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At least 1,513 records · Page 84Linked to original sources
PubMed2002

Augmented-view for restricted visual field: multiple device implementations.

PURPOSE: An augmented-view device for patients with severely restricted peripheral visual fields (tunnel vision) was proposed, combining a see-through head-mounted display and a simultaneous minified view of a wide field presented as contour information. Here we create and evaluate multiple implementations of the augmented-view concept and report responses from potential users. METHODS: Several prototypes using commercial off-the-shelf devices were implemented. Then they were evaluated in real environments in daylight and at night by two retinitis pigmentosa patients. RESULTS: Effective expansion of the visual field of patients was achieved. Patients indicated their preferences for different properties, devices, and combinations. CONCLUSIONS: Patients found the augmented-view concept of help for their impairment, but wanted much more ergonomic design than the prototypes provided. Benefits, limitations, and possible improvements for the evaluated devices are discussed.

Equipment Design↗
PubMed1982

Effects of sex, handedness, stimulus and visual field on "mental rotation".

Shepard's mental rotation paradigm (e.g. Shepard and Metzler, 1971) was modified to allow tachistoscopic presentation of stimuli at varying angles of orientation (0 degrees to 180 degrees) in the right and left visual fields. Thirty male and thirty female subjects divided into three handedness groups (right-handers, non-familial and familial left-handers) judged whether a stimulus was a standard form or its mirror image. In general response times for correct judgements (RTc) increased monotonically as a function of angle of orientation though the curves tended to be negatively accelerated rather than linear. Right-handers showed a slower rate of increase in RTc as a function of angle than either left-handed group. Mean RTc and the rate of increase in RTc were equivalent for the two sexes and for the two visual fields. Both mean RTcs and on the rate of increase in RTc varied as a function of the stimulus. Error rates also increased monotonically as a function of angle of orientation. No sex or handedness differences in error rates were found. However, errors increased significantly less rapidly when stimuli were presented in the left visual field. It is argued that right hemisphere specialization for spatial processing minimizes the rate of increase in errors. The present failure to find sex differences may be of interest and it is argued that rapid presentation of stimuli results in subjects setting maximum and minimum response times. Within this relatively restricted "bandwith" of response times males and females may perform spatial tasks equally efficiently. Some confirmation for this hypothesis vs. an alternative based upon differences in hemispheric organization was found in a second experiment.

Adolescent↗
PubMed2005

Central visual field changes using flicker perimetry in type 2 diabetes mellitus.

PURPOSE: To evaluate the efficacy of flicker perimetry compared with that of static perimetry in determining central visual field losses in participants with type 2 diabetes mellitus. METHODS: Flicker and static perimetry were performed using the Medmont field analyser on 20 participants with type 2 diabetes mellitus and 24 age-matched control participants. RESULTS: Flicker, but not static, perimetry demonstrated significant reductions in thresholds in those participants who had a recent diagnosis of diabetes or who had no or only minimal diabetic retinopathy compared to the control group at eccentricities close to fixation. CONCLUSION: Flicker perimetry is recommended for the evaluation of visual field losses in participants with recent onset of diabetes and minimal diabetic retinopathy.

Aged↗
PubMed2005

Visual field defect after posterior spine fusion.

STUDY DESIGN: Case report and literature review. OBJECTIVES: Review cases and literature regarding visual loss following posterior spine fusion for scoliosis and emphasize right-to-left atrial shunt as a risk factor for paradoxical embolus resulting in a postoperative visual field defect. SUMMARY OF BACKGROUND DATA: The existing literature discusses various possible etiologies of postoperative visual loss including direct pressure, hypotension, blood loss, and anemia. One study shows higher rates of cerebral microemboli in patients with right-to-left atrial shunts. METHODS: Chart and literature review. RESULTS: A paradoxical embolus to a branch of the central retinal artery resulted in a unilateral quadrant defect (homonymous quadrantanopsia) in a girl with a previously undiagnosed right-to-left atrial shunt. CONCLUSIONS: Right-to-left atrial shunts may predispose to cerebral emboli during scoliosis surgery. These emboli may be a cause of postoperative visual field defects.

Child↗
PubMed1997

The central visual field in homonymous hemianopia. Evidence for unilateral foveal representation.

