Infrared Oculography Research Articles

The prevalence of internuclear ophthalmoparesis in a population-based cohort of individuals with multiple sclerosis

BackgroundInternuclear ophthalmoparesis (INO) occurs in 15–52% of individuals with multiple sclerosis (MS) and is reliably detected by infrared oculography. Methods for diagnosing INO with infrared oculography and the association between INO and MS characteristics need confirmation. We aimed to describe INO prevalence and the clinical characteristics of individuals with MS and INO in a population-based cohort of individuals with MS born in the year 1966 (Project Y). MethodsPreviously described thresholds for the versional dysconjugacy index (VDI), assessed with standardized infrared oculography, were used to detect INO in participants of project Y. Clinical characteristics, visual functioning and complaints were compared between individuals with MS with INO and individuals with MS without INO. ResultsTwo-hundred-twenty individuals with MS and 110 healthy controls were included. VDI values exceeding the threshold for INO presented in 53 (24%) individuals with MS and 19 controls (13%). INO was associated with male sex, greater disability, worse cognition and worse arm function in individuals with MS. There was no association with disease duration, visual functioning or complaints. ConclusionsINO is prevalent among individuals with MS aged fifty-three and related to clinical characteristics of MS. INO was more frequently detected in healthy controls than previous studies, implying that oculography based diagnosis of INO requires further refinement.

Caffeine may disrupt the impact of real-time drowsiness on cognitive performance: a double-blind, placebo-controlled small-sample study

Caffeine is widely used to promote alertness and cognitive performance under challenging conditions, such as sleep loss. Non-digestive modes of delivery typically reduce variability of its effect. In a placebo-controlled, 50-h total sleep deprivation (TSD) protocol we administered four 200 mg doses of caffeine-infused chewing-gum during night-time circadian trough and monitored participants' drowsiness during task performance with infra-red oculography. In addition to the expected reduction of sleepiness, caffeine was found to disrupt its degrading impact on performance errors in tasks ranging from standard cognitive tests to simulated driving. Real-time drowsiness data showed that caffeine produced only a modest reduction in sleepiness (compared to our placebo group) but substantial performance gains in vigilance and procedural decisions, that were largely independent of the actual alertness dynamics achieved. The magnitude of this disrupting effect was greater for more complex cognitive tasks.

Saccadic delay in multiple sclerosis: A quantitative description

In multiple sclerosis (MS), eye movement disorders are common and can be quantified with infrared video-oculography. A well-known abnormality is internuclear ophthalmoplegia (INO). This study aims to describe saccadic abnormalities beyond INO and investigate their clinical relevance. A validated standardized infrared oculography protocol, DEMoNS, was used for quantifying saccadic eye movements in three different tasks in MS patients and healthy controls. The relationship between the saccadic parameters and disease characteristics was investigated. Furthermore, the association between saccadic parameters and visual functioning was analysed using logistic regression models, adjusted for possible confounders. This cross-sectional study included 218 subjects with MS and 58 healthy controls. The latency of all saccades was longer in MS patients than in healthy controls. This saccadic delay was larger in subjects with a longer disease duration and more disabled subjects. Furthermore, it was significantly related to presence of a lower vision-related quality of life. This study provided a comprehensive overview of performance of MS patients in different saccadic tasks, compared to healthy controls. Saccadic delay in MS patients was present in all saccadic tasks and was related to advancing disease and visual functioning in daily life.

Saccadic fatigability in the oculomotor system

BackgroundFatigue is one of the most common and disabling symptoms in multiple sclerosis (MS), but challenging to quantify. This prospective study investigated if repeated saccadic eye movements enable measurement of oculomotor fatigability and can reflect on perceived fatigue in MS. MethodsA standardized infrared oculography protocol (DEMoNS) was used for quantifying saccades in MS patients and healthy controls which included a first and a repeated pro-saccadic task (FPT and RPT). Saccadic peak velocity, latency, gain, area under the curve (AUC) and peak velocity divided by amplitude (Pv/Am) were calculated in both tasks. Perception based fatigue was assessed using the Checklist Individual Strength and the Neurological Fatigue Index (NFI). Linear regression models were used for assessing the relation between saccadic parameters and perceived fatigue. ResultsThis study included 181 MS patients and 58 healthy controls subjects. From FPT to RPT, there were significant changes in saccadic parameters. Latency of both tasks was significantly related to NFI summary score (FPT: β = 0.022, p = .049, RPT: β 0.023, p = .021). These relationships were weakened after adjustment for Expanded Disability Status score (p > .05). There was however no significant group difference in changes in saccadic parameters. ConclusionsThis study presents an objective and reproducible method for measuring saccadic fatigability. Saccadic fatigability was found to be of limited use in MS, and should be tested in conditions affecting ocular muscles or the neuromuscular junction.

