Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Depth Perception”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 919 records · Page 51Linked to original sources
PubMed2006

A biomechanical analysis of surgeon's gesture in a laparoscopic virtual scenario.

Minimally invasive surgery (MIS) has become very common in recent years thanks to many advantages that patients can get. However, due to the difficulties surgeons encounter to learn and manage this technique, several training methods and metrics have been proposed in order to, respectively, improve surgeon's abilities and assess his/her surgical skills. In this context, this paper presents a biomechanical analysis method of the surgeon's movements, during exercise involving instrument tip positioning and depth perception in a laparoscopic virtual environment. Estimation of some biomechanical parameters enables us to assess the abilities of surgeons and to distinguish an expert surgeon from a novice. A segmentation algorithm has been defined to deeply investigate the surgeon's movements and to divide them into many sub-movements.

Algorithms↗
PubMed1990

[Video-guided TUR].

Video-TUR has become a very important new technique in urology, causing far less discomfort than conventional techniques for the surgeon. A mini-chip camera (Olympus OTVS-2) is attached to the lens system of a continuous-flow resectoscope (Olympus). A television monitor (Sony PVM 1442) provides reliable guidance for the cutting loop when resection is necessary for the treatment of benign hypertrophy or carcinoma of the prostate or carcinoma of the bladder. To maintain a good intravesical flow system, which is very important for a clear field of view, a suprapubic cystostomy should be placed. The surgeon sits in a comfortable position with both eyes on the screen so that eye-strain, back pain and mental stress can be reduced. The excellent depth perception is due to a 50-times enlargement by the camera, so that tissue-orientated TUR is possible. Even when it is not possible to place the patient in an optimal position, because of scrotal hernia or coxarthrosis, TUR can still easily be performed. In 120 transurethral prostate resections and 30 transurethral bladder tumour resections, the video technique has proved comfortable for the surgeon and safe for the patient. Video-TUR has been helpful in the presentation of this technique in urologic teaching. TUR of the prostate has been freed from much of its mystique, since the procedure can be watched while it is in progress. The video technique has opened up a new epoch in endourology, whose importance cannot yet be realized.

Humans↗
PubMed2005

Optics of conductive keratoplasty: implications for presbyopia management.

PURPOSE: To define the corneal optics of conductive keratoplasty (CK) and assess the clinical implications for hyperopia and presbyopia management. METHODS: Four analyses were done. (1) Multifocal effects: In a prospective study of CK, uncorrected visual acuity (UCVA) for a given refractive error in 72 postoperative eyes was compared to control eyes. (2) Surgically induced astigmatism (SIA): 203 eyes were analyzed for magnitude and axis of SIA. (3) Higher-order optical aberrations: Corneal higher-order optical aberrations were assessed for 36 eyes after CK and a similar patient population after hyperopic laser in situ keratomileusis (LASIK). (4) Presbyopia clinical trial: Visual acuity, refractive result, and patient questionnaires were analyzed for 150 subjects in a prospective, multicenter clinical trial of presbyopia management with CK. RESULTS: (1) 63% and 82% of eyes after CK had better UCVA at distance and near, respectively, than controls. (2) The mean SIA was 0.23 diopter (D) steepening at 175 degrees (P < .001); mean magnitude was 0.66 D (SD, 0.43 D). (3) After CK, composite fourth- and sixth-order spherical aberration increased; change in (Z12) spherical aberration alone was not statistically significant. When compared to hyperopic LASIK, there was a statistically significant increase in composite fourth- and sixth-order spherical aberration (P < .01) and spherical aberration (Z12) alone (P < .02); spherical aberration change was more prolate after CK. (4) After the CK monovision procedure, 80% of patients had J3 or better binocular UCVA at near; 84% of patients were satisfied. Satisfaction was associated with near UCVA of J3 or better in the monovision eye (P = .001) and subjectively good postoperative depth perception (P = .038). CONCLUSIONS: CK seems to produce functional corneal multifocality with definable introduction of SIA and higher-order optical aberrations, and development of a more prolate corneal contour. These optical factors may militate toward improved near vision function.

