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At least 271 records · Page 15Linked to original sources
PubMed2005

Frequency doubling technology and scanning laser tomography in eyes with generalized enlargement of optic disc cupping.

PURPOSE: To characterize functional and structural changes in eyes with generalized enlargement of optic disc cupping (vertical cup/disc ratio > or = 0.8), normal intraocular pressure, normal standard achromatic automated perimetry (SAP) results, and no other ophthalmoscopic findings suggesting glaucoma (large C/D eyes) using frequency doubling technology (FDT) and the Heidelberg Retina Tomograph (HRT). METHODS: This comparative observational case series included 30 large C/D eyes (30 subjects), 17 eyes (17 patients) with early-stage normal tension glaucoma with generalized enlargement of optic disc cupping (NTG eyes), and 25 eyes from 25 normal subjects (normal eyes). Results with Humphrey 30-2, FDT N-30 threshold programs, and HRT were compared among these groups. Large C/D eyes were subdivided into FDT-normal and -abnormal eyes according to the predetermined criteria and HRT parameters were compared among them. RESULTS: No significant difference was seen in HRT parameters between the large C/D and NTG eyes. In the large C/D eyes, FDT mean deviation was lower than in the normal eyes and higher than in the NTG eyes, whereas FDT pattern standard deviation was smaller than in the NTG eyes (P = 0.02-0.03). Among HRT parameters, only cup shape measure (CSM) showed significant negative correlation with FDT mean deviation in the large C/D eyes. Between FDT-normal and -abnormal subgroups, only CSM showed significant difference (P < 0.01). CONCLUSION: Frequency doubling technology showed abnormalities in large C/D eyes. Only CSM showed significant correlation with FDT result and difference between those with normal and abnormal FDT results. In management of large C/D eyes, FDT and CSM will be useful to detect functional and structural change.

Adult↗
PubMed2005

More to ADHD than meets the eye: observable abnormalities in search behaviour do not account for performance deficits on a discrimination task.

Children with Attention Deficit/Hyperactivity Disorder (ADHD) often perform poorly on tasks requiring sustained and systematic attention to stimuli for extended periods of time. The current paper tested the hypothesis that such deficits are the result of observable abnormalities in search behaviour (e.g., attention-onset, -duration and -sequencing), and therefore can be explained without reference to deficits in non-observable (i.e., cognitive) processes. Forty boys (20 ADHD and 20 controls) performed a computer-based complex discrimination task adapted from the Matching Familiar Figures Task with four different fixed search interval lengths (5-, 10-, 15- and 20-s). Children with ADHD identified fewer targets than controls (p < 0.001), initiated searches later, spent less time attending to stimuli, and searched in a less intensive and less systematic way (p's < 0.05). There were significant univariate associations between ADHD, task performance and search behaviour. However, there was no support for the hypothesis that abnormalities in search carried the effect of ADHD on performance. The pattern of results in fact suggested that abnormal attending during testing is a statistical marker, rather than a mediator, of ADHD performance deficits. The results confirm the importance of examining covert processes, as well as behavioural abnormalities when trying to understand the psychopathophyiology of ADHD.

Journal Article↗
PubMed2005

Eye movement abnormalities in stiff person syndrome.

The authors describe a 38-year-old woman with stiff person syndrome (SPS) and gaze-holding nystagmus, limited abduction, vertical and horizontal ocular misalignment, deficient smooth pursuit, and impaired saccade initiation. There was no evidence of ocular myasthenia, indicating that abnormalities of ocular motor function can occur as a primary manifestation of SPS, perhaps from depletion of GABA.

Adult↗
PubMed2000

Otolith dysfunction in skew deviation after brain stem lesions. Abnormalities of eye movements induced by off-vertical-axis rotation (OVAR).

We investigated the horizontal and the vertical otolith-ocular reflex induced by off-vertical-axis rotation and subjective visual vertical in 14 patients with skew deviation due to brain stem lesion. Patients were divided into two groups: the group C (N = 7) with caudal brain stem lesions and the group R (N = 7) with rostral brain stem lesions as defined by the midpons level. The patient group was compared to a control group of 20 healthy subjects. The otolith-ocular reflex was evoked by constant velocity rotation in yaw plane around an axis tilted at 15 deg with respect to gravity. In group C, the horizontal off-vertical-axis nystagmus bias was negative i.e. anticompensatory to chair rotation, when directed toward the lesioned side. Furthermore, patients of group C were presenting with a significant tilt of subjective visual vertical. In group R, a vertical downward offset was induced predominantly in the hypotropic eye and in the direction of rotation away from the lesion. Finally, in patients of group R, horizontal and vertical modulation was increased for rotation away from the lesion. These results are discussed in terms of 1) asymmetrical horizontal and vertical dynamic otolith signals feeding the velocity storage network after brain stem lesion, 2) possible involvement of cerebellar function in OVAN modulation.

Adult↗
PubMed1996

Neuronal basis of amblyopia: a review.

Amblyopia is an acquired defect in vision due to an abnormal visual experience during a sensitive period of visual development. The neuronal basis of amblyopia is the study of the effects of "abnormal" environmental influences on the genetically programmed development of the visual processing system. Visual pathway development commences with ganglion cells forming the optic nerve. The process that guides these neurones initially to the lateral geniculate nucleus (LGN) and then onto the visual cortex is genetically programmed. Initially this process is influenced by spontaneously generated impulses and neurotrophic factors. Following birth, visual stimuli modify and refine the genetically programmed process. Exposure to the visual environment includes the risk of abnormal inputs. Abnormal stimuli disrupt the formation of patterned inputs allowing alteration of visual cortical writing with reduction in ocular dominance columns driven by the abnormal eye. Correction of the abnormal visual input and penalisation of the "normal" input is the mainstay of therapy for amblyopia. Further understanding of the mechanisms involved in the development of a normal visual processing system will allow trialing therapies for amblyopia not responding to occlusion therapy. Levodopa is one agent providing insights into recovery of visual function for short periods in apparently mature visual systems.

Amblyopia↗
PubMed1999

Asymmetric responses in cortical visually evoked potentials to motion are not derived from eye movements.

PURPOSE: Normal neonates and many adults after abnormal visual development have directional preferences for visual stimulus motions; i.e., they give better responses for optokinetic nystagmus (OKN) and visually evoked potentials (VEPs) in one direction than to those in the opposite direction. The authors tested whether the VEP responses were asymmetrical because of abnormal eye movements. METHODS: VEPs were recorded from the visual cortices of five macaque monkeys: one normal, one neonate, and three reared with alternating monocular occlusion (AMO). They were lightly anesthetized, followed by paralysis to prevent eye movements. They then had "jittered" vertical grating patterns presented in their visual fields. The steady state VEPs were analyzed with discrete Fourier transforms to obtain the amplitudes and phases of the asymmetries. RESULTS: The normal, control monkey had small, insignificant amplitudes of its asymmetrical Fourier component and random phases that were not 180 degrees out of phase across the left and right eyes. The neonatal monkey and the AMO monkeys all had large, significant asymmetries that were approximately 180 degrees out of phase between the left and right eyes. CONCLUSIONS: The neonate and abnormally reared monkeys continued to have asymmetrical responses even after their eyes were paralyzed. Therefore, eye movements cannot be the source of the asymmetrical amplitudes of the VEPs, and the visual cortex is at least one source responsible for asymmetries observed in neonates and adults reared under abnormal visual inputs.

Animals↗