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PubMed2002

Do specially designed visual display unit lenses create increased postural load compared with single-vision lenses during visual display unit work?

Three different types of spectacle lenses, specially designed for visual display unit (VDU) work, were compared with single-vision lenses regarding postural load. The different corrections effect on postural load was measured by using electromyography. Muscle loads were recorded from the trapezius muscle and the infraspinatus muscle. Continuous measurements of body posture were measured by using three dual axis inclinometers attached to the head, back, and upper arm. No significant differences were found between the single-vision lenses and the specially designed VDU lenses regarding muscle load. Small differences were found regarding the head angle. The study concludes that these new lens designs create interesting opportunities for the optometrist to optimize the visual conditions for VDU workers.

Arm↗

PubMed1975

Visual evoked responses in humans with abnormal visual experience.

1. The visual evoked response to a grating target of varying spatial frequency was examined for normal subjects and for subjects with meridional amblyopia. This condition, reduced visual resolution for specific target orientations, is associated with, and thought to result from, marked ocular astigmatism. 2. For normal subjects, the general relation between spatial frequency and the evoked response is similar to psychophysical contrast sensitivity data. Evoked response amplitudes to oblique gratings are typically reduced and this is analogous to the lower acuity for oblique compared to horizontal and vertical detail. 3. In addition to the oblique effect, the magnitude of the evoked response for meridional amblyopes depends upon grating orientation over most of the spatial frequency range tested (0-5-16 cycles/deg). The lowest evoked amplitude is found when stimulus grating orientation matches that for which acuity is reduced. 4. The evoked potentials spatial frequency response functions are qualitatively similar to contrast sensitivity functions determined with the same abnormal subjects. 5. From these results, it may be concluded that the physiological locus of meridional amblyopia is confined primarily to structures at or prior to the site of evoked potential generation.

Amblyopia↗

PubMed1988

Visual after-effects associated with the use of high-resolution visual display units.

A long-lasting visual after-effect associated with the use of a high-resolution green visual display unit (VDU) is described in eight normal volunteers. Its duration to a standard VDU exposure is measured. It is related to the McCollough effect and is thought to be either a fatiguing of green colour-coded edge-detectors or an associative phenomenon. A reduction or loss of the usual foveal peak of the critical flicker frequency (CFF) to red is also described.

Adult↗

PubMed1990

Difference between visual feedback and visual suppression upon the stabilization of body sway in normal subjects.

We developed a system to feedback the center of foot pressure by vision using a microcomputer. The subjects were instructed to adjust the center of foot pressure (displayed on the computer display at real time) to the point of intersection of the two stable (horizontal and vertical) lines on the computer display. The peak of the power spectra of body sway shifted significantly to the higher frequency range in the Y component (the lateral direction) in the visual feedback condition. Thus, we conclude that the visual feedback of body sway depends mainly on the error signals between the fovea and the image in the lateral direction to stabilize body sway.

Adult↗

PubMed1992

Are direction and speed coded independently by the visual system? Evidence from visual search.

Three visual search experiments examined whether motion is coded as two separate features, speed and direction. Increasing the heterogeneity of the directions in which stimuli moved disrupted detection of a target defined by speed (fast among medium and slow nontargets), suggesting that speed is coded integrally with direction. However, heterogeneity in speed did not disrupt detection of a target moving in a particular direction among nontargets with different directions. This suggests that direction is coded independently of speed. The apparent paradox raised by these contrasting conclusions is consistent with neurophysiological and computational models of motion-detection, which suggest that low-levels of the visual system contain direction-detectors insensitive to speed, while speed is coded at higher levels by detectors which are also sensitive to direction. Evidence consistent with the existence of the latter conjunction detectors was obtained in a final experiment which found search for a conjunction of speed and direction to be parallel.

Adult↗

PubMed1997

Visual Genome Explorer: a comparative visual interface to genome data.

In response to the deluge of genome data, we are developing Visual Genome Explorer, an interactive graphical interface to genome data. Given is a description of the prototype program, which introduces the concept of visual comparative genomics for complete bacterial genomes.

Computer Communication Networks↗

PubMed1997

Spatial visualization: running visualization for empty squares.

A technique is reported in which an oral description of empty squares had to be visualized. A tone signaled completion, and a response was made whether the last square had touched a previous square. The chain lengths varied from 10 to 19 squares at closure. Local closure sizes consisted of 4 to 10 squares. Closures up to 6 squares produced the least errors. There were biases in response as a function of response type and chain length. The technique could be useful for monitoring continuous spatial visualization.

