Pursuit Gain Research Articles

Metrics of two-dimensional smooth pursuit are diverse across participants and stable across days.

Smooth pursuit eye movements are used to volitionally track moving objects, keeping their image near the fovea. Pursuit gain, the ratio of eye to stimulus speed, is used to quantify tracking accuracy and is usually close to 1 for healthy observers. Although previous studies have shown directional asymmetries such as horizontal gain exceeding vertical gain, the temporal stability of these biases and the correlation between oculomotor metrics for tracking in different directions and speeds have not been investigated. Here, in testing sessions 4 to 10 days apart, 45 human observers tracked targets moving along two-dimensional trajectories. Horizontal, vertical, and radial pursuit gain had high test-retest reliability (mean intraclass correlation 0.84). The frequency of all saccades and anticipatory saccades during pursuit also had high test-retest reliability (intraclass correlation coefficients = 0.66 and 0.73, respectively). In addition, gain metrics showed strong intermetric correlation, and saccade metrics separately showed strong intercorrelation; however, gain and saccade metrics showed only weak intercorrelation. These correlations are likely to originate from a mixture of sensory, motor, and integrative mechanisms. The test-retest reliability of multiple distinct pursuit metrics represents a "pursuit identity" for individuals, but we argue against this ultimately contributing to an oculomotor biomarker.

The eyes have it: Alcohol-induced eye movement impairment and perceived impairment in older adults with and without alcohol use disorder.

While alcohol has been shown to impair eye movements in young adults, little is known about alcohol-induced oculomotor impairment in older adults with longer histories of alcohol use. Here, we examined whether older adults with chronic alcohol use disorder (AUD) exhibit more acute tolerance than age-matched light drinkers (LD), evidenced by less alcohol-induced oculomotor impairment and perceived impairment. Two random-order, double-blinded laboratory sessions with administration of alcohol (0.8 g/kg) or placebo. Participants (n = 117; 55 AUD, 62 LD) were 40-65 years of age. Eye tracking outcomes (pupil size, smooth pursuit gain, pro- and anti-saccadic velocity, latency, and accuracy) were measured at baseline and repeated at peak and declining breath alcohol intervals. Participants rated their perceived impairment during rising and declining intervals. Following alcohol consumption, older adults with AUD (vs. LD) showed less impairment on smooth pursuit gain and reported lower perceived impairment, but both groups showed similar pupil dilation and impairment on saccadic measures. While alcohol impaired older adults with AUD less than LD in terms of their ability to track a predictably moving object (i.e., smooth pursuit), both drinking groups were equally sensitive to alcohol-induced delays in reaction time, reductions in velocity, and deficits in accuracy to randomly appearing objects (i.e., saccade tasks). Thus, despite decades of chronic excessive drinking, older adults with AUD exhibited similar oculomotor tolerance on pro- and anti-saccade eye movements relative to their light-drinking counterparts. Given that these individuals also perceived less impairment during intoxication, they may be at risk for injury and harm when they engage in real-life drinking bouts.

The eye movement and gait variability analysis in Chinese patients with Huntington's disease.

Huntington's disease disease (HD) is characterized by motor, cognitive, and neuropsychiatric symptoms. Oculomotor impairments and gait variability have been independently considered as potential markers in HD. But there lacks an integration analysis of eye movement and gait. We assessed multiple examinations of eye movement and gait variability in HTT mutation carriers, analyzed the consistency between these parameters and clinical severity, then examined the association between oculomotor impairments and gait deficits. Seven pre-HD, 30 HD patients and 30 age-matched controls were included. We collected demographics and assessed the Unified Huntington's Disease Rating Scale (UHDRS). Examinations including saccade, smooth pursuit and optokinetic (OPK) test were performed to evaluate eye movement function. The parameters of gait include stride length, walking velocity, step deviation, step length and gait phase. There are significant impairments in HD patients in the latency and velocity of saccades, the gain of smooth pursuit as well as the gain and slow phase velocities (SPV) of OPK tests. Only the speed of saccades has significant difference between pre-HD and controls. There are significant impairments of stride length, walking velocity, step length and gait phase in HD patients. Parameters of eye movement and gait variability in HD patients showed consistency with the scores of UHDRS. There were significant correlations between eye movement and gait parameters. Our results show that eye movement and gait are impaired in HD patients, and speed of saccades is early impaired in pre-HD. Eye movement and gait abnormalities in HD are significantly correlated with clinical disease severities.

