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PubMed2003

Eye movement abnormalities in essential tremor may indicate cerebellar dysfunction.

Experimental and clinical data indicate that the cerebellum is involved in the pathophysiology of advanced stages of essential tremor (ET). The aim of this study was to determine whether a dysfunction also affects cerebellar structures involved in eye movement control. Eye movements of 14 patients with ET and 11 age-matched control subjects were recorded using the scleral search-coil technique. Vestibular function was assessed by electro-oculography. Eight ET patients had clinical evidence of intention tremor (ET(IT)); six had a predominantly postural tremor (ET(PT)) without intention tremor. ET patients showed two major deficits that may indicate cerebellar dysfunction: (i) an impaired smooth pursuit initiation; and (ii) pathological suppression of the vestibulo-ocular reflex (VOR) time constant by head tilts ('otolith dumping'). In the step ramp smooth pursuit paradigm, the initial eye acceleration in the first 60 ms of pursuit generation was significantly reduced in ET patients, particularly in ET(IT) patients, by approximately 44% (mean 23.4 degrees/s(2)) compared with that of control subjects (mean 41.3 degrees/s(2)). Subsequent steady-state pursuit velocity and sinusoidal pursuit gain (e.g. 0.4 Hz: 0.90 versus 0.78) were also significantly decreased in ET patients, whereas pursuit latency was unaffected. The intention tremor score correlated with the pursuit deficit, e.g. ET(IT) patients were significantly more affected than ET(PT) patients. Gain and time constant (tau) of horizontal VOR were normal, but suppression of the VOR time constant by head tilt ('otolith dumping') was pathological in 41% of ET patients, particularly in ET(IT) patients. Saccades and gaze-holding function were not impaired. The deficit of pursuit initiation, its correlation with the intensity of intention tremor, and the pathological VOR dumping provide additional evidence of a cerebellar dysfunction in the advanced stage of ET, when intention tremor becomes part of the clinical symptoms, and point to a common pathomechanism. The oculomotor deficits may indicate an impairment of the caudal vermis in ET.

Adult↗
PubMed1998

Developmental abnormalities in horseshoe crab embryos caused by exposure to heavy metals

We examined the effects of heavy metals on the development of horseshoe crabs using bioassays in which embryos at different stages were exposed either continuously or for 24 h. Abnormalities included segment-defective embryos, double embryos, embryos with abnormal eye areas, and no-posterior embryos. In terms of their ability to affect normal development, the pollutants are ranked as follows: Hg >== organotin > Cr falling dots Cd > Cu > Pb > Zn. Organotin treatment was associated with a high frequency of abnormal eye embryos and Hg with segment-defective embryos. The specific cause of segment-defective malformations by Hg was investigated by using SH inhibitors and cytochalasin B, an inhibitor of microfilaments. These inhibitors induced Hg-type segment-defective embryos; thus, Hg may also act by inhibiting SH-SS exchange and blocking morphogenetic movements. Horseshoe crab embryos from Delaware Bay and Sandy Hook Bay, New Jersey, were examined for developmental abnormalities. Malformed embryos were extremely rare (<0.6%) at five beaches along Delaware Bay as well as Sandy Hook Bay, suggesting that these horseshoe crab spawning areas are relatively unpolluted by heavy metals.

Journal Article↗
PubMed1992

Neuropsychological and eye movement abnormalities in first-episode and chronic schizophrenia.

It is well known that neurobehavioral deficits are associated with schizophrenia. Little is known, however, about whether these disturbances becomes more severe over the course of the illness. In the present study, 101 patients with schizophrenia, of whom 45 were first-episode cases, performed pursuit eye tracking tasks. A subset of 60 of these patients, including 27 first-episode cases, were administered a battery of neuropsychological tests. Patients with a history of prior psychotic episodes demonstrated more severe pursuit eye movement dysfunction than first-episode patients and more severe disturbances on neuropsychological tests sensitive to prefrontal and left temporal cortical dysfunction. Longitudinal studies of patients ascertained close to the point of illness onset are needed to determine whether these findings reflect a progressive deterioration in neurobehavioral functioning over the course of schizophrenia.