BACKGROUND: Controversy exists regarding the cortical representation of the foveal region in man. The most plausible explanation for foveal sparing in homonymous hemianopia is dual blood supply to the occipital pole. However, bilateral cortical representation has also been suggested. OBJECTIVE: To determine the representation of the foveal region in the primary human visual cortex. DESIGN: A case series correlating magnetic resonance imaging to the visual field defects of 6 patients with occipital lobe injuries. RESULTS: Four patients with foveal-sparing hemianopic defects demonstrated unilateral sparing of the posterior occipital cortex. In contrast, 2 patients with central homonymous defects showed isolated involvement of the posterior pole. One patient also demonstrated 5 degrees of field sparing along the horizontal meridian. CONCLUSIONS: On the basis of correlating the findings of magnetic resonance imaging and visual field defects in patients with occipital lobe injury, we conclude that the foveal region is unilaterally represented in the primary human visual cortex and that a major portion of the striate cortex is dedicated to the central 10 degrees of vision. The horizontal meridian of the visual field is represented deep within the calcarine banks at the fissure base.

Adult↗
PubMed1989

[The visual field of patients with pituitary adenoma surgically treated].

The authors report the evolution of 72 patient's visual field operated for one pituitary adenoma. They specify the constant amelioration of this investigation in chromophobic adenomas. The stability in prolactinic adenomas or somatotropic. Allowing the supervision of the visual case, at these patients, the visual field does not seem useful in the diagnosis of the tumors recurrence.

Adenoma↗
PubMed1986

Influence of pindolol and timolol treatment on the visual fields of glaucoma patients.

In a prospective, multicenter, randomized, double-masked study of glaucoma patients, visual fields, intraocular pressures, blood pressures, and pulse rates were measured after a 4-week wash-out period and after three and six months of treatment with either pindolol 1% or timolol 0.5% twice daily. Both drugs reduced significantly the IOP. The blood pressure was not changed significantly whereas the pulse rate was reduced more in the timolol treated group than in the pindolol treated group. The visual fields of the pindolol group showed on the average a slight tendency towards improvement and in the timolol treated group a very slight tendency for deterioration. The difference between these two trends was statistically significant (p less than 0.05).

Blood Pressure↗
PubMed1991

Visual field organization and peck localization in the pigeon (Columba livia).

Some aspects of the stimulus control of peck localization in the pigeon were examined using conditioning paradigms, visual occlusion procedures, and 'touch-screen' technology. Birds were reinforced for pecks made to a small circular (target) stimulus projected upon a computer monitor and located within an electronically defined contingency area. The terminal location of each peck was monitored under binocular and monocular viewing conditions and when using either the frontal or lateral visual fields. Peck localization was highly accurate under either binocular or monocular viewing conditions or with the frontal field alone; there were no systematic differences between the right and left eyes and differences between monocular and binocular localization performance, though significant, were minimal. When viewing with the lateral field alone, subjects were initially unable to locate the food hopper and, even after retraining, conditioned peck localization was profoundly disrupted. The results confirm previous reports of functional differences between the frontal and lateral visual fields, but suggest that monocular cues are sufficient for highly accurate peck localization.

Animals↗
PubMed1998

Isotropic visual field effect on spatial orientation and egocentric localization.

The aim of this paper is to demonstrate the presence of a similar visual field effect on both spatial orientation and egocentric localization. A first experiment explored an orientation task (Visually Perceived Vertical or VPV determination) and compared the effects of a frame inclined either in the midfrontal plane (in this condition subjects assessed roll VPV) or in the median plane (subjects assessed pitch VPV) or in both combined planes (subjects assessed both roll and pitch VPV). A second experiment compared the frame effects specified above to the frame effect observed in an egocentric localization task (Visually Perceived Eye Level judgment) performed with a frame slanted in the median plane. The results showed that angular frame variations from -15 to +15 deg result in the same psychometric function for both orientation and localization tasks. In each experiment, correlations showed that individual differences occur in relation to an overall sensitivity to the visual field. Individual sensitivity may be accounted for by a ratio of visual to graviceptive information which remains constant whatever the perception plane (midfrontal or median plane) and whatever the task (spatial orientation or localization).

Adult↗
PubMed1996

Anteroposterior dynamic balance reactions induced by circular translation of the visual field.

