[Anatomical visual field, physiological visual field and perception field in subjects without eye disease].
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Eye Diseases↗
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Results for “visualization”
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Studies on the visual perception and the visual field of moving objects.
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Humans↗
[SURVEY OF THE LITERATURE ON VISION AND VISUAL FUNCTION--VISION, VISUAL FIELDS, LIGHT PERCEPTION, ENTOPTIC PHENOMENA, REFRACTION, ACCOMMODATION--(FOR THE YEAR 1963)].
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Accommodation, Ocular↗
[Visual tract diseases and the visual field--with special reference to the significance of the flicker test in the diagnosis and therapy of optic nerve diseases].
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Abdomen↗
Vitamin A, visual pigments, and visual receptors in Drosophila.
The fly visual system has served for decades as a model for receptor spectral multiplicity and vitamin A utilization. A diverse armamentarium of structural techniques has dovetailed with convenient electrophysiology, photochemistry, genetics, and molecular biology in Drosophila to facilitate recent progress, which is reviewed here. New data are also presented. Ultrastructure of retinula cells of carotenoid-deprived flies shows that organelles associated with protein biosynthesis, i.e., rough endoplasmic reticulum and Golgi apparatus, are present, while organelles associated with rhabdomere turnover, i.e., multivesicular bodies (MVBs), are rare. Ultrastructure and morphometry suggest that retinoic acid-rearing stimulates membrane export and rhabdomere buildup, even though functional rhodopsin is missing. Confocal microscopy suggests that RH4, one of the ultraviolet rhodopsins, may reside in the previously-described pale fluorescent R7 cells with RH3 in the yellow fluorescent R7 cells.
Animals↗
Cognitive spatial-motor processes. 4. Specification of the direction of visually guided isometric forces in two-dimensional space: information transmitted and effects of visual force-feedback.
The information transmitted (Ti) by the direction of two-dimensional (2-D) isometric forces at different stereoscopic depths was studied in 50 naive human subjects using an isometric manipulandum and random dot stereograms generated in a color display (Massey et al. 1988). Subjects viewed the display through appropriate color filters and perceived the image of a disk rotated about a horizontal axis on the frontal plane; the top of the disk was rotated around that axis by 15, 45, 60 and 80 degrees away from the subject. Each of these disks involved a different amount of stereoscopic depth perception which was lowest for the 15 degrees and highest for the 80 degrees tilt. Subjects were instructed to exert force in the direction of a visual target presented on the disk in a reaction time task. The instantaneous force exerted by the subjects on the manipulandum was shown on the disk in the form of a feedback cursor. Information transmitted, reaction time (RT) and systematic directional deviations were calculated. We found the following. (a) Ti increased with input information but at a lower rate; at the highest level of input information studied (5.91 bits), Ti was 4.1 bits at the 15 degrees tilt. This high value of Ti suggests that directional information for isometric force is processed very efficiently. However, this Ti was consistently lower than that transmitted by the direction of movement (Georgopoulos and Massay, 1988). (b) Ti did not differ significantly among the 15-60 degrees tilt but was 0.19 bits less for the 80 degrees tilt. RT did not differ among the 15-80 degrees tilts.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Visual effects of opiates in pigeons: I. Target location in visual search.
Pigeons pecked at target forms, located in arrays of distractors. In experiment 1 the number of distractors and their similarity to the target varied. In experiment 2, similarity was varied over a more extended range. Drug tests used morphine in doses ranging from 1 to 6 mg/kg, naloxone (0.3-3 mg/kg) alone and combined with morphine. Morphine had relatively small effects on accuracy; however, it produced pronounced elevations in reaction time. Significant interactions with display variables indicated a visual component to the morphine effect. Naloxone alone had no effect; naloxone combined with morphine blocked the morphine effect.
Animals↗
Molecular mechanism for the initial process of visual excitation. III. Theoretical studies of optical spectra and conformations of chromophores in visual pigments, their analogues and intermdiates based on the torsion model.
