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PubMed1988

The role of the posterior vermis of monkey cerebellum in smooth-pursuit eye movement control. I. Eye and head movement-related activity.

1. The observation of smooth-pursuit eye and retinal image velocity signals in lobules VI and VII of the vermis has given rise to the hypothesis that a neural correlate of a target velocity signal exists in this region of the cerebellum (29). However, activity signaling head velocity is also required to regenerate a target velocity signal. Vermal Purkinje cell activity was, therefore, recorded during the performance of paradigms designed to dissociate head movement-related responses. 2. The activity of 107 Purkinje cells was found to be related to horizontal head velocity. Of these, 52% increased their discharge rate for ipsilaterally directed passive head movement (type I), and 48% were excited by contralateral head movements (type II). 3. In five Purkinje cells in which sufficient data were obtained, cell discharge rate increased monotonically with head velocity over the range of 5-40 deg/s. The sensitivity to head velocity at 0.4 Hz +/- 25 deg/s averaged approximately 0.5 spikes.s-1/deg.s-1 in a larger sample of cells (n = 39). The sensitivities to head velocity, at this same frequency and velocity, of type I and type II Purkinje cells were comparable at 0.44 and 0.51 spikes.s-1/deg.s-1, respectively. 4. The Purkinje cell responses led head velocity by an average of 12 degrees at 0.4 Hz +/- 25 deg/s of passive head rotation. The phase shifts associated with type I and II responses were similar with phase leads of 13 and 9 degrees with respect to head velocity, respectively. 5. A linear interaction of smooth-pursuit eye and head velocity signals was observed during the performance of a variety of antiphase and inphase eye and head movement paradigms. The results support the conclusion that some Purkinje cells in lobules VI and VII of the cerebellar vermis encode a gaze velocity signal. Contributions of the head velocity signal to the regeneration of target velocity are considered in a companion paper (32).

Animals↗
PubMed1998

Echobiometric evaluation of the axial length of the eye and intraocular lens calculation in pseudophakic eyes: our experience.

Intraocular lens (IOL) power calculation in 46 pseudophakic eyes (extracapsular cataract extraction with IOL in posterior chamber), utilizing a Javal keratometer, a Sonomed A 2000 echobiometer (probe 10 MHz, velocity=1,548 m/s) and the SRK2 formula, although there was a statistically significant reduction of the axial length, both in normal and hyperopic eyes, demonstrated no statistically significant differences of IOL power, when compared to the power previously calculated in the phakic eye.

Aged↗
PubMed1983

Ocular bobbing: abnormal eye movement or eye movement's abnormality?

Ocular bobbing is classified as an abnormal eye movement, resulting from pathological neuronal activity of the brain stem after bilateral pontine lesions. Clinical oculographic study of 5 patients suffering from ocular bobbing shows that upwards voluntary eye movements are abnormal. We suggest that ocular bobbing should not to be regarded as an abnormal eye movement, but, rather, as the only residual movement of patients which are totally deprived of both horizontal and upward movements.

Arterial Occlusive Diseases↗
PubMed1991

Studies on eye irritation caused by chemicals in rabbits--II. An in vitro testing method using rat red blood cells for the prediction of eye irritation potential of chemicals.

Rat red blood cells were used as an in vitro method to evaluate the eye irritation potential of chemicals in rabbits. The results using 116 chemicals of various categories including medicines, pesticides, detergents and solvents were analyzed for the prediction of possibility of eye irritation potentials. Eye irritation of chemicals was examined according to Draize method and chemicals were classified into three categories, (1) non or mild irritants, (2) moderate or severe irritants and (3) strong or corrosive irritants, based on the recovery of damages. The in vitro method consisted of two methods detecting the effects of chemicals mainly on protein and lipid in the membrane, which were evaluated by the induction of methemoglobin and hemolysis, respectively. Non- or mild irritants induced neither methemoglobin formation nor hemolysis. Most of moderate or severe irritants induced hemolysis, however, the potentials were low. Strong or corrosive irritants had high potentials for the induction of methemoglobin. The multivariate estimation by the above two in vitro data sets were 77.6% predictive of the in vivo classification.

Animals↗
PubMed1976

[Growth of eye and orbit in chick embryo. IX. Developement of eye and skull origin in 3-9 day old embryos with experimental bilateral microphthalmia].

Chick embryos in which on the third day of incubation the lens of both eye primordia was removed, were sacrificed at the ages of 5,7 and 9 days and fixed in a 70 per cent alcohol solution. An analysis was made of the consequences of the absence of normal large eyes upon the structure and growth of the skull. Immediately after the operation no changes in the head mesenchyme could be observed, but during the next days, as growth goes on, abnormal proportions and dimensions develop in the anterior part of the skull. Generally, this part of the skull is depressed and shorter than normal; cartilages around the eye have a different position and smaller dimensions. A perfect symmetry is only rarely maintained. There seems to be a very labile balance in the skull, as may be deduced from the presence of a buckled interorbital septum and the deviation of the upper beak.