The anteroposterior sway of subjects under conditions of spontaneous dynamic balance on a wobbly platform was measured during visual stimulation by a visual target executing a circular trajectory in the frontal plane. The target was either a component of the whole moving visual scene or moving on a stationary background. With the former stimulation, obtained through the use of rotating prismatic glasses, every point of the visual field appeared to describe a circular trajectory around its real position so that the whole visual field appeared to be circularly translated, undistorted, inducing a binocular pursuit movement. Under these conditions, stereotyped anteroposterior dynamic balance reactions synchronous with the position of the stimulus were elicited. The latter stimulation consisted of pursuing a luminous target describing a trajectory similar to that of the fixation point seen through the rotating prisms on the same, this time stable, visual background. Although pursuit eye movements were comparable, as demonstrated by electro-oculographic recordings, no stereotyped equilibration reaction was induced. It is concluded that the translatory motion of the background image on the retina in the latter experiments contributed to the body's stability as well as to the perception of a stable environment.

Adult↗
PubMed1994

Screening for glaucoma: the time taken by primary examiners to conduct visual field tests in practice.

A panel of 101 primary examiners (optometrists or their ancillary staff) in England and Wales prospectively recorded the time taken to examine the central visual fields of each of 10 (or more) of their patients. The results indicate that the time depended not only on the test procedure but on how frequently the examiner conducted such a test. A basic test with semi-automated field screening equipment, applied routinely by 30 examiners on 547 patients, took an average 3.7 min per patient; (lower quartile 2.8 min). For such examiners, a standard extended test took 4.9 min. Similar times applied whether tests were conducted by an optometrist or an assistant. It was concluded that visual field screening in a normal population could reasonably be assumed to take an average 4 min per patient.

Adult↗
PubMed1994

[Dependence of the sensitivity of the central visual field on hemoglobin-oxygen saturation].

Retinal function is very sensitive to changes in hemoglobin oxygen saturation. Characteristic ophthalmological symptoms of oxygen deficiency are: changes in color perception, visual field defect, eye flickering, reduction of visual acuity, seeing double images, defects in neural image interpretation. To test the dependency of changes in the central visual field sensitivity on different degrees of oxygen saturation, 48 probands (48 monocular tests) 20-50 years of age were examined in the altitude simulation chamber of the Aviation Medicine Institute of German Air Force at zero altitude (= 500 m) and at 10,000 ft (ca. 3,500 m height). Three types of experiments were performed: determination of abnormal quotient using a Heidelberg anomaloscope; determination of changes in color vision by saturated and disaturated panel D-15 test; determination of differences in light sensitivity for white, red, blue and green light by a threshold test using a Humphrey Field Analyzer (640) as perimeter. At zero level (500 m) hemoglobin-oxygen saturation was 97% +/- 1%. At 10,000 ft this value decreased to 83% +/- 3%. Hypoxic hypoxia caused neither significant AQ changes nor did it induce reproducible changes in color vision by the panel D-15 test. However, anoxia resulted in significant (P < 0.01) differences in light sensitivity in phototopic range.

Adult↗
PubMed1981

Glaucomatouslike visual field defects in chronic papilledema.

In 19 patients, 31 eyes with chronic papilledema were found to have visual field defects other than enlarged blind spots. In this series, the inferior nasal quadrant was most frequently involved. Dense paracentral scotomata were found in the Bjerrum area, some of which later progressed to form ring scotomata. Visual acuity usually deteriorated late in the course of the disease. The similarities of visual field defects in papilledema and glaucoma suggest common pathogenetic mechanisms of nerve fiber atrophy in both diseases.

Brain Diseases↗
PubMed1981

Sensation of rotation about a vertical axis with a fixed visual field in different illuminations and in the dark.

This paper compares the motion sensations of a subject rotated about a vertical axis for two fixed visual fields (a large peripheral field and a single central spot) and in darkness. Motion sensation is described in terms of threshold, frequency response, and subjective displacement and velocity. The perception of angular acceleration showed significantly lower threshold and reduced latency time for the illuminated presentation. The level of illumination, however, produced no significant difference in threshold. The subjective frequency response, measured by a nulling method, showed a higher gain in the illuminated presentation, particularly at low frequencies and accelerations. With the subject rotating a pointer to maintain a fixed heading during triangular velocity stimuli, subjective displacements showed no difference for all different visual cues. Magnitude estimates of the after-rotation associated with deceleration from a constant velocity showed a quicker rising speed, larger subjective velocity and longer duration in the illuminated presentation. All the results suggest that the oculogyral illusion is principally responsible for producing a lower threshold in the illuminated presentation, although the fixed peripheral visual field tends to reduce reliance upon vestibular signals. At lower intensity rotation stimuli, this effect is especially apparent.

