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PubMed1998

Extensive divergence and convergence in the thalamocortical projection to monkey somatosensory cortex.

This study examined the extent of thalamocortical divergence as a potential determinant of activity-dependent representational plasticity in area 3b of adult monkey somatosensory cortex. Single or paired injections of anterogradely transported tracers, of varying anteroposterior extent, were made horizontally from behind in defined parts of the body representation in the ventral posterior lateral (VPL) and/or ventral posterior medial (VPM) thalamic nuclei, and the distribution and density of labeled thalamocortical terminations were mapped in cortex. Injections of increasing size in any dimension of VPL or VPM resulted in increasing accumulation of labeled terminals within the region of projection, implying extensive convergence of individual axons. Anteroposteriorly elongated injections labeled mediolaterally extended but anteroposteriorly restricted zones in cortex. Dorsoventral placement of an injection in VPL or VPM determined anteroposterior location of labeling in cortex. Dual injections separated mediolaterally or dorsoventrally by approximately 1 mm, and in different parts of the thalamic body or head-face representation gave rise to labeled thalamocortical terminations that overlapped extensively. For injection sites at different anteroposterior levels in VPL or VPM, the area of cortical convergence was related to their extent of anteroposterior coincidence. Labeled terminations arising from injections in immediately adjacent parts of VPL and VPM did not overlap in cortex. The extent of thalamocortical divergence and convergence revealed by these experiments is greater than that predictable from labeling of single axons and is sufficiently great to account for representational plasticity that exceeds the 1.5 mm cortical "distance limit."

Animals↗

PubMed1998

Olfactory identification and Stroop interference converge in schizophrenia.

OBJECTIVE: To test the discriminant validity of a model predicting a dissociation between measures of right and left frontal lobe function in people with schizophrenia. PARTICIPANTS: Twenty-one clinically stable outpatients with schizophrenia. INTERVENTIONS: Patients were administered the University of Pennsylvania Smell Identification Test (UPSIT), the Stroop Color-Word Test (Stroop), and the Positive and Negative Syndrome Scale (PANSS). OUTCOME MEASURES: Scores on these tests and relation among scores. RESULTS: There was a convergence of UPSII and Stroop interference scores consistent with a common cerebral basis for limitations in olfactory identification and inhibition of distraction. There was also a divergence of UPSIT and Stroop reading scores suggesting that the olfactory identification limitation is distinct from a general limitation of attention or a dysfunction of the left dorsolateral prefrontal cortex. Most notable was the 81% classification convergence between the UPSIT and Stroop incongruous colour naming scores compared with the near-random 57% classification convergence of the UPSIT and Stroop reading scores. CONCLUSIONS: These data are consistent with a right orbitofrontal dysfunction in a subgroup of patients with schizophrenia, although the involvement of mesial temporal structures in both tasks must be ruled out with further study. A multifactorial model depicting contributions from diverse cerebral structures is required to describe the pathophysiology of schizophrenia. Valid behavioural methods for classifying suspected subgroups of patients with particular cerebral dysfunction would be of value in the construction of this model.

Adult↗

PubMed1976

[Convergent strabismus in the age of presbyopia (author's transl)].

Based on 15 case reports it can be shown, that the onset of a convergent squint is even possible in the age of presbyopia, independent of the patient's refraction. The clinical picture resembles that of a divergence paralysis or the convergent strabismus of the Bielschowsky type. In 13 cases the decompensation of a previous esophoria may have caused this distance-esodeviation; a divergence paralysis is not probable. In two cases change of orthophoria to esotropia could be observed. Therefore we share the opinion of v. Graefe, that an increased tonicity of the internal recti induced for compensation of weak convergence in aged individuals may cause esotropia. Treatment with prisms for distant vision is easy and effective. No case required surgery.

Aged↗

PubMed2003

Validity and reliability of the revised convergence insufficiency symptom survey in children aged 9 to 18 years.

