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Normal Visual Acuity (normal + visual_acuity)
Selected AbstractsCognitive visual dysfunctions in preterm children with periventricular leukomalaciaDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 12 2009ELISA FAZZI MD PHD Aim, Cognitive visual dysfunctions (CVDs) reflect an impairment of the capacity to process visual information. The question of whether CVDs might be classifiable according to the nature and distribution of the underlying brain damage is an intriguing one in child neuropsychology. Method, We studied 22 children born preterm (12 males, 10 females; mean age at examination 8y, range 6,15y; mean gestational age 30wks, range 28,36wks) with periventricular leukomalacia, spastic diplegia, normal intelligence (mean Full-scale IQ 84; mean Verbal IQ 97; mean Performance IQ 74), and normal visual acuity, focusing on higher visual functions. Brain magnetic resonance images (MRI) were analysed to establish the presence of lesions along the primary optic pathway, in the occipitoparietal and occipitotemporal regions. Results, Most children displayed an uneven cognitive profile, with deficits in visual object recognition, visual imagery, visual,spatial skills, and visual memory, and sparing of visual associative abilities, non-verbal intelligence, and face and letter recognition. Conventional brain MRI did not document major alterations of parietal and temporal white matter, or cortical alteration of areas involved in visual associative functions. Interpretation, We suggest a widespread involvement of higher visual processing systems, involving both the ventral and dorsal streams, in preterm children with periventricular leukomalacia. The lack of major alterations on conventional MRI does not exclude the possibility of malfunctioning of higher visual processing systems, expressing itself through discrete CVDs. Possible mechanisms underlying these neuropsychological deficits are discussed. [source] Neuroanatomical correlates of the near response: voluntary modulation of accommodation/vergence in the human visual systemEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2000Hans O. Richter Abstract This study identifies brain regions participating in the execution of eye movements for voluntary positive accommodation (VPA) during open-loop vergence conditions. Neuronal activity was estimated by measurement of changes in regional cerebral blood flow (rCBF) with positron emission tomography and 15O-water. Thirteen naive volunteers viewed a checkerboard pattern with their dominant right eye, while a lens interrupted the line of gaze during alternate 1.5 s intervals. Three counterbalanced tasks required central fixation and viewing of a stationary checkerboard pattern: (i) through a 0.0 diopter (D) lens; (ii) through a ,5.0-D lens while avoiding volitional accommodation and permitting blur; and (iii) through a ,5.0-D lens while maintaining maximal focus. The latter required large-amplitude, high-frequency VPA. As an additional control, seven of the subjects viewed passively a digitally blurred checkerboard through a 0.0-D lens as above. Optometric measurements confirmed normal visual acuity and ability to perform the focusing task (VPA). Large-amplitude saccadic eye movements, verified absent by electro-oculography, were inhibited by central fixation. Image averaging across subjects demonstrated multifocal changes in rCBF during VPA: striate and extrastriate visual cortices; superior temporal cortices; and cerebellar cortex and vermis. Decreases in rCBF occurred in the lateral intraparietal area, prefrontal and frontal and/or supplementary eye fields. Analysis of regions of interest in the visual cortex showed systematic and appropriate task dependence of rCBF. Activations may reflect sensorimotor processing along the reflex arc of the accommodation system, while deactivations may indicate inhibition of systems participating in visual search. [source] Unidirectional startle responses and disrupted left,right co-ordination of motor behaviors in robo3 mutant zebrafishGENES, BRAIN AND BEHAVIOR, Issue 5 2009H. A. Burgess The Roundabout (Robo) family of receptors and their Slit ligands play well-established roles in axonal guidance, including in humans where horizontal gaze palsy with progressive scoliosis (HGPPS) is caused by mutations in the robo3 gene. Although significant progress has been made toward understanding the mechanism by which Robo receptors establish commissural projections in the central nervous system, less is known about how these projections contribute to neural circuits mediating behavior. In this study, we report cloning of the zebrafish behavioral mutant twitch twice and show that twitch twice encodes robo3. We show that in mutant hindbrains the axons of an identified pair of neurons, the Mauthner cells, fail to cross the midline. The Mauthner neurons are essential for the startle response, and in twitch twice/robo3 mutants misguidance of the Mauthner axons results in a unidirectional startle response. Moreover, we show that twitch twice mutants exhibit normal visual acuity but display defects in horizontal eye movements, suggesting a specific and critical role for twitch twice/robo3 in sensory-guided behavior. [source] Squamous cell carcinoma: a rare complication of dermoid cystsNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 2 2002K. Ashkan Introduction:, Dermoid cysts constitute 0.3% of all brain tumours. Carcinomatous differentiation has been described only in a handful of cases. Material and methods:, A 44-year-old-man presented with a several-year history of headaches and a 5-week history of progressive visual deterioration in the left eye. Clinical examination confirmed a normal visual acuity but an impaired left visual field. A magnetic resonance imaging scan showed a lesion in the left paraclinoid area compressing the ipsilateral optic nerve. Signal characteristics of the lesion were consistent with a dermoid or epidermoid cyst. At operation, the lesion was thought to be typical of a dermoid cyst and a near-complete excision was achieved leaving behind parts adherent to the optic nerve. Histology showed invasive squamous cell carcinoma arising within the dermoid tumour. Postoperatively the patient received radiotherapy. Results:, The patient's clinical condition initially stabilized. At 15 months follow up, however, there was clinical and radiological evidence of tumour progression and he died 1 year later. Conclusion:, Squamous cell carcinoma may rarely arise from an intracranial dermoid tumour. This may hinder total excision of the lesion and confounds the prognosis. [source] Evaluation of spatial contrast sensitivity after the instillation of diclofenac eye dropsACTA OPHTHALMOLOGICA, Issue 2009V KARAMPATAKIS Purpose To evaluate if diclofenac eye drop instillation is related with spatial contrast sensitivity (CS) impairment. Methods Thirty ophthalmologically healthy Caucasian individuals (--male, --female), aged from 20 to 59 underwent CS testing. The examination was repeated 20 and 40 minutes after the instillation of diclofenac eye drops unilaterally. The fellow eye served as control. Results All the examined individuals had normal visual acuity, color vision and CS before the diclofenac drop instillation. Four of them complained of a temporary glare at the eye in which diclofenac was instilled. These four individuals had decreased CS in low spatial frequencies (1.5 & 3 cycles/degree), in the examination performed 20 minutes after the instillation. The CS normalized again in the third CS evaluation performed 40 minutes after the instillation. Conclusion The temporary glare that affects visual performance of some individuals after diclofenac eye drop instillation is related with a temporary decrease of spatial CS in low frequencies. Within this time period of 40 minutes after the instillation of diclofenac, individuals who experience visual disturbances should avoid activities that demand high visual efficacy or postpone the instillation for a more convenient time in relation to the duration of glare they have experienced. [source] | |||||||||||||