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Claudia Gargini - One of the best experts on this subject based on the ideXlab platform.

  • Cortical binocularity in Convergent Strabismus after section of the optic chiasm.
    Experimental Brain Research, 2002
    Co-Authors: Marirosa Di Stefano, Claudia Gargini
    Abstract:

    In Convergent Strabismus (esotropia) the spatial asynchrony of the two eye inputs unbalances the interocular interactions, leading to the functional advantage of the nondeviated eye and the inhibition of the esotropic eye. It may be argued that the strabismic suppression, if it is the effect of inhibitory interactions between the eyes, could be removed by interrupting the interocular pathways at the optic chiasm. After chiasmatic section, each eye is connected only to the ipsilateral cortex through the uncrossed retinal projections and so the functionality of each eye's input is no longer interfered with by interocular mechanisms. In strabismic cats submitted, as adults, to section of the optic chiasm, we performed electrophysiological recordings from the striate cortex. Results show that in these animals: (1) the cortical responsiveness to the strabismic eye is strikingly higher than in esotropes with an intact optic chiasm; (2) the effectiveness of stimulation of the deviated eye is not different from that of the nondeviated eye in driving neurons of corresponding cortex; (3) surprisingly, a high degree of binocular activation is present in the cortex ipsilateral to the deviated eye, while in the cortex connected to the nondeviated eye the greatest majority of neurons are monocularly driven. Cortical binocularity depends on the corpus callosum, which conveys the input from the nondeviated eye to the opposite cortex (which receives the direct strabismic input), but not vice versa. The asymmetry of callosal transmission parallels the morphological asymmetry of callosal connections that occur in Convergent Strabismus. All together the findings indicate that the impaired effectiveness of esotropic input does not result from developmental deficit of the strabismic afferents but, rather, from inhibitory influences that are actively exerted through the interocular pathways. Strabismic suppression may be accomplished by the same interocular mechanisms underlying binocular rivalry.

  • Interocular interactions in esotropia.
    Archives italiennes de biologie, 1997
    Co-Authors: Marirosa Di Stefano, Claudia Gargini
    Abstract:

    In cats the unilateral Convergent Strabismus surgically induced in the early postnatal life causes monocular spatial vision deficits and loss of binocular activation of the primary visual cortex. It is assumed that the asynchrony of inputs from the two eyes, by disrupting binocular convergence, leads to unbalanced binocular interactions that favour the non-deviated eye. The competitive advantage of this eye reduces both the excitatory drive to the cortex and the behavioural visual capabilities of the strabismic eye that exhibits the loss of the nasal portion of the visual field. Our experimental evidence indicate that the esotropic input, released by interocular influences by the chiasm section, recovers at least as much effectiveness to achieve orienting reactions in the previously neglected nasal field. In addition we found that the excitatory drive of the ipsilateral strabismic input, which is the one mostly impaired in esotropic animals, is fully preserved when the interocular interactions are impeded at birth and it is greatly improved in the esotropic cats with section of the optic chiasm performed in adulthood. All together these results suggest that functional impairment of the esotropic input prior of chiasmotomy does not reflect developmental changes of the visual afferents yet the active inhibition exerted by interocular mechanisms.

Jean-michel Vallat - One of the best experts on this subject based on the ideXlab platform.

  • Ataxia with oculomotor apraxia type 2: a clinical and genetic study of 19 patients.
    Journal of the Neurological Sciences, 2009
    Co-Authors: M. Tazir, L. Ali-pacha, A. M'zahem, J.p. Delaunoy, M. Fritsch, S. Nouioua, T. Benhassine, S. Assami, D. Grid, Jean-michel Vallat
    Abstract:

    Ataxia with oculo-motor apraxia type 2 (AOA2) is a recently described autosomal recessive cerebellar ataxia (ARCA) caused by mutations in the senataxin gene (SETX). We analysed the phenotypic spectrum of 19 AOA2 patients with mutations in SETX, which seems to be the third most frequent form of ARCA in Algeria after Freidreich ataxia and Ataxia with vitamin E deficiency. In AOA2 patients, the mean age at onset for all families was in the second decade. Cerebellar ataxia was progressive, slowly leading to disability which was aggravated by axonal polyneuropathy present in almost all the patients. Mean disease duration until wheelchair was around 20 years. Oculo-motor apraxia (OMA) was present in 32% of the patients while Convergent Strabismus was present in 37%. Strabismus is therefore also very suggestive of AOA2 when associated with ataxia and polyneuropathy even in the absence of OMA. Cerebellar atrophy was more severe in the eldest patients; however it may also be an early sign since it was present in the youngest and paucisymptomatic patients. The initial sign was gait ataxia in all but two patients who presented with head tremor and writer cramp, respectively. Serum alpha-fetoprotein, which was elevated in all tested patients, was a good marker to suggest molecular studies of the SETX gene.