Diagnosing and quantifying a common deficit in multiple sclerosis: Internuclear ophthalmoplegia.

ObjectiveWe present an objective and quantitative approach for diagnosing internuclear ophthalmoplegia (INO) in multiple sclerosis (MS).MethodsA validated standardized infrared oculography protocol (DEMoNS [Demonstrate Eye Movement Networks with Saccades]) was used for quantifying prosaccades in patients with MS and healthy controls (HCs). The versional dysconjugacy index (VDI) was calculated, which describes the ratio between the abducting and adducting eye. The VDI was determined for peak velocity, peak acceleration, peak velocity divided by amplitude, and area under the curve (AUC) of the saccadic trajectory. We calculated the diagnostic accuracy for the several VDI parameters by a receiver operating characteristic analysis comparing HCs and patients with MS. The National Eye Institute Visual Function Questionnaire–25 was used to investigate vision-related quality of life of MS patients with INO.ResultsTwo hundred ten patients with MS and 58 HCs were included. The highest diagnostic accuracy was achieved by the VDI AUC of 15° horizontal prosaccades. Based on a combined VDI AUC and peak velocity divided by amplitude detection, the prevalence of an INO in MS calculated to 34%. In the INO group, 35.2% of the patients with MS reported any complaints of double vision, compared to 18.4% in the non-INO group (p = 0.010). MS patients with an INO had a lower overall vision-related quality of life (median 89.9, interquartile range 12.8) compared to patients without an INO (median 91.8, interquartile range 9.3, p = 0.011).ConclusionsThis study provides an accurate quantitative and clinically relevant definition of an INO in MS. This infrared oculography-based INO standard will require prospective validation. The high prevalence of INO in MS provides an anatomically well described and accurately quantifiable model for treatment trials in MS.

Quantification of Visual Fixation in Multiple Sclerosis.

Eye movement abnormalities are common in multiple sclerosis (MS), and infrared oculography is a noninvasive method for quantification. This study aims to describe and classify abnormalities of visual fixation and their clinical relevance in MS. A validated standardized infrared oculography protocol, Demonstrate Eye Movement Networks with Saccades, was used for quantifying gaze stability during a fixation task in MS patients and healthy controls. Saccadic intrusions, gaze drift, and stability of fixation around the drift line were used to subclassify MS patients by performing receiver operating characteristic analyses of different parameters. The relationship between the presence of abnormalities of fixation and visual functioning was analyzed using logistic regression models, which was adjusted for possible confounders. This cross-sectional study included 213 subjects with MS and 57 healthy controls. Square wave jerk abnormalities were present in 24% of MS patients. The prevalence was higher in more disabled subjects. The presence of larger square wave jerks (with a higher amplitude) in the MS patients was related to complaints of focusing on stationary objects (odds ratio, 2.2; P = 0.035) and a lower vision-related quality of life (odds ratio, 2.56; P = 0.012). This study provided a comprehensive overview of the characteristics of problems with visual fixation in subjects with MS. The most important and most common finding was the presence of larger square wave jerks during fixation, which was related to visual functioning in daily life.

