Search results for "Eye"
showing 10 items of 2511 documents
Ten novel mutations found in Aniridia.
1998
Aniridia (AN) is a sight-threatening congenital ocular disorder characterized by iris hypoplasia, corneal pannus, foveal and optic nerve hypoplasia, cataract formation, and glaucoma. In two-thirds of the patients, AN is inherited in an autosomal dominant fashion with almost complete penetrance but variable expression. The remaining cases are sporadic. Aniridia has been shown to be associated with mutations in the PAX6 gene, located on chromosome 11p13, telomeric to the Wilms' tumor predisposition gene (WT1). This paper describes 14 mutations in the PAX6 gene in patients with AN. Among these 14 mutations, 10 have been unpublished until now. They result most probably in haploinsufficiency and…
Asymmetric modulation of human visual cortex activity during 10 degrees lateral gaze (fMRI study).
2005
We used BOLD fMRI to study the differential effects of the direction of gaze on the visual and the ocular motor systems. Fixation of a target straight ahead was compared to fixation of a target 10 degrees to the right and 10 degrees to the left from gaze straight ahead, and to eyes open in complete darkness in thirteen healthy volunteers. While retinotopic coordinates remained the same in all fixation conditions, the fixation target shifted with respect to a head-centered frame of reference. During lateral fixation, deactivations in higher-order visual areas (one ventral cluster in the lingual and fusiform gyri and one dorsal cluster in the postero-superior cuneus) and, as a trend, activati…
Visual Performance of Four Simultaneous-Image Multifocal Contact Lenses Under Dim and Glare Conditions
2014
To assess and compare the effects of four simultaneous-image multifocal contact lenses (SIMCLs), and those with distant-vision-only contact lenses on visual performance in early presbyopes, under dim conditions, including the effects of induced glare.In this double-masked crossover study design, 28 presbyopic subjects aged 40 to 46 years were included. All participants were fitted with the four different SIMCLs (Air Optix Aqua Multifocal [AOAM; Alcon], PureVision Multifocal [PM; BauschLomb], Acuvue Oasys for Presbyopia [AOP; JohnsonJohnson Vision], and Biofinity Multifocal [BM; CooperVision]) and with monofocal contact lenses (Air Optix Aqua, Alcon). After 1 month of daily contact lens wear…
Acquired monocular elevation paresis. An asymmetric upgaze palsy.
1992
Five patients with acquired monocular elevation paresis were investigated using direct current electrooculography. With recovery, upward saccade velocities significantly increased in both eyes in all patients. The gain of upward-following eye movements significantly increased in the paretic eye of all patients and in the opposite eye of four patients. These findings are interpreted in terms of an asymmetric upgaze palsy which clinically presented as monocular elevation paresis in the more severely affected eye. A brainstem lesion contralateral to monocular elevation paresis was suggested in four patients by contralateral Horner's syndrome and contralateral abduction paresis, each in one pat…
Eye closure in darkness animates sensory systems.
2003
Single subject and group analyses (n = 12) showed that the eyes-open and eyes-closed states in complete darkness considerably and consistently differ in the patterns of associated brain activation in fMRI. During nonchanging external stimulation, ocular motor and attentional systems were activated when the eyes were open; the visual, somatosensory, vestibular, and auditory systems were activated when the eyes were closed. These data suggest that there are two different states of mental activity: with the eyes closed, an "interoceptive" state characterized by imagination and multisensory activity and with the eyes open, an "exteroceptive" state characterized by attention and ocular motor act…
Direction‐dependent visual cortex activation during horizontal optokinetic stimulation (fMRI study)
2005
Looking at a moving pattern induces optokinetic nystagmus (OKN) and activates an assembly of cortical areas in the visual cortex, including lateral occipitotemporal (motion‐sensitive area MT/V5) and adjacent occipitoparietal areas as well as ocular motor areas such as the prefrontal cortex, frontal, supplementary, and parietal eye fields. The aim of this functional MRI (fMRI) study was to investigate (1) whether stimulus direction‐dependent effects can be found, especially in the cortical eye fields, and (2) whether there is a hemispheric dominance of ocular motor areas. In a group of 15 healthy subjects, OKN in rightward and leftward directions was visually elicited and statistically compa…
Functional Magnetic Resonance Imaging Activations of Cortical Eye Fields during Saccades, Smooth Pursuit, and Optokinetic Nystagmus
2009
Saccades, smooth pursuit, and optokinetic nystagmus (OKN) are three basic eye movements in our ocular motor repertoire that enable us to explore the visual field. These eye movements are cortically controlled in different cortical eye fields, including the frontal eye fields (FEF) and parietal eye fields (PEF), as well as the motion-sensitive visual area MT+/V5. It is not known if this cortical control is organized in parallel cortico-cortical networks or in adjacent subregions of one system. Nor do we know where the specific eye fields are exactly located. Functional magnetic resonance imaging (fMRI) was used to investigate these open questions about the FEF, PEF, and MT+/V5. Activations o…
Anatomical correlate of positive spontaneous visual phenomena: a voxelwise lesion study.
2010
Objectives: Visual phenomena such as phosphenes, photopsias, or complex visual hallucinations occur in patients with lesions affecting the occipital, parietal, or temporal lobe. Whether these phenomena are provoked by lesions in specific anatomical regions is still uncertain. To determine which brain regions might be involved in such visual phenomena, we used new brain imaging and lesion analysis tools that allow a direct comparison with control patients. Methods: Visual phenomena were investigated in a total of 23 patients with acute infarctions along the visual pathways (6 patients with left-sided and 17 patients with right-sided lesions). Results: Ten of these 23 patients (43%) reported …
fMRI signal increases and decreases in cortical areas during small-field optokinetic stimulation and central fixation
2001
Small-field optokinetic nystagmus (OKN) was performed in seven healthy volunteers in order to analyze the activation and deactivation patterns of visual motion, ocular motor, and multisensory vestibular cortex areas by means of fMRI during coherent visual motion stimulation. BOLD signal decreases (deactivations) were found in the first and second long insular gyri and retroinsular areas (the human homologue of the parietoinsular vestibular cortex and the visual posterior sylvian area in the monkey) of both hemispheres, extending into the transverse temporal gyrus and inferior-anterior parts of the superior temporal gyrus (BA 22), and the precentral gyri at two separate sites (BA 4 and 6). F…
Visual tracking combined with hand-tracking improves time perception of moving stimuli
2014
A number of studies have shown that performing a secondary task while executing a time-judgment task impairs performance on the latter task. However, this turns out not to be the case for certain motor secondary tasks. We show that concomitant secondary motor tasks involving pointing, when performed during a time-judgment task, can actually improve our time-judgment abilities. We compared adult participants' performance in a time-of-movement paradigm with visual pursuit-only and with visual pursuit plus hand pursuit. Rather than interfering with their estimation of stimulus movement duration, the addition of hand pursuit significantly improved their judgment. In addition, we considered the …