Auditory Perception↗

PubMed1999

Probing for the threshold energy for visual transduction: red-shifted visual pigment analogs from 3-methoxy-3-dehydroretinal and related compounds.

While azulenic retinal analogs failed to yield a red-shifted visual pigment analog, the 9-cis isomers of the push-pull polyenals 3-methoxy-3-dehydroretinal and 14F-3-methoxy-3-dehydroretinal yielded iodopsin pigment analogs with absorption maxima at, respectively, 663 and 720 nm. The former gave a relatively stable batho product (700 nm) and was able to activate transducin. A lower activity was observed for the latter. One possible explanation for the combined results is that the excitation energies of these red-shifted pigments are approaching the threshold energy for visual transduction (although at this time we cannot rigorously exclude a role of the added F-atom in reducing the transducin activity).

Retinal Pigments↗

PubMed2001

Visual assessment of the radiation distribution in the ISS Lab module: visualization in the human body.

The US Lab module of the International Space Station (ISS) is a primary working area where the crewmembers are expected to spend majority of their time. Because of the directionality of radiation fields caused by the Earth shadow, trapped radiation pitch angle distribution, and inherent variations in the ISS shielding, a model is needed to account for these local variations in the radiation distribution. We present the calculated radiation dose (rem/yr) values for over 3,000 different points in the working area of the Lab module and estimated radiation dose values for over 25,000 different points in the human body for a given ambient radiation environment. These estimated radiation dose values are presented in a three dimensional animated interactive visualization format. Such interactive animated visualization of the radiation distribution can be generated in near real-time to track changes in the radiation environment during the orbit precession of the ISS.

Computer Simulation↗

PubMed1975

Visual discrimination learning in cats with different early visual experiences.

Simultaneous object discrimination learning in an alimentary situation was strongly impaired in cats deprived from birth of patterned visual experience. The same impairment was observed in cats with experience limited to those objects that were used later in the discrimination task. Some impairment was also present in cats which were reared with opened eyes in the laboratory as compared with normal cats, that spent the early period of life outside of the laboratory. It is concluded that the deprived cats were impaired mainly because of the lack of opportunity during early development to use visual cues in alimentary tasks.

Animals↗

PubMed1989

[The visual fixation test in the study of visual-vestibular interactions. General aspects and results in normal subjects and patients].

Whenever we need to study visual-vestibular interactions, our method of choice among the ones based on thermal stimulation is the visual suppression test. In the vestibular laboratory of the II E.N.T. Clinic of the University of Parma the V.S.T. has been employed since 6 years systematically in all patients undergoing Electronystagmography. Our study was based on 10 normal patients and on 30 patients suffering from different pathologies. These patients were divided into groups according to the site of the lesion. The results we obtained are interesting: this test gives us important clinic data that we cannot obtain using other methods and allows us to discriminate the central or the peripheral site of the vestibular system lesion.

Adolescent↗

PubMed1977

Diurnal rhythms of visual accommodation and blink responses: implication for flight-deck visual standards.

The major purpose of this study was to determine whether 24-h variations in accommodation responses occur and, if they do, whether they should be considered in setting visual standards for flight-deck tasks. A recently developed servo-controlled optometer and focus stimulator were used to obtain monocular accommodation response data on four college-age subjects. No 24-h rhythm in accommodation was shown. Heart rate and blink rate also were measured and periodicity analysis showed a mean 24-h rhythm for both; however, blink rate periodograms were significant (p less than or equal to 0.003) for only two of the four subjects. Thus, with the qualifications that college students were tested instead of pilots and that they performed monocular laboratory tasks imstead of binocular flight-deck task, it is concluded that 24-h rhythms in accommodation responses need not be considered in setting visual standards for flight-deck task.

Accommodation, Ocular↗

PubMed1981

Visual-vestibular interactions: the directional component of visual background movement.

Legibility of a head-fixed display and visual suppression of the vestibulo-ocular reflex (VOR) were found to be superior when vestibular stimuli and optokinetic stimuli were of like direction (i.e. would produce the same directions of nystagmus) and inferior when they were opposite in direction. Velocities (relating to the head) of peripheral optokinetic stimuli ranging between -18 degrees/s and +180 degrees/s interacted effectively with vestibular stimuli to influence visibility of a head-fixed display. This indicates that peripheral optokinetic stimulation can influence visual suppression of the VOR at velocities that far surpass effective production of optokinetic nystagmus.