The torsion model with which we proposed to interpret the specific properties of the photoisomerization reaction of rhodopsin has been developed to apply to isorhodopsin I, isorhodopsin II and some intermediates. Based on this model, optical absorption wavelengths and oscillator strengths, as well as rotational strengths of visual pigments, analogues and intermediates at low temperatures are analyzed by varying twisted conformations of the chromophores. As a result, it was found that most of the optical data could be very well accounted for quantitatively by the torsion model. The twisting characters in the chromophore of rhodopsin are very similar to those of isorhodopsin. The obtained conformations of the chromophores are very similar in rhodopsin and its analogues, and in isorhodopsin and its analogues. Those of the chromophores of bathorhodopsin, lumirhodopsin and metarhodopsin I are similar to one another except that the conjugated chain of metarhodopsin I bends considerably when compared with the other intermediates.
Animals↗
Molecular mechanism for the initial process of visual excitation. IV. Energy surfaces of visual pigments and photoisomerization mechanism.
Using the twisted conformations of the chromophores for visual pigments and intermediates which were theoretically determined in the previous paper, energy surfaces of the pigment at - 190 degrees C were obtained as functions of the torsional angles theta 9-10 and theta 11-12 or of the torsional angles theta 9-10 and theta 13-14. In these calculations, the existence of specific reaction paths between rhodopsin (R) and bathorhodopsin (B), between isorhodopsin I (I) and bathorhodopsin, and between isorhodopsin II (I') and bathorhodopsin were assumed. It was shown that the total energy surfaces of the excited states had minima C1 at theta 9-10 approximately -10 degrees and theta 11-12 approximately -80 degrees, C2 at theta 9-10 approximately -85 degrees and theta 11-12 approximately -5 degrees, and C3 at theta 9-10 approximately -0 degree and theta 13-14 approximately -90 degrees. These minima are considered to correspond to the thermally barrierless common states as denoted by Rosenfeld et al. Using the total energy surfaces in the ground and excited states, the molecular mechanism of the photoisomerization reaction was suggested. Quantum yields for the photoconversions among R, I, I' and B were related to the rates of vibrational relaxations, radiationless transitions and thermal excitations. Some discussion was made of the temperature effect on the quantum yield. Similar calculations of the energy surfaces were also made at other temperatures where lumirhodopsin or metarhodopsin I is stable. Relative energy levels of the pigments and the intermediates were discussed.
Animals↗
Visual identification of the cystic duct-CBD junction during laparoscopic cholecystectomy (visual cholangiography): an additional step for prevention of CBD injuries.
Despite advances in technical skills, common bile duct (CBD) injury during laparoscopic cholecystectomy is not an uncommon major complication. We describe a technical step that can be taken during the dissection of the triangle of Calot to allow the junction between the cystic duct and CBD to be clearly visualized. This is a safe and simple maneuver that mimics the one done in open surgery. Its routine application serves as an additional safety measure to prevent injury to the common bile duct.
Cholecystectomy, Laparoscopic↗
Combating poster fatigue: how to use visual grammar and analysis to effect better visual communications.
Posters are increasingly being used as a medium for the communication of results and ideas. The organization and presentation of a poster plays an important role in the facilitation of effective communication. In this article John D. Woolsey describes how best to maximize the visual impact of a poster.
Audiovisual Aids↗
Prediction accuracy of computer-assisted surgical visual treatment objectives as compared with conventional visual treatment objectives.
PURPOSE: This present study used the conventional visualized treatment objectives (VTOs) as a tool to evaluate the predictive value of the Dolphin computer-assisted VTOs. MATERIALS AND METHODS: Presurgical cephalometric tracing predictions generated by oral and maxillofacial surgeons and the Dolphin Imaging software were compared with the postsurgical outcome as seen on lateral cephalometric tracings. Sixteen measurements of the predicted and actual postsurgical hard tissue landmarks were compared statistically. RESULTS: A paired Student's t test showed that 7 measurements had statistically significant differences for the conventional VTOs (facial angle, P < .0001; AOC, P < .0001; SNB, P = .003; ANB, P = .004; U1-NA-degrees, P = .01; U1-NA-mm, P = .02; and N perp Pog, P < .0001), while 9 measurements were statistically significant ( P = <.0001) for Dolphin (facial angle, P = .0001; AOC, P = .005; SNB, P = .001; ANB, I = .04; U1-NA-degrees, P = .003; PogNB, P = .04; U1-NA-mm, P = .002; N perp Pog, P = .0001; UFH, P = .03; and LFH, P = .03). CONCLUSION: From these data, it appears that both VTOs demonstrated good predictive comparative outcome and are equally precise.
