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.