Adult↗
PubMed1991

External rhinoplasty approach to unusual rhinologic procedures.

The technique of external rhinoplasty has enjoyed a renaissance over the last ten years primarily for cosmetic and functional septorhinoplasty. The versatility of this approach for a variety of rhinologic problems is exemplified by the previous case studies. More specifically, it affords unparalleled exposure of the nasal architecture and for the repair of septal perforations and nasal obstruction secondary to nasal valve deficiency. It may also aid the surgeon in defining the level of cartilage and skin thickness in the excision of rhinophyma. Beyond the unchallenged advantage of improved exposure that the external rhinoplasty approach affords, the surgeon is able to use both hands (as one is not occupied with the nasal speculum) and to view the procedure with binocular vision and greater depth perception. The teaching advantages are obvious. The method is not difficult, it may be done under local anesthesia and it entails no additional risk to the patient.

Aged↗
PubMed1990

[Anamnesis of brain-originated vision disorders].

A questionnaire for the subjective assessment of cerebral visual disorders was administered to 269 brain damaged patients. The patients' subjective complaints were correlated with the outcome of objective diagnostic procedures (visual perimetry, visual search, spatial contrast sensitivity, visual evoked potentials, depth perception, light- and dark-adaptation, reading, colour vision). A significant correlation was found between subjective complaints and objective diagnostic results for all fields. The prediction of visual impairments on the basis of subjective complaints and verified by objective tests was correct in 80 to 98% of the brain damaged patients tested. Interrater reliability was about 0.84. Thus, the questionnaire is suitable for the assessment of cerebral visual disorders because of its simplicity, short administration time (10-15 min) and high predictive value.

Accommodation, Ocular↗
PubMed1990

Effect of illuminance on the directions of chromostereopsis and transverse chromatic aberration observed with natural pupils.

The direction of chromostereopsis observed with a natural pupil and the direction of the monocularly perceived disparity between coloured targets (F and C lines - 486 and 656 nm) have been measured in a sample of 30 subjects at 10 and 1000 lx. At both illumination levels approximately equal numbers of subjects perceived positive and negative chromostereopsis. When the ambient illumination was increased, a reversal in the direction of the chromostereopsis occurred for 16 subjects. For six of them a change from a positive to a negative chromostereopsis was observed, a pattern not reported in previous studies. In most cases at both high and low illuminance, there was an absence of perception of a monocular disparity (transverse chromatic aberration), although chromostereopsis was reported, indicating that binocular information can be obtained from sub-threshold monocular disparities. At low illuminance, the lack of correlation between the direction of chromostereopsis and transverse chromatic aberration (TCA) may indicate that there may be a supplementary binocular factor in chromostereopsis.

Adult↗
PubMed1979

Aeromedical implications of the X-Chrom lens for improving color vision deficiencies.

A red contact lens (X-Chrom lens) worn on the nondominant eye by 12 color-defective subjects caused significant improvements on the Dvorine, Ishihara, and Hardy-Rand-Rittler pseudo-isochromatic color plate tests. Color vision scores on the Farnsworth Lantern, Color Threshold Tester, and Aviation Signal Light Gun were not improved. Minimal changes were found on the Farnsworth D-15 test, aeronautical chart color identification task, visual acuity, phoria, and stereoscopic depth perception. Control and color-defective subjects perceived a change in the path of a pendulum (Pulfrich test) when viewing through the X-Chrom lens or a monocular red filter. The X-Chrom lens may require extended wearing before its optimum effect becomes apparent.

Adult↗
PubMed1988

Combined atropine and 2-PAM Cl effects on tracking performance and visual, physiological, and psychological functions.

