Analysis Of Saccadic Eye Movements Research Articles

Correlating Eye-Tracking Fixation Metrics and Neuropsychological Assessment after Ischemic Stroke.

Background and Objectives: Stroke survivors commonly experience cognitive deficits, which significantly impact their quality of life. Integrating modern technologies like eye tracking into cognitive assessments can provide objective and non-intrusive measurements. Materials and Methods: This study aimed to evaluate the cognitive and visual processing capabilities of stroke patients using eye-tracking metrics and psychological evaluations. A cohort of 84 ischemic stroke patients from the N-PEP-12 clinical study was selected for secondary analysis, based on the availability of eye-tracking data collected during a visual search task using an adapted Trail Making Test. Standardized cognitive assessments, including the Montreal Cognitive Assessment (MoCA) and digit span tasks, were also conducted. Results: Correlation analyses revealed some notable relationships between eye-tracking metrics and cognitive measures, such as a positive correlation between Symbol Search performance and the number of fixations. Anxiety levels were found to be positively correlated with first fixation duration, while longer first fixation durations were associated with poorer cognitive performance. However, most correlations were not statistically significant. Nonparametric ANOVA showed no significant differences in fixation metrics across the visits. Conclusions: These findings suggest a complex relationship between cognitive status, gaze fixation behavior, and psychological well-being in stroke patients. Further research with larger sample sizes and analysis of saccadic eye movements is needed to better understand these relationships and inform effective interventions for stroke rehabilitation.

A nonlinear generalization of the Savitzky-Golay filter and the quantitative analysis of saccades.

The Savitzky-Golay (SG) filter is widely used to smooth and differentiate time series, especially biomedical data. However, time series that exhibit abrupt departures from their typical trends, such as sharp waves or steps, which are of physiological interest, tend to be oversmoothed by the SG filter. Hence, the SG filter tends to systematically underestimate physiological parameters in certain situations. This article proposes a generalization of the SG filter to more accurately track abrupt deviations in time series, leading to more accurate parameter estimates (e.g., peak velocity of saccadic eye movements). The proposed filtering methodology models a time series as the sum of two component time series: a low-frequency time series for which the conventional SG filter is well suited, and a second time series that exhibits instantaneous deviations (e.g., sharp waves, steps, or more generally, discontinuities in a higher order derivative). The generalized SG filter is then applied to the quantitative analysis of saccadic eye movements. It is demonstrated that (a) the conventional SG filter underestimates the peak velocity of saccades, especially those of small amplitude, and (b) the generalized SG filter estimates peak saccadic velocity more accurately than the conventional filter.

SacLab: A toolbox for saccade analysis to increase usability of eye tracking systems in clinical ophthalmology practice

PurposeMany open source software packages have been recently developed to expand the usability of eye tracking systems to study oculomotor behavior, but none of these is specifically designed to encompass all the main functions required for creating eye tracking tests and for providing the automatic analysis of saccadic eye movements. The aim of this study is to introduce SacLab, an intuitive, freely-available MATLAB toolbox based on Graphical User Interfaces (GUIs) that we have developed to increase the usability of the ViewPoint EyeTracker (Arrington Research, Scottsdale, AZ, USA) in clinical ophthalmology practice. MethodsSacLab consists of four processing modules that enable the user to easily create visual stimuli tests (Test Designer), record saccadic eye movements (Data Recorder), analyze the recorded data to automatically extract saccadic parameters of clinical interest (Data Analyzer) and provide an aggregate analysis from multiple eye movements recordings (Saccade Analyzer), without requiring any programming effort by the user. ResultsA demo application of SacLab to carry out eye tracking tests for the analysis of horizontal saccades was reported. We tested the usability of SacLab toolbox with three ophthalmologists who had no programming experience; the ophthalmologists were briefly trained in the use of SacLab GUIs and were asked to perform the demo application. The toolbox gained an enthusiastic feedback from all the clinicians in terms of intuitiveness, ease of use and flexibility. Test creation and data processing were accomplished in 52±21s and 46±19s, respectively, using the SacLab GUIs. ConclusionsSacLab may represent a useful tool to ease the application of the ViewPoint EyeTracker system in clinical routine in ophthalmology.

Saccadic eye movement performance as an indicator of driving ability in elderly drivers.