Adult↗
PubMed1999

Optical correction of induced axial myopia in the tree shrew: implications for emmetropization.

PURPOSE: To determine whether an active emmetropization mechanism is involved in the recovery from axial myopia through the use of a mammalian model of refractive development. Specifically, we sought to establish whether the emmetropization mechanism is visually guided by the level of clarity of the image falling on the retina, or if recovery is driven by a mechanism sensitive to abnormal eye shape. METHODS: Young tree shrews had axial myopia induced by monocular deprivation (MD) of pattern vision and then the myopic eye was either: (1) accurately corrected with a negative lens or (2) had a zero-powered lens placed in front of it. Their emmetropization response was monitored, both through the use of ocular refractive and biometric measures, as well as through the assessment of scleral dry weight and glycosaminoglycan synthesis, as indicators of scleral metabolism. RESULTS: Corrective lenses prevented recovery from induced myopia (-6.8 +/- 0.7 D after 5 days MD vs. -6.6 +/- 0.6 D after 5 days of lens wear), whereas animals fitted with zero-powered lenses displayed near full recovery from the induced myopia (-6.6 +/- 0.6 D vs. -1.7 +/- 0.3 D). Significant reductions in scleral dry weight (-4.6 +/- 1.3%) and glycosaminoglycan synthesis (-28.6 +/- 7.3%) were found in the posterior sclera of animals wearing corrective lenses. Conversely, animals wearing zero-powered lenses displayed elevated levels of glycosaminoglycan synthesis (+62.3 +/- 11.1%) in conjunction with scleral dry weights that did not differ significantly between treated and fellow control eyes (-1.5 +/- 2.6%). CONCLUSIONS: Accurate correction of induced axial myopia prevents the refractive, biometric and scleral metabolic responses that are normally observed in tree shrew eyes recovering from induced myopia. These findings support the hypothesis that recovery is driven by an active emmetropization response dependent on the clarity of image falling on the retina and not by a mechanism that is sensitive to abnormal eye shape.

Accommodation, Ocular↗
PubMed1995

Transgenic models for eye malformations.

Several lines of transgenic mice developing eye malformations have been described in the literature and appear to be of increasing interest for the study of eye teratology in humans, since gene expression and regulation can be studied in the developing animal. Transgenic applications are briefly described here and an overview of existing transgenic mouse models carrying different eye abnormalities is given according to the major diagnosis (e.g., cataract, microphthalmia, anterior segment dysgenesis, retinal dysplasia). Interestingly, many transgenic models exhibit pathological findings similar to those observed in human pediatric ophthalmology. Unfortunately, detailed embryological studies in transgenic mice bearing congenital eye malformations are not available for all lines. Thus, the importance of creating further transgenic models to study the function of morphogenes and growth factors in eye development is also discussed.

Animals↗
PubMed1994

Evaluation of ocular health among alachlor manufacturing workers.

Earlier toxicology studies found that one strain of rat (Long-Evans) developed severe ocular lesions when fed high doses of alachlor, a chloracetanilide active ingredient in some preemergent herbicides used for corn, soybean, and peanut crops. Because of a lack of eye effects in feeding studies conducted in dogs and other rodent species and strains, the effect was believed to be specific to Long-Evans rats. Nevertheless, to determine whether there were ocular effects among alachlor-exposed workers, we examined a group of the highest exposed alachlor production workers (n = 135) for the presence of a specific eye abnormality, analogous to the initiating lesion in Long-Evans rats, called pigmentary dispersion syndrome. A similar examination was given to unexposed coworkers and relatives (n = 84) to provide comparison rates. None of the exposed workers were found to have pigmentary dispersion syndrome, and prevalence rates for other eye abnormalities were similar for exposed and unexposed study participants. These results suggest that humans exposed to alachlor are not at increased risk of developing ocular disease.

Acetamides↗
PubMed1981

Collie eye anomaly in collies in the Netherlands.

The eyes of 160 Collies were examined for Collie Eye Anomaly, Progressive Retinal Atrophy, and any other eye abnormality present. The incidence of CEA in 160 Collies was 40.6 per cent. There were no cases of PRA. Other abnormalities noted were distichiasis, persistent pupillary membranes, distinct remnants of the hyaloid artery, corneal dystrophy and unilateral cataracts.