Simonsz H.j. - One of the best experts on this subject based on the ideXlab platform.

  • The early vs late infantile Strabismus surgery study: do sources for bias exist in this non-randomised trial
    'BMJ', 1998
    Co-Authors: Meyer K., Breitschwerdt H., Kolling G.h., Simonsz H.j.
    Abstract:

    Abstract Background—The Early vs Late Infantile Strabismus Surgery Study Group investigates whether early or late surgery is preferable in infantile Convergent Strabismus, in a non-randomised, prospective, multicentre clinical trial. The current state of the study after end of recruitment is reported here, focusing on the question of possible sources for bias in this nonrandomised trial. Method—The prognostic factors were analysed at baseline in order to check for imbalances between the two treatment groups. Reasons for possible differences are discussed. Results—There is no evidence for clinically relevant inhomogeneities between the two groups concerning the distribution of the three prognostic factors spherical equivalent, degree of amblyopia, and limitation of abduction. The fourth prognostic factor, horizontal angle of squint, differs significantly between the two groups. Conclusion—In the analysis of the final results we may have to account for differences in angle of squint at baseline by its inclusion as a covariate or by stratification

  • Quantitative perimetry under binocular viewing conditions in microStrabismus
    Published by Elsevier Ltd., 1997
    Co-Authors: Joosse M.v., Simonsz H.j., Van Minderhout H.m., De Jong P.t.v.m., Noordzij B., Mulder P.g.h.
    Abstract:

    AbstractIn order to elucidate the type, size and depth of suppression scotomata in microStrabismus and small angle Convergent Strabismus, we performed binocular static perimetry in 14 subjects with Strabismus and four normal observers. The strabismuc cases had an objective angle of Convergent squint between 1 and 8 deg, visual acuity between 0.1 and 1.25, and limited stereopsis. During testing the subjects fused pictures on two Friedmann visual field analyzers. Right and left eyes were studied separately under both monocular and binocular viewing conditions. In five Strabismus a suppression scotoma was found in the squinting eye, with a diameter of 5–30 deg and a depth ranging from 4 to 14 dB. No suppression scotomata could be detected in the nine other subjects nor in the four normal observers. In conclusion, only 36% of subjects with Strabismus were found to have a suppression scotoma. These scotomata were centered around the fixation point of the squinting eye, in some cases also encompassing the foveal area, and varying in depth and size

  • Quantitative visual field assessment of squinting eye under binocular conditions in ten patients with microStrabismus. Preliminary report.
    1994
    Co-Authors: Joosse M.v., Minderhout, H.m. Van, Simonsz H.j., P.t.v.m. De ,jong
    Abstract:

    Introduction: It is still not exactly known how strabismic patients perceive the surrounding world. It is commonly believed that patients with early onset Convergent Strabismus and microStrabismus do not suffer from diplopia because of two mechanisms: suppression and anomalous retinal correspondence (ARC). Suppression only occurs under binocular viewing conditions and concerns the central part of the visual field of the strabismic eye. Suppression is associated with a decrease of binocular functions in the central part of the visual field. ARC can be described as a form of internal squint that corrects for the image disparity due to external squint. It is the defence mechanism against diplopia in the more peripheral visual field. There is evidence however that this shift in retinal localisation does not affect the visual field equally. It seems that ARC is more outspoken in the periphery than in the centre of the visual field. This might be expl

  • Facilitation of vertical vergence by horizontal saccades, found in a patient with dissociated vertical deviation.
    'Informa UK Limited', 1994
    Co-Authors: Simonsz H.j., Dijk, L.j. Van
    Abstract:

    Abstract The authors examined vertical vergence in a Is-year-old girl with dissociated vertical deviation, a 60 Convergent Strabismus, no binocular vision, latent nystagmus, and a minimal left amblyopia. Eye movements were recorded during 4s-periods of (1) both eyes open, alternated with 4speriods of (2a) right eye covered, (2b) left eye covered or (2C) both eyes closed. The patient preferred fixation with the right eye; when this eye was covered, the left eye took over fixation with an almost completely monocular, downward saccade (a horizontal saccade occurred at the same time). The right eye only made a very small saccade, and then started to drift upward with an exponentially decreasing velocity. Enright has shown that fast convergence or divergence may occur when a horizontal saccade is performed at the same time. Similarly, the authors suspected that, in their patient, vertical vergence was facilitated by the horizontal saccade that resulted, in this case of horizontal Strabismus, from alternation of fixation. To examine whether this was the case, they compensated for the horizontal Strabismus by placing a 30 prism-dioptre base-out prism in front of the left eye (the patient had no binocular vision). With the prism in place, the horizontal saccade that occurred when the right eye was covered was smaller, and only little vertical vergence occurred together with the horizontal saccade. It seems possible that vertical vergence is also facilitated by horizontal saccades

Simonsz Huib - One of the best experts on this subject based on the ideXlab platform.