Adult↗
PubMed2004

Multidimensional visual field maps: relationships among local psychophysical and local electrophysiological measures.

Multidimensional psychophysical and electrophysical maps of the central retina are essential for assessing the functioning of the diseased retina. In this study, grating acuity, contrast sensitivity, duration for letter identification, multifocal electroretinograms, and Humphrey visual field thresholds were measured at equivalent positions throughout the central 20 degrees. We found that the rates of sensitivity loss were not equivalent for all psychophysical measures. The rate of loss in the duration required for letter identification as a function of eccentricity was the steepest, followed by acuity and contrast sensitivity. The rate of loss in luminance sensitivity as measured in the Humphrey visual field was the shallowest. The pattern of losses also varied across meridians. Specifically, the rate of loss as a function of eccentricity was highest in the vertical meridian and lowest in the horizontal meridian. These maps and the correlations among measures as a function of retinal position serve as a baseline so that we can examine disease effects throughout the retina. In addition, the development of vision rehabilitation programs focused on eccentric viewing training should consider the differential sensitivities of the peripheral retina.

Adult↗
PubMed2004

Test-retest reliability of the multifocal electroretinogram and humphrey visual fields in patients with retinitis pigmentosa.

We examined the reliability of Humphrey visual field thresholds and multifocal electroretinogram (mfERG) amplitudes and timing in a group of patients with Retinitis Pigmentosa (RP). Eight patients with RP and seven control subjects were tested five times: at baseline (visit #0), at three weekly follow-up visits (visits #1 - #3), and at three months (visit #4). For the Humphrey thresholds, differences between dB values on repeat visits were obtained. Differences between log values on repeat visits were calculated for mfERG amplitude and implicit time. We used the standard deviations of these difference scores as a measure of reliability and the means of the difference scores as a measure of progression. We found that the majority of the patients' repeat data were more variable than that of the control subjects for both the Humphrey and mfERG. We found no single factor that predicted the magnitude, or the variance, of the SD of differences scores for the patients. We recommend that each patient's reliability be assessed individually. Ultimately, the choice of an outcome measure must be guided by its reliability, as well as its ability to assess the visual function of interest.

Adult↗
PubMed1998

Frequency of asymmetric visual field defects in normal-tension and high-tension glaucoma.

OBJECTIVE: The purpose of the study was to evaluate the frequency of asymmetric visual field loss at presentation in patients with normal-tension glaucoma (NTG) and high-tension glaucoma (HTG). DESIGN: A retrospective cross-sectional study design was used. PARTICIPANTS: Four hundred and three NTG patients and 337 consecutive HTG patients (consecutive diagnoses between 1986 and 1996). INTERVENTION: Analysis of the frequency of unilateral field loss presentations in NTG and HTG. The visual fields of fellow eyes were compared to determine the side of more severe field loss. For the NTG patients, the relationship between the side with greater field loss and corresponding intraocular pressure (IOP) was investigated. MAIN OUTCOME MEASURES: Humphrey field analyzer mean defect (MD) and mean diurnal IOP. RESULTS: In the NTG group, 101 (25%) patients presented with unilateral field loss. The proportion of cases with unilateral field loss decreased with increasing age of presentation (chi-square test for trend = 26.9; P < 0.0001). Sixty-four percent of the patients had unilateral field loss in the left eye. Sixty-eight percent of the cases with bilateral field loss had a higher MD in the left eye. The diurnal IOP was estimated as 0.23 +/- 0.068 mmHg (mean +/- SE) higher in the left eye (P = 0.001). In the HTG group, 104 (31%) patients presented with unilateral field loss. The proportion of cases with unilateral field loss decreased with increasing age of presentation (chi-square test for trend = 4.6; P = 0.03). Right and left eyes had an equal chance of having field loss in unilateral cases and of being the side of more advanced field damage in bilateral cases. CONCLUSIONS: The frequency of cases with unilateral field loss was similar in HTG and NTG patients. Patients with unilateral field loss at presentation were more likely to be at the younger end of the age range. In the NTG population we studied, the left eye was more frequently the side of onset of field loss and 2.1 times more likely to present with a greater field defect than the right eye. In HTG patients, right and left eyes showed an equal chance of being the side of onset of field damage and the more affected side.

Aged↗