Communication Technologies Based on Voluntary Blinks: Assessment and Design

Some people with severe disabilities are confined in a state in which communication is virtually impossible, being reduced to communicating with their eyes or using sophisticated systems that translate thoughts into words. The EyeTrackers and Brain-Computer Interfaces (BCIs) are suitable systems for those people but their main drawback is their cost. More affordable devices are capable of detecting voluntary blinks and translating them into a binary signal that allows the selection, for example, of an ideogram on a communication board. We tested four different systems based on infrared, bioelectrical signals (Electro-Oculography (EOG) and Electro-Encephalography (EEG)), and video processing. The experiments were performed by people with/without disabilities and analyzed the systems' performances, usability, and method of voluntary blinking (long blinks or sequence of two short blinks). The best accuracy (99.3%) was obtained using Infrared-Oculography (IR-OG) and the worst with the EEG headset (85.9%) and there was a statistical influence of the technology on accuracy. Regarding the method of voluntary blinking, the use of long or double blinks had no statistical influence on accuracy, excluding EOG, and the time taken to perform double blinks was shorter, resulting in a potentially much faster interface. People with disabilities obtained similar values but with greater variability. The preferred technology and blinking methods were Video-Oculography (VOG) and long blinks, respectively. The several Open-Source Hardware (OSHW) devices have been developed and a new algorithm for detecting voluntary blinks has also been proposed, which outperforms most of the published papers in the reviewed literature.

Fatigue related impairments in oculomotor control are prevented by caffeine.

Strenuous exercise can result in an inability of the central nervous system to drive skeletal muscle effectively, a phenomenon known as central fatigue. The impact of central fatigue on the oculomotor system is currently unexplored. Fatigue that originates in the central nervous system may be related to perturbations in the synthesis and metabolism of several neurotransmitters. In this study we examine central fatigue in the oculomotor system after prolonged exercise. The involvement of central neurotransmission was explored by administering caffeine during exercise. Within a double-blind, randomized, repeated measures, crossover design, 11 cyclists consumed a placebo or caffeine solution during 180 min of stationary cycling. Saccadic eye movements were measured using infra-red oculography. Exercise decreased saccade velocity by 8% (placebo trial). This effect was reversed by caffeine, whereby velocity was increased by 11% after exercise. A non-oculomotor perceptual task (global motion processing) was unaffected by exercise. The human oculomotor system is impaired by strenuous exercise of the locomotor system. Caffeine exerts a protective effect on oculomotor control, which could be related to up-regulated central neurotransmission. In addition, cortical processes supporting global motion perception appear to be robust to fatigue.

Electrophysiological correlates of planning and monitoring in first episode schizophrenia

The aim of this study was to investigate the functional basis of frequently described cognitive deficits in schizophrenia patients by exploring the electrophysiological correlates of planning processes during performance of the Trail-Making Test-B (TMT-B). Via concurrent recording of behavioral test performance, exploratory eye movements and electrical brain activity functional components critical for task performance were extracted and characterized. Participants comprised 12 first episode patients and 12 matched healthy controls who were examined with concurrent infrared oculography and electroencephalography (EEG) while they carried out a computerized TMT-B. The performance process was segmented into planning and monitoring phases based on the interaction of eye and hand movements. Brain electrical activity was analyzed using low-resolution electromagnetic brain tomography (LORETA). During planning fixations compared to monitoring fixations, both groups showed enhanced current density in dorsolateral prefrontal cortex, cingulate gyrus and inferior parietal lobe. Concurrent with poorer performance, schizophrenia patients exhibited hypoactivity within prefrontal brain areas during planning. Thus, poorer performance in schizophrenia seems to be attributable to impaired planning behavior based on hypoactivity of prefrontal areas, involved in the temporal scheduling of deliberate actions as well as visuomotor integration.

Infrared Oculography as a Non Invasive Methods to Measure Visual Acuity before and after Surgery in Children with Congenital Nystagmus

Background: Congenital nystagmus is an involuntary, bilateral, conjugate oscillation of the eyes which is present at birth or develops within the first 6months of life. A specific surgical intervention may improve visual acuity in these subjects. However, measurement of visual acuity in children is difficult because of invasive procedures and scarce patient's collaboration. Infrared oculography (IROG) is a non invasive method validated to define time of foveation, an indirect measure of visual acuity.Aims: To evaluate the utility of IROG in children with congenital nystagmus treated by surgery. Methods. Prospective study enrolling children with congenital nystagmus and anomalous head position. All subjects underwent surgical intervention according to Anderson. Before and after surgical intervention visual acuity was measured by IROG.Results: We enrolled 18 subjects with congenital nystagmus (Age 12.1 ± 6.6 y, Male 11) and anomalous right (n=9) or left (n=9) head position. After surgery, head position was corrected in 9 out of 18 subjects. Visual acuity measured by IROG improves in all enrolled subjects after surgery (NAFP 0.68 ± 0.07 before vs 0.73±0.04 after surgery). IROG was well tolerated by all enrolled subjects.Conclusions: IROG is an useful non invasive tool to evaluate efficacy of surgery for congenital nystagmus in pediatric patients.

