Family study of inherited syndrome with multiple congenital deformities: symphalangism, carpal and tarsal fusion, brachydactyly, craniosynostosis, strabismus, hip osteochondritis.
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A syndrome of brachydactyly (absence of some middle or distal phalanges), aplastic or hypoplastic nails, symphalangism (ankylois of proximal interphalangeal joints), synostosis of some carpal and tarsal bones, craniosynostosis, and dysplastic hip joints is reported in five members of an Italian family. It may represent a previously undescribed autosomal dominant trait. (+info)
Risk factors for strabismus in children born before 32 weeks' gestation.
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AIM: To investigate risk factors associated with strabismus in children born prematurely. METHODS: Prospective study of all children born before 32 weeks' gestation between 1 January 1990 and 31 December 1991 in a geographically defined population of approximately 3 million in the Northern Region of the United Kingdom. All children were examined aged 2 years by the same ophthalmologist and paediatrician. RESULTS: 558 children (98.6% of study group) were examined. Logistic regression showed an increased risk of strabismus in children with cicatricial retinopathy of prematurity (p=0.02), refractive error (p=0.003), family history of strabismus (p<0.0001), and poor neurodevelopmental outcome (p<0.0001), in particular impaired locomotor skills (p=0.008) and hand-eye coordination (p=0. 001). Gestational age and regressed acute ROP were not independent risk factors for strabismus (p=0.92 and 0.85 respectively). CONCLUSIONS: This study has identified factors which are independently related to strabismus (although not necessarily causative) and others which are related only indirectly. This may contribute both to the management of children born prematurely and to future studies of the aetiology of strabismus. (+info)
A deficit in strabismic amblyopia for global shape detection.
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Using a task which relied upon the detection of sinusoidal deformations from circularity, we show that strabismic amblyopes exhibit deficits which are not critically dependent on either the scale of deformation or the spatial frequency characteristics of the stimulus (circular D4) itself. We show that this loss is not due to the restricted passband of the amblyopic eye. Furthermore, in a pedestal distortion experiment, we show that the suprathreshold form of this loss is consistent with an elevated level of 'intrinsic noise' rather than a loss in 'sampling efficiency'. (+info)
Orientation-based texture segmentation in strabismic amblyopia.
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Texture segmentation of 'target' Gabors from an array of 'background' Gabors was measured in terms of the difference in orientation between the two regions, as well as the difference in orientation within each region. Segmentation was shown to occur on the basis of local orientation differences at the boundary between the target and background regions (Nothdurft, H.C. (1992). Feature analysis and the role of similarity in preattentive vision. Perception and Psychophysics, 52, 355-375.). We obtained similar results for both the amblyopic and non-amblyopic eye of three strabismic amblyopes, and showed also that the effects of texture undersampling and positional jitter were similar for the two eyes. This pattern of results is consistent with intact mechanisms of texture perception in amblyopic cortex, and suggests also that any amblyopic deficits in first-order cortical units (undersampling and/or positional uncertainty) do not limit higher-order texture segmentation processes. Therefore, first- and second-order processes involved in perceptual grouping of oriented elements (that appear to be abnormal in amblyopic cortex; Kovacs, I., Polat, U., Norcia, A.M. (1996). Breakdown of binding mechanisms in amblyopia. Association for Research in Vision and Ophthalmology Abstracts; Mussap, A.J., Levi, D.M. (1995). Amblyopic deficits in perception of second-order orientation. Investigative Ophthalmology and Visual Science (Supplement), 36, S634; Mussap, A.J., Levi, D.M. (1998). Amblyopic deficits in perceptual grouping. Vision Research, submitted) do not contribute to texture perception based on orientation contrast. (+info)
Position jitter and undersampling in pattern perception.
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The present paper addresses whether topographical jitter or undersampling might limit pattern perception in foveal, peripheral and strabismic amblyopic vision. In the first experiment, we measured contrast thresholds for detecting and identifying the orientation (up, down, left, right) of E-like patterns comprised of Gabor samples. We found that detection and identification thresholds were both degraded in peripheral and amblyopic vision; however, the orientation identification/detection threshold ratio was approximately the same in foveal, peripheral and amblyopic vision. This result is somewhat surprising, because we anticipated that a high degree of uncalibrated topographical jitter in peripheral and amblyopic vision would have affected orientation identification to a greater extent than detection. In the second experiment, we investigated the tolerance of human and model observers to perturbation of the positions of the samples defining the pattern when its contrast was suprathreshold, by measuring a 'jitter threshold' (the amount of jitter required to reduce performance from near perfect to 62.5% correct). The results and modeling of our jitter experiments suggest that pattern identification is highly robust to positional jitter. The positional tolerance of foveal, peripheral and amblyopic vision is equal to about half the separation of the features and the close similarity between the three visual systems argues against extreme topographical jitter. The effects of jitter on human performance are consistent with the predictions of a 'template' model. In the third experiment we determined what fraction of the 17 Gabor samples are needed to reliably identify the orientation of the E-patterns by measuring a 'sample threshold' (the proportion of samples required for 62.5% correct performance). In foveal vision, human observers are highly efficient requiring only about half the samples for reliable pattern identification. Relative to an ideal observer model, humans perform this task with 85% efficiency. In contrast, in both peripheral vision and strabismic amblyopia more samples are required. The increased number of features required in peripheral vision and strabismic amblyopia suggests that in these visual systems, the stimulus is underrepresented at the stage of feature integration. (+info)
Assessment of cortical dysfunction in human strabismic amblyopia using magnetoencephalography (MEG).