Animals↗
PubMed2004

An objective method to define outlier optical coherence tomograms and repeatability of retinal nerve fibre layer measurements.

PURPOSE: To compare the variation in thickness and reflectivity of the retinal nerve fibre layer (RNFL), circumferentially and on repeated testing. METHODS: In 24 normal eyes and 38 eyes with different optic neuropathies or retinopathies, third-party optical coherence tomography (OCT) software defined the RNFL border based on the reflectivity pattern across the retina and also provided measurements of the mean reflectivity and total retinal thickness in addition to RNFL thickness. A new Gaussian filtering method was implemented so that the weight of the applied filter was varied for each of five individually repeated scans until an optimum weight filter was determined. RESULTS: The scans requiring the highest weight filter could be identified as 'outlier' scans that contained measurement or alignment artifacts. There was no difference in the weights of filtering needed for normal and abnormal eyes. The RNFL thickness and reflectivity, and retinal thickness were highly correlated with one another in normal and abnormal eyes. CONCLUSIONS: A new Gaussian filtering routine was devised that not only defined the most reproducible substructure of the RNFL for a given patient's eye, but also provided a new method of quantifying measurement variability and identification of scans with measurement or alignment artifacts.

Adult↗
PubMed1987

Assessment of visual impairment in patients with Alzheimer's disease.

We examined five patients with Alzheimer's disease who complained of poor vision. Two patients had mild Alzheimer's disease; they complained of problems with reading and of "bumping into things," yet both had normal visual acuities. One patient with moderate Alzheimer's disease had abnormal eye movements, visual-evoked potentials, and contrast sensitivity. The other two patients had severe Alzheimer's disease. Despite difficulties in performing the examination, we were able to see moderate impairments in visual acuity and visual fields, as well as marked dyschromatopsia, severe deficits in contrast sensitivity, and markedly abnormal eye movements and visual-evoked potentials.

Aged↗
PubMed1975

Internuclear ophthalmoplegia and associated abnormalities in eye motion timing (differential delays).

Studies of the dynamic characteristics of horizontal saccadic eye motion give velocity, acceleration, and timing information. Average time differences between the motion of the eyes on left and right gaze, termed "differential delays," are statistical measures of the average differences of right-going and left-going velocity waveforms, and can be determined to within 0.5 msec. These relative time measurements give information that is not necessarily apparent from the velocity or acceleration data, and provide a sensitive measure of early oculomotor dysfunction. Patients with internuclear ophthalmoplegia have been shown to give characteristic abnormal values, and two such patients are described in detail to illustrate how these measurements may be used both to help in diagnosis and to characterize the presumed lesions.

Adult↗
PubMed1998

Anterior structural defects by misexpression of Xgbx-2 in early Xenopus embryos are associated with altered expression of cell adhesion molecules.

The RNA of the noncluster homeobox gene, Xgbx-2, is localized during neurulation to a narrow band of tissue at the midbrain hindbrain boundary (anterior hindbrain). The localized expression of Xgbx-2 within the nervous system prompted us to assess its function during early development by injection of synthetic Xgbx-2 RNA into the animal pole region of both dorsal blastomeres at the four-cell stage. Injection of Xgbx-2 RNA leads to dose-dependent alterations in anterior dorsal structures. These defects include abnormal eye development including reduced and missing eyes, reduced or missing cement glands, and abnormal brain development. Additionally, coinjection with lineage label (either beta-galactosidase or green fluorescent protein) shows there is a dose-dependent misplacement of cells. These misplaced cells can be found in such locations as the blastocoele, gastrocoele, or ventricles in the brain. In some spawnings, misplaced cells are expelled from the embryo into the periviteline space. In general, the phenotype of Xgbx-2 RNA-injected embryos is strikingly similar to the phenotypes observed when dominant-negative RNA constructs of Ca2+-dependent cell-adhesion molecules are injected into similar regions of early embryos. Xgbx-2 misexpression enhanced the dissociation of animal hemisphere cells, and inhibited Ca2+-dependent cell adhesion in dissociated animal hemisphere cells in vitro. Additionally, when the expression of various calcium-dependent cadherins was tested, it was shown that misexpression of Xgbx-2 prevents N-cadherin expression during early neurulation. These observations suggest that the transcription factor, Xgbx-2, functions normally in the regionalization of the neural tube (specifically the anterior hindbrain) by regulating differential cell adhesion and subsequently cell identity.