Adolescent↗
Visual perception of extent and the geometry of visual space.
The question of how perceived extents are related to the corresponding physical extents is a very old question that has not been satisfactorily answered. The common model is that perceived extent is proportional to the product of image size and perceived distance. We describe an experiment that shows that perceived extents are substantially larger than this model predicts. We propose a model that accounts for our results and a large set of other results. The principal assumption of the model is that, in the computation of perceived extent, the visual angle signal undergoes a magnifying transform. Extent is often perceived more accurately than the common model predicts, so the computation is adaptive. The model implies that, although the perception of location and the perception of extent are related, they not related by Euclidean geometry, nor by any metric geometry. Nevertheless, it is possible to describe the perception of location and extent using a simple model.
Humans↗
Characteristics and prevalence of transient visual disturbances indicative of migraine visual aura.
The objective of this study was to estimate the prevalence of and to compare the characteristics of transient visual disturbances (TVDs) of possible migraine origin in a clinical and a general population. Data were obtained in interviews from 100 consecutive female migraine patients (17-69 years) and 245 women (40-75 years) from the general population. The lifetime prevalences were 37% and 13%, respectively. We did not detect any differences in characteristics of TVDs between patients and women in the general population. A gradual onset of five or more minutes was stated by as few as 45% and 46%, respectively. The typical headache phase in conjunction with a TVD had more migrainous features in patients. We conclude from our data that the TVDs in this study, which do not fulfill the IHS criteria for migraine with aura, more likely represent poorly described or abortive migraine phenomena, rather than phenomena of other origin.
Adolescent↗
[Is the visual fixation mark adequate visual attraction for babies in the 1st year of life?].
One of the most important clinical examinations in strabology is the test for foveal fixation. This test presupposes a mature primary visual pathway with well established afferent and efferent reactions, which certainly does not exist from birth. The presumed retinal fixation of 234 infants was critically examined during continuous observation in their first year of life.
Attention↗
Central visual persistences: I. Visual and kinesthetic interactions.
Phenomena associated with 'central visual persistences' (CPs) are new to both medical and psychological literature. Five subjects have reported similar CPs: positive afterimages following brief fixation of high-contrast objects or drawings and eye closure. CPs duplicate shapes and colors of single objects, lasting for about 15 s. Unlike retinal afterimages, CPs do not move with the eyes but are stable in extrapersonal space during head or body rotations. CPs may reflect sustained neural activity in neurons of association cortex, which mediate object perception. A remarkable finding is that CPs can be moved in any direction by the (unseen) hand holding the original seen object. Moreover, a CP once formed will 'jump' into an extended hand and 'stick' in that hand as it moves about. The apparent size of a CP of a single object is determined by the size of the gap between finger and thumb, even when no object is touched. These CPs can be either magnified or minified via the grip of the extended hand. The felt orientation of the hand-held object will also determine the orientation of the CP seen in that hand. Thus, kinesthetic signals from hand and arm movements can determine perceived location, size, and orientation of CPs. A neural model based on physiological studies of premotor, temporal, parietal, and prefrontal cortices is proposed to account for these novel phenomena.
Adult↗
Structures of the visual chromophores and related pigments: a conformational basis of visual excitation.
A detailed conformational analysis of the known crystal structures of vitamin A, carotenoid, and xanthenoid derivatives has been made. These studies suggest that the visual chromophore 11-cis retinal and its isomers may each occur in several different conformational states, which would be expected to have different lightabsorbing characteristics. The presence of such states for 11-cis retinal and all-trans retinal may contribute to the observed rhodopsin intermediates that have been characterized by different lambda(max) values, and to the breadth of spectral response in scotopic and color vision.
Carotenoids↗
Visual prostheses and visual rehabilitation in low vision research, assessment, and management.
This review is a highly selective and personal viewpoint regarding the past year's publications in low vision clinical practice and clinical research. This article reviews and provides references on selected aspects of low vision technology, reading, pediatric considerations, visual assessment for the multiply handicapped, and the psychosocial aspects of low vision and rehabilitation. We are impressed that the wealth of current publications underscores that this is an important, productive, and growing area of research and clinical activity.
Aged↗