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PubMed2006

Advantage of dichromats over trichromats in discrimination of color-camouflaged stimuli in humans.

This study investigated whether 12 participants with color-vision deficiency had superior visual discrimination of color-camouflaged stimuli shown on a computer screen compared with 12 participants with normal trichromatic vision. Participants were asked to distinguish a circular pattern from other patterns in which textural elements differed from the background in orientation and thickness. In one condition, stimuli were single-colored, green or red; in the other condition, stimuli were color camouflaged with a green and red mosaic overlaid onto the pattern. Color-vision deficient participants selected the correct stimuli in the color-camouflaged condition as quickly as they did in the single-colored condition. However, normal color-vision participants took longer to select the correct choice in the color-camouflaged condition than in the single-colored condition. These results suggest that participants with color-vision deficiency may have a superior visual ability to discriminate the color-camouflaged stimuli.

Adult↗
PubMed1990

Components of high-level vision: a cognitive neuroscience analysis and accounts of neurological syndromes.

Neuroanatomical, neurophysiological, and computational constraints are used to motivate a set of hypotheses about the functional organization of high-level vision. A set of processing subsystems is posited that underlies the later stages of visual object recognition and identification; these subsystems have been implemented in a running computer simulation model. The model is damaged in a variety of ways, and its performance on a set of tasks is observed. Dysfunctions arise from disruptions of the subsystems, disruptions of their interconnections, compensations by intact subsystems, and diminished activational capacity. The most common dysfunctions of high-level vision following brain damage are then reviewed, and accounts are offered by reference to the stimulation model. According to the theory and model, each type of dysfunction can arise from numerous underlying causes, all of which are potentially distinguishable by empirical methods.

Animals↗
PubMed2002

Occipital hypoperfusion in a patient with psychogenic visual disturbance.

A patient with bilateral diminished visual acuity and blurred vision was given the diagnosis of psychogenic visual disturbance after extensive psychiatric and ophthalmological examinations. Single photon emission computed tomography with Tc-99m-ethylcysteinate dimer demonstrated remarkably reduced regional cerebral blood flow (rCBF) in the bilateral occipital lobes. More specifically, rCBF was reduced in the visual association areas, but not in the primary visual areas. These findings suggest that functional suppression of the visual association area is associated with the development of psychogenic visual disturbance.

Adult↗
PubMed2000

Chiasmal cavernous malformation. A rare cause of acute visual loss.

A rare cause of acute visual loss due to a chiasmal cavernous malformation is presented. Acute visual loss was due to local hemorrhage and volume expansion of the cavernous malformation inside and outside of the optic chiasma. This unique location of cavernous malformation is associated with a risk of permanent loss of the vision. Cavernous malformations of optic chiasma should be carefully evaluated and considered for possible preventative surgical resection before it becomes symptomatic.

Acute Disease↗
PubMed1998

Sphenoid sinus brown tumor of secondary hyperparathyroidism: case report.

OBJECTIVE AND IMPORTANCE: Brown tumor is a misnomer for a reparative cellular process caused by primary or, less commonly, secondary or tertiary hyperparathyroidism. Atypical involvement of the base of the cranium in the area of the sphenoid sinus and the orbit is exceedingly rare and may produce a neurological deficit as a primary clinical presentation. Those neurosurgeons dealing with cranial base and pituitary lesions should be aware of this disease entity, and it should be listed in the differential diagnosis. CLINICAL PRESENTATION: A 21-year-old woman with end-stage renal failure on chronic dialysis was referred to the Department of Neurosciences at King Faisal Specialist Hospital and Research Centre with a 4-month history of progressive impairment of vision, associated with headache and nausea. Computed tomography and magnetic resonance imaging demonstrated an expansive mass lesion in the sphenoid sinus with erosion of the sellar floor and posterior medial wall of the orbit causing compression of the optic nerves. The biochemical laboratory studies showed elevation of parathyroid hormone and confirmed the diagnosis of hyperparathyroidism. INTERVENTION: The transnasal-transsphenoidal approach was used for extensive microsurgical removal of the lesion. The postoperative course was uneventful, and the improvement in vision was dramatic. CONCLUSION: Brown tumor, although rare, should be listed in the differential diagnosis of expansive mass lesions in the area of the sphenoid sinus and cranial base. The management is multidisciplinary, and therapeutic options should target the underlying cause.

