Demet Yüksel
UCLouvain (University of Louvain), Ophthalmology, Faculty Member
Research Interests: Neuroscience, Psychology, Neurophysiology, Medicine, Humans, and 14 moreFemale, Saccades, Male, Smooth Pursuit, Aged, Middle Aged, Perseveration, Eye Movement, Alzheimer Disease, Frontal Lobe, Case Control Studies, Psychomotor Performance, Psychology and Cognitive Sciences, and Medical and Health Sciences
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PurposeTogether with anisometropia and organic causes of visual deprivation, strabismus, if not treated before the age of 7 or earlier, depending on studies, leads to amblyopia and loss of binocularity. In this study, we first examined... more
PurposeTogether with anisometropia and organic causes of visual deprivation, strabismus, if not treated before the age of 7 or earlier, depending on studies, leads to amblyopia and loss of binocularity. In this study, we first examined which parameters of strabismus influenced the motor development in children. Second, we assessed to what extent different motor skills were impacted by strabismus.MethodsTo this end, we evaluated the motor skills of 40 children between 3 and 12 years old suffering from strabismus using the Movement Assessment Battery for Children – Second Edition (MABC‐2).ResultsAccording to MABC‐2, 19 children had no motor disability, and 21 had risk of or significant motor disabilities. As for the first question, results at MABC‐2 were significantly lower for children without compared to those with binocularity (p‐value = 0.002), and significantly lower for participants with binocularity but without stereoscopy in comparison with those with stereoscopy (p‐value = 0.099). However, results did not differ significantly according to the type of strabismus, that is infantile, secondary or acquired strabismus. Differences were not significant either according to the angle of deviation. Regarding our second question, binocularity significantly impacted static balance (p‐value = 0.003) and to a smaller extent dynamic balance (p‐value = 0.05). Performance for catching, but not for shooting, was significantly affected by binocularity (p‐value = 0.042).ConclusionsOur study shows that the development of motor skills in children is significantly affected when binocularity and stereoscopy are absent, independently from the type of strabismus. Among the motor skills, static balance and catching are significantly impacted by that absence of binocularity. These results should be confirmed with a larger sample, including older patients, to assess the compensation mechanisms put in place and the actual impact of strabismus on overall motor performance.
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Research Interests: Psychology, Eye tracking, Eye Tracking and Oculomotor Control, Aging, Neurophysiology, and 15 moreAdolescent, Medicine, Humans, Child, Visual tracking, Animals, Saccades, Young Adult, Smooth Pursuit, Adult, Eye Movement, Age Factors, Child preschool, Psychology and Cognitive Sciences, and Medical and Health Sciences
PURPOSE. Sweep visual evoked potentials (sVEPs) provide an implicit, objective, and sensitive evaluation of low-level visual functions such as visual acuity and contrast sensitivity. For practical and traditional reasons, sVEPs in... more
PURPOSE. Sweep visual evoked potentials (sVEPs) provide an implicit, objective, and sensitive evaluation of low-level visual functions such as visual acuity and contrast sensitivity. For practical and traditional reasons, sVEPs in ophthalmologic examinations have usually been recorded over a single or a limited number of electrodes over the medial occipital region. Here we examined whether a higher density of recording electrodes improves the estimation of individual low-level visual thresholds with sVEPS, and to which extent such testing could be streamlined for clinical application. METHODS. To this end, we tested contrast sensitivity and visual acuity in 26 healthy adult volunteers with a 68-electrode electroencephalogram (EEG) system. RESULTS. While the most sensitive electrophysiologic response was found at the traditional medial occipital electrode Oz in a small majority of individuals, it was found at neighboring electrodes for the remaining participants. At the group level, lower spatial frequencies were also associated with right lateralized responses. More generally, visual function was evaluated more sensitively based on EEG recorded at the most sensitive electrode defined individually for each participant. Our data suggest that recording over seven posterior electrodes while limiting the testing session to less than 15 minutes ensures a sensitive and consistent estimation of acuity and contrast sensitivity threshold estimates in every individual. CONCLUSIONS. The present study shows that sampling from a larger number of posterior scalp electrodes is relevant to optimize visual function assessment and could be achieved efficiently in the time-constrained clinical setting.