  • The early vs late infantile Strabismus surgery study: do sources for bias exist in this non-randomised trial
    1998
    Co-Authors: Meyer Kristina, Breitschwerdt Heike, Kolling Gerold, Simonsz Huib
    Abstract:

    textabstractAbstract Background—The Early vs Late Infantile Strabismus Surgery Study Group investigates whether early or late surgery is preferable in infantile Convergent Strabismus, in a non-randomised, prospective, multicentre clinical trial. The current state of the study after end of recruitment is reported here, focusing on the question of possible sources for bias in this nonrandomised trial. Method—The prognostic factors were analysed at baseline in order to check for imbalances between the two treatment groups. Reasons for possible differences are discussed. Results—There is no evidence for clinically relevant inhomogeneities between the two groups concerning the distribution of the three prognostic factors spherical equivalent, degree of amblyopia, and limitation of abduction. The fourth prognostic factor, horizontal angle of squint, differs significantly between the two groups. Conclusion—In the analysis of the final results we may have to account for differences in angle of squint at baseline by its inclusion as a covariate or by stratification

  • Quantitative perimetry under binocular viewing conditions in microStrabismus
    'Elsevier BV', 1997
    Co-Authors: Joosse Maurits, Simonsz Huib, Minderhout H.m., Jong Paulus, Noordzij Bastiaantje, Mulder Paul
    Abstract:

    textabstractIn order to elucidate the type, size and depth of suppression scotomata in microStrabismus and small angle Convergent Strabismus, we performed binocular static perimetry in 14 subjects with Strabismus and four normal observers. The strabismic cases had an objective angle of Convergent squint between 1 and 8 deg, visual acuity between 0.1 and 1.25, and limited stereopsis. During testing the subjects fused pictures on two Friedmann visual field analyzers. Right and left eyes were studied separately under both monocular and binocular viewing conditions. In five strabismics a suppression scotoma was found in the squinting eye, with a diameter of 5-30 deg and a depth ranging from 4 to 14 dB. No suppression scotomata could be detected in the nine other subjects nor in the four normal observers. In conclusion, only 36% of subjects with Strabismus were found to have a suppression scotoma. These scotomata were centered around the fixation point of the squinting eye, in some cases also encompassing the foveal area, and varying in depth and size

  • Quantitative visual field assessment of squinting eye under binocular conditions in ten patients with microStrabismus. Preliminary report.
    1994
    Co-Authors: Joosse Maurits, Simonsz Huib, Minderhout H.m., Jong Paulus
    Abstract:

    textabstractIntroduction: It is still not exactly known how strabismic patients perceive the surrounding world. It is commonly believed that patients with early onset Convergent Strabismus and microStrabismus do not suffer from diplopia because of two mechanisms: suppression and anomalous retinal correspondence (ARC). Suppression only occurs under binocular viewing conditions and concerns the central part of the visual field of the strabismic eye. Suppression is associated with a decrease of binocular functions in the central part of the visual field. ARC can be described as a form of internal squint that corrects for the image disparity due to external squint. It is the defence mechanism against diplopia in the more peripheral visual field. There is evidence however that this shift in retinal localisation does not affect the visual field equally. It seems that ARC is more outspoken in the periphery than in the centre of the visual field. This might be explained by the fact that in early childhood the receptive fields are larger in the periphery than in the centre and that during constriction of the receptive fields in the period of early development, suppression is first needed in the centre of the visual field, permitting ARC to develop in the retinal periphery. ..

  • Facilitation of vertical vergence by horizontal saccades, found in a patient with dissociated vertical deviation.
    1994
    Co-Authors: Simonsz Huib, Dijk Laurens
    Abstract:

