SEARCH · PubMed Health

Results for “Depth Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources

PubMed1996

Sensory impairments and physical disability in aged women living at home.

BACKGROUND: Studies of the impact of visual or hearing impairments on physical disability in older people have provided conflicting results. Furthermore, the consequences of the loss of such visual functions as depth perception or contrast sensitivity have rarely been studied. We examined the relationship of visual acuity, depth perception, contrast sensitivity, and hearing difficulty to the ability of older women living at home to accomplish instrumental activities of daily living independently. METHODS: Data on self-reported physical disability and hearing impairment, as well as objective measures of functional vision and physical ability were collected from a sample of 1210 community-dwelling women aged 75 years and older. Multivariate logistic regression modelling was used to assess the strength of the association between physical disability and sensory impairments, controlling for age, education level, motor limitations, and prevalent chronic diseases. RESULTS: Women with low visual acuity or low contrast sensitivity were significantly more likely to be physically dependent than women with good vision. Contrast sensitivity was, however, a better predictor than functional acuity, after controlling for age, education level, motor limitations and chronic medical conditions (adjusted odds ratio: 5.1; 95% confidence interval: 2.0-12.9). Depth perception was not related to physical disability. Women with serious hearing difficulty had significantly increased odds of dependency (4.1; 1. 4-12.1). CONCLUSIONS: Severe sensory impairments are strongly related to physical dependency in older women. It may be useful to add a test of contrast sensitivity to the traditional acuity test to predict better which elderly individuals may have difficulty carrying out routine daily activities.

Activities of Daily Living↗

PubMed1997

The three-dimensional video system; an essential component of the endosurgical suite of the future.

Minimal access surgery has revolutionized the practice of surgery. It has been shown that patients may experience less postoperative discomfort, shorter hospitalization, and quicker recuperation. The centerpiece of this revolution resides in the development of optical equipment which allowed the surgeon and his or her assistants to visualize on two-dimensional (2-D) monitors the site of the procedure to be performed. However, as techniques become more complicated, there is more need for accurate depth perception. In other surgical disciplines like neurosurgery, otorhynolaryngology, and microvascular surgery, for instance, magnification is used to perform fine manipulations; to prevent loss of depth perception, microscopes are binocular. They permit stereoscopic vision with accurate depth perception. We have used and evaluated a three-dimensional (3-D) videocamera system, designed for laparoscopy, in an in vitro situation, in the experimental laboratory and clinically, and we report our experience in this chapter. We also discuss the rationale for use of 3-D video systems.

Journal Article↗

PubMed1998

Cortical computation of stereo disparity.

Our ability to see the world in depth is a major accomplishment of the brain. Previous models of how positionally disparate cues to the two eyes are binocularly matched limit possible matches by invoking uniqueness and continuity constraints. These approaches cannot explain data wherein uniqueness fails and changes in contrast alter depth percepts, or where surface discontinuities cause surfaces to be seen in depth, although they are registered by only one eye (da Vinci stereopsis). A new stereopsis model explains these depth percepts by proposing how cortical complex cells binocularly filter their inputs and how monocular and binocular complex cells compete to determine the winning depth signals.

Contrast Sensitivity↗

PubMed1989

The power of shadows: shadow stereopsis.

Our ability to localize objects in three-dimensional space relies primarily on the stereoscopic capability of our visual system. It is generally believed that parallax disparities in the retinal images in our two eyes are required for experiencing stereovision. Traditionally, parallax disparities refer to points that are well defined within the objects, such as edges or boundaries. Shadows can create abrupt luminance changes in the scene but are neither edges nor boundaries, and their position varies with the position of the light sources. It is demonstrated that retinal images with no parallax disparity but with different shadows are fused stereoscopically, imparting depth perception to the imaged scene. Shadows are shown to be an important, hitherto undescribed stereoscopic cue for depth perception.

Depth Perception↗

PubMedDate not supplied

Chromatic assimilation unaffected by perceived depth of inducing light.