Establishment of Normal Values for Objective Evaluation of Ocular Movements Using Videonystagmography.

This study aims to establish a set of normal values for the objective evaluation of ocular movements using videonystagmography (VNG). Thirty individuals aged between 18 and 50 years, with no history of vestibular symptoms, recurrent headaches, central nervous system (CNS) symptoms, or cochlear symptoms, were selected. The assessment of five types of ocular movements (saccades, pursuit, optokinetic tests, spontaneous nystagmus, and gaze tests) were conducted using VNG. Normal ranges were established for different parameters of saccades, including latency, precision, and velocity in both horizontal and vertical directions for each eye. Pursuit gain was calculated for each eye in all four directions. Optokinetic gain was determined when the stimulation screen moved in all four directions. Symmetric responses were observed in all subjects. No spontaneous nystagmus was observed with fixation, although two participants exhibited nystagmus upon removal of fixation. Gaze tests revealed no abnormalities.

Oculomotor differences in adults with and without probable developmental coordination disorder.

Adults with Developmental Coordination Disorder (DCD), sometimes referred to as dyspraxia, experience difficulties in motor development and coordination, which impacts on all aspects of their daily lives. Surprisingly little is known about the mechanisms underlying the difficulties they experience in the motor domain. In childhood DCD, aspects of oculomotor control have been shown to be altered. The purpose of this study was to determine whether oculomotor differences are present in adults with and without probable DCD. Visual fixation stability, smooth pursuit, and pro-and anti-saccade performance were assessed in 21 adults (mean age 29 years) with probable DCD/dyspraxia (pDCD) and 21 typically-developing (TD) adults (mean age 21 years). Eye tracking technology revealed that oculomotor response preparation in the pro- and anti-saccade tasks was comparable across groups, as was pursuit gain in the slower of the two smooth pursuit tasks. However, adults with pDCD made significantly more saccades away from the fixation target than those without DCD and significantly more anti-saccade errors. Further, compared to TD adults, adults with pDCD demonstrated difficulties in maintaining engagement and had lower pursuit gain in the faster pursuit task. This suggests that adults with pDCD have problems with saccadic inhibition and maintaining attention on a visual target. Since this pattern of results has also been reported in children with DCD, oculomotor difficulties may be persistent for those with DCD across the lifespan. An awareness of the impact of atypical oculomotor control in activities of daily living across the lifespan would support clearer understanding of the causes and impacts of these difficulties for those with DCD.

Oculometric biomarkers of visuomotor deficits in clinically asymptomatic patients with systemic lupus erythematosus undergoing long-term hydroxychloroquine treatment.

This study examines a set of oculomotor measurements, or "oculometric" biomarkers, as potential early indicators of visual and visuomotor deficits due to retinal toxicity in asymptomatic Systemic Lupus Erythematosus (SLE) patients on long-term hydroxychloroquine (HCQ) treatment. The aim is to identify subclinical functional impairments that are otherwise undetectable by standard clinical tests and to link them to structural retinal changes. We measured oculomotor responses in a cohort of SLE patients on chronic HCQ therapy using a previously established behavioral task and analysis technique. We also examined the relationship between oculometrics, OCT measures of retinal thickness, and standard clinical perimetry measures of visual function in our patient group using Bivariate Pearson Correlation and a Linear Mixed-Effects Model (LMM). Significant visual and visuomotor deficits were found in 12 asymptomatic SLE patients on long-term HCQ therapy compared to a cohort of 17 age-matched healthy controls. Notably, six oculometrics were significantly different. The median initial pursuit acceleration was 22%, steady-state pursuit gain 16%, proportion smooth 7%, and target speed responsiveness 31% lower, while catch-up saccade amplitude was 46% and fixation error 46% larger. Excluding the two patients with diagnosed mild toxicity, four oculometrics, all but fixation error and proportion smooth, remained significantly impaired compared to controls. Across our population of 12 patients (24 retinae), we found that pursuit latency, initial acceleration, steady-state gain, and fixation error were linearly related to retinal thickness even when age was accounted for, while standard measures of clinical function (Mean Deviation and Pattern Standard Deviation) were not. Our data show that specific oculometrics are sensitive early biomarkers of functional deficits in SLE patients on HCQ that could be harnessed to assist in the early detection of HCQ-induced retinal toxicity and other visual pathologies, potentially providing early diagnostic value beyond standard visual field and OCT evaluations.