Electronystagmography↗

PubMed1982

Visual pigment and visual receptor cells in fetal and adult sheep.

The visual pigments, and the structure of the visual cells, were investigated by spectrophotometry and by light and electron microscopy in fetal and adult sheep. The rhodopsin system in adult sheep closely resembles that of cattle. The absorbance maxima of rhodopsin, lumirhodopsin, and metarhodopsin I are at 498, 490, and 480 nm, respectively. The estimated molar absorbance coefficient at the wavelength of maximum absorption of rhodopsin is 40,000M-1 . cm-1. Rhodopsin was detected from a fetal age of 85 days (term at 145 days). Partial bleaching of extracts from fetal eyes (95, 105, and 115 days) did not demonstrate cone pigments, although cones were present in fair numbers at a fetal age of about 105 days. The time course of rhodopsin formation between 85 and 140 days resembles a growth curve. The amount of rhodopsin shortly before birth (140 days) is about 0.6 times that in the adult. The number and dimensions of rod outer segments as well as packing of the discs were studied structurally and related to the rhodopsin content. A fairly good correlation was found at the earliest stages (95 and 105 days gestation age), when rhodopsin concentration was very low and rod outer segments were few and small, as well as at the latest stage (140 days). At 115 days the rhodopsin content observed by spectrophotometry was less than that indicated by the outer segment volume, probably mainly due to the outer segment discs and possibly to the rhodopsin molecules being less tightly packed than at 140 days.

Animals↗

PubMed1976

[Visual processing of 12,000 electrocardiograms according to the USPHS code and comparison of visual and automatic processing of about 6,000 electrocardiograms in accordance with the USPHS code].

Multistage screening in Hesse (W. Germany) and the visual processing of about 12,000 ECG's in accordance with the USPHS (Riedel programme) are reported. A good fit was found with data obtained from a similar study in another part of the country. Comparison is then made with the visual and computerised processing of about 6,000 ECG's in accordance with the same code, using four classes: "normal", "conditionally within the limits of normal", "suspect" and "definitely pathological". The encouraging result on comparison between "normal" and "pathological" in the 6.3% consisting of false negatives (only 2.1% definitely pathological) suggests that "normal" and "conditionally normal" ratings by the computer can be accepted, whereas considerable possibilities for cardiological diagnosis would remain in the case of pathological traces, which would always be accepted, where as considerable possibilities recognised standards set down by the USPHS code are considered reliable. They can be used under hospital or screening conditions. On the other hand, the "scale of values" programme offered as a model requires further checking. Notes on future development are also offered.

Coronary Disease↗

PubMed2003

Increased detection rate of glaucomatous visual field damage with locally condensed grids: a comparison between fundus-oriented perimetry and conventional visual field examination.

OBJECTIVE: To compare detection rates of glaucomatous visual field defects (VFDs) between the conventional 6 degrees x 6 degrees stimulus grid and locally condensed target arrangements in morphologically suspicious regions. METHODS: A total of 66 eyes of 66 patients with glaucoma or patients suspected of having glaucoma (34 females and 32 males; age range, 14-85 years) were enrolled in this study. Individual, local target condensation was realized by fundus-oriented perimetry (FOP) using a campimeter and compared with the results of conventional automated perimetry (CAP), obtained with the Humphrey Field Analyzer (30-2 grid). RESULTS: Twenty-three of the 66 patients showed normal findings with both methods; 27 had concordantly pathological results. In 15 patients we obtained normal findings with CAP, whereas FOP revealed early glaucomatous VFDs. Only one patient showed VFDs with CAP, whereas FOP results were normal. Scotoma detection rates significantly differed between the 2 methods (P<.001, sign test). Test duration with FOP was more than doubled compared with CAP. When considering only FOP points coinciding with the 6 degrees spacing of the 30-2 grid, there was no longer a significant difference between FOP and CAP (P>.25, sign test). This indicated that the target pattern, rather than the perimetric device, was most relevant for detecting glaucomatous VFDs. Follow-up throughout a series of 3 subsequent sessions at 6-month intervals revealed repeatable results in more than two thirds of all eyes for both FOP and CAP. CONCLUSIONS: Fundus-oriented perimetry that uses individually condensed test grids significantly increases the detection rate of glaucomatous VFDs in morphologically conspicuous areas compared with CAP using equidistant (6 degrees x 6 degrees) target arrangements. Repeatability is comparable between both methods.

