The binocular alignment of the eyes involves both voluntary and reflexive mechanisms, but little is known about the visual input and neurological pathway of the reflex component. Our studies examined ...the role of spatiotemporal frequency and contrast in the control of reflex eye alignment, and compared the contrast sensitivity of the alignment reflex with psychophysical contrast sensitivity. We measured the contrast sensitivity of vertical disparity-driven vergence eye movements in response to bandwidth filtered static or 6 Hz counterphase flickering noise and measured psychophysical detection sensitivity for the same stimuli. Contrast thresholds for producing a detectable vertical alignment change (measured with nonius lines) were determined using a staircase method for 7 spatial frequencies 0.25-16 cycles per degree and 3 vertical disparities 5, 10, and 30 arcmin in 7 adults with normal or corrected to normal vision. The main findings of this study are, (1) the vertical alignment reflex had overall relatively high contrast sensitivity, comparable to but somewhat less than visual detection thresholds, (2) the most effective stimulus spatial frequency scaled in inverse proportion to the disparity being stimulated, and (3) unlike psychophysical contrast sensitivity, the eye alignment reflex contrast sensitivity was not improved by flickering low spatial frequencies.
Phase curve observations provide an opportunity to study the energy budgets of exoplanets by quantifying the amount of heat redistributed from their daysides to their nightsides. Theories of phase ...curves for hot Jupiters have focused on the balance between radiation and dynamics as the primary parameter controlling heat redistribution. However, recent phase curves have shown deviations from the trends that emerge from this theory, which has led to work on additional processes that may affect hot Jupiter energy budgets. One such process, molecular hydrogen dissociation and recombination, can enhance energy redistribution on ultra-hot Jupiters with temperatures above ∼2000 K. In order to study the impact of H2 dissociation on ultra-hot Jupiters, we present a phase curve of KELT-9b observed with the Spitzer Space Telescope at 4.5 m. KELT-9b is the hottest known transiting planet, with a 4.5 m dayside brightness temperature of and a nightside temperature of . We observe a phase curve amplitude of 0.609 0.020 and an offset of . The observed amplitude is too small to be explained by a simple balance between radiation and advection. General circulation models (GCMs) and an energy balance model that include the effects of H2 dissociation and recombination provide a better match to the data. The GCMs, however, predict a maximum phase offset of 5°, which disagrees with our observations at >5 confidence. This discrepancy may be due to magnetic effects in the planet's highly ionized atmosphere.
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an uncommon hematologic malignancy with poor outcomes. Existing data on the clinical behavior of BPDCN are limited because reported outcomes ...are from small retrospective series, and standardized treatment guidelines are lacking. The interleukin-3 cytotoxin conjugate tagraxofusp was recently tested in phase 1/2 trials that led to US Food and Drug Administration approval, the first ever for BPDCN. However, because there was no matched internal comparator in this or any clinical study to date, results of BPDCN trials testing new drugs are difficult to compare with alternative therapies. We therefore sought to define the clinical characteristics and outcomes of a group of patients with BPDCN treated at 3 US cancer centers in the modern era but before tagraxofusp was available. In 59 studied patients with BPDCN, the median overall survival from diagnosis was 24 months, and outcomes were similar in patients with “skin only” or with systemic disease at presentation. Intensive first-line therapy and “lymphoid-type” chemotherapy regimens were associated with better outcomes. Only 55% of patients received intensive chemotherapy, and 42% of patients underwent stem cell transplantation. Clinical characteristics at diagnosis associated with poorer outcomes included age >60 years, abnormal karyotype, and terminal deoxynucleotidyltransferase (TdT) negativity in the BPDCN cells. We also identified disease responses to pralatrexate and enasidenib in some patients. This study highlights poor outcomes for patients with BPDCN in the modern era and the need for new treatments. Outcomes from ongoing clinical trials for BPDCN can be evaluated relative to this contemporary cohort.
•Outcomes in a multicenter BPDCN population in the modern era provide a benchmark before targeted therapy.•Age <60 years, normal karyotype, and TdT positivity were associated with improved survival; pralatrexate and enasidenib had activity in BPDCN.
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Knowledge of eye position in the brain is critical for localization of objects in space. To investigate the accuracy and precision of eye position feedback in an unreferenced environment, subjects ...with normal ocular alignment attempted to localize briefly presented targets during monocular and dichoptic viewing. In the task, subjects' used a computer mouse to position a response disk at the remembered location of the target. Under dichoptic viewing (with red (right eye)-green (left eye) glasses), target and response disks were presented to the same or alternate eyes, leading to four conditions green target-green response cue (LL), green-red (LR), red-green (RL), and red-red (RR). Time interval between target and response disks was varied and localization errors were the difference between the estimated and real positions of the target disk. Overall, the precision of spatial localization (variance across trials) became progressively worse with time. Under dichoptic viewing, localization errors were significantly greater for alternate-eye trials as compared to same-eye trials and were correlated to the average phoria of each subject. Our data suggests that during binocular dissociation, spatial localization may be achieved by combining a reliable versional efference copy signal with a proprioceptive signal that is unreliable perhaps because it is from the wrong eye or is too noisy.
► Objective eye-movement recording has been performed for a little over a century. ► Eye-movement recordings provide information about a range of clinical conditions. ► Several types of clinical ...instruments can potentially provide eye-movement data.