Animals↗
PubMed1982

[The pontine reticular formation syndrome. Physiopathologic data on voluntary eye movement abnormalities].

A new clinical case of Pontine Reticular Formation (P.R.F.) syndrome is reported and analysed using electro-oculograms. The CAT scan showed a probably metastatic tumour, clearly limited and located in the ventral part of the left tegmentum in the lower pons. The oculomotor disorders were typical of the P.R.F. syndrome and similar to those previously reported in pathological studies. The left P.R.F. damage was clinically evidenced by the loss of all leftward saccades (voluntary saccades and quick phases of nystagmus), including also those situated in the right hemifield of movement. It was noticed that the voluntary return movement driving both eyes from the right lateral position to the midline was remarkably slow and twice slower for the left eye (10 degrees/s) than for the right one (20 degrees/s). The loss of pursuit movements in the left hemifield of movement suggested that the lower part of the left P.R.F. was affected by the lesion. The preservation of normal leftward oculocephalic movements for the right eye indicated that the left abducens nucleus was spared. Lastly, the complete abductive paralysis of the left eye including the oculocephalic movement implied that the left abducens motoneurons passing through the lower part of the P.R.F. were damaged. All these functional and structural correlates are consistent with the location of the lesion given by the CAT scan. They are reviewed in the light of recent experimental and clinico-pathological data. A detailed physiopathological interpretation accounting for the slow voluntary movements, observed in place of the leftward return saccades in the right hemifield of movement, is proposed. The slowness of the movements of both eyes results from lack of phasic excitation of the motoneurons of the agonist muscles and from lack of phasic inhibition of the motoneurons of the antagonist muscles, both mechanisms being suppressed by the lesion which damages the excitatory burst neurons of the left P.R.F. As the tonic cells of the left P.R.F. are also out of action, these slow movements could mainly be controlled by the tonic cells of the right P.R.F. For the left eye, as the root fibres of the left abducens nucleus are damaged, no excitation can occur on the agonist muscle (left lateral rectus) and there is only a voluntary tonic disfacilitation of the motoneurons of the antagonist muscle (left medial rectus). For the right eye, the same mechanism involving the antagonist muscle (right lateral rectus) would be combined with some tonic excitation of the motoneurons of the agonist muscle (right medial rectus), thus accounting for the twice faster velocity of this eye. This tonic excitation reaching the right medial rectus could be mediated either by one of the other afferent neurons of the left abducens nucleus encoding eye position--namely those arising from the vestibular nuclei or from both prepositus hypoglossi nuclei--or by the right ascending tract of Deiters projecting to the right medial rectus motoneurons.

Abducens Nerve↗
PubMed1998

Abnormal saccadic eye movements in autistic children.

The saccadic eye movements, generated during a visual oddball task, of autistic children, normal children, children with attention deficit disorder and hyperactivity (ADDH), and dyslexic children were examined to determine whether autistic children differed from these other groups in saccadic frequency. Autistic children made more saccades during the presentation of frequent stimuli (than normals and ADDH children), and between stimulus presentations. Also, unlike the normal and dyslexic groups, their saccadic frequency did not depend on stimulus type. This abnormal pattern of saccades may negatively influence the ability to attend to stimuli, and thereby learning processes. Suggestions are made with respect to possible abnormalities in subcortical mechanisms involved in saccade generation.

Attention↗
PubMed1998

[Joubert syndrome: a report of 5 cases].