Evidence for an Association Between a pH-Dependent Potassium Channel, TWIK-1, and the Accuracy of Smooth Pursuit Eye Movements.

Within the healthy population there is a large variation in the ability to perform smooth pursuit eye movements. Our purpose was to investigate the genetic and physiological bases for this variation. We carried out a whole-genome association study, recording smooth pursuit movements for 1040 healthy volunteers by infrared oculography. The primary phenotypic measure was root mean square error (RMSE) of eye position relative to target position. Secondary measures were pursuit gain, frequency of catch-up saccades, and frequency of anticipatory saccades. Ten percent of participants, chosen randomly, were tested twice, giving estimates of test-retest reliability. No significant association was found with three genes previously identified as candidate genes for variation in smooth pursuit: DRD3, COMT, NRG1. A strong association (P = 3.55 × 10-11) was found between RMSE and chromosomal region 1q42.2. The most strongly associated marker (rs701232) lies in an intron of KCNK1, which encodes a two-pore-domain potassium ion channel TWIK-1 (or K2P1) that affects cell excitability. Each additional copy of the A allele decreased RMSE by 0.29 standard deviation. When a psychophysical test of visually perceived motion was used as a covariate in the regression analysis, the association with rs701232 did not weaken (P = 5.38 × 10-12). Variation in the sequence or the expression of the pH-dependent ion channel TWIK-1 is a likely source of variance in smooth pursuit. The variance associated with TWIK-1 appears not to arise from sensory mechanisms, because the use of a perceptual covariate left the association intact.

Smooth pursuit deficits impact dynamic visual acuity in macular degeneration.

Prior studies with large, highly visible targets report low smooth pursuit gains in individuals with macular degeneration (MD). We show that lower gains persist even when observers are pursuing a target that requires discrimination at the acuity limit. This low gain causes retinal slip, potentially leading to motion blur and target disappearance in the scotoma, which further compromise the visibility of moving object. In this study, we examine whether the characteristics of smooth pursuit (pursuit gain and placement of the fixational locus relative to the target) change when the task requires dynamic visual acuity. Using the scanning laser ophthalmoscope, we recorded smooth pursuit eye movements in 10 eyes of 6 MD participants and 7 eyes of 4 age-matched controls in response to leftward- or rightward-moving annular targets (O) that briefly (300 milliseconds) changed to a Landolt C at one of several time points during the pursuit trial. Participants were asked to pursue the target and indicate the direction of the C opening. Individuals with MD had lower pursuit gains and fewer saccades during the C presentation than during the O, compared with their age-matched peers. Further, pursuit gain, but not the distance of the retinal pursuit locus from the target, predicted task performance in the MD group. Our findings suggest that compromised pursuit gain in MD participants likely further compromises their dynamic visual acuity and thus ability to view moving targets.

Elevated Smooth Pursuit Gain in Collegiate Athletes with Sport-related Concussion Immediately Following Injury.

Although there is evidence that sport-related concussion (SRC) affects oculomotor function and perceptual ability, experiments are often poorly controlled and are not replicable. This study aims to test the hypothesis that there are decreased values when assessing oculomotor impairment indicating poorer performance in SRC patients. Fifteen DI athletes presenting with SRC (7 females, 8 males) and 15 student volunteers (CON) (12 females, 3 males) completed a dynamic visual acuity (DVA) task that involved answering the direction of a moving stimulus (Landolt C) while wearing a head-mounted binocular eye tracker. There were 120 trials total with 60 trials presenting at 30º per second and 60 presenting at 90º per second. Various eye movement measurements, including horizontal smooth pursuit eye movements (SPEM) gain and saccadic peak velocity, were analyzed between groups using univariate ANOVAs. Saccade count in SPEM trials, accuracy, and vision were analyzed using Kruskal-Wallis tests. There was no statistical difference in saccadic peak velocity: SRC = 414.7 42º/s, CON = 406.6 40.6º/s. A significant difference was found between SRC patients and healthy controls in horizontal SPEM gain (SRC = 0.9 0.04, CON = 0.86 0.03, F(1,28) = 7.243, P = 0.012) indicating that patients demonstrated compensatory eye movements when tracking the target. There were significantly more saccades in all SPEM trials (P = 0.001). SRCoculomotor deficits manifest as elevated horizontal SPEM gain when assessed within 48 hours of injury and compared to healthy controls within the same age range. SRC demonstrates altered oculomotor ability. While accurate in tracking a stimulus, SRC patients may conduct less controlled eye movements.