Animals↗
PubMedDate not supplied

Disturbances in the control of saccadic eye movement and eye-head coordination in schizophrenics.

Some schizophrenic patients have been known to have frontal cortical dysfunction. In view of the evidence that voluntary purposive eye movements and rapid head movements involve areas of the frontal cortex, investigations of saccade performance have been carried out on schizophrenics in various laboratories. We have compared performance of schizophrenic patients in tasks involving inhibition of reflexive saccades (no-saccade) and initiation of saccades without target (memory-saccade) with performance in the antisaccade task. These measures were also compared with results of eye-head coordination tasks. Schizophrenics showed more errors and significantly longer latencies, with lower peak velocities at large amplitudes, in both the antisaccade task and the memory-saccade task. Performance with coordinated eye-head movement was basically similar, except for significantly longer latencies of head movement. These results suggest that schizophrenics may have a disturbance in initiating and executing purposive saccades without targets, and that dysfunction of the frontal cortex may contribute to this disturbance.

Adolescent↗
PubMed1987

Comparative tonometric measurements of eye bank eyes.

A comparison was made of the accuracy of the Tono-Pen, Pneumatonometer, and Perkins hand-held tonometers by measuring the hydrostatically controlled intracular pressure from 10 to 50 mm Hg in human eye bank eyes. The open stopcock method was used in which the cannulated eye, the hydrostatic pressure controlling column, and a manometer were continuously open to each other. The Pneumatonometer gave accurate results at 50 mm Hg but overestimated the lower intraocular pressures; whereas, the Perkins gave satifactory results at 10 and 20 mm Hg but underestimated higher intraocular pressures. The Tono-Pen displayed the least deviation from the controlled pressure over the entire range studied. Another aspect of this study involved determining that a therapeutic soft contact lens did not have any noticeably adverse effect on the accuracy of the Pneumatonometer and Tono-Pen tonometers.

Contact Lenses, Hydrophilic↗
PubMed1980

Control of unsteady, eccentric fixation in amblyopic eyes by auditory feedback of eye position.

A technique for providing amblyopes with auditory feedback signals of eye position errors is described. With auditory cues, 12 adult eccentrically fixing amblyopes with strabismus and/or anisometropia have been able to maintain steady and foveal fixation with the amblyopic eye. The changes observed in fixation patterns with auditory feedback were both quantitative and qualitative; with such feedback, amblyopes often exhibited sequences of normal-appearing fixation. Some of our subjects have been successful in maintaining steady foveal fixation for short periods of time after feedback is turned off, apparently using visual error signals. For two subjects, feedback also promoted major improvements in smooth tracking performance. We conclude that the use of auditory feedback of eye position has significant value for basic studies of the mechanisms underlying amblyopia and potentially for the clinical treatment of this condition.

Acoustic Stimulation↗
PubMed1996

[The Bratislava International Eye Bank--a member of the International Federation of Eye Banks].

The International Eye Bank in Bratislava has assembled during its two-year activities 1007 corneae with a 2mm scleral margin by excision performed in the donor in situ, 11 total eye-balls and 43 sclerae. From this total number 1331 eye tissues had to be eliminated because of serum positivity (115 HBsAg, 12 HCV, 2 HIV 1,2 + HCV + HBsAg, 2 HBsAg + HCV, 2 HIV 1.2 + HBsAg). The most frequent cause of death in donors of corneae were carcinomas, injuries and cerebro- and cardiovascular diseases. Corneal grafts are stored at a temperature of +2 degrees C to +6 degrees C in Optisol GS medium. The most frequent indication for keratoplasty in Slovakia was keratopathia bullosa (28.6%), keratoconus (23.9%) and leukoma corneae (18.7%).

Antibodies, Viral↗
PubMed1996

Associations of types of lens opacities between and within eyes of individuals: an application of second-order generalized estimating equations. The Framingham Eye Studies Group.

The lens opacity characteristics of individuals constitute multivariate data. Our goal was to estimate the associations between the three main types of age-related lens opacities (nuclear, cortical, posterior subcapsular) both between and within eyes of individuals using cross-sectional data from the Framingham (Massachusetts) Eye Studies. We describe use of a recently proposed extension of the generalized estimating equations approach to marginal logistic models (GEE2), and we demonstrate that a variety of research problems can be investigated with this methodology. For example, in our data, there were strong associations of the same opacity types between the two eyes of individuals and weak associations between different types of opacities. We also note that estimation of such associations may be limited in other epidemiologic settings.

Age Factors↗
PubMed1995

Relationship of presaccadic activity in frontal eye field and supplementary eye field to saccade initiation in macaque: Poisson spike train analysis.