Adolescent↗

PubMed2005

Normal visual field test results following glaucomatous visual field end points in the Ocular Hypertension Treatment Study.

OBJECTIVE: To compare the occurrence of normal visual field (VF) test results following 2 vs 3 consecutive, abnormal, reliable test results in the Ocular Hypertension Treatment Study. METHODS: The Ocular Hypertension Treatment Study is a prospective, multicenter follow-up study as part of a longitudinal randomized clinical trial. Sixty-four (68 eyes) of 1636 participants developed a VF primary open-angle glaucoma (POAG) end point. We compared the proportion of normal VF test results after a VF POAG end point among eyes whose VF abnormality was confirmed by 2 (n = 9 eyes) vs 3 (n = 59 eyes) consecutive, abnormal, reliable VF test results. RESULTS: The proportion of VF test results that were normal subsequent to a VF POAG end point in eyes whose abnormality was confirmed by 2 consecutive, abnormal, reliable test results was significantly higher (73 [66%] of 110) compared with eyes whose abnormality was confirmed by 3 consecutive, abnormal, reliable test results (46 [12%] of 381) (P = .01). CONCLUSIONS: A VF POAG end point confirmed by 3 consecutive, abnormal, reliable VF test results appears to have greater specificity and stability than either 1 or 2 consecutive, abnormal, reliable VF test results. However, some eyes whose VF POAG end point was confirmed by 3 consecutive, abnormal, reliable test results nonetheless had 1 or more normal test results on follow-up.

Adult↗

PubMed1993

Chemoarchitectonic subdivisions of the visual pulvinar in monkeys and their connectional relations with the middle temporal and rostral dorsolateral visual areas, MT and DLr.

The organization of the inferior pulvinar complex (PI) in squirrel monkeys was studied with histochemical localization of the calcium binding proteins calbindin-D28k and parvalbumin, and of cytochrome oxidase. With each of these markers, the inferior pulvinar complex can be subdivided into four distinct regions. Calbindin-D28k immunoreactivity is densely distributed in cells and neuropil within PI, except for a distinct centromedially located gap. This calbindin-poor zone, termed the medial division of the inferior pulvinar (PIM), corresponds precisely to a region that contains elevated cytochrome oxidase activity and parvalbumin immunostaining. The PIM extends slightly above and behind the classically defined limit of the inferior pulvinar, the corticotectal tract. Regions of inferior pulvinar with intense immunostaining for calbindin-D28k were the posterior division of the inferior pulvinar (PIP, medial to PIM) and the central division (PIC, lateral to PIM). A newly recognized lateral region, PIL, adjoins the lateral geniculate nucleus and stains more lightly for calbindin and parvalbumin immunoreactivity and for cytochrome oxidase. Staining patterns for calbindin, parvalbumin, and cytochrome oxidase in the pulvinar of rhesus monkeys closely resemble those shown in squirrel monkey inferior pulvinar, suggesting that a common organization exists in all primates. In order to examine cortical connection patterns of the histochemically defined compartments in the inferior pulvinar, injections of up to five neuroanatomical tracers (wheat germ agglutinin conjugated to horseradish peroxidase and fluorescent retrograde tracers) were placed in the same cerebral hemisphere. Single injection sites were in the middle temporal area (MT), and several separate injections were placed in a strip corresponding to the rostral subdivision of the dorsolateral area (DLr). Injections that involved only DLr and not MT labeled principally the PIC, and more sparsely PIP and PIL. DLr connections occupied a "shell" region dorsal to PIM that extended from PIC into the lateral and medial divisions of the pulvinar, PL and PM. Injection sites that included MT or were largely restricted to MT produced dense label in PIM and moderate label in PIC and PIL. The retinotopic organization within the inferior pulvinar was inferred from patterns of connections. Connections with cortex related most closely to central vision were found posteriorly in PIM and in adjacent portions of PIC as it wraps around the caudal pole of PIM. Cortex related to more peripheral locations in the lower visual field connected with more rostral PIM and PIC. Patterns of label within the portions of PL and PM that were immediately adjacent to PIM roughly paralleled those in PIM and PIC.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