Individual differences link sensory processing and motor control.

Research on saccadic and pursuit eye movements led to great advances in our understanding of sensorimotor processing and human behavior. However, studies often have focused on isolated saccadic and pursuit eye movements measured with respect to different sensory information (static vs. dynamic targets). Here, we leveraged interindividual differences across a carefully balanced combination of different tasks to demonstrate that critical links in the control of oculomotor behavior were previously missed. We observed correlations in eye movement behavior across tasks, but only when compared with the same sensory information (e.g., pursuit gain and accuracy of saccades to moving targets). Within the same task, the coordination of saccadic and pursuit eye movements was tailored to the strengths of the individual: observers with more accurate saccades to moving targets rely on them more to catch up with moving targets. Our results have profound implications for the theoretical understanding of sensorimotor processing for oculomotor control. They necessitate a reevaluation of previous data used to map brain circuits for saccadic and pursuit eye movements measured with different types of relevant sensory information. Additionally, they underscore the importance of moving beyond average observations to embrace individual differences as a rich source of information. These individual differences not only reveal the strengths and weaknesses of observers. When combined across different tasks, they allow insights about why observers behave differently in a given task. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The role of prediction and visual tracking strategies during manual interception: An exploration of individual differences.

The interception (or avoidance) of moving objects is a common component of various daily living tasks; however, it remains unclear whether precise alignment of foveal vision with a target is important for motor performance. Furthermore, there has also been little examination of individual differences in visual tracking strategy and the use of anticipatory gaze adjustments. We examined the importance of in-flight tracking and predictive visual behaviors using a virtual reality environment that required participants (n = 41) to intercept tennis balls projected from one of two possible locations. Here, we explored whether different tracking strategies spontaneously arose during the task, and which were most effective. Although indices of closer in-flight tracking (pursuit gain, tracking coherence, tracking lag, and saccades) were predictive of better interception performance, these relationships were rather weak. Anticipatory gaze shifts toward the correct release location of the ball provided no benefit for subsequent interception. Nonetheless, two interceptive strategies were evident: 1) early anticipation of the ball's onset location followed by attempts to closely track the ball in flight (i.e., predictive strategy); or 2) positioning gaze between possible onset locations and then using peripheral vision to locate the moving ball (i.e., a visual pivot strategy). Despite showing much poorer in-flight foveal tracking of the ball, participants adopting a visual pivot strategy performed slightly better in the task. Overall, these results indicate that precise alignment of the fovea with the target may not be critical for interception tasks, but that observers can adopt quite varied visual guidance approaches.

Schizophrenia and Orthoptic Conditions: A Literature Review.

A narrative review of the literature reporting ocular abnormalities in patients with schizophrenia was undertaken to determine the types and prevalence of orthoptic conditions in this patient cohort. A systematic search of multiple databases yielded 1,974 studies published between January 1992 and January 2022. All were screened for relevance based on their title and abstract. Seventeen studies were included in the final review. Ocular abnormalities reported in schizophrenia included a high incidence of strabismus, reduced visual acuity and reduced stereopsis compared to controls. Additionally, eye movement abnormalities (including reduced smooth pursuit gain and increased prosaccade latency) were frequently reported. Reduced visual acuity was associated with negative symptoms and reduced quality of life in schizophrenia. Orthoptists and eye care professionals should be aware that a higher incidence of strabismus, reduced visual acuity, reduced stereoacuity, and eye movement abnormalities are reported in patients with schizophrenia. Further research is required to determine whether, or to what extent, ocular abnormalities and visual disturbances influence or exacerbate the symptoms of schizophrenia, and whether there is an effect of schizophrenia medication on these orthoptic conditions.

