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At least 1,693 records · Page 94Linked to original sources
PubMed2004

Anterior ischemic optic neuropathy in eyes with optic disc drusen.

BACKGROUND: There have been anecdotal reports of anterior ischemic optic neuropathy (AION) occurring in eyes with optic disc drusen (ODD), but the clinical features of this condition have not been well characterized. OBJECTIVES: To better describe the clinical features of AION associated with ODD and to compare the clinical features of this condition with those of "garden variety" nonarteritic AION. METHODS: We reviewed the medical records of 20 patients who experienced an episode of AION in an eye with ODD. In 4 patients, both eyes were affected; thus, 24 eyes were studied. The diagnosis of ODD was made by ophthalmoscopic identification, orbital ultrasonography, or computed tomographic scanning. We recorded age, sex, vascular risk factors, symptoms, visual acuity, visual fields, and results of the follow-up examination in all patients. These findings were compared with data from previously reported series of patients with nonarteritic AION. RESULTS: Our 20 patients included 14 men and 6 women (age range, 18-69 years; mean, 49.4 years). Vascular risk factors were identified in 10 patients (50%). Three patients reported episodes of transient visual loss before their fixed deficit. The visual acuity at the initial examination was 20/60 or better in 15 (62%) of the 24 eyes; 8 had a visual acuity of 20/20. The predominant pattern of visual field loss was an altitudinal or arcuate defect in 19 (79%) and a centrocecal scotoma in 5 (21%) of the 24 eyes. There was subjective worsening of vision before the initial neuro-ophthalmic examination in 11 eyes (46%) and objective documentation of progression in 7 eyes (29%). The final visual acuity was 20/40 or better in 13 (62%) of 21 eyes and 20/200 or worse in 3 (14%) of 21 eyes. CONCLUSIONS: Our patients were strikingly similar to those with nonarteritic AION unassociated with drusen in regard to prevalence of vascular risk factors, pattern of visual field loss, and occurrence of a subsequent similar event in the fellow eye. In contrast, however, patients with ODD-AION were younger than those with nonarteritic AION, were more likely to report preceding episodes of transient visual obscuration, and enjoyed a more favorable visual outcome.

Adolescent↗
PubMed2005

[Severe bilateral visual loss as the presenting sign of cerebral venous sinus thrombosis: case report].

Our purpose is to report a case of cranial venous thrombosis causing pseudotumor syndrome, where the principal clinical manifestation was severe bilateral vision loss. A 24-year-old man presented with severe bilateral vision loss, transient obscuration of vision, headache, bilateral papilledema and constricted visual fields. Computed tomography as well as neurologic examination was unrevealing. A lumbar puncture disclosed an increased cerebrospinal fluid opening pressure and complete blood count (CBC) showed increased numbers of platelets. A brain magnetic resonance imaging disclosed characteristic sings of chronic papilledema and suggestive signs of superior sagittal sinus thrombosis. A cranial magnetic resonance venography disclosed thrombosis of superior sagittal, transverse and sigmoid sinuses. The patient was treated with an optic nerve sheath decompression in the left eye, acetazolamide and anticoagulation. His ocular evaluation showed reduction of the papilledema, but severe vision loss remained. Pseudotumor cerebri with severe vision loss can be the presenting sign of cranial venous thrombosis secondary to a potentially life-threatening hematologic disorder.

Adult↗
PubMed2000

A programmable VLSI filter architecture for application in real-time vision processing systems.

An architecture is proposed for the realization of real-time edge-extraction filtering operation in an Address-Event-Representation (AER) vision system. Furthermore, the approach is valid for any 2D filtering operation as long as the convolutional kernel F(p,q) is decomposable into an x-axis and a y-axis component, i.e. F(p,q)=H(p)V(q), for some rotated coordinate system [p,q]. If it is possible to find a coordinate system [p,q], rotated with respect to the absolute coordinate system a certain angle, for which the above decomposition is possible, then the proposed architecture is able to perform the filtering operation for any angle we would like the kernel to be rotated. This is achieved by taking advantage of the AER and manipulating the addresses in real time. The proposed architecture, however, requires one approximation: the product operation between the horizontal component H(p) and vertical component V(q) should be able to be approximated by a signed minimum operation without significant performance degradation. It is shown that for edge-extraction applications this filter does not produce performance degradation. The proposed architecture is intended to be used in a complete vision system known as the Boundary-Contour-System and Feature-Contour-System Vision Model, proposed by Grossberg and collaborators. The present paper proposes the architecture, provides a circuit implementation using MOS transistors operated in weak inversion, and shows behavioral simulation results at the system level operation and electrical simulation and experimental results at the circuit level operation of some critical subcircuits.

