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Results for “Distance Perception”

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At least 1,207 records · Page 67Linked to original sources
PubMed2002

Monocular accommodation response for totally occluded objects.

PURPOSE: To investigate the accuracy and stability of the monocular accommodation response when attention is directed toward a totally occluded distant object. METHODS: A static infrared optometer was used to measure the monocular accommodative response in 16 participants while they viewed a distant letter target in the presence or absence of an intervening object that totally occluded the distant target from view. Participants were instructed to attend to and focus for the distant target. RESULTS: Participants differed widely in their accommodative responses for a totally occluded distant object, focusing close to the distant object, close to the intervening object, in between the two objects, and beyond the distant object. Some of this variability could be attributed to individual differences in the dark focus. Accommodation was more variable when the distant target was totally occluded by an obstruction at an intermediate distance (50 cm). CONCLUSIONS: Many individuals focus poorly in the presence of a visual obstruction that totally occludes the object of regard.

Accommodation, Ocular↗
PubMed2003

Is binocular contrast sensitivity at distance compromised with multifocal soft contact lenses used to correct presbyopia?

PURPOSE: The purpose of this investigation was to determine whether new experimental multifocal optical designs incorporating diffractive/refractive optics for correction of presbyopia in a soft contact lens would compromise binocular contrast sensitivity at distance while achieving 20/20 binocular visual acuity at near. METHODS: Thirty presbyopic volunteers were fitted with Acuvue Bifocal soft lenses, two (FO1 and 3B1) experimental diffractive/refractive multifocal soft lenses separately and in combination as a pair and soft spherical lenses. Visual performance was evaluated via binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity after 1 week of lens wear. RESULTS: The experimental lenses FO1 and the combination FO1/3B1 performed as well for binocular contrast sensitivity, binocular distance high-contrast visual acuity, and binocular distance low-contrast visual acuity as the habitual presbyopic correction and the spherical soft distance correction. A strong correlation (r = 0.73 and 0.53, respectively) was found between binocular contrast sensitivity and binocular distance low-contrast visual acuity with experimental FO1 and FO1/3B1 lenses. However, the correlation (r = 0.37 and 0.60, respectively) between binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity with FO1 was weaker than that with the combination FO1/3B1 lenses. Subjective responses support the objective data. DISCUSSION: The data show that experimental FO1 lens and the experimental combination of the FO1/3B1 lenses can be prescribed to not compromise distance binocular contrast sensitivity.

Adult↗
PubMed1977

Two-point discrimination distances in the normal hand and forearm: application to various methods of fingertip reconstruction.

Two-point discrimination in the hand and forearm is best during the third decade of life. In the fingertips, the ulnar digits are more discriminating than the radial digits. Males and females have equal two-point discrimination during each age decade. Fingertips are twice as discriminating as the thenar and hypothenar areas, and the thenar and hypothenar areas are twice as discriminating as the volar side of the wrist; the wrist is twice as discriminating as the forearm. The Kleinert and Kutler flaps demonstrated the best two-point discrimination among the repaired fingertips.

Adolescent↗
PubMed1976

Management of intermittent esotropia.

Management of patients with intermittent esotropia having either normal or high accommodative convergence to accomodation (AC:A) ratios is discussed. Treatment should be based on liberal use of miotics to build up fusional reserves and use of hyperopic corrections or bifocals or both whenever specifically indicated. Divergent fusional reserve training is time-consuming and the cost/benefit ratio so low that most patients and doctors prefer the former treatment.

Accommodation, Ocular↗
PubMed2005

A comparison of eye movement behavior of inexperienced and experienced drivers in real traffic environments.

PURPOSE: The importance of the visual system as the input channel for sensory information necessary when driving is often stated. There are several reports on differences in visual search strategies between experienced and inexperienced drivers, as well as in relation to the roadway. However, the results are ambiguous and are not sampled by similar procedures. Based on previous findings, the aim of the present study was to gain further knowledge on these differences by testing the hypotheses that inexperienced drivers, in comparison to experienced drivers, fixate closer to the vehicle, fixate more often on in-vehicle objects, spread their fixations less along the horizontal meridian, fixate more often on relevant traffic cues, and fixate more often on objects classified as potential hazards. METHODS: Data from eye-tracker recordings of visual search strategies of the driver in real-world traffic were used for the analyses. RESULTS: The results confirmed all stated hypotheses regarding differences between inexperienced and experienced drivers, with the exception of fixations closer to the vehicle, in which ambiguous results were found. CONCLUSIONS: The present study provides normative data for the understanding of the development of visual search strategies among drivers. The methodology used in the present study, i.e., to combine a quantitative analysis with a qualitative analysis proved, to be useful to compare visual search strategies among inexperienced and experienced drivers.

Adolescent↗
PubMed2006

Distance and near visual acuity in infantile nystagmus.