Chromatic assimilation is a shift toward the color of nearby light. Several studies conclude that a neural process contributes to assimilation but the neural locus remains in question. Some studies posit a peripheral process, such as retinal receptive-field organization, while others claim the neural mechanism follows depth perception, figure/ground segregation, or perceptual grouping. The experiments here tested whether assimilation depends on a neural process that follows stereoscopic depth perception. By introducing binocular disparity, the test field judged in color was made to appear in a different depth plane than the light that induced assimilation. The chromaticity and spatial frequency of the inducing light, and the chromaticity of the test light, were varied. Chromatic assimilation was found with all inducing-light sizes and chromaticities, but the magnitude of assimilation did not depend on the perceived relative depth planes of the test and inducing fields. We found no evidence to support the view that chromatic assimilation depends on a neural process that follows binocular combination of the two eyes' signals.

Calibration↗

PubMed1999

Alcohol and visual performance.

1. The authors examined the effect of acute alcohol consumption on a set of visual tasks: visual short term memory, depth perception, and attention. 2. In a repeated measurement design, thirteen subjects performed the tasks once sober and once intoxicated with 0.8 g/kg body weight pure ethanol in orange juice (33% alcohol). Subjects underwent a neuropsychological (Benton test) and a psychophysical test (vernier discrimination) both assessing visual short term memory, the test d2 as a measure of attention and concentration, and a psychophysical depth perception task. 3. Subjects demonstrated significant alcohol-related impairments in depth perception and in visual short term memory as assessed by the vernier discrimination task. However, the neuropsychological Benton test and test d2 failed to reveal alcohol-related changes in performance-probably due to superimposed learning effects. Performance was neither correlated with blood alcohol levels (BAL) nor perceived intoxication. Even though the current BAL was known to the subjects, only half of them demonstrated a close correlation between BAL and perceived intoxication.

Adult↗

PubMed2000

The effects of age upon the perception of depth and 3-D shape from differential motion and binocular disparity.

The ability of younger and older adults to perceive the 3-D shape, depth, and curvature of smooth surfaces defined by differential motion and binocular disparity was evaluated in six experiments. The number of points defining the surfaces and their spatial and temporal correspondences were manipulated. For stereoscopic sinusoidal surfaces, the spatial frequency of the corrugations was also varied. For surfaces defined by motion, the lifetimes of the individual points in the patterns were varied, and comparisons were made between the perception of surfaces defined by points and that of more ecologically valid textured surfaces. In all experiments, the older observers were less sensitive to the depths and curvatures of the surfaces, although the deficits were much larger for motion-defined surfaces. The results demonstrate that older adults can extract depth and shape from optical patterns containing only differential motion or binocular disparity, but these abilities are often manifested at reduced levels of performance.

Adult↗

PubMed1997

Constructional dyspraxia in preterm diplegia: isolation from visual and visual perceptual impairments.

OBJECTIVE: To evaluate ophthalmological profiles, visual perception and constructional function in preterm children with spastic diplegia (SD) and to clarify their neuropsychological deficits in comparison with a control group. METHODS: Thirty-five SD and 34 control children were investigated for visual acuity, eye position, stereoacuity, depth perception, visual perception, visuo-spatial construction and constructional praxis. Each of the results was compared among the four groups as SD with and without strabismus, and control with and without strabismus. RESULTS: Strabismic SD showed worse visual acuity, worse stereoacuity and worse depth perception than the other groups. Constructional dyspraxia was detected in 94.1% of SD either with or without strabismus, while it was rare in the control group. There was no significant contribution of visual acuity, eye position, stereoacuity or depth perception to constructional dyspraxia by stepwise multiple linear regression analysis. CONCLUSION: Strabismic preterm SD children are at high risk for visual dysfunction. Constructional dyspraxia was frequently found in SD children and may be a dysfunction isolated from ophthalmological and visual perceptual dysfunctions.

Adolescent↗

PubMed1995

Colour induced stereopsis in images with achromatic information and only one other colour.

Based on a model of transverse chromatic aberration (TCA) of the eye and perceptual effects previously discussed by the same author, it was predicted that colour induced binocular depth perception (chromostereopsis) is possible from images containing red or blue along with achromatic information (grey and black); that the direction of the perceived depth from certain colours should differ for the same TCA conditions; and that a greater depth perception should be possible in a blue/achromatic image than a red/achromatic image. Results of TCA manipulations support all three predictions and demonstrate that colour induced depth effects can be perceived in images having only achromatic information and a single non-achromatic colour. It is argued that optical factors, image characteristics and perceptual factors all play an important role in colour depth effects under natural viewing conditions. Further, the possibility is raised that colour and texture patterns which produce colour depth effects have evolved within certain species for camouflage or other behavioural purposes.

