Hypoxanthine-guanine phosphoribosyltransferase and deutan colour blindness: the relative positions of their loci on the X-chromosome.
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Carbon Radioisotopes↗
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Results for “Computer vision”
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SOME FACTORS INFLUENCING THE FREQENCY RESPONSE OF THE HUMAN ERG.
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Adaptation, Ocular↗
Primary myxoma of the posterior fossa.
A rare case of primary intracranial myxoma of the posterior fossa is described in a 32-year old woman. The patient presented with a history of headaches, disequilibrium, nausea and abnormal vision for several months. Computed tomography (CT) showed a well-demarcated hypodense mass. After contrast administration the mass appeared as an inhomogeneously enhancing lesion surrounded by a small rim of edema. The mass was surgically excised with histological examination revealing a true myxoma. Echocardiography revealed no evidence of a cardiac myxoma. The CT appearance of other case reports of non-cardiac myxomas in the literature is reviewed.
Adult↗
The visual field examination and its automation.
An automated system for examination of the visual fields is described. The entire campimetric examination was simulated in order to enable an in-depth analysis of actual examinations. The program runs on a HP2100 computer with a 16K core. The main advantages of the system are: greater speed, less patient fatigue, greater reliability, repeatability and accuracy.
Diagnosis, Computer-Assisted↗
Further studies on a male monozygotic triplet with schizophrenia: cytogenetical and neurobiological assessments in the patients and their parents.
We previously described a Swedish set of male schizophrenic monozygotic triplets. In this study the patients as well as their parents were further characterized. By high-resolution chromosomal analysis an extra band at chromosome 15p was found in all the triplets and the father. Microdissection, degenerate oligonucleotide-primed PCR (DOP-PCR) amplification and reverse painting indicates that the extra band probably contains only repetitive DNA sequences with no known effect on the phenotype. Magnetic resonance imaging (MRI) showed similar borderline ventricular enlargement and widened subarachnoid spaces over frontoparietal and basal regions as well as around the pituitary gland (empty sella) in all the triplets. The father also had widened subarachnoid spaces over the frontal and basal regions. The mother had an empty sella indicating widened subarachnoid spaces. All the boys also had a right-sided conductive hearing defect, probably due to malformation and fixation of the ossicular chain. The parents did not present any otological abnormalities. Neuropsychological assessment demonstrated similar marked reductions of attentional, mnestic, and executive functions in all the triplets, but the mother showed a normal pattern. Possible joint etiological mechanisms for the psychological and somatic abnormalities recorded in the triplets are discussed.
Adult↗
The role of size and binocular information in guiding reaching: insights from virtual reality and visual form agnosia III (of III).
Reaching out to grasp an object requires information about the size of the object and the distance between the object and the body. We used a virtual reality system with a control population and a patient with visual form agnosia (DF) in order to explore the use of binocular information and size cues in prehension. The experiments consisted of a perceptual matching task in addition to a prehension task. In the prehension task, control participants modified their reach distance in response to step changes in vergence in the absence of any clear reference for relative disparity. Their reach distance was unaffected by equivalent step changes in size, even though they used this information to modify grasp and showed a size bias in a distance matching task. Notably, DF showed the same pattern of results as the controls but was far more sensitive to step changes in vergence. This finding complements previous research suggesting that DF relies predominantly on vergence information when gauging target distance. The results from the perceptual matching tasks confirmed previous findings suggesting that DF is unable to make use of size information for perceptual matching, including distance comparisons. These data are discussed with regard to the properties of the pathways subserving the two visual cortical processing streams.
Agnosia↗
[Multifocal steady-state pattern-reversal electroretinography in glaucoma patients].
