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PubMed1983

Prevalence of increased intraocular pressure in Graves' disease--evidence of frequent subclinical ophthalmopathy.

Graves' exophthalmos is frequently associated with elevated intraocular pressure on upgaze. Eighty patients with Graves' disease were evaluated prospectively by applanation tonometry to assess the prevalence of ophthalmopathy in this disorder. Whereas 21 (26 per cent) of the 80 patients had exophthalmos, 61 (76 per cent) had abnormal intraocular pressure (delta greater than or equal to 3 mm Hg). All patients with exophthalmos had elevated intraocular pressure on upgaze; 40 (68 per cent) of 59 patients without proptosis had abnormal pressure readings. The mean interval between the onset of Graves' disease and this study was 6.3 +/- 1.0 years (S.E.M.) for those patients who had exaggerated positional changes in intraocular pressure, as compared with 3.0 +/- 1.0 years for those with normal intraocular pressure (P less than 0.005). All but 1 of 15 patients in whom the diagnosis of Graves' disease had been documented 10 or more years earlier had increased intraocular pressure on upgaze. We conclude that Graves' ophthalmopathy is more common than is recognized clinically and that eye involvement is an inevitable complication of the disease.

Adult↗
PubMed2001

Forming classes by stimulus frequency: behavior and theory.

Visual classification is the way we relate to different images in our environment as if they were the same, while relating differently to other collections of stimuli (e.g., human vs. animal faces). It is still not clear, however, how the brain forms such classes, especially when introduced with new or changing environments. To isolate a perception-based mechanism underlying class representation, we studied unsupervised classification of an incoming stream of simple images. Classification patterns were clearly affected by stimulus frequency distribution, although subjects were unaware of this distribution. There was a common bias to locate class centers near the most frequent stimuli and their boundaries near the least frequent stimuli. Responses were also faster for more frequent stimuli. Using a minimal, biologically based neural-network model, we demonstrate that a simple, self-organizing representation mechanism based on overlapping tuning curves and slow Hebbian learning suffices to ensure classification. Combined behavioral and theoretical results predict large tuning overlap, implicating posterior infero-temporal cortex as a possible site of classification.

Adult↗
PubMed1999

Stereotactic intracavitary therapy of recurrent cystic craniopharyngioma by instillation of 90yttrium.

Six consecutively presenting patients with craniopharyngiomas, (F:M = 4.2; mean age: 35.2 years, range 17-58) histologically proven by one or more previous operations, and with recurrence of a wholly or predominantly cystic nature, were treated by 90yttrium (90Y) radioisotope instillation into the cyst. Five patients had undergone external beam radiotherapy and the remaining patient had concomitant stereotactic radiosurgery to a co-existing solid component. Seven cysts in six patients have been treated. Five cysts, previously requiring repeated aspiration at intervals of 2-20 weeks have required no further surgical intervention following 90Y treatment (FU mean 3.5 years, range 1.2-7), although two of these required a second 90Y treatment. No patient developed a visual field defect or evidence of hypothalamic dysfunction. One patient died within a month of treatment from complications related to a solid recurrence. One patient developed a large solid/cystic recurrence at 4 months and died shortly thereafter from an unrelated cause. We summarize results from other series that have demonstrated the efficacy of this technique, usually as primary therapy, but this is the first series to demonstrate its usefulness as salvage therapy. The prospect of survival with good quality of life can be offered to patients with multiply recurrent disease who have exhausted all conventional means of treatment. In our experience intracavitary 90Y is a safe and highly effective means of controlling cystic recurrence in refractory craniopharyngioma. Some patients require more than one treatment.

Adult↗
PubMed2003

Long-term sequelae in children treated for brain tumors: impairments, disability, and handicap.