Adult↗
PubMedDate not supplied

[Diagnosis and treatment of children with acute inflammatory diseases of the orbit].

The role of computer tomography within the differential diagnosis of acute inflammatory lesions of orbit tissues as well as an appropriate tactics of treatment were evaluated. Computer tomography, "Somafom AR-T", 512 x 512 pix matrix, Siemens (Germany), was made in the axial and coronary projections to delineate the inflammatory zone. The findings of computer tomography denoted explicitly the spatial features of pathology within the orbit with anatomic structures. In periostitis and reactive edema in retrobulbar fat of the orbit, the treatment of patients was conservative made jointly with otolaryngologist. Orbitotomy with drainage or with lancing of affected sinuses was made in abscess and phlegmon of the orbit. There was a complete recovery in a majority of patients with acute diseases of the orbit; they preserved their functions of the organ of vision and of its appendages. Therefore, computer tomography is a valuable and highly effective examination tool within the differential diagnosis of acute inflammatory diseases of the orbit. The diagnosis and treatment of such diseases call for a board of doctors including ophthalmologist, otolaryngologist and oral surgeon.

Abscess↗
PubMed2001

Appearance of images through a multifocal intraocular lens.

The appearance of images through a multifocal intraocular lens (IOL) was simulated. The optical transfer function (OTF) of a model eye containing the multifocal lens was measured and divided by the OTF of the model eye with a monofocal IOL. This ratio was used to filter digital images, generating simulations that represent the retinal images seen through a multifocal intraocular lens when viewed through an eye with a monofocal lens. A dichoptic side-by-side display was used to present the original image to one eye, implanted with the multifocal lens, while the other eye, implanted with monofocal lens, viewed the simulations and variations on the simulations to derive a point of subjective equivalence. Four subjects with such bilateral lens implants were tested for near and distance vision. The results validate the test methodology and the simulations. Referenced to the nominal theoretical filter, the prediction was within a 0.25-diopter (D) blur for distance simulation and within a 0.50-D blur for the near-vision simulation.

Aged↗
PubMed1994

Shunt failure without ventriculomegaly proclaimed by ophthalmic findings.

Four patients who developed increased intracranial pressure from ventricular shunt failure suffered a delay in diagnosis because magnetic resonance imaging of the brain did not show ventriculomegaly and because ophthalmic findings were initially overlooked or misinterpreted. None of the patients had the conventional manifestations of shunt failure: severe headache, nausea, vomiting, and depressed consciousness. Three patients suffered marked, permanent vision loss from chronic papilledema. These cases affirm that increased intracranial pressure may occur in shunt dependency without producing either conventional clinical symptoms or signs on imaging of the brain. Because ophthalmic manifestations may be the major clues to diagnosis, and because irreversible loss of vision is possible if these clues are overlooked, consideration should be given to periodic ophthalmological examination of shunt-dependent patients.

Adolescent↗
PubMed2002

Assessing visual performance with progressive addition lenses.

PURPOSE: As a result of lens design limitations, progressive addition lenses (PAL's) present a limited field of view for tasks at intermediate distances, such as with computers. To assess whether this limitation results in diminished visual performance, PAL's were compared with single-vision lenses in four different types of reading tasks in a computer workplace environment. METHODS: Adult subjects performed four computer-based reading tasks using both single-vision lenses and PAL's at an intermediate distance of 64 cm. RESULTS: Single-vision lenses performed significantly better than PAL's in one task, with a trend for better performance in another task. There was no difference in performance for the remaining two tasks. CONCLUSIONS: Visual performance tests that involved stimuli subtending the widest visual angles and demanded more fixational shifts were more sensitive in discerning performance differences between the lens designs. In general, PAL's showed marginally diminished performance compared with single-vision lenses, presumably due to their restricted intermediate channel.

Adult↗
PubMed2001

Biophysical vision model and learning paradigms about vision: review.