PURPOSE: Infantile nystagmus (IN) has been reported to decrease with convergence. However, previous studies reported equivocal results regarding a corresponding improvement in acuity with near viewing. The aim of this study was to determine whether visual acuity improves with near viewing in patients with IN. METHODS: In the first experiment, visual acuities were measured using clinical test charts at standard test distances of 3 or 6 m and 40 cm and using S Charts at 3.75 m and 40 cm. In the second experiment, visual acuities were measured using a Bailey-Lovie chart at distance and a Lighthouse modified ETDRS near card held by each subject at his or her preferred working distance. S-chart acuities were obtained again at 3.75 m and 40 cm for comparison. Horizontal eye movements were recorded using infrared limbal reflection for 20 of the 34 subjects in the first experiment and for all 20 subjects in the second experiment. RESULTS: The S-chart acuities measured at distance and near were almost all within 0.1 logMAR (logarithm of the minimum angle of resolution) in experiments 1 and 2. Clinically measured acuity averaged nearly one line better at 40 cm than at distance in experiment 1, but the mean difference between near acuity using the ETDRS card and distance acuity using the Bailey-Lovie chart was less than one letter in experiment 2. No consistent relationship existed between the changes in visual acuity with viewing distance and the subject's eye movements. CONCLUSION: Despite a reduction of nystagmus at near distances in many patients with IN, the visual acuity at near does not improve significantly. These results imply that visual acuity in patients with IN is determined primarily by sensory limitations rather than by the moment-by-moment characteristics of these patients' eye movements.

Adolescent↗
PubMed2002

The development of virtual reality therapy (VRT) system for the treatment of acrophobia and therapeutic case.

Virtual reality therapy (VRT), based on this sophisticated technology, has been recently used in the treatment of subjects diagnosed with acrophobia, a disorder that is characterized by marked anxiety upon exposure to heights and avoidance of heights. Conventional VR systems for the treatment of acrophobia have limitations, over-costly devices or somewhat unrealistic graphic scenes. The goal of this study was to develop an inexpensive and more realistic virtual environment (VE) in which to perform exposure therapy for acrophobia. It is based on a personal computer, and a virtual scene of a bunge-jump tower in the middle of a large city. The virtual scenario includes an open lift surrounded by props beside a tower, which allows the patient to feel a sense of heights. The effectiveness of the VE was evaluated through the clinical treatment of a subject who was suffering from the fear of heights. As a result, it was proved that this VR environment was effective and realistic at overcoming acrophobia according not only to the comparison results of a variety of questionnaires before and after treatment but also to the subject's comments that the VE seemed to evoke more fearful feelings than the real situation.

Chronic Disease↗
PubMedDate not supplied

The development of memory for location: what role do spatial prototypes play?

Two experiments investigated the role of spatial prototypes in estimates of location. In Experiment 1 (N = 144), children and adults learned the locations of 20 objects in an open, square box designed to look like a model house. In two conditions, opaque lines or walls divided the house into four regions, and in the other condition, no boundaries were present. Following learning, the dots marking the locations were removed, and participants attempted to replace the objects. Children and adults overestimated distances between target locations in different regions. Contrary to Huttenlocher, Hedges, and Duncan's hierarchical theory of spatial memory, none of the groups displaced the objects toward the region centers. In Experiment 2 (N = 96), boundaries were removed during testing to determine whether children and adults were more likely to displace objects toward region centers when uncertainty about location increased. Again, all age groups overestimated distances between target objects in different regions. In addition, adults and 11-year-olds in the most salient boundary condition displaced objects toward the region centers. Discussion focuses on the implications of these results for understanding how children and adults estimate location.

Adult↗
PubMedDate not supplied

Generalizing the dynamic field theory of the A-not-B error beyond infancy: three-year-olds' delay- and experience-dependent location memory biases.

Thelen and colleagues recently proposed a dynamic field theory (DFT) to capture the general processes that give rise to infants' performance in the Piagetian A-not-B task. According to this theory, the same general processes should operate in noncanonical A-not-B-type tasks with children older than 12 months. Three predictions of the DFT were tested by examining 3-year-olds' location memory errors in a task with a homogeneous task space. Children pointed to remembered locations after delays of 0 s to 10 s. The spatial layout of the possible targets and the frequency with which children moved to each target was varied. As predicted by the DFT, children's responses showed a continuous spatial drift during delays toward a longer term memory of previously moved-to locations. Furthermore, these delay-dependent effects were reduced when children moved to an "A" location on successive trials, and were magnified on the first trial to a nearby "B" location. Thus, the DFT generalized to capture the performance of 3-year-old children in a new task. In contrast to predictions of the DFT, however, 3-year-olds' responses were also biased toward the midline of the task space-an effect predicted by the category adjustment (CA) model. These data suggest that young children's spatial memory responses are affected by delay- and experience-dependent processes as well as the geometric structure of the task space. Consequently, two current models of spatial memory-the DFT and the CA model-provide incomplete accounts of children's location memory abilities.