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Research Interests: Psychology, Child Development, Motion perception, Neurophysiology, Adolescent, and 15 moreDevelopment, Medicine, Proprioception, Humans, Child, Cerebellum, Internal Model, Adult, Occlusion, Eye Movement, Psychomotor Performance, Child preschool, photic stimulation, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Predicting the consequences of our own actions through internal models is an essential component of motor control. Previous studies showed improvement of anticipatory behaviors with age for grasping, drawing and postural control. Since... more
Predicting the consequences of our own actions through internal models is an essential component of motor control. Previous studies showed improvement of anticipatory behaviors with age for grasping, drawing and postural control. Since these actions require visual and proprioceptive feedback, these improvements might reflect both the development of internal models and the feedback control. In contrast, visual tracking of a temporarily invisible target gives specific markers of prediction and internal models for eye movements. Therefore, we recorded eye movements in 50 children (aged from 5 to 19 years) and in 10 adults who were asked to pursue a visual target that is temporarily blanked. Results show that the youngest children (5-7y) have a general oculomotor behavior in this task qualitatively similar to the one observed in adults. However, the overall performance of older subjects in terms of accuracy at target reappearance and variability in their behavior was much better than th...
Research Interests: Psychology, Child Development, Motion perception, Neurophysiology, Adolescent, and 15 moreDevelopment, Medicine, Proprioception, Humans, Child, Cerebellum, Internal Model, Adult, Occlusion, Eye Movement, Psychomotor Performance, Child preschool, photic stimulation, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Sweep visual evoked potentials (sVEPs) provide an implicit, objective, and sensitive evaluation of low-level visual functions such as visual acuity and contrast sensitivity. For practical and traditional reasons, sVEPs in ophthalmologic... more
Sweep visual evoked potentials (sVEPs) provide an implicit, objective, and sensitive evaluation of low-level visual functions such as visual acuity and contrast sensitivity. For practical and traditional reasons, sVEPs in ophthalmologic examinations have usually been recorded over a single or a limited number of electrodes over the medial occipital region. Here we examined whether a higher density of recording electrodes improves the estimation of individual low-level visual thresholds with sVEPS, and to which extent such testing could be streamlined for clinical application. To this end, we tested contrast sensitivity and visual acuity in 26 healthy adult volunteers with a 68-electrode electroencephalogram (EEG) system. While the most sensitive electrophysiologic response was found at the traditional medial occipital electrode Oz in a small majority of individuals, it was found at neighboring electrodes for the remaining participants. At the group level, lower spatial frequencies w...
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When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from... more
When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from one type of eye movement to the other are still poorly understood, even though they could bring a significant contribution to the understanding of how the CNS combines different kinds of control strategies to achieve a common motor and sensory goal. In this study, we investigated the oculomotor responses to a large range of different combinations of position error and velocity error during visual tracking of moving stimuli in humans. We found that the oculomotor system uses a prediction of the time at which the eye trajectory will cross the target, defined as the "eye crossing time" (T(XE)). The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e...
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Surgical results after symmetrical and asymmetrical surgery performed by the same surgeon (M.S.) as initial procedure for basic intermittent exotropia were retrospectively analysed in 55 young patients. Twenty-five patients underwent... more
Surgical results after symmetrical and asymmetrical surgery performed by the same surgeon (M.S.) as initial procedure for basic intermittent exotropia were retrospectively analysed in 55 young patients. Twenty-five patients underwent unilateral recess-resect surgery on the non-fixating eye (Groupe 1) and 30 patients bilateral lateral rectus recessions (Group 2). The average age at surgery was 6.5 yrs (range: 2-18). The average post-operative follow-up was 2.81 yrs (range: 0.50-8 yrs), (p = 0.143). Sensory fusion was assessed by the Bagolini straited glasses and/or the Worth test and stereopsis by either the TNO and/or Lang stereoacuity test prior and after surgery. Prior to surgery, 84% of the patients had reached isoacuity. Ocular motility was normal in all patients. The average size of preoperative exotropia measured by prism and alternate cover test was 28 PD (SD = 5) for both Groups. In the immediate postoperative period, 53% of the patients were overcorrected without any statis...