The purpose of this study was to investigate the temporal relationship between presaccadic neuronal discharges in the frontal eye fields (FEF) and supplementary eye fields (SEF) and the initiation of saccadic eye movements in macaque. We utilized an analytical technique that could reliably identify periods of neuronal modulation in individual spike trains. By comparing the observed activity of neurons with the random Poisson distribution generated from the mean discharge rate during the trial period, the period during which neural activity was significantly elevated with a predetermined confidence level was identified in each spike train. In certain neurons, bursts of action potentials were identified by determining the period in each spike train in which the activation deviated most from the expected Poisson distribution. Using this method, we related these defined periods of modulation to saccade initiation in specific cell types recorded in FEF and SEF. Cells were recorded in SEF while monkeys made saccades to targets presented alone. Cells were recorded in FEF while monkeys made saccades to targets presented alone or with surrounding distractors. There were no significant differences in the time-course of activity of the population of FEF presaccadic movement cells prior to saccades generated to singly presented or distractor-embedded targets. The discharge of presaccadic movement cells in FEF and SEF could be subdivided quantitatively into an early prelude followed by a high-rate burst of activity that occurred at a consistent interval before saccade initiation. The time of burst onset relative to saccade onset in SEF presaccadic movement cells was earlier and more variable than in FEF presaccadic movement cells. The termination of activity of another population of SEF neurons, known as preparatory set cells, was time-locked to saccade initiation. In addition, the cessation of SEF preparatory set cell activity coincided precisely with the beginning of the burst of SEF presaccadic movement cells. This finding raises the possibility that SEF preparatory set cells may be involved in saccade initiation by regulating the activation of SEF presaccadic movement cells. These results demonstrate the utility of the Poisson spike train analysis to relate periods of neuronal modulation to behavior.

Action Potentials↗
PubMed2005

The rat pink-eyed dilution (p) mutation: an identical intragenic deletion in pink-eye dilute-coat strains and several Wistar-derived albino strains.

We identified the rat pink-eyed dilution (p) and pink eye Mishima (p(m)) mutations. The p(m) mutation, which was isolated from a wild rat caught in Mishima Japan in 1961 and is carried in the NIG-III strain, is a splice donor site mutation in intron 5. The p mutation, which was first described in 1914 and is carried in several p/p rats including the RCS and BDV strains, is an intragenic deletion including exons 17 and 18. In addition to RCS and BDV strains, several albino strains, KHR, KMI and WNA, all descendants of albino stock of the Wistar Institute, are homozygous for the p allele. Analyses revealed that the colored p strains and the Wistar-derived albino p strains had the same marker haplotype spanning approximately 4 Mb around the P locus. This indicates that these p strains share a common ancestor and the p allele did not arise independently via recurrent mutations. The historical relationship among the p strains suggests that the p deletion had been maintained in stock heterogeneous for the C and P loci and then was inherited independently by the ancestor of the Wistar albino stock and the ancestor of the pink-eyed agouti rats in Europe.

Albinism↗
PubMed1997

[Nuclear magnetic resonance tomography diagnosis of eye motility disorder in high-grade myopia for planning an eye muscle operation].

BACKGROUND: This study was conducted to elucidate the etiology of the acquired, restrictive motility disorder in patients with severe myopia by magnetic resonance imaging (MRI) and intraoperative situs and to verify existing theories about strabismus to develop appropriate methods of eye muscle surgery. METHODS: Thirty-five patients with unilateral or bilateral high-degree myopia and strabismus, i.e., axial length of the globe averaged 29.4 mm. Multiple coronal, transversal and parasagittal MRI planes were obtained using a Siemens Magnetom (SP 63) 1.5 Tesla MRI scanner (TR = 550 ms, TE = 15 ms; field of view = 21 x 21 cm; pixel matrix = 256 x 512; 3 acquisitions; slice thickness 2 mm; distance factor 0.25). In addition, in a dynamic MRI the patient had to fixate with the less restricted eye for 50 s in different gaze positions. All data were validated by measurements during strabismus surgery. Twenty normal orbits were studied in control MRI scans. RESULTS: The major MRI finding was dislocation of the lateral rectus in the anterior and midorbital region at an average of 3.4 mm into the temporocaudal quadrant in 13 cases with the typical eso- and hypotropia. This dislocation will reduce the abducting torque of the lateral rectus and create depressing and extorting torques. Two-anatomical explanations are possible: (1) increasing stretch of the lateral rectus because of temporocranial distension of the globe and inability of intermuscular membranes and pulleys to stabilize the path of the lateral rectus; (2) dehiscence of the lateral levator aponeurosis. The restrictive motility disorder was never caused by contact between the enlarged globe and the bones of the orbital apices. CONCLUSIONS: Until now, an abnormal path of recti EOMs has been known only in Duane's syndrome. Prior to strabismus surgery in patients with high-degree myopia, an orbital MRI scan may be useful. If misalignment of the lateral rectus is detected, the most important aim of eye muscle surgery is to normalize the pathological path of the lateral rectus. MRI morphometry in severe myopia may give additional information on the anatomy of the orbit and biomechanical mechanisms of strabismus. Our findings demonstrate the necessity of fixation-controlled MRI scans.