Attention↗
PubMedDate not supplied

Testing the dynamic field theory: working memory for locations becomes more spatially precise over development.

The dynamic field theory predicts that biases toward remembered locations depend on the separation between targets, and the spatial precision of interactions in working memory that become enhanced over development. This was tested by varying the separation between A and B locations in a sandbox. Children searched for an object 6 times at an A location, followed by 3 trials at a B location. Two- and 4-year-olds', but not 6-year-olds', responses were biased toward A when A and B were 9-in. and 6-in. apart. When A and B were separated by 2 in., however, 4- and 6-year-olds' responses were biased toward A. Thus, the separation at which responses were biased toward A decreased across age groups, supporting the predictions of the theory.

Adult↗
PubMed2000

Cognitive distance of stairways: a multi-stairway investigation.

The present study had two major purposes. First it sought to determine to what extent in an earlier study of distance estimation in stairways (Hanyu & Itsukushima, 1995) would generalize to other types of stairway. Second, it sought to examine which hypothesis, information storage or effort, better explain the earlier results, in which people overestimated distance and traversed time estimates. We obtained four distance and time measures: distance estimate, traversal time estimate, mental walking time and actual traversal time. To measure information, we had participants rate each stairway for complexity (simple-complex) and effort (effortless-effortful) before and after the distance and time measurement tasks. The results revealed that the earlier findings (Hanyu & Itsukushima, 1995) did not fully generalize. The results also did not support either the information storage or the effort hypothesis.

Adult↗
PubMed2004

Don't stand so close to me: the effects fo self-construal in interpersonal closeness.

Three studies investigated the effects of self-construal activation on behavior conducive to interpersonal proximity. Study 1 revealed that compared with control participants, participants who were primed with the independent (or personal) self sat further away from where they anticipated another person would sit in a waiting room. Results of Study 2 indicated that participants primed with the interdependent (or social) self sat closer to the anticipated other person than did those primed with the independent self. Finally, Study 3 used the chronic self-construal of participants to predict the seating distance in dyadic settings. Results showed that greater independence of participants' self-construals was associated with greater spatial distance during the interaction. Together, the studies provide clear evidence that self-construal activation automatically influences interpersonal behavior as reflected in the actual distance between the self and others. Results are discussed in terms of the functions and motives connected to self-construals.

Attitude↗
PubMed1977

Clobazam, a 1,5-benzodiazepine, and car-driving ability.

1 The effects of clobazam, a new anxiolytic agent (a 1,5-benzodiazepine) on car-driving ability and other tests of psychomotor performance were investigated in a double-blind, cross-over study v. placebo in normal volunteers. 2 Clobazam (20 mg) or placebo was given nightly for six nights to ten volunteers and subjective ratings of sleep and subjective and objective assessments of behaviour and psychomotor performance on the morning following drug ingestion were recorded. 3 Clobazam significantly improved the subjective ratings of sleep induction and quality of induced sleep. 4 Clobazam did not significantly impair performance in a variety of psychomotor tests and car-driving ability. 5 The validity of the measures used and the relevance of the findings to real life car-driving situations are discussed.

Adult↗
PubMed1980

Comparative studies of squirrel monkeys (Saimiri) and titi monkeys (Callicebus) in travel tasks.

Squirrel and titi monkeys were observed in a series of experiments in which the subjects' task was to move to a distant goal along above-ground pathways. The pathways were entirely visible to the subjects in all experiments. However, visual cues along the pathways (in Experiment I) and physical and spatial properties of the pathways (in Experiments II and III) were varied systematically in order to determine what effect features had upon selection of travel paths for monkeys of each species. Marked performance differences between the species were evident in these experiments, including differences in latency to move past the choice point, proportion of trials in which the shortest route was chosen first, and changes over test sessions in frequency of initial choice of the shortest route. In particular, titis tended to move past the choice point more slowly than squirrel monkeys; to pay more attention to distant properties of the pathways prior to making a decision, especially after experience in the test setting; and to prefer habitual pathways when these were available, whereas squirrel monkeys preferred novel routes when these were available. The relative "optimality" of decision making in these tasks in relation to species-typical modes of traveling and foraging in natural habitats is discussed. An alternative view of decision making, in which optimality is not assumed to be the only decision-making strategy, is suggested as an appropriate vehicle for further investigation into the sources of short-term variability in choice behavior.

Animals↗
PubMed1983

The effect of alcohol on the visual and ocular motor systems.

Alcohol is generally considered to be a central nervous system (CNS) depressant. This effect is progressive from higher cortical centres through to fundamental body functions. The effect of alcohol ingestion on the visual and ocular motor systems of ten healthy subjects was the basis of this study. Significant changes in the following resulted from the ingestion of 0.375 g/kg of 10% ethanol alcohol: prism measurements of deviations for near and distance, ocular movements, convergence near point, and visual acuity at six metres. No significant change was observed following testing of stereopsis or near visual acuity.

Adult↗