Color Perception↗

PubMed2005

Multimedia article. The keys to the new laparoscopic world Thumbs up! knot and Tornado knot.

Most laparoscopic surgeons feel some anxiety when performing intracorporeal knotting with conventional techniques [1, 2]. Two factors contribute to this anxiety. The first is the necessity of recognizing three dimensions on a two-dimensional monitor. The conventional intracorporeal knotting techniques make loops by twisting the thread with a second pair of forceps. This necessitates cooperative movement of both hands, with the added difficulties of depth perception. Regular touch confirmations reduce problems with depth perception. However, touch confirmation is more complicated in laparoscopic surgery than in laparotomy. The second problem is that tied loops can come loose and escape the instruments, especially with hard thread. This is not only stressful but also increases operation time.

Humans↗

PubMed1992

The history of stereoscopy.

Ptolemy (127-148 AD) studied physiological diplopia, correspondence and the horopter. He had all the data to build a theory of depth perception through disparity detection, but left that undone. Alhazen (1000 AD) associated depth perception with the sensation of binocular convergence, just as Kepler (1611) and Descartes (1637). With the development of the concept of retinal correspondence and the fusion of the retinal images in the brain (Huygens 1667, Newton 1704) a cerebral mechanism of disparity detection became thinkable. The rise of Empiricism (Molyneux' Premise, the case of Cheselden) postponed the solution of the problem, finally reached by Wheatstone (1838). Physiological proof of Wheatstone's theory came from the experiments of Barlow et al. (1967).

Depth Perception↗

PubMed2001

Ernst Mach and the episode of the monocular depth sensations.

Although Ernst Mach is widely recognized in psychology for his discovery of the effects of lateral inhibition in the retina ("Mach Bands"), his contributions to the theory of depth perception are not as well known. Mach proposed that steady luminance gradients triggered sensations of depth. He also expanded on Ewald Hering's hypothesis of "monocular depth sensations," arguing that they were subject to the same principle of lateral inhibition as light sensations were. Even after Hermann von Helmholtz's attack on Hering in 1866, Mach continued to develop theories involving the monocular depth sensations, proposing an explanation of perspective drawings in which the mutually inhibiting depth sensations scaled to a mean depth. Mach also contemplated a theory of stereopsis in which monocular depth perception played the primary role.

Austria↗

PubMed2002

Visual depth encoding in populations of neurons with localized receptive fields.

Stereopsis is the ability to perceive three-dimensional structure from disparities between the two-dimensional retinal images. Although disparity-sensitive neurons have been proposed as a neural representation of this ability many years ago, it is still difficult to link all qualities of stereopsis to properties of the neural correlate of binocular disparities. The present study wants to support efforts directed at closing the gap between electrophysiology and psychophysics. Populations of disparity-sensitive neurons in V1 were simulated using the energy-neuron model. Responses to different types of stimuli were evaluated with an efficient statistical estimator and related to psychophysical findings. The representation of disparity in simulated population responses appeared to be very robust. Small populations allowed good depth discrimination. Two types of energy neurons (phase- and position-type models) that are discussed as possible neural implementations of disparity-selectivity could be compared to each other. Phase-type coding was more robust and could explain a tendency towards zero disparity in degenerated stimuli and, for high-pass stimuli, exhibited the breakdown of disparity discrimination at a maximum disparity value. Contrast-inverted stereograms led to high variances in disparity representation, which is a possible explanation of the absence of depth percepts in large contrast-inverted stimuli. Our study suggests that nonlocal interactions destroy depth percepts in large contrast-inverted stereograms, although these percepts occur for smaller stimuli of the same class.

Action Potentials↗

PubMed1995

Disabled stereopsis may be the norm among well-educated people.

Most well-educated people, where the author lives, have lost the ability to perceive the third dimension in space during everyday life. This has passed unnoticed because poor depth perception is not a serious handicap in an urban environment and because clinical depth perception tests have not been designed to detect this deficit. The author's hypothesis is that disabled stereopsis is a global phenomenon. A simple way of testing for disabled stereopsis is presented, in the hope that investigators in other parts of the world will test a sample of their local population and send the results to the author.

