive approaches are no longer feasible. The next big step will be to implement mathematical modeling approaches to interrogate the enormous amount of data being produced and extract useful answers (a "top-down" approach to biology and medicine). METHODS: Quantitative simulation of clinically relevant cancer situations-based on experimentally validated mathematical modeling-provides an opportunity for the researcher, and eventually the clinician, to address data and information in the context of well-formulated questions and "what if" scenarios. RESULTS AND CONCLUSIONS: At the Vanderbilt Integrative Cancer Biology Center (VICBC), we are integrating cancer researchers, oncologists, chemical and biological engineers, computational biologists, computer modelers, theoretical and applied mathematicians, and imaging scientists, in order to implement a vision for a combined web site and computational server that will be a home for our mathematical modeling of cancer invasion. The web site (www.vanderbilt.edu/VICBC/) will serve as a portal to our code, which simulates tumor growth by calculating the dynamics of individual cancer cells (an experimental "bottom-up" approach to complement the top-down model). Eventually, cancer researchers outside of Vanderbilt will be able to initiate a simulation based on providing individual cell data through a web page. We envision placing the web site and computer cluster directly in the hands of biological researchers involved in data mining and mathematical modeling. Furthermore, the web site will also contain teaching props for a new generation of biomedical researchers fluent in both mathematics and biology. This is unconventional bioinformatics: We will be incorporating biological data and functional information into a unified community-based mathematical framework. The result will be a tool for cancer modeling that will ultimately have basic research, therapeutic and educational value.

Animals↗
PubMed1993

Impact of new and emerging instrumentation in optometry.

Traditional tests of vision emphasize visual acuity, visual fields, and testing for hereditary color vision defects. New instrumentation for testing vision has proliferated due to advances in our knowledge of the visual system, the availability of new technologies, the introduction of computers into practice, and the expanded scope of optometric practice. Each is discussed in relation to the subsequent symposium papers by other authors.

Color Perception↗