PURPOSE: To assess the validity and reliability of the Convergence Insufficiency Symptom Survey (CISS) in children aged 9 to 18 years. The CISS is the primary outcome measure for a pilot study evaluating two different treatments for convergence insufficiency (CI). METHODS: Children with CI were given the CISS twice to assess reliability. CISS scores for the first administration were also compared with scores from children with normal binocular vision to assess the validity of the CISS. RESULTS: Forty-seven children with CI and 56 children with normal binocular vision participated in the study. Reliability was assessed using intraclass correlation and 95% limits of agreement for the children with CI. For children with CI, the intraclass correlation was 0.77 (95% confidence interval, 0.613 to 0.873), and the 95% limits of agreement were -10.2 to +12.1. The mean (+/-SD) CISS score was 30.8 +/- 8.4 for the children with CI and 8.4 +/- 6.4 for the children with normal binocular vision. These means were significantly different (p < 0.0001). Good discrimination (sensitivity, 96%; specificity, 88%) was obtained using a score of >/=16. CONCLUSIONS: Children with CI showed a significantly higher CISS symptom score than children with normal binocular vision. The results of the study indicate that the CISS is a valid and reliable instrument to use as an outcome measure for children aged 9 to 18 who are enrolled in clinical research concerning CI.

Adolescent↗

PubMed2004

Validity and reliability of the revised convergence insufficiency symptom survey in adults.

PURPOSE: To assess the validity and reliability of the revised Convergence Insufficiency Symptom Survey (CISS) in adults aged 19-30 years. The CISS was developed to be the primary outcome measure for studies evaluating various treatments for convergence insufficiency (CI). METHODS: CISS mean scores from adults with symptomatic CI and adults with normal binocular vision (NBV) were compared to assess the survey's validity. Adults with symptomatic CI were given the CISS twice to evaluate reliability, which was assessed using intraclass correlation coefficient (ICC) and 95% limits of agreement. RESULTS: Forty-six adults with CI and 46 adults with NBV participated in the study. The mean CISS score for the CI group was 37.3 (S.D. = 9.3) and 11.0 (S.D. = 8.2) for the NBV group. These mean values were significantly different (p < 0.0001). Good discrimination (sensitivity = 97.8%, specificity = 87%) was obtained using a score of 21 or higher. For the CI group the ICC was 0.885 (95% CI of 0.798, 0.936) and the 95% limits of agreement were -9.0 to 7.6. CONCLUSIONS: Adults with symptomatic CI had a significantly higher CISS score than adults with NBV. The results of the study demonstrate that the CISS is a valid and reliable instrument that can be used clinically or as an outcome measure for research studies of adults with CI.

Accommodation, Ocular↗

PubMed1987

Treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio.

We conducted a prospective, randomized, masked comparison of two treatments for the nonaccommodative element in esotropic patients with a high accommodative convergence-accommodation ratio. One group received symmetric medial rectus recessions with posterior fixation sutures; the other received symmetric medial rectus recessions without posterior fixation sutures but augmented according to formula taking into account the near deviation. Previous experience had suggested that our surgical formula based solely on the distance deviation would lead to excessive undercorrections. A higher percentage of the augmented recession group achieved satisfactory alignment and were able to discontinue wearing bifocals postoperatively than the posterior fixation group. The data also showed a trend (though not statistically significant) suggesting that more members of the augmented recession group were able to discontinue wearing spectacles entirely. We concluded that the posterior fixation suture technique is not as effective as the augmented recession technique for the treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio.

Accommodation, Ocular↗

PubMed2006

Xenopus fibrillin regulates directed convergence and extension.

Fibrillin-based human diseases such as Marfan syndrome and congenital contractural arachnodactyly implicate fibrillins in the function and homeostasis of multiple adult tissues. Fibrillins are also expressed in embryos, but no early developmental role has been described for these proteins. We use three independent methods to reveal a role for Xenopus fibrillin (XF) at gastrulation. First, expressing truncated forms of XF in the embryo leads to failure of gastrulation concomitant with a dominant-negative effect on native fibrillin fibril assembly. Expressing truncated XF also inhibits normal progression of the patterned, polarized cell motility that drives convergence and extension at gastrulation and perturbs directed extension in cultured explants of dorsal mesoderm. Second, injection of a synthetic peptide encoding a cell-binding domain of XF into midgastrula embryos causes acute failure of gastrulation associated with defective fibrillin fibril assembly. These injections also reveal a critical role for this peptide in the fibril assembly process. Third, morpholino-mediated knockdown of translation of XF in the embryo also perturbs normal gastrulation and directed extension. Together, these data show that native Xenopus fibrillin is essential for the process of directed convergent extension in presumptive notochord at gastrulation.