The clinical vision examination routinely includes an evaluation of ocular motor function. In a number of diverse situations, thorough objective recording of eye movements is warranted, using any of a variety of eye-tracking technologies that are available currently to clinicians. Here we review the clinical uses of eye tracking, with both an historical and contemporary view. We also consider several new imaging technologies that are becoming available in clinics and include inbuilt eye-tracking capability. These highly sensitive eye trackers should be useful for evaluating a variety of subtle, but important, oculomotor signs and disorders.
Interocular suppression is the phenomenon in which the signal from one eye inhibits the other eye in the presence of dissimilar images. Various clinical and laboratory-based tests have been used to ...assess suppression, which vary in color, contrast, and stimulus size. These stimulus variations may yield different spatial extents of suppression, which makes it difficult to compare the outcomes. To evaluate the role of stimulus characteristics, we measured the suppression zone using a binocular rivalry paradigm in normally-sighted observers by systematically varying the stimulus parameters. The stimuli consist of a constantly visible horizontal reference seen by one eye while two vertical suppressors were presented to the other eye. With a keypress, the suppressors appeared for 1 s, to induce a transient suppression zone in the middle part of the reference. Subjects adjusted the width between the suppressors to determine the zone. The zone decreased significantly with increasing spatial frequency and lower contrast. The width was 1.4 times larger than the height. The zone was smaller with negative compared to positive contrast polarity but independent of eye dominance, luminance, and colored filters. A departure from scale invariance was captured with a model suggesting a stimulus-dependent and a small fixed non-stimulus-dependent portion.
Visual spatial attention has been shown to influence both contrast detection and suprathreshold contrast perception, as well as manual and saccadic reaction times (SRTs). Because SRTs are influenced ...also by stimulus contrast, we investigated if the enhancement of perceived contrast that accompanies attention could account for the shorter SRTs observed for attended targets locations. We conducted two dual-task experiments to assess psychophysical and oculomotor responses to non-foveal targets of various contrast for different spatial-attention-cueing conditions. Cues were either: valid, an arrow at fixation pointing in the direction of the upcoming target; invalid, an arrow pointing in a different direction from the target; or neutral, a small circle instead of an arrow. In both experiments, subjects were instructed to make a saccade to the location of a subsequent, briefly flashed target. In the first experiment, the psychophysical judgment was a two-alternative-forced-choice (2AFC) contrast-detection task, in which subjects reported whether the flashed target was at a near (3°) or far (6°) eccentricity. In the second experiment, the judgment was a contrast matching task, in which subjects reported whether the target’s contrast was higher or lower than a remembered standard contrast. The results exhibit a robust, ∼40–50 ms reduction of SRTs with a valid compared to an invalid cue. Cueing effects on contrast detection and matching were small and inconsistent across subjects. Hence, the observed decrease in SRTs could not be accounted for fully by an enhancement in the target’s effective contrast due to attention, as attended and unattended targets that were equally detectable or were perceived to have the same suprathreshold contrast showed substantial differences in SRT.
Background:
Objective tools for prognosis and disease progression monitoring in multiple sclerosis (MS) are lacking. The visuomotor system could be used to track motor dysfunction at the micron scale ...through the monitoring of fixational microsaccades.
Aims:
The aim of this study was to evaluate whether microsaccades are correlated with standard MS disability metrics and to assess whether these methods play a predictive role in MS disability.
Method:
We used a custom-built retinal eye tracker, the tracking scanning laser ophthalmoscope (TSLO), to record fixation in 111 participants with MS and 100 unaffected controls.
Results:
In MS participants, a greater number of microsaccades showed significant association with higher Expanded Disability Status Scale score (EDSS, p < 0.001), nine-hole peg test (non-dominant: p = 0.006), Symbol Digit Modalities Test (SMDT, p = 0.014), and Functional Systems Scores (FSS) including brainstem (p = 0.005), cerebellar (p = 0.011), and pyramidal (p = 0.009). Both brainstem FSS and patient-reported fatigue showed significant associations with microsaccade number, amplitude, and peak acceleration. Participants with MS showed a statistically different average number (p = 0.020), peak vertical acceleration (p = 0.003), and vertical amplitude (p < 0.001) versus controls. Logistic regression models for MS disability were created using TSLO microsaccade metrics and paraclinical tests with ⩾80% accuracy.
Conclusion:
Microsaccades provide objective measurements of MS disability level and disease worsening.
Observers with central field loss typically fixate within a non-foveal region called the preferred retinal locus, which can include localized sensitivity losses, or micro-scotomas (Krishnan and ...Bedell, 2018). In this study, we simulated micro-scotomas at the fovea and in the peripheral retina to assess their impact on reading speed. Ten younger (<36 years old) and 8 older (>50 years old) naïve observers with normal vision monocularly read high and/or low contrast sentences, presented at or above the critical print size for young observers at the fovea and at 5 and 10 deg in the inferior visual field. Reading material comprised MNREAD sentences and sentences taken from novels that were presented in rapid serial visual presentation (RSVP) format. Randomly distributed 13 × 13 arc min blocks corresponding to 0–78% of the text area (corresponding to ∼0–17 micro-scotomas/deg2) were set to the background luminance to simulate micro-scotomas. A staircase algorithm estimated maximum reading speed from the threshold exposure duration for each combination of retinal eccentricity, contrast and micro-scotoma density in both age groups. Log10(RSVP reading speed) decreased significantly with simulated micro-scotoma density and eccentricity. Across conditions, reading speed was slower with low-compared to high-contrast text and was faster in younger than older normal observers. For a given eccentricity and contrast, a higher density of random element losses maximally affected older observers with normal vision. These outcomes may explain some of the reading deficits observed in older observers with central field loss.
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