Computer Simulation↗
PubMed2006

Fixational eye movements in normal and pathological vision.

Most of our visual experience is driven by the eye movements we produce while we fixate our gaze. In a sense, our visual system thus has a built-in contradiction: when we direct our gaze at an object of interest, our eyes are never still. Therefore the perception, physiology, and computational modeling of fixational eye movements is critical to our understanding of vision in general, and also to the understanding of the neural computations that work to overcome neural adaptation in normal subjects as well as in clinical patients. Moreover, because we are not aware of our fixational eye movements, they can also help us understand the underpinnings of visual awareness. Research in the field of fixational eye movements faded in importance for several decades during the late 20th century. However, new electrophysiological and psychophysical data have now rejuvenated the field. The last decade has brought significant advances to our understanding of the neuronal and perceptual effects of fixational eye movements, with crucial implications for neural coding, visual awareness, and perception in normal and pathological vision. This chapter will review the type of neural activity generated by fixational eye movements at different levels in the visual system, as well as the importance of fixational eye movements for visual perception in normal vision and in visual disease. Special attention will be given to microsaccades, the fastest and largest type of fixational eye movement.

Fixation, Ocular↗
PubMedDate not supplied

The High-Performance Computing and Communications program, the national information infrastructure and health care.

The High-Performance Computing and Communications (HPCC) program is a multiagency federal effort to advance the state of computing and communications and to provide the technologic platform on which the National Information Infrastructure (NII) can be built. The HPCC program supports the development of high-speed computers, high-speed telecommunications, related software and algorithms, education and training, and information infrastructure technology and applications. The vision of the NII is to extend access to high-performance computing and communications to virtually every U.S. citizen so that the technology can be used to improve the civil infrastructure, lifelong learning, energy management, health care, etc. Development of the NII will require resolution of complex economic and social issues, including information privacy. Health-related applications supported under the HPCC program and NII initiatives include connection of health care institutions to the Internet; enhanced access to gene sequence data; the "Visible Human" Project; and test-bed projects in telemedicine, electronic patient records, shared informatics tool development, and image systems.

Computer Communication Networks↗
PubMed1986

Analog "neuronal" networks in early vision.

Many problems in early vision can be formulated in terms of minimizing a cost function. Examples are shape from shading, edge detection, motion analysis, structure from motion, and surface interpolation. As shown by Poggio and Koch [Poggio, T. & Koch, C. (1985) Proc. R. Soc. London, Ser. B 226, 303-323], quadratic variational problems, an important subset of early vision tasks, can be "solved" by linear, analog electrical, or chemical networks. However, in the presence of discontinuities, the cost function is nonquadratic, raising the question of designing efficient algorithms for computing the optimal solution. Recently, Hopfield and Tank [Hopfield, J. J. & Tank, D. W. (1985) Biol. Cybern. 52, 141-152] have shown that networks of nonlinear analog "neurons" can be effective in computing the solution of optimization problems. We show how these networks can be generalized to solve the nonconvex energy functionals of early vision. We illustrate this approach by implementing a specific analog network, solving the problem of reconstructing a smooth surface from sparse data while preserving its discontinuities. These results suggest a novel computational strategy for solving early vision problems in both biological and real-time artificial vision systems.

Humans↗
PubMedDate not supplied

[Computer method for evaluating disorders in sense of color].

A new method for evaluating disorders in the sense of color has been developed and offered for practice. A total of 340 patients with diseases of the retina and optic nerve and 80 normal subjects were examined. The results indicate that different conditions of examination, selection of combination by the color, brightness, and deepness of the stimulus and background allow detection of decreased sensitivity of one, two, or three color perceptors (disorders in sense of color--color blindness) and permit a quantitative evaluation of functional disorders in the color channels of visual system. The new method can be used in the diagnosis of the initial pathological processes of different origin, involving the cone system at any level of visual route and associated with acquired disorders in color vision.