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Fifty non-strabismic children with primary anisometropia were reviewed retrospectively. At entry, patients ranged in age from 1 to 10 years with an average of 4.5 years. The follow-up ranged from 0.5 to 9 years with an average of 3.5... more
Fifty non-strabismic children with primary anisometropia were reviewed retrospectively. At entry, patients ranged in age from 1 to 10 years with an average of 4.5 years. The follow-up ranged from 0.5 to 9 years with an average of 3.5 years. Criteria for inclusion were a difference in refractive error between the two eyes of at least 1.00 D of spherical value and/or 0.75 D of cylindrical value. In all cases, anisometropia was totally corrected by prescribing glasses. Anisometropic amblyopia was considered to be present when isoacuity at far was not reached despite the glasses, part-time occlusion therapy of the good eye was prescribed. Amblyopia was present in 86% of the patients and was found with all types of anisometropia. It was more severe in anisohyperopia and/or anisoastigmatism. After adequate treatment, amblyopia was clinically cured or less severe in 78% of the patients.
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PURPOSE. To improve understanding of the binocular control of saccades by making high-resolution eye movement recordings in patients with unilateral Duane retraction syndrome (DRS) type I (marked by congenital absence of the sixth cranial... more
PURPOSE. To improve understanding of the binocular control of saccades by making high-resolution eye movement recordings in patients with unilateral Duane retraction syndrome (DRS) type I (marked by congenital absence of the sixth cranial nerve). METHODS. Binocular eye movements were recorded in four patients in binocular viewing conditions during a saccade task. RESULTS. Affected-side gaze showed normal saccades of the sound eye and undershooting saccades of the affected eyeevidence of intact interneurons, but deficient motoneurons, in the sixth-nerve nucleus on the affected side. Postsaccadic smooth onward drift followed undershooting saccades of the affected eye. Sound-side gaze, in the centripetal direction, showed relatively accurate saccades despite large offsets in initial position between the two eyes. In the centrifugal direction, there was a consistent undershoot of the affected eye. The sound eye showed unexpected overshoot. Postsaccadic drifts in opposite directions in t...
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We report a case of a 4 months old boy with esotropia of the left eye with large bilateral chorioretinal toxoplasmic macular scars. Chorioretinal scars are the most common eye finding in congenital toxoplasmosis and are often located in... more
We report a case of a 4 months old boy with esotropia of the left eye with large bilateral chorioretinal toxoplasmic macular scars. Chorioretinal scars are the most common eye finding in congenital toxoplasmosis and are often located in the macular region. Most infants with congenital infection are asymptomatic at birth but will develop retinal and/or neurologic damage later in life with consequent loss of vision. A routine examination of the fundus and computed tomography of the head can be negative. Serologic testing is essential for the diagnosis and the follow-up of the infection. Every infant with evident or suspected congenital infection by Toxoplasma gondii must be treated by Pyrimethamine, Sulphadiazine and Folinic Acid during at least the first year of life with regular serologic testing and ophthalmologic examination. Neurologic outcome is better with treatment and the risk of chorioretinitis seems reduced.
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“Canine Tooth Syndrome” may be induced by direct trauma to the peritrochlear area producing a SO paresis plus a Brown's syndrome due to scarring of the tendon-trochlea complex. A 57 year old man presented acquired vertical and... more
“Canine Tooth Syndrome” may be induced by direct trauma to the peritrochlear area producing a SO paresis plus a Brown's syndrome due to scarring of the tendon-trochlea complex. A 57 year old man presented acquired vertical and torsional diplopia following sinus surgery. A large ethmoidal adenoid cystic carcinoma was resected and inadvertent damage to the tendon-trochlea complex of SO occured. Postoperative radiation therapy was performed. The management and clinical course of the patient are described. Radiological images documenting the surgical excision of the tumor with damage to the tendon-trochlear area are discussed. In addition, the entity known as ‘canine tooth syndrome’ is reviewed.