Slow saccades in bulbar-onset motor neurone disease

Historical studies of eye movements in motor neurone disease (MND) have been conflicting although current findings suggest that eye movement abnormalities relate to frontal lobe impairment. Numerous case reports, however, describe slow saccades and supranuclear gaze palsies in patients with MND often associated with bulbar-onset disease. We performed a study of saccades and smooth pursuit in a large group of patients with MND to examine for any differences between bulbar-onset and spinal-onset patients. Forty-four patients (14 bulbar-onset and 30 spinal-onset patients) and 45 controls were recruited. Reflexive saccades, antisaccades and smooth pursuit were examined using infra-red oculography and all subjects then underwent neuropsychological evaluation. Reflexive saccades were found to be slower in bulbar-onset compared to spinal-onset patients and controls (p = 0.03, p = 0.05). Antisaccade latency (p = 0.01) and antisaccade type 1 errors (p = 0.03, p = 0.04) were increased in patients compared to controls. 'Proportion of time spent in smooth pursuit' and smooth pursuit 'velocity gain' were reduced in patients compared to controls (p = 0.000, p = 0.001). Antisaccade errors and velocity gain correlated with neuropsychological measures sensitive to lesions of the frontal lobes. This is the first study to highlight the presence of slow saccades in bulbar-onset MND. These findings suggest that slow saccades may be due to increased brainstem pathology in bulbar-onset disease that involves burst cell neurons. Furthermore these observations highlight the potential for overlap between bulbar-onset MND and progressive supranuclear palsy (PSP) as both can have a bulbar palsy and slowed saccades.

P03-124 - Frontal brain function and visual exploration of natural scenes in schizophrenia

Scanpaths are the patterns of ocular fixations and saccades produced during visual exploration of a scene. Schizophrenia is associated with a restricted style of visual scanning, characterised by fewer fixations and saccades and shorter scanpath lengths compared with well viewers. Such patterns are reflective of chronic dysfunction in real-world visual processing in schizophrenia. Scanpath measures are also emerging as strong discriminatory tools in schizophrenia trait marker research. However, little is understood about the neurocognitive mechanisms underlying atypical viewing patterns. We conducted an exploratory study of the relationships between patterns of visual exploration and neuropsychological test performance in individuals with schizophrenia to further understand the neural substrates of scanpath abnormalities in this group. Fifty-one individuals meeting DSM-IV criteria for schizophrenia completed a range of neuropsychological tests and viewed a battery of static natural scenes while eye movements were recorded using non-invasive infra-red oculography. Restricted scanpath behaviours were unrelated to measures of sustained attention, visual memory, cognitive interference or general cognitive decline. Restricted scanpath patterns were most strongly associated with short term verbal memory, manipulation of information in working memory and verbal fluency performance. Such functions are unlikely to directly impinge on visual exploration in schizophrenia but may be commensurate with dysfunction of the dorsolateral prefrontal cortex, a region known to play a number of key roles in oculomotor control. The results support a role of frontal brain dysfunction in the formation and execution of viewing behaviours in schizophrenia.

Ocular fixation instabilities in motor neurone disease

Eye movements are classically felt to be spared in motor neurone disease (MND). Although a range of ocular motor disorders have been reported, no consistent pattern has been established. Disturbances of ocular fixation have been noted in MND; however, fixation has not yet been formally examined. With the recent characterization of ocular fixation using saccadic intrusion amplitude and fixation periods, we performed a cross-sectional study to examine for abnormalities of ocular fixation in non-dementing patients with MND. A total of 44 patients and 45 controls were recruited. Fixation was examined using infra-red oculography and all subjects then underwent a neuropsychological evaluation. Saccadic intrusion amplitude was found to be greater in patients compared to controls and in particular, spinal-onset patients. Saccadic intrusion amplitude in patients correlated with neuropsychological measures sensitive to lesions of the frontal lobes. This is the first study to identify abnormalities of fixation in MND and these results indicate that ocular fixation instabilities may be a marker of the sub-clinical frontal lobe dysfunction in MND. A longitudinal study to examine if saccadic intrusion amplitude deteriorates with time would be of interest as this could provide a quantifiable objective marker of disease progression.