Monoaminergic Degeneration and Ocular Motor Abnormalities in De Novo Parkinson's Disease.

Evaluating eye movements in Parkinson's disease (PD) provides valuable insights into the underlying pathophysiological changes. The aim was to investigate the relationship between monoaminergic degeneration and ocular motor abnormalities in de novo PD. Drug-naive PD patients who underwent N-(3-[18 F]fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl) nortropane positron emission tomography scans and video-oculography at diagnosis were eligible. Measurements of saccadic accuracy, latency, and smooth pursuit gain and square wave jerk frequency were collected. Patients underwent Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and detailed cognitive tests. We investigated the associations between ocular motor measurements and specific tracer uptake ratios (SUR) in the caudate nucleus, anterior and posterior putamen, thalamus, and dorsal raphe nuclei, along with motor and cognitive symptoms. One-hundred twenty-four subjects were included in this study. Saccadic accuracy was positively associated with parkinsonian motor severity expressed as Hoehn and Yahr stages, MDS-UPDRS Part III scores, and subscores for bradykinesia and rigidity but not with tremor scores (PFDR < 0.05). Saccadic accuracy correlated with poor performances in the Rey-Complex-Figure copy, and latency with the Digit Symbol Coding and the Montreal Cognitive Assessment scores (PFDR < 0.05). Prolonged saccadic latency correlated with reduced thalamic SUR, whereas decreased saccadic accuracy correlated with reduced SUR in the anterior and posterior putamen (PFDR < 0.05). Reduced smooth pursuit gain showed associations with reduced SUR in the dorsal raphe, a serotonin-predominant region, but did not correlate with parkinsonism severity scores. Defective dopaminergic and nondopaminergic neural systems may discretely influence ocular motor function in de novo PD patients. © 2023 International Parkinson and Movement Disorder Society.

Changes in saccadic eye movement and smooth pursuit gain in patients with acquired comitant esotropia after strabismus surgery.

This study investigates the change in horizontal saccadic eye movement and smooth pursuit in patients with acquired comitant esotropia (ACE), before and after strabismus surgery. The horizontal saccades and pursuit in 11 patients with ACE were recorded using a video eye-tracker under binocular viewing before and after strabismus surgery. Participants were instructed to fixate on the new target as rapidly as possible when it randomly appeared at either 18.3° rightward or 18.3° leftward. For smooth pursuit, participants were asked to track, as accurately as possible, a step-ramp target moving at ±6.1°/s. The asymmetry of adduction-abduction and the binocular coordination in gains of saccade and pursuit were compared between the pre- and post-surgical data. The asymmetry of adduction-abduction saccade gain in each eye after surgery tended to be smaller than that before surgery. The binocular coordination of saccade showed significant improvement after surgery in only the non-dominant eye direction. Adduction-abduction asymmetry in the smooth pursuit gain in each eye after surgery tended to be smaller than before surgery. After surgery, the binocular coordination of pursuit was improved significantly in both directions. In patients with ACE, binocular coordination of saccade and smooth pursuit was poor. Binocular coordination of saccade and pursuit seems to be improved due to the improvement in ocular deviation angle and binocular visual function after surgery.

Eye movements during motor imagery and execution reveal different visuomotor control strategies in manual interception.

Previous research has investigated the degree of congruency in gaze metrics between action execution (AE) and motor imagery (MI) for similar manual tasks. Although eye movement dynamics seem to be limited to relatively simple actions toward static objects, there is little evidence of how gaze parameters change during imagery as a function of more dynamic spatial and temporal task demands. This study examined the similarities and differences in eye movements during AE and MI for an interception task. Twenty-four students were asked to either mentally simulate or physically intercept a moving target on a computer display. Smooth pursuit, saccades, and response time were compared between the two conditions. The results show that MI was characterized by higher smooth pursuit gain and duration while no meaningful differences were found in the other parameters. The findings indicate that eye movements during imagery are not simply a duplicate of what happens during actual performance. Instead, eye movements appear to vary as a function of the interaction between visuomotor control strategies and task demands.