Adult↗
PubMed2004

Visual improvement during psychophysical training in an adult amblyopic eye following visual loss in the contralateral eye.

BACKGROUND: Recent publications have demonstrated neural plasticity in adult amblyopes subjected to psychophysical training based on perceptual learning. The purpose of this case report is to present rarely available prospective data of visual acuity development in a strabismic amblyope undergoing psychophysical training and pleoptic treatment after loss of function of the non-amblyopic eye. METHODS: The design is a prospective, observational and interventional case report. Visual acuity was tested monthly, with constant optical correction. The 60-year-old female patient participated in a psychophysical training implemented in our laboratory, and in pleoptic treatment. RESULTS: Slow functional improvement of the amblyopic eye was observed during a period of 10 months, both in the tests used for training and in visual acuity: single optotypes increased by 4 chart lines, crowded optotypes by 2-3 lines. CONCLUSIONS: To our knowledge, this is the first report of the new approach of perceptual learning in an adult amblyope after loss of vision in the contralateral eye. Our results represent further evidence that the visual system of adult amblyopes preserves a certain degree of neural plasticity, whether spontaneous or enhanced by training. Furthermore, that plasticity in adults is limited, and early diagnosis and treatment of amblyopia must remain the primary goal.

Amblyopia↗
PubMed1989

Is a retinal input involved in the generation of eye resetting fast phases in the frog eye optokinetic nystagmus?

An intravitreal injection of cis-2,3-piperidine dicarboxylic acid (PDA), a glutamate analog, in one eye only, decreased or even totally suppressed the eye resetting fast phases (ERFPs) of the frog optokinetic nystagmus (OKN) in monocular as in binocular situations. On the opposite, for low drum speeds, the slow phase eye velocity was not affected by PDA. Moreover, it seems that intravitreally injected PDA does not act upon central structures responsible for OKN. Our experiments suggest that a retinal input may be involved in triggering the ERFPs in the OKN.

Animals↗
PubMed2006

Role of the human supplementary eye field in the control of saccadic eye movements.

The precise function of the supplementary eye field (SEF) is poorly understood. Although electrophysiological and functional imaging studies are important for demonstrating when SEF neurones are active, lesion studies are critical to establish the functions for which the SEF is essential. Here we report a series of investigations performed on an extremely rare individual with a highly focal lesion of the medial frontal cortex. High-resolution structural imaging demonstrated that his lesion was confined to the region of the left paracentral sulcus, the anatomical locus of the SEF. Behavioural testing revealed that the patient was significantly impaired when required to switch between anti- and pro-saccades, when there were conflicting rules governing stimulus-response mappings for saccades. Similarly, the results of an arbitrary stimulus-response associative learning task demonstrated that he was impaired when required to select the appropriate saccade from conflicting eye movement responses, but not for limb movements on an analogous manual task. When making memory-guided saccadic sequences, the patient demonstrated hypometria, like patients with Parkinson's disease, but had no significant difficulties in reproducing the order of saccades correctly on a task that emphasized accuracy with a wide temporal segregation between responses. These findings are consistent with the hypothesis that the SEF plays a key role in implementing control when there is conflict between several, ongoing competing saccadic responses, but not when eye movements need to be made accurately in sequence.

Association Learning↗
PubMedDate not supplied

A red eye and then a really red eye.

A 90-year-old woman presented with a 4-week history of a presumed infectious conjunctivitis resistant to topical antibiotic medications. Examination revealed tortuous, dilated conjunctival vessels in the right eye, retinal hemorrhages, and an orbital bruit suggestive of a carotid-cavernous sinus fistula (CCF). While awaiting a magnetic resonance imaging study, she returned to the clinic the next day with a painful, swollen right eye and an intraocular pressure of 69 mm Hg. A cerebral arteriogram confirmed a direct CCF. Because of the tortuosity of the systemic vascular anatomy, a right carotid artery cut-down with balloon occlusion was performed with successful closure of the fistula and prompt resolution of the orbital congestion. This case illustrates the spectrum of subtle to conspicuous ocular manifestations that can be seen in patients with CCF and its potential to present as an emergency. CCF should be included in the differential diagnosis of an "atypical" red eye. Recognition of arteriolized conjunctival vessels and auscultation of an orbital bruit raises the possibility of a CCF, requiring prompt diagnostic studies.

Aged↗