Abnormal antisaccades and smooth pursuit eye movements in patients with Wilson's disease

Neurological symptoms in Wilson's disease (WD) may include oculomotor abnormalities. However, to date, eye movements in WD patients were rarely investigated and the data concerning this issue are sparse. The purpose of this study was to evaluate reflexive and voluntary eye movements in WD patients. We examined horizontal saccadic and smooth pursuit eye movements using infra-red oculography in 50 WD patients, including 29 neurologically symptomatic (WDn) and 21 asymptomatic ones (WDa), and in 29 healthy controls. We found statistically significant increase in mean antisaccadic latency (378 ms) and in mean antisaccadic error rate (22.5) in the WDn group, when compared with WDa group (317 ms and 9.1, respectively) and controls (318 ms and 9.7, respectively). In contrast, there were no statistically significant differences in mean latency of prosaccades and in size of the gap effect. Patients with neurological manifestations had also abnormal smooth pursuit-increased number of saccadic intrusions (mean: 8.6) and decreased gain (mean: 0.69) comparing with WDa patients (4.1 and 0.83, respectively) and controls (2.2 and 0.91, respectively). The data suggest that WD is associated both with impairment of voluntary control of saccades and with disturbed smooth pursuit eye movements while reflexive saccades seem to be preserved.

Infrared oculography—validation of a new method to monitor startle eyeblink amplitudes during fMRI

Amplitude modulation of the eyeblink component of the startle response is a commonly used index for the emotional state of an organism. The use of electromyography (EMG) to determine startle eyeblink amplitudes during functional magnetic resonance imaging (fMRI) is limited as interactions between strong switching magnetic fields, radio pulses and electrodes introduce large artefacts in EMG recordings. We demonstrate a robust linear correlation between time courses and amplitudes of startle eyeblinks recorded by EMG and infrared oculography (IOG), an fMRI compatible technique based on infrared light reflection from the subject's eye. Moreover, our data indicate that IOG, like EMG, recordings of startle eyeblink amplitudes are predicted by verbal ratings of the emotional valence of pictorial foreground stimuli. Thus, IOG provides a valid method to record startle eyeblinks and might be used to monitor affective state during fMRI.

The effect of diabetes and ageing on the initiation of smooth pursuit eye movement

Aim: To examine the initiation of smooth pursuit in a group of elderly, diabetic subjects, and to compare their performance with a group of age-matched non-diabetic subjects and a group of healthy young subjects. Methods: Smooth pursuit was assessed quantitatively in 10 diabetic subjects (mean age 69.2 ± 6.8: range 58-80 years), 10 age-matched non-diabetic subjects (mean age 69.8 ± 5.2; range 64-81 years) and 10 healthy young subjects (mean age 21 ± 2.3: range 19-26 years), using infra-red oculography. Results: Qualitatively, pursuit performance was similar in the healthy elderly, diabetic and young subjects. However, quantitatively statistical analysis indicated smooth pursuit latency was significantly higher in both elderly diabetic and age-matched healthy individuals when compared with healthy young individuals (p 0.05). Conclusion: Given that we have demonstrated there is no statistically significant difference in smooth pursuit latency between healthy elderly and diabetic elderly subjects, systemic disease in general does not appear to exacerbate the age-related alteration in pursuit we have previously reported. This result suggests that quantitative assessment of smooth pursuit might provide a means of assessing the general state of the cortex in elderly subjects.