Visual attentional guidance during smooth pursuit eye movements: Distractor interference is independent of distractor-target similarity.

In the current study, we used abrupt-onset distractors similar and dissimilar in luminance to the target of a smooth pursuit eye-movement to test if abrupt-onset distractors capture attention in a top-down or bottom-up fashion while the eyes track a moving object. Abrupt onset distractors were presented at different positions relative to the current position of a pursuit target during the closed-loop phase of smooth pursuit. Across experiments, we varied the duration of the distractors, their motion direction, and task-relevance. We found that abrupt-onset distractors decreased the gain of horizontally directed smooth-pursuit eye-movements. This effect, however, was independent of the similarity in luminance between distractor and target. In addition, distracting effects on horizontal gain were the same, regardless of the exact duration and position of the distractors, suggesting that capture was relatively unspecific and short-lived (Experiments 1 and 2). This was different with distractors moving in a vertical direction, perpendicular to the horizontally moving target. In line with past findings, these distractors caused suppression of vertical gain (Experiment 3). Finally, making distractors task-relevant by asking observers to report distractor positions increased the pursuit gain effect of the distractors. This effect was also independent of target-distractor similarity (Experiment 4). In conclusion, the results suggest that a strong location signal exerted by the pursuit targets led to very brief and largely location-unspecific interference through the abrupt onsets and that this interference was bottom-up, implying that the control of smooth pursuit was independent of other target features besides its motion signal.

Istradefylline Improves Impaired Smooth Pursuit Eye Movements in Parkinson's Disease.

Patients with Parkinson's disease (PD) exhibit alterations in eye movement control, primarily diverse oculomotor deficits which include hypometric saccade and impaired smooth pursuit with reduced pursuit-gain necessitating catch-up saccades. The effects of dopaminergic treatment of PD on eye movements are controversial. Previous studies suggest that smooth pursuit eye movements (SPEMs) are not directly influenced by the dopaminergic system. The nondopaminergic drug istradefylline, a selective adenosine A2A receptor antagonist, reduces the OFF time and improves somatomotor function in levodopa-treated PD. Here, we investigated whether istradefylline improves SPEMs in PD, and determined whether oculomotor performance is associated with somatomotor performance. Using an infrared video eye tracking system, we quantified horizontal SPEMs in six patients with PD before and 4-8weeks after initiation of istradefylline administration. A further five patients with PD were tested before and after a 4-week interval without istradefylline to control for practice effects. We evaluated smooth pursuit gain (eye velocity/target velocity), accuracy of smooth pursuit velocity, and saccade rate during pursuitbefore and after istradefylline administration during the ON state. Patients received istradefylline by single daily oral administration at 20 to 40mg. Eye tracking data were obtained 4-8weeks after initiation of istradefylline administration. Istradefylline increased smooth pursuit gain and the accuracy of smooth pursuit velocity, and tended to decrease saccade rates during pursuit. Istradefylline ameliorated the oculomotor deficit in SPEM of patients with PD, although differences in somatomotor performance before and after istradefylline treatment were not significant during ON periods. The discrepancy observed between the oculomotor and somatomotor responses to istradefylline supports previous findings that SPEM is at least partially under nondopaminergic control.

Differential saccade-pursuit coordination under sleep loss and low-dose alcohol.

Ocular tracking of a moving object requires tight coordination between smooth pursuit and saccadic eye movements. Normally, pursuit drives gaze velocity to closely match target velocity, with residual position offsets corrected by catch-up saccades. However, how/if common stressors affect this coordination is largely unknown. This study seeks to elucidate the effects of acute and chronic sleep loss, and low-dose alcohol, on saccade-pursuit coordination, as well as that of caffeine. We used an ocular tracking paradigm to assess three metrics of tracking (pursuit gain, saccade rate, saccade amplitude) and to compute "ground lost" (from reductions in steady-state pursuit gain) and "ground recouped" (from increases in steady-state saccade rate and/or amplitude). We emphasize that these are measures of relative changes in positional offsets, and not absolute offset from the fovea. Under low-dose alcohol and acute sleep loss, ground lost was similarly large. However, under the former, it was nearly completely recouped by saccades, whereas under the latter, compensation was at best partial. Under chronic sleep restriction and acute sleep loss with a caffeine countermeasure, the pursuit deficit was dramatically smaller, yet saccadic behavior remained altered from baseline. In particular, saccadic rate remained significantly elevated, despite the fact that ground lost was minimal. This constellation of findings demonstrates differential impacts on saccade-pursuit coordination with low-dose alcohol impacting only pursuit, likely through extrastriate cortical pathways, while acute sleep loss not only disrupts pursuit but also undermines saccadic compensation, likely through midbrain/brainstem pathways. Furthermore, while chronic sleep loss and caffeine-mitigated acute sleep loss show little residual pursuit deficit, consistent with uncompromised cortical visual processing, they nonetheless show an elevated saccade rate, suggesting residual midbrain and/or brainstem impacts.