AIM: This study was designed to answer the question of whether multifocal steady-state pattern-reversal electroretinography (ERG) is capable of detecting glaucomatous visual field defects. METHOD: Sixteen patients (28 eyes) and ten normal subjects (20 eyes) were examined. Multifocal pattern ERGs were recorded with the RETIscan system and DTL electrodes. We stimulated with a steady-state checkerboard pattern reversal (three reversals during 171 ms sweep length, congruent with 17.5 reversals/s). The multifocal pattern ERG amplitudes were evaluated using discrete Fourier transformation (DFT) across three reversals. In cases of advanced glaucoma, the DFT-calculated amplitudes were combined in hemispheres and checked for correlations with corresponding visual field defects. In all binocularly examined persons, side comparisons ("worse" eye vs "better" eye), and interindividual comparisons (glaucoma vs normal) were carried out. RESULTS: In interindividual comparisons and interocular side comparisons, significant amplitude reductions of the "worse" eyes were seen in the foveal records. No topographical correlation between multifocal pattern ERG amplitudes and visual field defects could be found. CONCLUSIONS: In glaucomatous visual field defects, multifocal steady-state pattern-reversal ERG using the present stimulation was significantly reduced in its foveal records but seems to be incapable of detecting them topographically.
Adult↗
Frontotemporal lobar degeneration with ubiquitin pathology: an autopsy case presenting with semantic dementia and upper motor neuron signs with a clinical course of 19 years.
We report a case of a right-handed 74-year-old man who showed semantic dementia with a disease duration of 19 years. He initially presented with excessive use of pronouns and semantic paraphasia at the age of 55 years. Impairment of object recognition developed 5 years after the onset. Face recognition impairment and stereotypic behaviors developed 11 years after onset, and pyramidal signs 2 years before death. Pathological examination disclosed circumscribed severe atrophy in not only the bilateral temporal tips but also in the left precentral gyrus and pars opercularis in a motor speech field. Pyramidal tract involvement and loss of Betz cells were also evident. On the other hand, neurons in the anterior horns and hypoglossal nuclei were spared in number, although astrocytes were mildly proliferated. Ubiquitin-positive lesions were observed in the hippocampus, and frontal and temporal cortices. Neither Bunina bodies nor Pick bodies were present. These features clinically fit the international diagnostic criteria of semantic dementia and, histopathologically, frontotemporal lobar degeneration with motor neuron disease (FTLD-MND). This case suggests that (1) the distribution of cortical lesions associated with language disturbance is not uniform in FTLD-MND. It may be that only some cases of FTLD with ubiquitin pathology develop semantic dementia despite the high incidence of language disturbance, and (2) the precentral gyrus can be severely affected in FTLD-MND. After reviewing previous cases of FTLD-MND with a clinical course of more than 10 years, we also noticed that (3) FTLD-MND cases with a long disease duration often show upper motor neuron-predominant involvement.
Age of Onset↗
Spontaneous compressive orbital emphysema of rhinogenic origin.
We report the case of a young patient who developed spontaneous compressive orbital emphysema after an attack of coughing. At admission the patient presented left proptosis, diplopia, vision impairment and headache. Computer tomography showed air in the lateral part of left orbit compressing the eyeball and the optic nerve medially. It also revealed a sphenoid bone dysplasia with hyperpneumatization of the left greater wing and with two dehiscences in its wall. It was very intriguing to discover that this sphenoid dysplasia and the flap of mucosa covering one dehiscence were causing a ball-valve effect, allowing air to enter but not leave the orbit. Endoscopic sinus surgery was successfully used to treat this case.
Adolescent↗
Disparity tuning as simulated by a neural net.
Previous research has suggested that the processing of binocular disparity in complex cells may be described with an energy formalism. The energy formalism allows for a representation of disparity by differences in the position or in the phase of monocular receptive subfields of binocular cells, or by combination of these two types. We studied the coding of disparities with an approach complementary to previous algorithmic investigations. Since realization of these representations is probably not genetically determined but learned during ontogeny, we used backpropagation networks to study which of these three possibilities were realized within neural nets. Three types of networks were trained with noise patterns in analogy to the three types of energy models. The networks learned the task and generalized to untrained correlated noise pattern input. Outputs were broadly tuned to spatial frequency and did not respond to anti-correlated noise patterns. Although the energy model was not explicitly implemented, we could analyze the outputs of the networks using predictions of the energy formalism. After learning was completed, the model neurons preferred position shifts over phase shifts in representing disparity. We discuss the general meaning of these findings and the correspondences and deviations between the energy model, V1 neurons, and our networks.