Color Perception↗
PubMed2005

[Treatment of a complication after surgical removal of an aneurysmal cyst of the ethmoid].

INTRODUCTION: An aneurysmal cyst (AC) is a rare benign bony tumor with a possible aggressive extension. We present a complication following the surgical ablation of an ethmoidal AC. CLINICAL HISTORY AND FINDINGS: A 40-year-old man with a left ethmoidal AC extending to the orbital roof underwent 2 surgeries. After the second one involving a neuro-surgical approach, a bilateral palsy of the superior oblique muscles (SO) appeared. The diplopia did not improve following a bilateral asymmetrical recession of the inferior recti muscles done elsewhere. There was an excyclotorsion up to 20 degrees in down gaze and a vertical deviation of 10 degrees in primary position. THERAPY AND OUTCOME: We performed a bilateral tucking of the anterior SO fibres with, on the left, an advancement of the inferior rectus and a resection of the medial rectus muscles. Two weeks after surgery the absence of cyclotorsional deviation allowed a binocular vision. CONCLUSION: The double vision due to the excyclotorsion, which was the main complaint, could be alleviated by an anterior strengthening of the SO. A precise measurement of the cyclotorsion is required for the surgical procedure.

Adult↗
PubMedDate not supplied

Sudden visual loss secondary to an orbital varix.

A 45-year-old man presented with precipitous loss of vision and rapidly changing field defects in one eye. Computerized tomography and B-scan ultrasonography revealed a small orbital mass adjacent to the optic nerve. This was removed via lateral orbitotomy. On pathologic examination it was diagnosed as a small orbital varix. Drs. Frederick C. Blodi and Stephen Trokel comment on the case.

Exophthalmos↗
PubMed2003

[Treatment of subarachnoid hemorrhages in an isolated mountainous area].

From January 1997 to December 2001, patients with subarachnoid hemorrhage (SAH) among 14,008 residents in an isolated mountainous area; Oguni and Minamioguni towns in Kumamoto Prefecture, were evaluated. The subjects were patients being treated at Oguni Municipal Hospital. Over a period of 5 years, 19 patients were found to be suffering from SAH in this area, 3 of whom were visitors (residing outside this area). The annual incidence rate of SAH in this area was calculated as 22.9 per 100,000. The sex ratio (men:women) was 4:12. The average age was 67.9 years; 65.0 years for men and 68.8 years for women. Eleven patients were older than 65, and constituted 68.8% of the subjects. The risk factors of SAH were recognized, and both hypertension and smoking constituted 31.6%. Alcohol was 21.1% and hyperlipemia was 15.8%. In 13 clipping operated cases excluding 1 test craniotomy, Hunt & Kosnik's Grades at admission were G.I: 2, G.II: 5, G.III: 3, G.IV: 2 and G.V: 1, and Fisher's Groups were G.I: 0, G.II: 8, G.III: 3 and G.IV: 2. The sites of 16 operated aneurysms were internal carotid-posterior communicating artery (IC-PC): 2, anterior communicating artery (A Co.A): 4, middle cerebral artery (MCA): 10 and vertebral artery-basilan artery (VA-BA): 0. The aneurysmal size were < 5 mm: 5, 6-10 mm: 9 and 11 mm < :2 (average 7.6 mm, 2-15 mm). The results were evaluated at discharge, excluding 1 SAH of unknown etiology. 9 were good, 2 were dependent and 7 including 5 non-operative cases had died. We were satisfied with these results, because we were treating older patients. Although we attempted the clipping operation using only a three dimensional computed tomographic angiograply (3D-CTA; X-Vision GX (TOSHIBA) & X-Tension), we had no problem, except for 1 test craniotomy. 3D-CTA was useful during the clipping operation in the small hospital, especially, in regard to cost.

Aged↗
PubMed2000

The Ouchi illusion as an artifact of biased flow estimation.