Regular checking of the fitness to drive of elderly car-license holders is required in some countries, and this will become increasingly important as more countries face aging populations. The present study investigated whether the analysis of saccadic eye movements could be used as a screening method for the assessment of driving ability. Three different paradigms (prosaccades, antisaccades, and visuovisual interactive (VVI) saccades) were used to test saccadic eye movements in 144 participants split into four groups: elderly drivers who came to the attention of road authorities for suspected lack of fitness to drive, a group of elderly drivers who served as a comparison group, a group of neurology patients with established brain lesion diagnoses, and a young comparison group. The group of elderly drivers with suspected deficits in driving skills also underwent a medical examination and a practical on-road driving test. The results of the saccadic eye tests of the different groups were compared. Antisaccade results indicated a strong link to driving behaviour: elderly drivers who were not fit to drive exhibited a poor performance on the antisaccade task and the performance in the VVI task was also clearly poorer in this group. Testing saccadic eye movements appears to be a promising and efficient method for screening large numbers of people such as elderly drivers. This study indicated a link between antisaccade performance and the ability to drive. Hence, measuring saccadic eye movements should be considered as a tool for screening the fitness to drive.

Biometric verification of a subject with eye movements, with special reference to temporal variability in saccades between a subject's measurements

We recently studied the application of saccadic eye movements, measured with video cameras, to biometric verification using subjects who receive identical stimulation. The properties of a subject's saccades may vary between measurements over the course of time, so to be useful as a means of biometric verification, the temporal variability of saccades should not distort verification results significantly. We investigated the effects of such variability by repeating the same test several times with the same groups of subjects. We found that temporal variability had only a minor effect on verification results when intervals were from a few hours to two months. Compared with the classification accuracies of approximately 90% of our earlier studies when measurements were run immediately one after another, our present verification accuracies were a few percent lower. In contrast, a long interval of approximately 16 months reduced the accuracies considerably. Our results indicate that reasonably short intervals between a subject's saccade measurements do not hinder verification based on them, while very long intervals between logins can pose a problem. Since most common electronic devices, such as computers and mobile phones, are used at frequent intervals, the analysis of saccadic eye movements seems to be a viable technique for enabling biometric verification.

Utility of saccadic eye movement analysis as an objective biomarker to detect the sedative interaction between opioids and sleep deprivation in opioid-naive and opioid-tolerant populations

Analysis of saccadic eye movements (SEMs) has previously been used to detect drug- and sleep-deprivation-induced sedation, but never in combination. We compared the effects of sleep deprivation and opioids on 10 opioid-naive with nine opioid-tolerant participants. The naive-participant study evaluated the effects of sleep deprivation alone, morphine alone and the combination; the tolerant-participant study compared day-to-day effects of alternate-daily-dosed buprenorphine and the combination of buprenorphine on the dosing day with sleep deprivation. Psychomotor impairment was measured using SEMs, a 5-minute pupil adaptation test (PAT), pupil light reflex (PLR) and alertness visual analogue scale (AVAS). The PAT and PLR did not detect sleep deprivation, in contrast to previous studies. Whilst consistently detecting sleep deprivation, the AVAS also detected buprenorphine in the tolerant study, but not morphine in the naive study. SEMs detected morphine alone and sleep deprivation alone as well as an additive interaction in the naive study and the effect of sleep deprivation in the tolerant study. The alternate-day buprenorphine dosing did not alter SEMs. The current study revealed greater SEMs, but not AVAS impairment in tolerant versus naive participants. The current study demonstrates that objective measures provide additional information to subjective measures and thus should be used in combination.

Eye Movement Impairment Recovery in a Gaucher Patient Treated with Miglustat

In Gaucher Disease (GD) the enzyme (imiglucerase) replacement therapy (ERT) is not able to stop the progression of the neurological involvement, while the substrate reduction therapy (SRT), performed by N-Butyldeoxynojirimycin (miglustat), is an alternative that should be evaluated. Two sisters, presenting the same genotype (R353G/R353G), were diagnosed as suffering from GD; one of them later developed neurological alterations identified by quantitative saccadic eye movements analysis. The aim of the study was to quantitatively measure the miglustat effects in this GD neurological patient. Eye movement analysis during subsequent controls was performed by estimating the characteristic parameters of saccadic main sequence. The study demonstrates that the SRT alone can be effective in GD3. Moreover, it confirms that quantitative eye movement analysis is able to precociously identify also slight neurological alterations, permitting more accurate GD classification.