Amino Acid Sequence↗

PubMed2002

Accommodation and convergence palsy caused by lesions in the bilateral rostral superior colliculus.

PURPOSE: To report a patient who developed accommodation and convergence palsy caused by lesions in the bilateral rostral superior colliculus. DESIGN: Observational case report. METHODS: A 30-year-old right-handed man experienced sudden onset of diplopia and blurred vision at near vision. RESULTS: The patient showed accommodation and convergence palsy. Magnetic resonance imaging revealed lesions located in the bilateral rostral superior colliculus. CONCLUSION: These findings suggest that the rostral superior colliculus is involved in the control of accommodation and vergence eye movements.

Accommodation, Ocular↗

PubMed1995

Convergence insufficiency secondary to subdural hematoma.

PURPOSE/METHODS: Symptomatic convergence insufficiency developed in a 56-year-old man after he sustained head trauma and developed subdural hematoma. RESULTS/CONCLUSION: All symptoms resolved after surgical evacuation of the subdural hematoma. Convergence insufficiency developing after head trauma could be the result of a subdural hematoma.

Brain Injuries↗

PubMed1988

Accommodation and convergence insufficiency with left middle cerebral artery occlusion.

We studied accommodation and vergence eye movements in a patient with a left middle cerebral artery embolism. Accommodation was monitored by an infrared optometer with the accommodative target being controlled by a microcomputer. Computed tomography showed low-density areas in the left cortex, with intact brainstem. The patient had convergence palsy and accommodation abnormalities. The amplitude of the accommodative responses was reduced and the accommodation velocity was markedly lowered. Our results further substantiate the neurologic relationship between the cerebral cortex and accommodation and convergence.

Accommodation, Ocular↗

PubMed1998

Judging distance from ocular convergence.

Subjects misjudge distances considerably when forced to rely on extra-retinal information. Nevertheless, they can reproducibly set a target to the same distance as a reference, or to double or half that distance, even when they have to look back and forth between them because they are prevented from seeing one when looking at the other. Our explanation for this apparent discrepancy is that people have access to reasonably accurate extra-retinal information on changes in ocular convergence, but can only use this information to judge distances if they had reliable information about the orientation of the eyes before the convergence changed.

Convergence, Ocular↗

PubMed2005

The long-term result of slanted medial rectus resection in exotropia of the convergence insufficiency type.

PURPOSE: To evaluate the long-term results of slanted medial rectus (MR) resection for intermittent exotropia (X(T)) of the convergence insufficiency type. METHODS: In all, 10 patients with an X(T) greater at near than at distance by 10 prism diopters (PD) or more were included in this prospective study. Patients received slanted bilateral MR resection. The upper edge of the MR was resected according to the distance exodeviation and the lower edge of the MR was resected according to near exodeviation. The postoperative follow-up period was between 6 and 62 months with a mean of 38.9 months. The paired t-test was used to compare: mean distance angle of deviation preoperatively and postoperatively; mean near angle of deviation preoperatively and postoperatively; and mean near-distance exodeviation difference preoperatively and postoperatively. RESULTS: Bilateral slanted MR resections reduced mean exodeviation at distance from 23.0+/-7.2 to 16.3+/-5.4 PD (P=0.03); mean exodeviation at near from 34.3+/-7.7 to 24.6+/-6.9 PD (P=0.01); and mean near-distance difference from 11.4+/-2.6 to 8.3+/-3.5 PD (P=0.04). At the final follow-up examination, all patients demonstrated an exodeviation of 10 PD or more at distance and near, and the exodeviation difference between distance and near deviation was within 10 PD in five of the 10 patients. Three patients had an esodeviation at distance after surgery, but all resolved within 4 weeks. CONCLUSIONS: Bilateral slanted MR resections in patients with X(T) of the convergence insufficiency type resulted in undercorrection in all patients.

Adolescent↗

PubMed2003

[Asthenopic complaints and ocular convergence at the computer workstation: new test procedures for practice and research].