Sixty-one long-term survivors, treated for brain tumors in childhood, were evaluated in term of neurological impairments, disability, and handicap. Thirty-eight patients (pts) (62%) had at least one impairment. Visual impairment was detected in 14 pts (24%), associated with recurrence (p = .012). Thirty-four patients (56%) had motor impairment, associated with sex (female) in irradiated patients; 13 (21%) had epilepsy, associated with supratentorial tumor site (p = .001). The same number of patients had brain atrophy; risk factors were hydrocephalus at diagnosis and perioperative complications. Sixteen patients (30%) had IQ score < 80, associated with young age at first treatment (p = .006) and recurrence (p = .043). Twenty-seven out of 61 of our patients (44%) were disabled: 12 mildly, 14 moderately, and 1 severely. Epilepsy was the most important risk factor for disability. Cognitive impairment, motor impairment, and epilepsy were associated with employment (43%); cognitive impairment was also associated with education.

Adolescent↗
PubMed1986

Late cortical cerebellar atrophy. Clinical and oculographic features.

Ten patients with late cortical cerebellar atrophy documented with computerized tomography (CT) and magnetic resonance (MR) imaging presented a uniform pattern of oculomotor abnormalities. All had deficits in smooth pursuit and fixation suppression of the vestibulo-ocular reflex (VOR). The gain of the VOR was often increased but the dynamics of the VOR were not different from normals. Full-field optokinetic responses and visual-vestibular interaction mediated via the VOR velocity storage element were preserved. Just as in lower primates, the cerebellum in humans is a critical relay station for foveal pursuit and visual-vestibular interaction requiring foveal pursuit. Vestibular responses and visual-vestibular interaction mediated through the VOR velocity storage element are relatively independent of the cerebellum.

Adult↗
PubMed1995

Fractures of the floor of the anterior cranial fossa.

We treated 28 patients with anterior cranial fossa floor fractures. Computed tomography (CT) scans adjusted to bone density disclosed three fracture types: (1) penetrating fractures through the orbita or ethmoid sinus; (2) simple or multiple linear fractures; and (3) extensive comminuted anterior cranial fossa floor fractures. Thirteen patients underwent emergent surgery for treatment of open depressed fractures (most common in type 3 fractures), for foreign bodies (in type 1 fractures), and for optic canal decompression. Large dural lacerations were always present in patients with type 3 fractures, and repairs were made with dural substitutes. Only one patient developed postoperative cerebrospinal fluid leakage. Nine (32%) of the patients in our series had visual involvement, but visual acuity recovered or improved in six patients. Our study shows that initial neuroradiologic evaluation with CT scans is important in patients with frontobasal fractures, and that secure dural repair during primary operation helps prevent cerebrospinal fluid leakage.

Adolescent↗
PubMed2002

Fourth ventricle central neurocytoma: case report.

OBJECTIVE AND IMPORTANCE: Central neurocytomas (CNs) are typically located in the lateral ventricle. Primary origins in the fourth ventricle are very rare. We discuss the clinical symptoms, imaging findings, and microscopic features of these rare tumors. CLINICAL PRESENTATION: We report a case of a fourth ventricle CN in a 35-year-old male patient with the initial symptoms of progressive headaches and blurred vision for more than 2 months. Computed tomography and magnetic resonance imaging of the brain revealed a slightly enhanced tumor in the fourth ventricle, with obstructive hydrocephalus. INTERVENTION: Total surgical removal of the tumor was performed. The tumor was initially diagnosed as an oligodendroglioma. The final definitive diagnosis as a CN was made after special immunohistochemical studies. CONCLUSION: CNs located in the fourth ventricle are extremely rare. Immunohistochemical stains and transmission electron microscopy can provide useful diagnostic information. Total tumor excision is associated with favorable prognoses. Postoperative radiotherapy may be considered for cases of subtotal excision, anaplastic histological variants, or recurrent tumors.

Cerebral Ventricle Neoplasms↗
PubMedDate not supplied

High-quality extraction of isosurfaces from regular and irregular grids.

Isosurfaces are ubiquitous in many fields, including visualization, graphics, and vision. They are often the main computational component of important processing pipelines (e.g. , surface reconstruction), and are heavily used in practice. The classical approach to compute isosurfaces is to apply the Marching Cubes algorithm, which although robust and simple to implement, generates surfaces that require additional processing steps to improve triangle quality and mesh size. An important issue is that in some cases, the surfaces generated by Marching Cubes are irreparably damaged, and important details are lost which can not be recovered by subsequent processing. The main motivation of this work is to develop a technique capable of constructing high-quality and high-fidelity isosurfaces. We propose a new advancing front technique that is capable of creating high-quality isosurfaces from regular and irregular volumetric datasets. Our work extends the guidance field framework of Schreiner et al. to implicit surfaces, and improves it in significant ways. In particular, we describe a set of sampling conditions that guarantee that surface features will be captured by the algorithm. We also describe an efficient technique to compute a minimal guidance field, which greatly improves performance. Our experimental results show that our technique can generate high-quality meshes from complex datasets.