A learning paradigm of a new biophysical vision model (BVM) is presented. It incorporates anatomical and physiological evidence from micro- and macroscopic research on vision as reported in the literature during the past five years. Anatomical and physiological vision research tends to drift away from the technological foundations of encoding and reproducing size-defined images of real ongoing life scenarios. White and color light waves reflecting life scenarios are converted by the retina to encoded electrical train pulses with attached real information to be decoded by cortical vision neurons. The BVM paradigm is based on the ideas that: (1) cinema technology reproduces real-life scenes just as the human eye sees them; (2) virtual reality and robotics are computerized replications of categorized human vision faculties in operation. We believe that vision-related technology may extend our knowledge about vision and direct vision research into new horizons. The biophysical vision model has three prerequisites: (1) The faculties of human vision must be categorized. (2) Logic circuits of the 'hardware' of neuronal vision must be present. (3) Vision faculties are operated by self-induced 'software'. Vision research may be enhanced with devices constructed according to BVM that would enable biophysical vision experiments in both humans and animals.

Animals↗
PubMed1997

[Reconstruction of orbital floor fractures using autologous materials].

Bone and Cartilage Autograft gather all the necessary qualities for an interpositional material to be used in the fractured orbital floor reconstruction, leading to the binocular vision recovery and in term of tolerance. The initial material choice depends on the clinic and orbital tomodensitometry datas, but the final decision is made on the operating findings. However, schematic indications can be drawn up, depending on material characteristics, curve, rigidity and resorption degree, and fracture particularities.

Bone Transplantation↗
PubMed2003

Vision impairment as presenting symptom of a sphenoidal mucocele.

We present a case of a 27-year-old woman with a sphenoid mucocele, presenting with bilateral visual disturbance and pituitary gland dysfunction but without nasal or sinus complaints. We would like to emphasize the importance of early diagnosis and prompt surgical treatment.

Adult↗
PubMed1997

Childhood optic chiasm gliomas: radiographic response following radiotherapy and long-term clinical outcome.

PURPOSE: In children with chiasmal gliomas, radiation therapy can arrest progressive visual and neurologic impairment. We examined the radiographic response and clinical outcomes after irradiation. METHODS AND MATERIALS: Forty-two children (median age at diagnosis, 6.6 years) with chiasmal gliomas were managed as follows: 11 asymptomatic patients with neurofibromatosis-1 (NF-1) were observed only; 2 patients, less than 3 years old, underwent surgery and chemotherapy to delay irradiation; and 29 patients with progressive disease received radiation with or without prior surgery or chemotherapy. Time to radiographic response, long-term tumor control and late sequelae were reviewed for the 29 irradiated patients. RESULTS: The probability of at least 50% radiographic response at 24 months after irradiation was 18.1% and increased to 38.2% by 48 months and 45.9% by 60 months. By actuarial analysis, the median time for such radiographic response was 62 months. For the 29 irradiated patients, the 10-year freedom from progression and overall survival rates were 100% and 89%, respectively (median follow-up for surviving patients, 108 months). Stabilization or improvement in vision occurred in 81% of 26 evaluable irradiated patients. CONCLUSIONS: Notable radiographic response may be observed years after irradiation. Radiation therapy provides excellent long-term tumor control and vision preservation or improvement in the majority of patients with progressive chiasmal gliomas.

Adolescent↗
PubMed1997

Recombinant interferon alfa-2b in the treatment of vision-threatening capillary hemangiomas in childhood.