Computer Simulation↗
Depth cue reliance in surgeons and medical students.
BACKGROUND: Depth perception is reduced in endoscopic surgery, although little is known about the effect this has on surgical performance. METHODS: To assess the role of depth cues, 45 subjects completed tests of depth cue reliance. Surgical skill was assessed using the Minimally Invasive Surgical Trainer-Virtual Reality, a previously validated laparoscopic simulator. RESULTS: We could demonstrate no difference in cue reliance for three depth cues--namely stereo, texture, and outline--between surgeons and medical students. Greater dominance on stereo for medical students was a positive finding and a negative finding for the surgeons when correlated with surgical performance. CONCLUSIONS: We suggest that surgeons learn to adapt to the nonstereo environment in MIS, and this is the first study to show evidence of this phenomenon. This difference in stereo reliance is a reflection of the experience that surgeons have with laparoscopy compared with medical students, who have none.
Adult↗
Tissue consistency perception in laparoscopy to define the level of fidelity in virtual reality simulation.
BACKGROUND: What degree of fidelity must a laparoscopic simulator have to achieve a training objective? This difficult question is addressed by studying the sensory interaction of surgeons in terms of a surgical skill: tissue consistency perception. METHODS: A method for characterizing surgeon sensory interaction has been defined and applied in an effort to determine the relative importance of three components of perceptual surgical skill: visual cues, haptic information, and previous surgical knowledge and experience. Expert, intermediate, and novel surgeons were enrolled in the study. Users were asked to rank tissue consistency in four different conditions: a description of the tissue alone (Q), visual information alone (VI), tactile information alone (TI), and both visual and tactile information (VTI). Agreement between these stages was assessed by a coefficient of determination (R2). RESULTS: Tissue is a determinant factor (p < 0.001) in the perception of tissue consistency, whereas the expertise of the surgeon is not (p = 0.289). Tissue consistency perception is based mainly on tactile information (TI-VTI agreement is high, R2 = 0.873), although little sensory substitution is present (VI-VTI agreement is low, R2 = 0.509). Agreement of Q-VI increases with experience (R2 = 0.050, 0.290, and 0.573, corresponding with to novel, intermediate, and expert surgeons), which has been associated with the "visual haptics" concept. CONCLUSIONS: Virtual reality simulators need haptic devices with force feedback capability if tissue consistency information is to be delivered. On the other hand, the visual haptics concept has been associated with a kind of tactile memory developed by surgical experience.
Clinical Competence↗
Cerebral vasculitis and intracerebral hemorrhage in Henoch-Schönlein purpura treated with plasmapheresis.
Severe neurological complications in Henoch-Schonlein purpura (HSP) are rare. We report a 13-year-old girl with HSP receiving oral steroid therapy for HSP nephritis who presented with acute onset of headache, confusion, and loss of bilateral vision. However, immediate cranial computed tomography showed merely a small intracranial hematoma in the left occipital area, which was not consistent with her clinical manifestations. The subsequent magnetic resonance imaging of the brain demonstrated bilateral, multifocal abnormalities with features consistent with cerebral vasculitis. Therapeutic plasmapheresis was performed immediately and there was rapid clinical improvement. In conclusion, we propose that plasmapheresis is a reliable and effective therapy and may be considered as the first-line treatment in this critical condition to prevent massive intracerebral hemorrhagic complication of this immune complex-mediated cerebral vasculitis leading to irreversible neurological sequelae or mortality.
Adolescent↗
Gamma knife radiosurgery for circumscribed choroidal hemangioma.