Oculomotor Findings in Videonystagmography across the Lifespan.

When performing oculomotor testing during standard videonystagmography (VNG), the vestibular system is not actively stimulated. Therefore, responses are generated from the cerebellum, brainstem, and oculomotor tract. Many patients seen for vestibular testing fall outside of the standard age norms, making it difficult to determine whether an abnormal finding is due to age or oculomotor dysfunction. The purpose of this study was to further evaluate the effect of age on a standard clinical VNG oculomotor test battery consisting of saccades, smooth pursuit, and optokinetic (OPK) testing. This is a cross-sectional, between-group prospective study comparing oculomotor tests between age groups. Twenty-one older adults between the ages of 60 and 90 years with no history of central or peripheral vestibular dysfunction were included in the study. Previously collected data from 29 children aged 4 to 6 years and 33 adults aged 20 to 60 years were also included. Participants completed oculomotor testing using infrared goggles consisting of saccades, smooth pursuit, and OPK. Statistical analyses were completed using multivariate analysis of variance and analysis of variance and follow-up analysis when indicated. Significant group differences were noted for saccade latency and speed, smooth pursuit gain, and OPK gain and speed. Children and older adults demonstrated longer saccade latencies compared with the controls, and older adults exhibited slower saccade speed than the controls and children. These results also indicated that smooth pursuit gain was reduced for children and older adults compared with controls, and gain decreased across all groups as frequency increased. Analyses of OPK results indicated older adults had reduced gain and speed compared with the children and control group. The findings of prolonged saccade latencies and reduced smooth pursuit gain in both children and older adults suggest possible cerebellar rather than attentional effects. However, other findings such as reduced saccade speed and reduced OPK gain were noted only in the older adults, which suggests oculomotor degeneration and/or insufficient coverage of the visual field during testing, respectively. These results also indicate the importance of age-specific normative data for use in clinical oculomotor testing.

Video-Oculography Assessment in Neurodegenerative Ataxias and Niemann Pick Type C.

Deceleration of vertical saccades, an early and characteristic finding of Niemann-Pick Type C (NP-C), may help diagnosis. Our aim in this study was to demonstrate the role of video-oculography (VOG), in the differential diagnosis of ataxia syndromes, particularly of NP-C, using this technique in the evaluation of saccadic velocity and smooth pursuit gain of ataxia patients. We recruited consecutive 50 ataxia patients and 50 healthy control subjects who were age and sex-matched with the patient group. Saccadic eye movements and smooth pursuit eye movements for different angles and different directions from patients and healthy subjects were recorded by using VOG. Saccadic eye movement velocity and smooth pursuit gain values of the patients were significantly lower in all directions and at all angles as compared to healthy subjects. In the patient group, 3 cases out of 50 were selected as suspected NP-C, based on the dissociation between their markedly impaired vertical saccadic velocity and near normal to slightly impaired horizontal one and relatively intact smooth pursuit eye movements; the diagnoses in all 3 cases were confirmed with positive genetic testing, and thereupon Miglustat treatment was started. Our findings support that cerebellar pathology in degenerative ataxia patients is associated with both impaired saccadic velocity and smooth pursuit gain, whereas in NP-C, only the impaired vertical saccades as opposed to relatively preserved other eye movements are seemingly a diagnostic marker for the entity. We conclude that recording of eye movements could be useful for differential diagnosis and monitorization of the treatment of ataxia syndromes as an easy and objective method.