Saccadic Eye Movement Velocity Measured with the Infrared Reflection and Search Coil Eye-Tracking Systems in Patients with Thyroid-Associated Ophthalmopathy

Background Assessment of changes in saccade velocity may be useful in the early detection of thyroid-associated ophthalmopathy (TAO). Two eye-tracking systems were used to measure the velocity of saccadic eye movements in patients with TAO. Method Fourteen patients with active TAO and 14 healthy controls were enrolled for recordings with two eye-tracking systems: the magnetic scleral search coil (MSC; Skalar Medical) and the infrared reflection systems (IR; Orbit XY-1000). The MSC is generally considered the “gold standard” method for tracking of rapid eye movements. The IR system uses novel computer technology and is based on sampling of reflected infrared light from the surface of the eyes. Main sequence plots constructed from the recorded saccadic peak velocity and amplitude were analyzed for differences between patients and healthy controls. Results There were no significant differences between patients with TAO and healthy controls in the constructed main sequence plots of maximum velocity (VMAX) and the slope constant (C). Conclusions Main sequence analysis of saccadic eye movements was not useful for detecting TAO in this experimental setting with either of the two eye-tracking methods. This is hypothesized to be due to compensation for the early orbital changes in TAO by neural adaptation of the saccades in the brain stem. The contradictory results between this and previous studies cannot be easily explained. We assume that there is a large heterogeneity in the saccadic eye movement performance in both the normal population and the TAO-population. Also, differences in the study design may cause dissimilar outcomes and hence incoherent conclusions. A non-invasive recording system that is able to generate a minimum amount of intra- and inter-individual variability and a study design where normal variability can be reduced to a minimum may be useful for future identification of early eye muscle changes in TAO.

A Clinical Pharmacological Study to Evaluate the Sedative Effects of the Antihistaminic Drug, Diphehydramine Hydrochloride (Drewell): Objective Evaluation of the Sedative Effects by Analysis of Saccadic Eye Movement

The purpose of the present clinical study was to evaluate the sedative effects of Drewell® (50mg of diphenhydramine hydrochloride). The study was conducted with a randomized, placebo-controlled, cross over design in eight healthy male volunteers. Subjects took either a Drewell® or a matched placebo tablet on two occasions with more than a 6-day wash-out period. The sedative effects on central nervous system (CNS) were assessed using both objective evaluation (saccadic eye movement analysis) and subjective evaluation (Visual Analogue Scale: VAS). Statistical analyses for pharmacodynamic parameters were performed by repeated measures-ANOVA. Saccadic peak velocity (SPV), one of the sensitive parameters for sedative effects, showed a significant decline in the Drewell group compared with the placebo group.In the VAS evaluation, a sedative effect was also detected in the Drewell group.Despite some inter-individual differences of SPV values, in both the Drewell and the placebo sessions SPV baseline values within the same subject were quite similar. This suggests that subjects might have their own SPV values and those values might be reproducible. In addition, it was also confirmed that objective and quantitative evaluations of the sedative effects of Drewell® were possible using saccadic eye movement analysis.

A comparison between the magnetic scleral search coil and infrared reflection methods for saccadic eye movement analysis

A non-invasive eye tracking system, based on pulsed infrared light (IR), was compared with the magnetic scleral search coil method (MSC) for saccadic eye movement recordings. Ten normal subjects performed horizontal and vertical saccades recorded with both methods. Eight recordings were complete and analysed for maximum peak velocity (V(MAX)) and constant (C) of the main sequence curve. The IR recordings showed significantly higher peak velocity values than the MSC system and generally more inter-individual variability. No significant difference regarding peak velocity was detected between abducting and adducting saccades or between upward and downward saccades with either of the systems. Horizontal saccades had higher peak velocities with both techniques. Comparison of the main sequence plots of the IR and MSC eye tracking techniques reveals that the IR system yields higher values of maximum peak velocity and the constant, the differences being similar for eye movements in different directions. There are various possible explanations for the lower maximum velocity of the MSC recordings, e.g. slipping of the coil annulus on the surface of the eye and a change of the oculomotor command signal induced by wearing the coil. Also, artefacts associated with the IR recording system may cause over-estimations of the saccadic velocity and, furthermore, contribute to the higher variability of the IR recordings.