A pattern by Ouchi has the surprising property that small motions can cause illusory relative motion between the inset and background regions. The effect can be attained with small retinal motions or a slight jiggling of the paper and is robust over large changes in the patterns, frequencies and boundary shapes. In this paper, we explain that the cause of the illusion lies in the statistical difficulty of integrating local one-dimensional motion signals into two-dimensional image velocity measurements. The estimation of image velocity generally is biased, and for the particular spatial gradient distributions of the Ouchi pattern the bias is highly pronounced, giving rise to a large difference in the velocity estimates in the two regions. The computational model introduced to describe the statistical estimation of image velocity also accounts for the findings of psychophysical studies with variations of the Ouchi pattern and for various findings on the perception of moving plaids. The insight gained from this computational study challenges the current models used to explain biological vision systems and to construct robotic vision systems. Considering the statistical difficulties in image velocity estimation in conjunction with the problem of discontinuity detection in motion fields suggests that theoretically the process of optical flow computations should not be carried out in isolation but in conjunction with the higher level processes of 3D motion estimation, segmentation and shape computation.

Artifacts↗
PubMed2003

CT of orbital trauma.

In a patient with acute orbital trauma, visual acuity and extraocular muscle motility are the two most important ophthalmologic functions to be evaluated emergently. The assessment of these capabilities may sometimes be difficult due to the severity of the head injury, the extent of periorbital soft tissue edema, inadequate cooperation in alert patients, and a reduced level of consciousness in obtunded individuals. Consequently, computed tomography (CT) has come to play a major role in the orbital examination of acute trauma patients. In this study, in conjunction with clinical evaluation, we have sought to utilize CT to determine the various prevalences of the causes of decreased visual acuity and extraocular muscle motility resulting from orbital trauma. We retrospectively reviewed the records of all patients admitted to our emergency facility who, having suffered head trauma, underwent a CT study for diagnosis. CT examinations of the head using a multidetector scanner were performed from the base of the skull to the vertex at 5-mm intervals. Orbital CT was obtained when a routine CT of the head showed periorbital soft tissue edema and/or facial bone fractures. The orbital CT examination was performed using axial 1-mm and coronal 3-mm slices. Coronal reformation images were prepared if the patient was unable to tolerate the prone position for direct coronal imaging. The imaging findings were correlated with ophthalmologic observations. The orbit floor was the most common and the orbital roof the least common site of fracture of the bony coverings of the eye. Twenty-three patients suffered decreased visual acuity. In order of declining frequency, the causes of reduced vision consequent to trauma were retrobulbar hemorrhage, optic nerve thickening presumably secondary to edema, intraorbital emphysema, optic nerve impingement, detached retina and ruptured globe. Five patients had visual impairment without demonstratable radiographic abnormalities. The most common finding associated with diminished extraocular muscle motility was muscle impingement by fracture fragments, followed in decreasing frequency by thickened muscle due to edema or contusion, intraconal emphysema, muscle entrapment, and retrobulbar fat herniation. Six patients with decreased extraocular muscle activity had no abnormalities demonstrated on CT images. The overwhelming majority of patients with decreased visual acuity or reduced extraocular muscle motility consequent to trauma had abnormalities demonstrated by orbital CT. Hence, CT examinations should play a major role in the evaluation of the intraorbital contents in patients with orbital trauma.

Adolescent↗
PubMed1998

Colour vision in AIDS patients without HIV retinopathy.

Patients suffering from AIDS develop ocular complications, the most frequent being HIV retinopathy. It is however not clear, if functional visual impairments can be observed as early indicators of ocular complications, before clinical diagnosis of HIV retinopathy is made at fundus examination. To address this issue, we measured colour vision in a group of 49 AIDS subjects with normal clinical fundi using the 'two equation method'. This method, combining red-green Rayleigh and the blue-green Moreland metameric matches, enables more complete and quantitative assessments of colour vision than those based on pigmentary tests. Data were collected on our computer controlled colorimeter and compared to those of normal subjects. While most AIDS subjects without HIV retinopathy demonstrated normal colour vision, a significant portion of them had wider matches than normal subjects (11% for the Rayleigh equation and 16% for the Moreland equation). Furthermore, matching ranges of the Moreland equation were significantly correlated with CD4 lymphocyte counts. Patients with low CD4 values tended to produce larger matching ranges than the patients with high CD4 values. A within subject study on 17 patients confirmed this trend and showed that the patients who increased/decreased their CD4 blood counts generally improved/impaired their colour discrimination in the Moreland match. No such correlation was found between the matching ranges of the Rayleigh equation and the CD4 counts. These results show that colour discrimination is slightly reduced in some AIDS subjects, although there are no detectable ocular complications. They also suggest two different types of colour vision impairments in AIDS patients without retinopathy: one reversible process affecting colour discrimination in the blue-green range; and another irreversible process affecting colour discrimination in the red-green range.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Effects of passive physical exercise on peripheral vision in muscular dystrophic children.