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a b s t r a c t Disconjugate oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision in Duane Retraction Syndrome (DRS) patients is normal in half of their horizontal field of gaze (i.e.,... more
a b s t r a c t Disconjugate oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision in Duane Retraction Syndrome (DRS) patients is normal in half of their horizontal field of gaze (i.e., sound-side of gaze), we wondered whether oculomotor adaptive capabilities are efficient despite such a severe impairment of eye motility towards the other half of the horizontal field of gaze (i.e., affected-side gaze). We compared properties of horizontal saccades of patients with congenital unilateral Duane Retraction Syndrome type I in binocular viewing and monocular viewing conditions by simultaneously recording both eyes with the search coil technique. Our results show a mismatch between the pulse and the step signal of the innervation for saccades. When tested in the affected eye viewing condition (sound eye covered), the eyes showed not only similarly-directed increases of the saccadic gain (pulse signal) in the two eyes but also disjunctive post-sacc...
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Prediction and time estimation are all but required for motor function in everyday life. In the context of eye movements, for instance, they allow predictive saccades and eye re-acceleration in anticipation of a target re-appearance.... more
Prediction and time estimation are all but required for motor function in everyday life. In the context of eye movements, for instance, they allow predictive saccades and eye re-acceleration in anticipation of a target re-appearance. While the neural pathways involved are not fully understood, it is known that the frontal lobe plays an important role. As such, neurological disorders that affect it, such as frontotemporal (FTD) dementia, are likely to induce deficits in such movements. In this work, we study the performances of frontotemporal dementia patients in an oculomotor task designed to elicit predictive saccades at different rates, and compare them to young and older adults. Clear deficits in the production of predictive saccades were found in patients, in particular when the time between saccades was short (~500 ms). Furthermore, one asymptomatic C9ORF72 mutation bearer showed patterns of oculomotor behavior similar to FTD patients. He exhibited FTD symptoms within 3 years post-measure, suggesting that an impairment of oculomotor function could be an early clinical sign. Taken together, these results argue in favor of a role of the frontal lobe in predictive movements timing over short timescales, and suggest that predictive saccades in FTD patients warrant further investigation to fully assess their potential as a diagnostic aid.
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To improve understanding of the binocular control of saccades by making high-resolution eye movement recordings in patients with unilateral Duane retraction syndrome (DRS) type I (marked by congenital absence of the sixth cranial nerve).... more
To improve understanding of the binocular control of saccades by making high-resolution eye movement recordings in patients with unilateral Duane retraction syndrome (DRS) type I (marked by congenital absence of the sixth cranial nerve). Binocular eye movements were recorded in four patients in binocular viewing conditions during a saccade task. Affected-side gaze showed normal saccades of the sound eye and undershooting saccades of the affected eye-evidence of intact interneurons, but deficient motoneurons, in the sixth-nerve nucleus on the affected side. Postsaccadic smooth onward drift followed undershooting saccades of the affected eye. Sound-side gaze, in the centripetal direction, showed relatively accurate saccades despite large offsets in initial position between the two eyes. In the centrifugal direction, there was a consistent undershoot of the affected eye. The sound eye showed unexpected overshoot. Postsaccadic drifts in opposite directions in the two eyes brought both e...
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Disconjugate oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision in Duane Retraction Syndrome (DRS) patients is normal in half of their horizontal field of gaze (ie, sound-side of gaze), we... more
Disconjugate oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision in Duane Retraction Syndrome (DRS) patients is normal in half of their horizontal field of gaze (ie, sound-side of gaze), we wondered whether oculomotor adaptive capabilities are efficient despite such a severe impairment of eye motility towards the other half of the horizontal field of gaze (ie, affected-side gaze). We compared properties of horizontal saccades of patients with congenital unilateral Duane Retraction Syndrome ...
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In view of all the reported evidence by electromyography in the 1970s, by histology in the 1980s, and by cerebral imagery since the 2000s, Duane retraction syndrome (DRS) has been described as the consequence of a congenital anomaly of... more
In view of all the reported evidence by electromyography in the 1970s, by histology in the 1980s, and by cerebral imagery since the 2000s, Duane retraction syndrome (DRS) has been described as the consequence of a congenital anomaly of the 6th cranial nerve nuclei with aberrant innervations by supply from the 3rd cranial nerve. Both genetic and environmental factors are likely to play a role when the cranial nerves and ocular muscles are developing between the 4th and the 8th week of gestation. New data from eye ...