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

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

Visual fields and results for glaucoma participants in Experiment 2.

<p>Greyscale age matched normal visual field plots are shown on the left and precision plots on the right for each of the eight glaucoma patients. On the greyscale plots, the eye that was used for monocular testing has a border. The location of test stimuli are illustrated by the <i>x</i> symbols in the top-left greyscale panel. The precision plots show monocular (left) and binocular (right) visual localisation (•) and pointing (▿) precision as a function of visual field sensitivity for each test location. The numbers in the top left corner of each panel represent the percentage of pointing data that was used in the analysis. If less than 50% of trials were to the wrong quadrant, all data for that quadrant was excluded from analysis, as seen in row 5. The locations of the numbers correspond to the appropriate quadrants.</p

Linear regression of pointing precision against 95% confidence ellipse area for pointing at 15° eccentricity.

<p>Data of older participants is represented with open symbols and dashed regression lines, while younger participants are shown with filled symbols and unbroken regression lines. Panels A–D represent the four quadrants that were tested in Experiment 1.</p

Schematic of the methods.

<p>Testing paradigm (referenced visual localisation, Panel A; pointing, Panel B) and example data for a single observer (and for the case of Panel D, a single quadrant). Stimuli were presented for 100 ms after the button press that initiated each trial. For the visual localisation task (Panel A), the target spot appeared at one of 28 (7 MOCS steps x 4 isoeccentric locations) possible target locations. For the pointing task (Panel B), the target appeared at one of 4 possible target locations. Pointing precision was calculated as the reciprocal of the standard deviation (SD) of the population of pointing errors in the radial direction (Panel D), and visual localisation precision calculated as the reciprocal of the SD of the psychometric function fitted to the frequency of responding that the spot appeared outside the reference circle (Panel C). We also performed an unreferenced visual localisation task (not shown) wherein the reference circle (12 circularly arranged target spots, with 4 gaps) was displayed only once at the beginning of a block of trials.</p

Results of Experiment 1.

<p>This plot shows the precision of (A) referenced visual localisation, (B) unreferenced visual localisation and (C) pointing for younger (closed symbols) and older (open symbols) observers at eccentricities of 5°, 10° and 15°. Symbols represent the group mean, with error bars showing 95% confidence intervals for the mean.</p

Average pointing time vs. visual field global indices for glaucoma participants.

<p>Visual field global indices provide an indication of visual field abnormality relative to an age-matched normative database. Absolute defect status (left panel) is an indication of general visual field loss, with increasingly negative numbers associated with greater levels of visual field loss. Pattern deviation (right panel) describes areas of local visual field loss, with increasingly positive numbers associated with higher levels of localised visual field loss. For both panels data points more to the left indicate greater loss of visual field sensitivity. The grey bands indicate the mean ±2 standard deviations of the older control data.</p

Results of Experiment 2.

<p>Pointing and visual localisation precision of glaucoma patients and older controls. Individual data has been plotted next to the mean and 95% confidence interval of the mean for both monocular and binocular conditions.</p

WARRIOR-trial - is routine radiography following the 2-week initial follow-up in trauma patients with wrist and ankle fractures necessary: Study protocol for a randomized controlled trial

Background: Extremity fractures such as wrist and ankle fractures are a common and costly healthcare problem. The management of these fractures depends on fracture type and loss of congruity of the joint, resulting in cast immobilization or operative treatment. Loss of congruity or displacement leading to uneven joint loading, osteoarthritis and an increased probability of a poor functional outcome should be identified within the first 2 weeks post-trauma, based upon radiographs to determine optimal treatment. After this period, routine radiographs are scheduled for monitoring the bone-healing process. Current protocols describe imaging at 1, 2, 6 and 12 weeks post-trauma. However, it is questionable whether routine radiography following the initial follow-up ( 2-weeks post-trauma) is cost effective. The aim of this study is to determine whether a modification of the radiographic follow-up protocol can be conducted with no worse outcome and less cost than the current standard of care for patients with a wrist or ankle fracture. Methods/design: In a multicenter randomized controlled trial, 697 patients aged 18 years or older will be included: 385 wrist fracture- and 312 ankle fracture patients. Patients will be randomized into two groups: Group 1 receives usual care, consisting of radiographs 1, 2, 6 and 12 weeks post-trauma; Group 2 receives radiographs beyond the initial follow-up only when clinically indicated. The primary outcome is the overall extremity-specific function. For wrist fractures, this includes the Disabilities of the Arm, Shoulder and Hand Score; for the ankle fractures, this includes the Olerud and Molander ankle score. Secondary outcomes include: healthcare cost, the specific function measured with the Patient Rated Wrist and Hand Evaluation for wrist fractures and American Academy of Orthopaedic Surgeons foot and ankle questionnaire for ankle fractures, pain-intensity, health-related quality of life, self-perceived recovery, and complications. Both groups will be monitored at 1, 2, and 6 weeks and 3, 6, and 12 months. Discussion: This study will provide data on (cost) effectiveness of routine radiography in the follow-up of wrist and ankle fractures, and could pave the way for a change in (inter)national protocols

WARRIOR-trial - is routine radiography following the 2-week initial follow-up in trauma patients with wrist and ankle fractures necessary:Study protocol for a randomized controlled trial

Background: Extremity fractures such as wrist and ankle fractures are a common and costly healthcare problem. The management of these fractures depends on fracture type and loss of congruity of the joint, resulting in cast immobilization or operative treatment. Loss of congruity or displacement leading to uneven joint loading, osteoarthritis and an increased probability of a poor functional outcome should be identified within the first 2 weeks post-trauma, based upon radiographs to determine optimal treatment. After this period, routine radiographs are scheduled for monitoring the bone-healing process. Current protocols describe imaging at 1, 2, 6 and 12 weeks post-trauma. However, it is questionable whether routine radiography following the initial follow-up ( 2-weeks post-trauma) is cost effective.The aim of this study is to determine whether a modification of the radiographic follow-up protocol can be conducted with no worse outcome and less cost than the current standard of care for patients with a wrist or ankle fracture.Methods/design: In a multicenter randomized controlled trial, 697 patients aged 18 years or older will be included: 385 wrist fracture- and 312 ankle fracture patients. Patients will be randomized into two groups: Group 1 receives usual care, consisting of radiographs 1, 2, 6 and 12 weeks post-trauma; Group 2 receives radiographs beyond the initial follow-up only when clinically indicated. The primary outcome is the overall extremity-specific function. For wrist fractures, this includes the Disabilities of the Arm, Shoulder and Hand Score; for the ankle fractures, this includes the Olerud and Molander ankle score. Secondary outcomes include: healthcare cost, the specific function measured with the Patient Rated Wrist and Hand Evaluation for wrist fractures and American Academy of Orthopaedic Surgeons foot and ankle questionnaire for ankle fractures, pain-intensity, health-related quality of life, self-perceived recovery, and complications. Both groups will be monitored at 1, 2, and 6 weeks and 3, 6, and 12 months.Discussion: This study will provide data on (cost) effectiveness of routine radiography in the follow-up of wrist and ankle fractures, and could pave the way for a change in (inter)national protocols.</p