Cortical Control of Smooth Pursuit Eye Movements: Sensory and Motor Components. An fMRI study

Smooth pursuit eye movements (SP) serve to keep a moving object in our fovea, the place of highest visual acuity. For this purpose, the SP system must detect the object moving across our retina (sensory input), process its velocity, and prepare a motor command signal being sent to the eye muscles (motor output), which enables the eyes to follow the object. The purpose of this study is to identify which cortical regions process the sensory input information, which process the motor output signals, and which are related to both processes (possibly sensorimotor transformation sites). For this purpose we measured cortical activation related to pure visual (sensory), pure oculomotor, and combined visuo-oculomotor stimulation. A central fixation dot and a second dot, 4° below the center dot, were presented in darkness. Subjects always fixated the center dot. Moving the lower dot sinusoidally in the horizontal plane yielded a visual (sensory) stimulation. Moving both dots while subjects pursued the upper dot yielded oculomotor (but almost no sensory) stimulation. Moving only the upper dot while subjects tracked this dot yielded oculomotor plus sensory stimulation. Eye movements were measured with an infrared light technique (MR-Eyetracker), cortical activation with a 3T Siemens Trio scanner. Twelve healthy subjects participated in this study. SP gain was close to one, indicating that subjects followed the moving dot accurately. Analysis of saccadic eye movements showed that small saccades occurred during both fixation (rest) periods and pursuit (stimulation) periods, such that these saccades do not add to the cortical activation investigated here. Cortical activation was found in areas V5/V5A, precuneus, intraparietal sulcus, SEF, FEF, cingulate gyrus. Visual stimulation activated mainly occipito-parietal regions V5/V5A, precuneus and the intraparietal sulcus, while oculomotor stimulation activated predominantly the frontal regions FEF and SEF and the cingulate gyrus. This was confirmed by the combined visuo-oculomotor stimulation which activated all these regions. Parts of V5/V5A and the intraparietal sulcus seem to be involved in both sensory and motor processing. Our data show that the occipito-parietal regions are processing the sensory input signals of pursuit eye movements, while the FEF and SEF are related to the motor output signal. Parts of V5/V5A and the intraparietal sulcus are possible sites for sensorimotor transformation

A method for measuring eye movements using Hall-effect devices.

A system for precise recording of eye position and movements in laboratory animals, by means of Hall-effect devices, is described. The system, useful in neurophysiological and neurobehavioral studies, allows the analysis of saccadic eye movements, optokinetic- and vestibular-induced nystagmus, slow tracking movements, eye vergences, and so forth. This small, light-weight, and inexpensive system uses a set of Hall-effect devices and associated electronics to sense variations in the position of high-power magnets fixed in the eye sclera or in scleral contact lenses. The output of the Hall-effect devices is amplified by operational amplifiers, collected through an A/D converter, and analyzed in a PC computer by specific software.

The analysis of saccadic eye movements from gap and overlap paradigms

This protocol describes the acquisition and evaluation of saccadic eye movement data for use in basic neuroscience research and clinical application. The experimental protocol requires the subject to make saccadic eye movements in response to visual stimuli presented, in random order, on consecutive trials. The gap and overlap paradigms are described together with the instruction to generate pro- or antisaccades. The protocol includes the description of saccade detection, the determination of the beginning, the end, the size, and the velocity of a saccade, the exact way of calculating the proportion of different kinds of trials, and the treatment of erratic or artifact trials. Relevant variables are defined. The results obtained from a large number (300) of subjects of different ages (8–65 years) are described and analysed with respect to their development with age. The protocol allows to test a subject's saccadic status in many different circumstances in particular with respect to diagnostic help in neurology, psychiatry and psychology.

Precision of measures of saccadic eye movements and conventional psychomotor function tests

AbstractMeasures of variability are rarely quoted in drug studies of psychomotor function. Five recent studies were therefore analysed to calculate the coefficients of variation for different tests of psychomotor function, both during and between study days. Saccadic eye movement analysis and critical flicker fusion threshold were found to have low coefficients of variation (ranging from 2·7 to 7·5 per cent) while visual analogue rating scales and the digit symbol substitution test were found to have much higher coefficients of variation (ranging from 7·9 to 17·6 per cent). It is suggested that measures of test variability be routinely assessed in psychomotor studies as a check on test methodology.

Quantitative evaluation of saccadic eye movements

Saccadic eye movement analysis is becoming increasingly quantitative; thus, an appropriate statistical methodology is needed both for normative data and for single subject evaluation. By assessing normative data in 76 healthy subjects, the authors demonstrated that the amplitude/duration (A/D) and amplitude/peak velocity (A/Vp) relationships, as well as latency, are age-dependent. They did not find a relationship between precision and, respectively, age and target offset. Accordingly, they propose that single subject evaluation should be based on A/D and A/Vp relationships in their entirety, with both the mean and distribution of individual values as the basis for precision and latency.

