Jan Ober

The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task.

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. Amblyopia is associated with abnormal visual experience (e.g., anisometropia) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears—what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic/non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30 ± 11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28 ± 8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10°) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262 ± 48 ms) and dominant (mean 237 ± 45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226 ± 32 ms) and non-dominant (mean 230 ± 29 ms) eye was not significantly different. By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central retina in subjects with anisometropic amblyopia.

Statistical characteristics of finger-tapping data in Huntington’s disease

Measuring the rate of finger tapping is a technique commonly used as an indicator of impairment in degenerative neurological conditions, such as Huntington’s disease. The information it provides can be greatly enhanced by analysing not simply the overall tapping rate, but also the statistical characteristics of the individual times between each successive response. Recent technological improvements in the recording equipment allow the responses to be analysed extremely quickly, and permit modification of the task in the interest of greater clinical specificity. Here we illustrate its use with some pilot data from a group of manifest HD patients and age-matched controls. Even in this small cohort, differences in the responses are apparent that appear to relate to the severity of the disease as measured by conventional behavioural tests.

Not only amblyopic but also dominant eye in subjects with strabismus show increased saccadic latency.

Amblyopia is a developmental disorder of vision usually associated with the presence of strabismus and/or anisometropia during early childhood. Subject literature has shown that both the amblyopic and fellow eyes (especially in strabismic subjects) may manifest a variety of perceptual and oculomotor deficits. Previous studies using simple saccadic responses (pro-saccades) showed an increased saccadic latency only for the amblyopic eye viewing conditions. So far, there have appeared no saccadic latency studies in strabismic amblyopia for more complex volitional saccades. In order to maximize the contribution of the central retina in the process of saccade initiation, we decided to use delayed saccadic responses in order to test the hypothesis about saccadic latency increase in both eyes in strabismic amblyopes. The results from our study have shown that saccadic latency is increased both in the dominant and amblyopic eyes. In addition, the amblyopic eye in the strabismic group showed greater increase in saccadic latency compared to an amblyopic eye in the anisometropic group from our previous study. The observed increase in saccadic reaction time for the dominant eye is novel and provides further evidence that the visual pathway associated with the dominant eye might be also impaired in strabismic amblyopia. Since an abnormal binocular input during visual system development may affect gaze stability in both eyes, we speculate that unsteady fixation accompanied with subtle perceptual deficits contribute to an increase in saccadic latency that is observed in the dominant eye. Moreover, it appears that the cortical processes related to saccade decisions are delayed both for amblyopic and fellow eyes in strabismic subjects.

Objective Assessment of the Hemisphere-Specific Neurological Outcome of Carotid Endarterectomy: A Quantitative Saccadometric Analysis

BACKGROUND: Carotid endarterectomy (CEA) improves the cerebrovascular prognosis of patients with carotid stenosis but carries a risk of causing postoperative neurological deterioration. OBJECTIVE: We assessed hemisphere-specific changes in saccadic eye movements to determine the utility of saccadometry as a quantitative neurosurgical outcome measure. METHODS: Visually evoked saccades were recorded at the bedside before and 2 days after surgery from 30 patients undergoing CEA for symptomatic carotid stenosis. Hemisphere-specific latency distributions were compared using Kolmogorov-Smirnov statistics. Latency distributions were fitted using the Linear Approach to Threshold with Ergodic Rate model and compared with binomial logistic regression. RESULTS: There were 21 males and mean age at surgery was 71 ± 7 years. Following CEA, the distribution of saccades initiated by the cerebral hemisphere distal to the operated artery significantly changed in 25 patients. By contrast, there were 14 significant contralateral-hemisphere saccadic changes (P < .001). Significant contralateral saccadic changes always co-occurred with significant ipsilateral changes and 10 of 14 patients with contralateral saccadic change had contralateral carotid stenosis. There was a significantly greater postoperative reduction in early saccades generated by the ipsilateral hemisphere than by the contralateral hemisphere (P < .02) CONCLUSION: CEA leads to significant hemisphere-specific subclinical changes in saccadic performance and, in particular, differentially affects the proportion of early saccades, a measure of the ability of the frontal cortex to successfully inhibit lower centers, generated by the 2 hemispheres. Saccadometry, a bedside test, provides data that can be statistically compared for individual and groups of patients. It could allow the neurological outcome of carotid surgery to be objectively quantified.

I04 Palm-size oculomotor laboratory for field testing of saccadic system potentially applicable for monitoring of HD development

Saccadic eye movement measurement is reported as potential sensitive biomarker of Huntingtons disease (HD), in both pre-manifest and manifest stages. While definitely less specific than imagining techniques, it possess potential for quick, low cost and non invasive quantitative assessment of brain functional status. It is also less prone to neuronal compensation mechanism which continues to conceal the evidence of functional motor impairment, especially when voluntary component is involved in saccadic test paradigm (antisaccade-peripherial-conflict). According to recent findings, the changes of saccadic metrics accompany HD progression and they can be considered as a means of tracking the current patient condition and outcome of new therapeutic interventions. Authors present portable, integrated diagnostic environment, Saccadometer Clinical. The system is designed as minimal-setup for evaluation of saccadic metrics, allowing to establish subjects functional deterioration profile based on the repetitive measurements (status samples) accumulated over the time. The key component is small factor, battery powered, head-mounted intelligent sensor, capable of generating laser dot stimuli for both reflex and volitional decision based saccadic tests, and performing automated eye movement acquisition and classification. Due to portability, ease of use, and build-in telemetry link for wireless communication, the measurement can be carried by patient her/himself in home environment, providing facility for continuous, remote monitoring of patients functional status. In order to broaden the spectrum of measured parameters, current development efforts aim to include the smooth pursuit and the vestibule-ocular (postural sway) tests within the same miniaturised system, serving as complementary biomarkers of HD.