INTRODUCTION: Hemangiomas of the orbit and eyelids may cause serious ocular problems usually related to amblyopia and astigmatism. Steroids have become the accepted treatment. However, some hemangiomas are resistant to steroids or require prolonged use,with unacceptable side effects. Interferon alfa-2b, an antiangiogenic protein, was used in this prospective study to treat visually threatening hemangiomas that were unresponsive to oral or intralesional steroid treatment. METHODS: Forty patients aged 2 to 36 months with life- or organ-threatening hemangiomas were prospectively enrolled to evaluate the efficacy and safety of interferon alfa treatment for hemangiomas. Sixteen of these 40 patients had hemangiomas causing serious ocular dysfunction. The patients were treated with 3 x 10(6) U/m2 interferon alfa-2b subcutaneously daily for 3 months; treatment was then tapered or retreated according to response and protocol. Therapeutic responses were documented. RESULTS: Fifteen patients with ocular hemangiomas have finished treatment. The pretreatment volume measured by computed axial tomographywas an average of 22.3 cm3. Clinical response with eye opening was observed at an average of 6 weeks. There was a significant regression of the hemangioma in all patients, with an average 82% reduction in volume. Patients were treated with glasses and occlusion therapy as appropriate. Final visual acuities with a follow-up averaging 14 months after cessation of interferon treatment were normal, except that five of 15 patients had amblyopia; one of these patients had 20/40, two had 20/60, and two had 20/70. There were no major illnesses or serious adverse side effects. CONCLUSION: Interferon alfa-2b treatment resulted in good to excellent regression of all the hemangiomas. This regression was clinically significant,with patients able to open the affected eye an average of 6 weeks into treatment. Visual results were good, with moderate amblyopia occurring only in patients treated at a later age. Interferon alfa-2b was well tolerated by these young patients, and no significant illness or side effect has occurred.

Amblyopia↗
PubMed1989

A new test of luminous efficiency for babies.

We used the minimum motion method devised by Anstis and Cavanagh (1983) to measure the luminous efficiency of red and green and of yellow and blue for "normal" 1- 3-month-old babies and for one 3-month-old boy destined to be color-deficient because of a deutan mother. Subjects watched a display which created apparent motion, the direction of which depended on the relative luminance of the colors. To determine the equiluminant points, we observed the optokinetic nystagmus elicited by the display as the relative luminance of the colors was varied. The equiluminant points of the normal mothers and their infants were similar to each other but different from those of the deutan mother and her son. Our new method demonstrates the early maturation of input from red and green cones into achromatic pathways. It can also be used to identify some color-deficient infants.

Color Perception↗
PubMedDate not supplied

[Neuro-ophthalmological examinations in craniopharyngiomas in childhood].

The results of ophthalmologic examinations of 50 children with craniopharyngiomas are analyzed. The condition was diagnosed on the basis of clinical examinations, roentgenography, angiography, brain scintigraphy, and computer-aided tomography. In 48 cases the diagnosis was confirmed by histologic findings. The mean age of the patients was 9 years 6 months, both boys and girls were included in the study group. Vision acuity deterioration was detected in 69.6% of children, optic disk edema in 22% and atrophic changes of the disk in 52% of the examinees. Vision field defects were revealed in 67.7%, nystagmus in 4 cases, oculomotor nerve paresis in 6 cases. The authors emphasize timely employment of conventional and present-day x-ray examinations, that are highly informative in such conditions, in all the patients with vision disorders of unknown origin and with suspected compression of the visual routes.

Adolescent↗
PubMed2003

Changes in visual acuity associated with shunt failure.

OBJECT: The object of this article was to report on a retrospective analysis of the clinical findings in a series of patients with changes in visual acuity associated with shunt failure. METHODS AND RESULTS: Over a 10-year period, 350 patients underwent revisions for shunt failure. The clinical course of patients who demonstrated changes in visual acuity (VA) before or during hospitalization were reviewed; follow-up was achieved using outpatient records and telephone calls with physicians, family, or caregivers. Six patients (4 male) ranging in age from 2.5 years to 40 years demonstrated changes in vision associated with shunt failure. The youngest patient lapsed into coma before transfer and showed bilateral occipital lobe infarctions on the CT scan. Three patients had no complaints referable to the visual system prior to revision. Two patients with symptoms lasting more than 21 days showed unequivocal signs of increased intracranial pressure. Serial CT scans remained unchanged in 2 patients. A 3rd patient showed questionable progression in ventricular volume, while another patient's ventricles dilated after a period of 48-72 h. Four patients demonstrated a pattern of aqueductal stenosis, long-term shunting without revision, small ventricles, and poor outpatient follow-up. Four patients showed partial or complete recovery following revision. CONCLUSIONS: Changes in vision are uncommon and can be an isolated finding associated with shunt failure. Patients with aqueductal stenosis, long-term shunting without revision, and small, potentially non-compliant ventricles may be at risk of this complication. Misdiagnosis or inadequate follow-up places these patients at additional risk, but rapid revision can result in partial or complete recovery.

Adolescent↗