A pharmacodynamic study of quazepam and triazolam

AbstractA double‐blind single oral dose study in 10 healthy volunteers was performed during the day to compare the diurnal effects of quazepam (15 mg) and triazolam (0.25 mg) on psychomotor performance. The central effect of the two benzodiazepines was assessed by means of a computer analysis of visually guided saccadic eye movements (SEM), critical flicker fusion threshold (CFFT), and choice reaction time (CRT). The results obtained suggest that: computer analysis of SEM is more sensitive than CRT and CFFT to detect sedative drug effects at a subclinical level; the presumed equipotent doses of quazepam and triazolam tested do not show the same sedative activity; the minimal impairment produced by quazepam on CNS function does not seem to be related to the property to bind to BZ1 receptors; the pharmacodynamic profile of quazepam seems to be characteristic of a “non‐sedative” agent, while triazolam behaves as a “sedative” benzodiazepine.

Saccadic eye movements analysis in the early diagnosis of myasthenia gravis

Saccadic eye movements were examined by electro-oculography in 21 patients with suspected myasthenia gravis. The presence of dissociated nystagmus and quiver eye movements was also assessed. The aim of the study was to assess the diagnostic value of saccadic abnormalities in the early stage of the disease. Pathological oculographic findings consisted of intra and post saccadic disorders and intersaccadic variability. A fatigue test was useful in detecting latent disorders in most patients. A Tensilon test was positive in 11 out of 16 patients with oculographic abnormalities. Diagnostic problems, apparently paradoxical findings and differential involvement of extraocular muscle fibers are discussed.

A comparison of the sensitivities of adaptive tracking, eye movement analysis, and visual analog lines to the effects of incremental doses of temazepam in healthy volunteers

The effects of single oral doses of 5, 10, and 20 mg temazepam were evaluated with the adaptive tracking test, analysis of smooth-pursuit and saccadic eye movements, and visual analog lines in a placebo-controlled, double-blind, crossover experiment with 12 healthy volunteers. Pharmacodynamic testing was performed until 10 hours and pharmacokinetics were evaluated until 24 hours. Temazepam, 20 mg, caused effects in all tests, with peak effects occurring at 30 minutes. The 10 mg dose caused effects on saccadic eye movements and subjective scores of alertness, whereas 5 mg temazepam was detected only by analysis of saccadic eye movements. Linear relationships between plasma concentrations and effects were found in nine subjects for saccadic peak velocity and eight subjects for subjective scores of alertness. The results of this study demonstrate manifest differences in the sensitivities of performance tests and stress the importance of validation of methods when effects of drugs on human performance are studied.

Assessment of the Sedative Effects of Dexmedetomidine, an α2‐Adrenoceptor Agonist, with Analysis of Saccadic Eye Movements

Single intravenous doses (0.5 microgram/kg and 1.0 microgram kg) of dexmedetomidine (4(5)-(1-(2,3-dimethylphenyl)ethyl)imidazole), a selective alpha 2-adrenoceptor agonist, and saline placebo were administered to six healthy volunteers (4 males and 2 females) in a double-blind, placebo-controlled cross-over study. The effects on vigilance were assessed using both subjective estimation (visual analogue scale, VAS) and objective tests (critical flicker fusion frequency, CFF; the Maddox wing; saccadic eye movement analysis). Dose-dependent subjective sedation was seen in VAS measurements, and impairment of vigilance was observed in CFF, Maddox wing and peak saccadic velocity, while saccade latency was not influenced by dexmedetomidine. The changes in vigilance were concurrent with moderate reductions in blood pressure and heart rate. CFF, the Maddox wing and peak saccadic velocity all proved sensitive in the assessment of sedation induced by dexmedetomidine.

Multisystem involvement of the central nervous system in Strümpell's disease A neurophysiological and neuropsychological study

The multisystem involvement of the central nervous system (CNS) in familial spastic paraplegia (FSP) has not been fully investigated by means of complete neurophysiological and neuropsychological examinations. The classification which distinguishes pure and complicated forms of FSP, is based on clinical features and does not take into account the possibility that clinically silent lesions of the CNS can be identified by means of adequate tests. The study was intended to assess the subclinical and multisystem involvement of the CNS in a group of 11 patients affected by FSP, clinically distinguished in 7 pure forms and 4 complicated forms. Neurophysiological tests included saccadic eye movements analysis, visual and auditory brain stem evoked responses. Neurophysiological examination was devised by means of a special purpose mental deterioration battery. Our results, showing a high incidence of multisystemic subclinical involvement of the CNS, confirm and extend the concept that FSP is a multisystemic degenerative disease of the CNS, and that the existence of “pure” forms should be reconsidered.