Depth Perception↗

PubMed2007

Robotic surgery in the pediatric airway: application and safety.

OBJECTIVE: To assess the application and safety of transoral robotic surgery in the pediatric airway. DESIGN: An institutional review board-approved study. Experimental laryngeal surgery was performed on 4 pediatric cadaver larynxes as controls. Application of robotic equipment for laryngeal surgery was attempted on 5 patients. SETTING: Tertiary care pediatric medical center. PATIENTS: Five patients with laryngeal cleft and 4 pediatric cadaver larynxes. INTERVENTIONS: (1) The da Vinci Surgical Robot (Intuitive Surgical Inc, Sunnyvale, Calif) was used on 4 cadaver larynxes and assessed for the dexterity, precision, and depth perception that it allowed the surgeon during laryngeal surgery. Procedures were documented with still and video photography. (2) The da Vinci Surgical Robot was used through a transoral approach to attempt repair of a laryngeal cleft in 5 pediatric patients who were under spontaneously breathing general anesthesia. RESULTS: (1) Use of the surgical robot on cadaver larynxes provided great dexterity and precision, delicate tissue handling, good 3-dimensional depth perception, and relatively easy endolaryngeal suturing. (2) The surgical robot could not be used for repair of laryngeal cleft on 3 patients owing to limited transoral access. However, 1 patient with a type 1 laryngeal cleft and 1 patient with a type 2 laryngeal cleft underwent transoral robotic repair with great success. CONCLUSIONS: Surgical robots provide the ability to manipulate instruments at their distal end with great precision, increased freedom of movement, and excellent 3-dimensional depth perception. The size of the equipment can be a limiting factor with regard to the application and success of the transoral approach to airway surgery. We believe that further advances in device technology and a new generation of robotic equipment will facilitate the incorporation of surgical robotics in the advancement of minimally invasive endoscopic airway surgery.

Adolescent↗

PubMed1980

The vision of submariners and National Guardsmen: A longitudinal study.

This study was designed to differentiate among possible causes of an increased incidence of myopia and related symptoms among submariners by making a longitudinal comparison of the visual functions of two groups of subjects, submariners and National Guardsmen. Refractive error, visual acuity, phorias, accommodation, and depth perception were measured. Submariners showed statistically significantly greater losses in visual acuity, accommodation, and depth perception over a 3.5-year period than did the guardsmen, but the differences were very small. Comparison with data in the literature gives evidence of large shifts in refractive error for young men, both submariners and guardsmen, born in recent years. it is suggested that whatever factors are responsible for the increase in myopia in the general population are operating even more effectively among submariners.

Accommodation, Ocular↗

PubMed1996

Image blur as a pictorial depth cue.

A range of cues are already known to mediate depth perception in pictures and have been exploited by artists in drawings and paintings. Modern images are commonly generated by photographic or video equipment, and these images contain a depth cue that cannot be found in artistic depictions of natural scenes: different image regions are often blurred by different amounts, because of depth of focus limitations. Demonstrations presented here show that this selective image blur also acts as a pictorial depth cue, even when other pictorial cues are removed. Experimental data indicate that the degree of blur at borders between blurred and sharp image regions is used by the visual system to establish the depth ordering of different regions. Selective image blur is thus a potentially useful addition to computer-generated and cartoon images to enhance the impression of depth they convey. It may well also contribute to depth perception in natural retinal images, because the depth of focus of the human eye is limited.

Computer Graphics↗

PubMed1994

Infants' perception of kinetic depth and stereokinetic displays.

Studies examined infants' perceptions of 3-dimensional form, using a kinetic depth effect (KDE) display and displays containing subsets of the motion present in the KDE display. One subset consisted of "between-contour" motion, and the second consisted of "within-contour" motion. Research with adults has suggested that only between-contour motion leads to a compelling depth percept. In Experiments 1 and 2, infants generalized habituation from a KDE display to the between-contour but not the within-contour changes. In Experiments 3 and 4, infants generalized habituation from a KDE display to the between-contour display viewed from a novel orientation but not to the within-contour display viewed from the original orientation. Results indicate sensitivity to between-contour but not within-contour information, suggesting that infants perceive the 3-dimensional form of these displays.

Depth Perception↗