Combinations of atropine (up to 4 mg.70 kg-1) and 2-PAM Cl (up to 1200 mg.70 kg-1) were studied for their effects on a pursuit tracking task, six visual functions, heart rate and blood pressure, and cognitive functions as measured by six psychological tests. Tracking performance in both bright light and dim light was significantly degraded up to 3.5 h after injection. High- and low-contrast near acuity was significantly altered up to 6 h after injection, whereas accommodation and pupil size remained altered for 24 h. Elevated pulse rates were observed for 4 h. Elevated systolic blood pressures were observed for 2 h while diastolic pressures remained elevated for 6 h. No drug effects were found for the psychological tests. Overall, the observed effects of these two drugs in combination are qualitatively similar to those of atropine alone although they are of greater magnitude. On two measures (accommodation and diastolic blood pressure), 2-PAM Cl was found to significantly potentiate the atropine effect.

Accommodation, Ocular↗
PubMed1988

Central serous chorioretinopathy in U.S. Air Force aviators: a review.

Idiopathic central serous chorioretinopathy (ICSC) is an uncommon disease with the potential to cause loss of visual acuity, decreased color vision, and decreased depth perception. These visual changes may become permanent and require removal of aviators from flight status. This study reviews 55 eyes of 47 USAF aviators with ICSC examined at the United States Air Force School of Aerospace Medicine (USAFSAM), Brooks AFB, TX. Clinical and aeromedical findings, both on initial and on follow-up ophthalmic examination were studied. Ninety-seven percent of aviators otherwise medically qualified were ultimately returned to flight status. Overall, 51% had recurrent episodes, 17% had bilateral disease, and 13% underwent laser photocoagulation. Visual acuity correlated with active disease, and there was a trend toward poor stereopsis and diminished color vision with worsening visual acuity. Eighty-six percent attained a final visual acuity of 20/20 or better. On final examination, 90% had normal stereopsis, 87% had normal color vision, and 49% had a normal central visual field. Eyes with recurrent disease tended to have degraded final visual acuity, stereopsis, color vision, and central visual field. The visual and aeromedical prognosis from a single attack of ICSC is generally favorable, but repeated attacks can lead to a significant decrease in visual functions that may jeopardize flying status.

Adult↗
PubMed1984

Human visual development over the first 6 months of life. A review and a hypothesis.

The behavioural changes that occur in visual development in the first 6 months of human life are discussed in relation to the possible underlying changes in neurophysiological mechanisms, with inter-species comparisons being made when appropriate. Recent data on the developing infant's changing capacity to discriminate various stimulus attributes is considered. It appears that orientation discrimination and cortically related visual evoked potentials are present at, or soon after, birth. However, data on colour discrimination, field differences in detection tasks and control of visual attention suggest a subcortical site for control of behaviour for the first month of life. The improvements in spatial and temporal resolution depend on maturation of both peripheral and central structures in the visual pathway and so do not provide a clear distinction between cortical and subcortical function. There is clear evidence that binocular function in the cortex does not emerge until three months postnatally. A hypothesis is proposed that maturation of a number of pathways between cortex and subcortical structures underlies the observed behavioural changes starting at around 2 months of age. The initial immaturity of connections between cortex and pretectum may give rise to asymmetrical monocular OKN. Maturation of pathways from cortex to colliculus could account for improvements in convergence, allowing development of cortical binocularity, and for the developing ability to control shifts of visual attention.

Accommodation, Ocular↗
PubMed1995

Vision in dogs.

Compared with the visual system in human beings, the canine visual system could be considered inferior in such aspects as degree of binocular overlap, color perception, accommodative range, and visual acuity. However, in other aspects of vision, such as ability to function in dim light, rapidity with which the retina can respond to another image (flicker fusion), field of view, ability to differentiate shades of gray, and perhaps, ability to detect motion, the canine visual system probably surpasses the human visual system. This has made the dog a more efficient predator in certain environmental situations and permits it to exploit an ecological niche inaccessible to humans.

Animals↗