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The aim of this study was to use the technique of magnetoencephalography (MEG) to determine the effects of strabismic amblyopia on the processing of spatial information within the occipital cortex of humans. We recorded evoked magnetic responses to the onset of a chromatic (red/green) sinusoidal grating of periodicity 0.5-4.0 c deg-1 using a 19-channel SQUID-based neuromagnetometer. Evoked responses were recorded monocularly on six amblyopes and six normally-sighted controls, the stimuli being positioned near the fovea in the lower right visual field of each observer. For comparison, the spatial contrast sensitivity function (CSF) for the detection of chromatic gratings was measured for one amblyope and one control using a two alternate forced-choice psychophysical procedure. We chose red/green sinusoids as our stimuli because they evoke strong magnetic responses from the occipital cortex in adult humans (Fylan, Holliday, Singh, Anderson & Harding. (1997). Neuroimage, 6, 47-57). Magnetic field strength was plotted as a function of stimulus spatial frequency for each eye of each subject. Interocular differences were only evident within the amblyopic group: for stimuli of 1-2 c deg-1, the evoked responses had significantly longer latencies and reduced amplitudes through the amblyopic eye (P < 0.05). Importantly, the extent of the deficit was uncorrelated with either Snellen acuity or contrast sensitivity. Localization of the evoked responses was performed using a single equivalent current dipole model. Source localizations, for both normal and amblyopic subjects, were consistent with neural activity at the occipital pole near the V1/V2 border. We conclude that MEG is sensitive to the deficit in cortical processing associated with human amblyopia, and can be used to make quantitative neurophysiological measurements. The nature of the cortical deficit is discussed. (+info)
The puzzle of autism: an ophthalmologic contribution.
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PURPOSE: A previous study of 86 thalidomide-affected subjects with ophthalmic manifestations revealed the unexpected finding of autism in 4 of the 5 severely retarded individuals. The subjects had anomalies associated with an early gestational effect of thalidomide, including facial nerve palsy and incomitant strabismus. Because autism has been observed in a few cases of Mobius sequence (Mobius syndrome), a condition characterized by involvement of the sixth and seventh cranial nerves, the similarity to early thalidomide embryopathy suggested a relation between cranial nerve involvement and autism. The present study was undertaken to further evaluate the association of autism with patients manifesting findings of Mobius syndrome. METHODS: A prospective study of 25 Swedish patients with Mobius sequence was conducted. The patients had a complete multidisciplinary evaluation, including ophthalmologic and psychiatric examinations and standard testing for autism. Findings associated with autism were compared with the ocular and systemic anomalies of the 4 thalidomide-affected subjects. RESULTS: In the Mobius group 6 patients had autism, achieving the criteria for autism according to all the diagnostic manuals that were used. One patient showed autistic-like conditions meeting fewer numbers of the criteria. A few were too young to be meeting evaluated. Incomitant strabismus ranging from primary abduction defects alone to a horizontal gaze paresis pattern was noted in these patients, in addition to characteristic findings of seventh nerve paresis. Aberrant lacrimation was observed in many cases, especially often associated with autism. CONCLUSION: The common group of anomalies noted in both cases of thalidomide embryopathy and Mobius sequence suggests that brain-stem damage probably early in embryogenesis can sometimes be associated with autism. (+info)
The therapy of amblyopia: an analysis of the results of amblyopia therapy utilizing the pooled data of published studies.
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CONTEXT: Although the treatment of amblyopia with occlusion has changed little over the past 3 centuries, there is little agreement about which regimes are most effective and for what reasons. OBJECTIVE: To determine the outcome of occlusion therapy in patients with anisometropic, strabismic, and strabismic-anisometropic amblyopia employing the raw data from 961 patients reported in 23 studies published between 1965 and 1994. DESIGN: Analysis of the published literature on amblyopia therapy results during the above interval, utilizing primary data obtained from the authors of these articles or tables published in the articles detailing individual patient outcomes. PARTICIPANTS: 961 amblyopic patients, participants in 23 studies, undergoing patching therapy for amblyopia from 1965 to 1994 with anisometropia, strabismus, or anisometropia-strabismus. MAIN OUTCOMES: In the pooled data set, success of occlusion therapy was defined as visual acuity of 20/40 at the end of treatment. RESULTS: Success by the 20/40 criteria was achieved in 512 of 689 (74.3%) patients. By category, 312 of 402 (77.6%) were successful in strabismic amblyopia, 44 of 75 (58.7%) in strabismic-anisometropic amblyopia, and 72 of 108 (66.7%) in anisometropic amblyopia. Success was not related to the duration of occlusion therapy, type of occlusion used, accompanying refractive error, patient's sex, or eye. Univariate analyses showed that success was related to the age at which therapy was initiated; the type of amblyopia; the depth of visual loss before treatment for the anisometropic patients and the strabismic patients, but not for the anisometropic-strabismic patients; and the difference in spherical equivalents between eyes, for the anisometropic patients. Logistic/linear regression revealed that 3 were independent predictors of a successful outcome of amblyopia therapy. CONCLUSIONS: Factors that appear most closely related to a successful outcome are age, type of amblyopia, and depth of visual loss before treatment. These may be related to factors, as yet undetermined in the pathogenesis of amblyopia. With present emphasis on the value of screening and prevention and the development of new screening tools, such a look at the results of amblyopia therapy in a large population seems indicated. (+info)