The authors report a case of circumscribed choroidal hemangioma (CCH) treated by stereotactic radiosurgery with gamma knife. A thirteen-year-old boy presented with a 4-year history of progressive visual loss in his right eye. Because of the large size and fluid collection under the macula, gamma knife radiosurgery was done. During 2 years of follow-up, there was resolution of retinal detachment, regression in tumor thickness, and no complications. Gamma knife radiosurgery may be a reasonable alternative treatment option for symptomatic CCHs which are difficult to manage using standard therapeutic options such as photocoagulation.
Adolescent↗
Effects of an eyeglass-free 3-D display on the human visual system.
PURPOSE: To investigate the effect on the human visual system of viewing 3-dimensional (3-D) computer graphics (CG) images with an eyeglass-free rear-cross-lenticular-type 3-D display. METHODS: Positive accommodation velocity (GRAD) during the accommodative step response was measured in ten healthy young adults before and after they viewed CG images. Although the distance between the viewer and the 3-D display was 600 mm, the apparent distance between the viewer and the virtual object was varied (515, 600, and 722 mm) by changing the visual disparity. RESULTS: A significant slowdown of average GRAD was observed by 60 min after a 30-min 3-D viewing of 3-D CG images [P<0.05, analysis of variance (ANOVA)] but not after a 30-min viewing of the CG images on a 2-D display or after a 15-min 3-D viewing. When the virtual object was at 722 mm, a significant slowdown of average GRAD was observed only at 30 min after the 30-min 3-D viewing (P<0.05, ANOVA). When the virtual object was at 515 mm, a significant slowdown of average GRAD was observed at 30 and 60 min after the 3-D viewing (P<0.05, ANOVA). CONCLUSIONS: The effect on the human visual system of 3-D viewing of 3-D CG images depends on both the duration of the viewing and the apparent distance between the viewer and the virtual objects.
Accommodation, Ocular↗
Ganglioglioma of the optic nerve.
We examined a 15-year-old boy who had a ganglioglioma involving the left optic nerve, which caused proptosis, decreased vision, and optic atrophy. Computed tomography demonstrated an intraconal mass along the course of the orbital portion of the optic nerve. The only evidence of systemic neurofibromatosis was axillary freckling. The patient underwent a combined medial and lateral orbitotomy and excision of the tumor. Histologic examination demonstrated a mass composed of neurons and glial cells characteristic of ganglioglioma. After a one-year follow-up period, we have found no evidence of recurrence.
Adolescent↗
Viewing speed and frequency resolution in digital EEG.
This study of viewing speed and frequency resolution of a digital electroencephalograph (EEG) system explains how, in spite of limited video monitor resolution, technological advances permit digital EEG presently to approach paper EEG performance, and in the foreseeable future to exceed it. Analyses of aspects of eye and brain physiology and elements of digital technology reveal how an image traditionally inscribed on paper can be displayed on a video monitor so that viewing and interpretation are as quick and accurate as on paper. Results are compared to standards set by capabilities of the eye and paper EEG.
Brain↗
User metaphors for health care professional workstations.
The problem encountered by health care professionals and software developers has been a lack of demonstrable visions (prototypes) for Computer-based Patient Record (CPR) and Clinical Information System (CIS) applications. This deficiency has resulted in a quest for and consideration of models, metaphors, and mind maps for the Healthcare Professional Workstation (HPW)--the access mechanism for the CPR and the CIS. The familiar physician desktop and traditional paper-based metaphors are not adequate for all aspects of clinical information processes. In the clinical care environment, the flowsheet is a transporting metaphor because many different applications and tasks can be 'transported' into the flowsheet. 3D Rooms, Gopher and Genes are familiar and transporting metaphors to be exploited for HPWs. Using transporting metaphors for HPW software emphasizes commonality and de-emphasizes diversity. Each model and metaphor has an associated mind map. Only the mental model, mental metaphor or mind map for HPW software is important. Metaphors communicate real-world analogies, and communication is at the core of what defines usability. A mind map facilitates communication by building a model in the user's mind. The barriers to HPWs are not technical; they are related to economics, ownership of patient information, liability and information standards.
Computer Systems↗