    textabstractAbstract The authors examined vertical vergence in a Is-year-old girl with dissociated vertical deviation, a 60 Convergent Strabismus, no binocular vision, latent nystagmus, and a minimal left amblyopia. Eye movements were recorded during 4s-periods of (1) both eyes open, alternated with 4speriods of (2a) right eye covered, (2b) left eye covered or (2C) both eyes closed. The patient preferred fixation with the right eye; when this eye was covered, the left eye took over fixation with an almost completely monocular, downward saccade (a horizontal saccade occurred at the same time). The right eye only made a very small saccade, and then started to drift upward with an exponentially decreasing velocity. Enright has shown that fast convergence or divergence may occur when a horizontal saccade is performed at the same time. Similarly, the authors suspected that, in their patient, vertical vergence was facilitated by the horizontal saccade that resulted, in this case of horizontal Strabismus, from alternation of fixation. To examine whether this was the case, they compensated for the horizontal Strabismus by placing a 30 prism-dioptre base-out prism in front of the left eye (the patient had no binocular vision). With the prism in place, the horizontal saccade that occurred when the right eye was covered was smaller, and only little vertical vergence occurred together with the horizontal saccade. It seems possible that vertical vergence is also facilitated by horizontal saccades

Ottmar Distl - One of the best experts on this subject based on the ideXlab platform.

  • PLXNC1 and RDH13 associated with bilateral Convergent Strabismus with exophthalmus in German Brown cattle
    2016
    Co-Authors: Steffen Fink, Stefanie Mömke, Ottmar Distl
    Abstract:

    Purpose: We performed an association study for bilateral Convergent Strabismus with exophthalmus (BCSE) in German Brown cattle using single nucleotide polymorphisms (SNPs) located within six positional candidate genes and additional SNPs from bovine SNP databases surrounding these candidate genes. Mutation analyses included synaptotagmin 3 and 5 (SYT3, SYT5), carnitine palmitoyl-transferase 1C (CPT1C) on bovine chromosome 18 (BTA18), and plexin C1 (PLXNC1), intracellular suppressor of cytokine signaling-2 (SOCS2), and kinesin family member 21A (KIF21A) on BTA5. Methods: For all six candidate genes, we performed cDNA analyses using eye tissues of three BCSE-affected and three unaffected controls and searched the sequences for polymorphisms. Furthermore, we screened a total of 213 SNPs on BTA5 and 136 SNPs on BTA18 from the bovine SNP databases in 29 BCSE-affected German Brown cattle and 23 breed and sex matched controls for association with BCSE. All SNPs detected within the open reading frame (ORF) of the candidate genes and all SNPs from bovine databases putatively associated with BCSE in the detection sample were genotyped in a random sample of 179 BCSE-affected German Brown cows and 161 breed and sex matched controls and tested for association with BCSE. Results: In total, we detected five novel SNPs within the coding sequence of the candidate genes PLXNC1 and KIF21A. The association analyses for single SNPs and haplotypes in 340 German Brown cattle revealed significant associations for five SNPs with BCSE. Four of these five SNPs were located within PLXNC1 and RDH13 and one SN

  • INAUGURAL-DISSERTATION zur Erlangung des Grades eines
    2014
    Co-Authors: Tierärztliche Hochschule Hannover, Doktors Der Veterinärmedizin, Steffen Martin Fink, Ottmar Distl
    Abstract:

    Molecular genetic analysis of bilateral Convergent Strabismus with exophthalmus in German Brown cattl

  • © 2008 Molecular Vision Genes on bovine chromosome 18 associated with bilateral Convergent Strabismus with exophthalmos in German Brown cattle
    2013
    Co-Authors: Steffen Fink, Stefanie Mömke, A. Wöhlke, Ottmar Distl
    Abstract:

    Purpose: Bilateral Convergent Strabismus with exophthalmos (BCSE) is a widespread inherited eye defect in several cattle populations. Its progressive condition often leads to blindness in affected cattle and shortens their length of productive life. Furthermore, breeding with BCSE-affected animals is forbidden by the German animal welfare laws. We performed a mutation and association analysis for three candidate genes (troponin T type 1 [TNNT1], retinol dehydrogenase 13 [RDH13], and TCF3 fusion partner [TFPT]), which are located within the previously identified BCSE-linked region on the telomeric end of bovine chromosome 18 (BTA18). In addition, we developed single nucleotide polymorphisms (SNPs) within these three candidate genes and nine other genes that are contained in this genomic BCSE-region to perform association analyses with BCSE in German Brown cattle. Methods: We performed cDNA analyses of all three candidate genes using eye tissues of three affected German Brown cows and three unaffected controls. Furthermore, we screened the exonic and the adjacent genomic sequences of RDH13, TNNT1, and TFPT using four BCSE-affected and four controls of German Brown cattle. Here, we included all exons of RDH13 and those exons of TNNT1 and TFPT for which SNPs were detected by cDNA analyses. In addition, we developed 21 polymerase chain reaction (PCR) products for 17 more genes in the BCSE region and searched them for polymorphisms. All markers detected were genotyped in 48 BCSE-affected German Brown cows and 48 breed and sex matched controls and tested for association with BCSE