BACKGROUND: The present paper summarizes a series of ergonomic studies on the relation between asthenopic complaints and binocular vision at the computer workstation. In particular, the paper reports on measurements of the accuracy of ocular convergence during fixation of central fusion stimuli (i. e. fixation disparity) as a function of viewing distance. METHODS: Different versions of subjective tests for fixation disparity (using dichoptic nonius lines) are presented, including a computer-controlled procedure (the eye-test PC). RESULTS: These new tests suggest that non-presbyopic subjects with normal binocular vision may suffer from asthenopic complaints if they have - in near vision - an exo fixation disparity larger than average. CONCLUSION: In these cases, the stress exercised on the convergence system can be reduced by using a longer viewing distance at the workplace.

Accommodation, Ocular↗

PubMed1992

[Congenital nystagmus and intermittent exotropia. Suppression of nystagmus by fusional convergence].

We report on a patient with a combination of congenital nystagmus and intermittent exotropia. When the exotropia became manifest, a gross nystagmus appeared. When, however, the exotropia was overcome by fusinal convergence, the nystagmus was largely suppressed. The angle of squint was surgically reduced by such an amount that the exodeviation was just compensated, and the fusional convergence required to overcome the remaining angle sufficed to suppress the nystagmus.

Convergence, Ocular↗

PubMed1994

Convergence as a cue for distance.

Binocular eye movements were measured in subjects experiencing the wallpaper illusion. It was found that a physical displacement of the fixation point by more than 1 m out of the plane of apparent localisation of the strips had no influence on the illusory location of these strips. Hence, illusory localisation in the wallpaper illusion is independent of the actual magnitude of the subject's convergence angle, once the illusion has come into existence. This result suggests that convergence does not serve as a source of information about apparent distance, at least in the wallpaper illusion.

Adult↗

PubMed2000

The optimal stimulus to elicit suppression in small-angle convergent strabismus.

PURPOSE: To determine the optimal stimulus duration as well as the most appropriate luminance profile to elicit suppression in small-angle convergent strabismus. METHODS: In 10 subjects with small-angle convergent strabismus, using a device allowing binocular viewing and peripheral fusion, we determined what the optimal stimulus would be to elicit suppression. Three control subjects were also included in the study. Stimuli were shown randomly in the central 3 degrees of the visual field of either eye. Stimulus durations were varied in seven steps from 50 to 1000 ms and three luminance-time profiles were used: square wave, triangle and half-sinus, thus yielding 21 different stimuli. The peak light intensity was the same for all stimuli. RESULTS: Suppression, defined as the difference in the threshold sensitivities under monocular vs. binocular viewing, was found with our test device in five of the ten subjects, and ranged between 3 and 33 dB. Suppression was deepest with triangular or half-sinusoidal stimuli of 400 ms duration. Square wave stimuli elicited the smallest amount of suppression. CONCLUSION: Stimuli with a gradual increment and decrement, like triangular or half-sinusoidal stimuli, with a duration of 400 ms are the most effective to elicit suppression

Adolescent↗

PubMed1985

Models of mutual interactions between accommodation and convergence.

Several possible models of interactions between accommodation and convergence are compared. Accommodative and fusional vergence effort are predicted for each model using the same set of clinical data. Only one model makes predictions that are consistent with clinical and laboratory observations of fixation disparity. The results support the clinical use of graphical analysis of mutual interactions between accommodation and convergence in the diagnosis of accommodative vergence disorders.

Accommodation, Ocular↗

PubMed1988

Characteristics of convergence insufficiency.

Convergence insufficiency (CI) is a well-known syndrome of binocular visual dysfunction. In a review of 58 papers, considerable variation was noted in the criteria used to define the condition. Symptoms and decreased positive fusional vergences (both at the nearpoint) were the only criteria named in more than one-half of the studies. An extended nearpoint of convergence (NPC) and increased exophoria at near were criteria in about one-third of the papers. Examination of data in the reviewed papers shows that although considerable variability was noted, the distance exodeviation, distance negative vergences, visual acuity, refraction, and stereopsis were about the same as population norms. Positive vergences, negative vergence at near, and NPC were somewhat less than population norms. Vergences relative to Sheard's criterion, the near exophoria, accommodative amplitude, and the AC/A ratio were consistently below those derived from population norms. This considerable variation may largely be a result of different criteria used for diagnosis, subpopulations within the data, and other confounding factors.

Accommodation, Ocular↗