OBJECTIVE: To review clinical features, radiological findings and prognosis in Joubert syndrome. MATERIAL AND METHODS: We report 5 children (3 male and 2 female) with the diagnosis of Joubert syndrome by clinical and radiological findings. They were diagnosed in the first year of life, in the Hospital Infantil La Paz (Madrid, Spain), from 1971 to 1996. Three patients have already been published, and here, we report two new cases. RESULTS: Partial absence of the cerebellar vermis, hypotonia and developmental delay were seen in all patients. Other cardinal findings were episodic hyperpnoea (5/5) with periods of apnoea (2/5), abnormal eye movements (2/5) and strabismus (3/5), tongue protrusion (2/5), seizures (1/5), hemifacial spasms (1/5) and occipital meningocele (2/5). Clinical manifestations were first noticed soon after birth. Two patients died in the first 5 years of life, and the rest of the cases actually show severe mental retardation. CONCLUSIONS: Joubert syndrome is a rare and probably underdiagnosed syndrome with bad prognosis. This inherited condition is characterized by agenesis of the cerebellar vermis, mental retardation, hypotonia, episodic hyperpnoea and abnormal eye movements. Additional manifestations have been reported since the original cases were described.

Apnea↗
PubMed1999

History of Joubert syndrome and a 30-year follow-up of the original proband.

The 1960s were a period of great flowering in the recognition of neurologic disorders in children. The so-called ataxic cerebral palsies were an especially fertile field waiting for clarification. Congenital ataxia coupled with hyperpnea-apnea, abnormal eye movements, and retardation was identified as an autosomal-recessive syndrome eponimically associated with the senior author, Marie Joubert. The disorder, though rare, is increasingly recognized and a lay society dedicated to family support and research has been formed. In preparation for a recent symposium the original proband was re-examined 30 years later and the manifestations in adults clarified. Severe dysarthria was the most striking feature in this man, the hyperpnea-apnea had diminished, and the abnormal eye movements were less striking. Ataxia was still present but not severe. Poor judgment and borderline intelligence rounded out the clinical picture. Modern imaging has clarified, in part, the anatomic basis of this syndrome.

Adult↗
PubMed2002

[Paroxysmal tonic upgaze of childhood].

We described a child who developed paroxysmal abnormal eye movement. At the age of 12 months, she had a high fever and a febrile seizure. On the next day she showed tonic upward deviation of the eyes for 1 to 2 seconds, and downward saccades on attempted downward gaze. The upward deviation was repeated for a period of 2 to 3 hours, and disappeared during sleep. The administration of L-dopa was not effective. The symptoms subsided gradually over 10 months without other neurological impairment. She walked alone at 1 year and 6 months. At the beginning of her walking she showed truncal ataxia, but it gradually disappeared and her development was normal at the age of 2 years and 6 months. These abnormal eye movements and another symptoms were similar to paroxysmal tonic upgaze of childhood (PTU) that has been first described by Ouvrier and Billson (1988) as intermittent upward deviations of eyes. In Japan there was only one report of this syndrome with periventricular leukomalacia and hypomyelination.

Electroencephalography↗
PubMed2005

Patients with premature coronary artery disease who carry the ABCC6 R1141X mutation have no Pseudoxanthoma Elasticum phenotype.

BACKGROUND: Pseudoxanthoma elasticum (PXE) is an inherited disorder of elastic tissue. We recently found that heterozygosity for the frequent (0.8% prevalence in Dutch population) R1141X mutation in the PXE gene coding for the ABCC6 transporter, is associated with a fourfold risk of premature coronary artery disease. Yet, it is not clear whether or not heterozygosity for this mutation results in a mild PXE phenotype. The objective of our study was to determine if skin and/or eye abnormalities related to a PXE phenotype could be found in patients with premature coronary artery disease, with and without the R1141X mutation. METHODS: R1141X mutation carriers with premature coronary artery disease (cases) and patients with premature coronary artery disease with no-or not known-mutation (controls) were studied. Cases and controls were examined for PXE-like skin changes and retinal angioid streaks, peau d'orange or pigment epithelium changes. RESULTS: 7 cases and 31 controls were analysed. In both the mutation-positive and the control group, skin inspection and eye fundus examination did not reveal any dermatological or ocular signs of PXE. CONCLUSIONS: Carriers for the ABCC6 R1141X mutation, which is frequent and confers a high risk of premature coronary artery disease, do not commonly have skin or eye abnormalities consistent with a mild PXE phenotype.

Adult↗