To investigate the effects of passive exercise of the extremities on peripheral vision of muscular dystrophic children aged 9 to 13 yr. these subjects were either not exercised (control days) for a 6-min. period or were exercised (experimental days) for a 6-min. period after a 5-min. rest. Peripheral vision was recorded after each condition. Analysis of variance with repeated measures on the exercise and no exercise conditions was computed for each measure. 6 min. of passive exercise significantly increased peripheral vision. It was assumed that exercise increased blood flow through the lungs allowing for greater oxygen diffusion in the brain and other facilitory responses which increased effective cerebral activity. Curriculum revisions for such children indicate the importance of activity in facilitating subsequent learning.

Adolescent↗
PubMed2004

A silicon early visual system as a model animal.

Examples that show the transfer of our basic knowledge of brain function into practical electronic models are rare. Here we present a user-friendly silicon model of the early visual system that contributes to animal welfare. The silicon chip emulates the neurons in the visual system by using analog Very Large Scale Integration (aVLSI) circuits. It substitutes for a live animal in experiment design and lecture demonstrations. The neurons on this chip display properties that are central to biological vision: receptive fields, spike coding, adaptation, band-pass filtering, and complementary signaling. Unlike previous laboratory devices whose complexity was limited by the use of discrete components on printed circuit boards, this battery-powered chip is a self-contained patch of the visual system. The realistic responses of the chip's cells and the self-contained adjustment-free correct operation of the chip suggest the possibility of implementation of similar circuits for visual prosthetics.

Animals↗
PubMed1992

Limitations of image enhancement for the visually impaired.

Image enhancement as an aid for the visually impaired may improve visibility of TV programs and provide portable visual aid. This paper describes the current techniques for image enhancement and their underlying models. The limitations of the various techniques and of potential methods of implementation are high-lighted. Initial work in this area was based on a linear model. The finite dynamic range available in the video display and contamination of the enhanced image by high spatial frequency noise limited the model's usefulness. I propose a method to address some limitations of the original model that considers the nonlinear response of the visual system and requires enhancement of subthreshold spatial information only. This modification may increase the dynamic range available by decreasing the range previously used by the linear models to enhance visible details. However, for the modified technique to be most effective, the enhancement has to be continuously tuned, based on the patient's visual loss and the spatial frequency content of the displayed images. The implications of these limitations for the potential implementation in TV are discussed. Implementation of an image-enhancing visual aid in a head-mounted, binocular, full-field, virtual vision device may cause substantial difficulties. Patient adaptation may be difficult due to head movement and interaction of the vestibular system response with the head-mounted display. An alternate, bioptic design is proposed in which the display is positioned above or below the line of sight to be examined intermittently, possibly in a freeze-frame mode. Such implementation is also likely to be less expensive, enabling more users access to the device.

Audiovisual Aids↗
PubMed1992

Obstacles encountered in the development of the low vision enhancement system.

The Johns Hopkins Wilmer Eye Institute and the NASA Stennis Space Center are collaborating on the development of a new high technology low vision aid called the Low Vision Enhancement System (LVES). The LVES consists of a binocular head-mounted video display system, video cameras mounted on the head-mounted display, and real-time video image processing in a system package that is battery powered and portable. Through a phased development approach, several generations of the LVES can be made available to the patient in a timely fashion. This paper describes the LVES project with major emphasis on technical problems encountered or anticipated during the development process.

Audiovisual Aids↗