324 research outputs found

    Effects of stimulus size and luminance on oscillopsia in congenital nystagmus

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    AbstractAlthough the absence of oscillopsia is a common feature of congenital nystagmus (CN), it is occasionally noted by patients under poor viewing conditions and has been provoked in laboratory settings with stabilised images. In the present study, the effects of reductions in background stimulus size and luminance on perceptual stability in CN were examined. Sixteen CN subjects were first interviewed using a structured questionnaire about whether they ever experienced oscillopsia and, if so, under what circumstances and with what perceptions. They next fixated an LED centred in projected images of three sizes (21×14°, 10×6° and 7×4°) and four luminance levels (115.5, 24.5, 2.7 and 0.1 cd/m2, with contrasts from 96 down to 20%). Eye movements were recorded with a limbal tracker. They were asked after viewing each image “whether anything happened to the image while they watched it.”Occasional oscillopsia was reported by 12/16 of the CN subjects on the questionnaire. In the laboratory, 13/16 subjects experienced oscillopsia in some manner for at least one of the stimuli. 8/13 CN subjects experienced it for the dimmest and smallest slides. 11/13 perceived certain parts (either the LED or background) of the visual stimuli as moving, with the perception of LED movement most pronounced at low background luminance. Foveation did not differ when trials with and without reported oscillopsia were compared (independent samples t-test, p>0.05).Oscillopsia may occur in CN with normal viewing of bright fixation targets against dim backgrounds. Under these conditions, the oscillopsia may be spatially inhomogeneous. Luminance differences between the fixation point and surround may have caused transmission time differences as the image moved across the retina, therefore leading to the perception of motion in one portion of the scene and not the other

    Video game training in traumatic brain injury patients: an exploratory case report study using eye tracking

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    Remediation of attentional impairments is an essential component of cognitive rehabilitation after traumatic brain injury (TBI). Evidence from healthy participants has demonstrated attentional improvement following playing an action video game. This exploratory study investigated its application in TBI participants in a multiple baselines single case experimental design (SCED). Saccadic eye movements, recognized as the visible indicators of visual attention, were assessed to evaluate the effectiveness of the game training. Three severe TBI participants were trained in an action game for 10 hours. Saccadic eye movements during a self-paced saccade and an abstract visual search task were investigated during baseline, mid training and post-training. Using Percentage of Non-overlapping Data (PND), analysis showed consistent increase in the rate of the self-paced saccades in participants 1 (PND=80%) and 2 (PND=70%). In abstract search, fixation duration showed a minimally effective decrease for participant 2 (PND= 60%) and a moderately effective reduction in participant 3 (PND= 80%). Search time showed a highly effective reduction in participant 2 (PND = 100%) and moderately effective decrease in participant 3 (PND=70%). Overall, video game training might modify allocation of attention in eye movements. More evidence is required to validate the usefulness of this novel method of the cognitive training

    The essentials of leadership for successful principals

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    The high school principal wears many faces in the community in which she/he lives and works (Cavanaugh and Yoder, 1984). Most patrons of the school district know who the principal is and hold high expectations for him/her. At the same time, when the residents of a school district are asked to define the principal\u27s job in their school district, it is often hard for them to come up with a clear-cut statement. This is due to a lack of understanding of the principal \u27s responsibilities in the school system, and to the complexity of the principal \u27s role in education (Hallinger and Murphy, 1983)

    Optokinetic Nystagmus Suppression as an Index of the Allocation of Visual Attention

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    PURPOSE. To use the suppression of optokinetic nystagmus (OKN) as an objective measure of subjects' ability to distribute their visual attention to different elements-static or dynamic, simple or complex-in their visual environment. METHODS. Large-field, constant-velocity projected images, along with a stationary central fixation target were presented to 25 young participants (13 women). Images were either black O's with a few X's or red C's, blue T's, and a few red T's, with the X's and red T's as the search targets. Stationary targets at either 0°or Ϯ12.5°were either blinking squares or a rapid succession of colored shapes-blinks or green stars were the target events. Central fixation was maintained at all times. OKN gain was calculated for all tasks and analyzed in a mixed 4-way ANOVA, with the sex of the subjects as the group variable and dynamism, location, and complexity as within-subject effects. RESULTS. There was no effect of sex; all three main withinsubject effects were significant, as were the two-way interactions between them and an interaction between dynamism and sex. The most striking result was that there was little difference across static tasks but that dynamic tasks showed significantly more OKN breakthrough, particularly for the complex search presented centrally. CONCLUSIONS. In this group of normal-sighted young subjects, OKN breakthrough was sensitive to a range of stimulus characteristics. This finding allows a single outcome measure to be used across a wide range of possible tasks and may be useful in assessing the effects of age and disease. (Invest Ophthalmol Vis Sci. 2011;52:462-467
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