Impaired Trail-Making Test-B performance in patients with acute schizophrenia is related to inefficient sequencing of planning and acting

In order to investigate the functional basis of the frequently described deficits of schizophrenia patients in Trail Making Test B (TMT-B) performance, the performance process was analyzed based on the interaction of eye and hand movements. In a longitudinal design, 23 acute schizophrenia patients, 17 acute depressive inpatients, and 21 healthy controls were assessed twice within 4 weeks. Computer versions of both TMT-A and TMT-B were used, which require to connect different targets with a cursor, with concurrent infrared oculography. In both TMT-versions, schizophrenia patients demonstrated poorer performance and longer “planning periods”—as defined by fixations outside the cursor area—containing more fixations, which were stable over time. However, these “planning fixations” were only also longer in duration during TMT-B and differed in time and context of their occurrence compared with healthy controls. Schizophrenia patients demonstrated more fixations while the cursor rested between targets. Significant correlations with performance time gave evidence that it is important for short planning periods to be performed parallel to ongoing connection of targets, to obtain a satisfactory result. No relationship between “planning variables” with psychopathology and medication could be found. Accordingly, poorer TMT-B performance in schizophrenia patients was found to be related to insufficient sequencing of planning and acting, which appears to be a trait-like characteristic. Though depressive patients also performed poorer in TMT-B, they did not differ from either of the other groups in the main process variables, which may hint to different underlying causes of the performance deficits in both groups of patients.

MRI characteristics of the MLF in MS patients with chronic internuclear ophthalmoparesis.

The authors imaged the medial longitudinal fasciculus (MLF) in 58 patients with MS and chronic internuclear ophthalmoparesis (INO) to determine which MRI technique best shows the characteristic lesion associated with this ocular motor syndrome. Using quantitative infrared oculography, the authors determined the ratios of abduction to adduction for velocity and acceleration, to confirm the presence of INO and to determine the severity of MLF dysfunction in 58 patients with MS and INO. Conventional MRI techniques, including proton density imaging (PDI), T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR) imaging, were used to ascertain which technique best shows MLF lesions within the brainstem tegmentum. T1-weighted imaging was performed to determine the frequency of brainstem tegmentum hypointensities. All patients studied had evidence of an MLF lesion hyperintensity on PDI, whereas T2-weighted imaging and FLAIR imaging showed these lesions in 88% and 48% of patients, respectively. With PDI, dorsomedial tegmentum lesions were seen in the pons in 93% of patients and in the midbrain of 66% of patients. Lesions were observed at both locations in 59% of patients. One patient had an MLF lesion with a corresponding T1 hypointensity. PDI best shows the MLF lesion in patients with MS and INO.

The misclassification of blinks as saccades: Implications for investigations of eye movement dysfunction in schizophrenia

It is important to have a simple, accurate method for recording eye movements. Of the two popular approaches commonly adopted, electro-oculography (EOG) and infrared oculography (IROG), IROG is often accepted as the more accurate, and it is the method that is currently used most frequently to examine eye movements in schizophrenia. This study investigated whether the misclassification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both vertical electro-oculography (VEOG), which can be used to objectively identify blinks, and IROG were recorded while 17 schizophrenia patients and 19 healthy controls were presented with sinusoidal stimuli. Of the blinks identified with the VEOG for the total group of participants, a substantial number (37%) were misclassified as catch-up and anticipatory saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassification of blinks as anticipatory saccades. Therefore, when IROG alone is used to identify blinks, the misclassification of blinks as saccades is likely to introduce measurement error into estimates of saccade rates, particularly estimates of anticipatory saccade rates in schizophrenia patients.

The misclassification of blinks as saccades: Implications for investigations of eye movement dysfunction in schizophrenia

It is important to have a simple. accurate method for recording eye movements. Of the two popular approaches commonly adopted, electro-oculography (EOG) and infrared oculography (IROG), IROG is often accepted as the more accurate, and it is the method that is currently used most frequently to examine eye movements in schizophrenia. This study investigated whether the misclassification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both vertical electro-oculography (VEOG), which can be used to objectively identify blinks, and IROG were recorded while 17 schizophrenia patients and 19 healthy controls were presented with sinusoidal stimuli. Of the blinks identified with the VEOG for the total group of participants, a substantial number (37%) were misclassified as catch-up and anticipatory saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassification of blinks as anticipatory saccades. Therefore, when IROG alone is used to identify blinks, the misclassification of blinks as saccades is likely to introduce measurement error into estimates of saccade rates, particularly estimates of anticipatory saccade rates in schizophrenia patients.