Algorithms↗
PubMed1993

Computer hardware and software to assist the visually impaired and blind.

Modern developments in computer hardware and software for the business world have been adapted to allow the partially sighted and blind to participate successfully in computer usage in education, employment and recreation. Adaptations such as the enlargement of the whole screen display, production of enlarged print and voice output of screen contents can assist the partially sighted. Conversion of computer screen information into speech or braille can be used in conjunction with sound boards and touch pads to allow the totally blind access to the exact spatial layout of screen contents. Optical character recognition devices whereby the printed page can be accessed by computer, and recent voice recognition techniques which allow a computer to interpret voiced commands, can also be used to assist the totally blind. Developments in these areas are discussed together with specific examples of equipment now available which make use of the various methods described.

Blindness↗
PubMed2006

Comparison of logMAR ETDRS chart and a new computerised staircased procedure for assessment of the visual acuity of children.

The validity and repeatability of visual acuity measures are particularly important in the detection and monitoring of childhood visual anomalies such as amblyopia. The repeatability and sensitivity of a new computerised visual acuity test, 'Staircased Procedure' is compared with the now gold standard visual acuity test, the early treatment of diabetic retinopathy study (ETDRS). Twenty-seven visually normal children (mean age: 6.7 +/- 1.1 years) and 27 children with amblyopia (mean age: 6.1 +/- 0.7 years) were tested with the ETDRS and Staircased Procedure. A retest was administered 4-5 weeks later and 30 min later for the visually normal and the amblyopic children, respectively. The staircased procedure produced significantly better visual acuity than the ETDRS for visually normal and amblyopic children. Repeatability was similar for both tests (ETDRS: 0.11 log units; staircased procedure: 0.13 log units). In conclusion, the Staircased Procedure was an acceptable test with high repeatability and validity.

Amblyopia↗
PubMed2004

Exploring the third dimension in root resorption.

OBJECTIVE: To review and investigate the validity of various 2D quantitative measurement techniques, and to explore the third dimension of root resorption. DESIGN: A review of the literature involving various quantitative evaluation of root resorption. RESULTS: Quantitative evaluation of resorption using radiographs has proven to be highly inaccurate because of magnification errors and their inability to be readily repeated and reproduced. Studies using histology sections of samples have proven to be laborious and technique sensitive. Inherent parallax errors and loss of material in data transfer have denied the true understanding of this 3D event. CONCLUSION: With the evolution in computing technology and digital imaging, the vision of evaluating the extent of root resorption in 3D has materialized. It was demonstrated that 3D volumetric quantitative evaluation of root resorption craters was feasible and its accuracy and repeatability was high.

Humans↗
PubMed1966

Evoked potential in relation to subsequent alpha frequency.

A series of 24 visually evoked potentials was obtained from a normnal human subject under a set of unvarying experimental conditions. The 24 trials were ordered according to the alpha frequency subsequent to presentation of the stimulus. The evoked potentials fromt the 12 higher- and 12 lower-frequency trials were averaged separateb. These two average curves differed significantly at each of the six nodal points.

Computers↗
PubMed1996

Effect of binocular cortical misalignment on ocular dominance and orientation selectivity.

We model a two-eye visual environment composed of natural images and study its effect on single cell synaptic modification. In particular, we study the effect of binocular cortical misalignment on receptive field formation after eye opening. We show that binocular misalignment affects principal component analysis (PCA) and Bienenstock, Cooper, and Munro (BCM) learning in different ways. For the BCM learning rule this misalignment is sufficient to produce varying degrees of ocular dominance, whereas for PCA learning binocular neurons emerge in every case.

Learning↗