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Results for “Color Vision Defects”

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At least 1,207 records · Page 67Linked to original sources
PubMed1993

Visual object agnosia, prosopagnosia, achromatopsia, loss of visual imagery, and autobiographical amnesia following recovery from cortical blindness: case M.H.

A number of higher visual deficits accompanied by severe retrograde autobiographical memory loss following bilateral medial occipital infarctions are described in case M.H. Assessment of M.H.'s visual object agnosia and prospagnosia suggested that he was unable to integrate the elements of a percept to form a meaningful whole. This deficit may occur at the level the percept is encoded into the visual buffer and inspected. M.H. also describes a loss of visual memories, and it is hypothesized that this may similarly be a result of an inability to integrate the elements of the visual representation (e.g. of an object or face) following its generation from long-term visual memory store into the visual buffer. M.H.'s retrograde autobiographical memory loss is postulated to be a consequence of the severe impoverishment of episodic memories that must occur when events originally stored multimodally, must be recalled without any visual component.

Adult↗
PubMed1996

Preserved color imagery in an achromatopsic.

The loss of color vision secondary to central nervous system disease (achromatopsia) is thought to preclude visual imagery of colors. We report a patient with achromatopsia, secondary to bilateral temporo-occipital infarcts inclusive of the lingual and fusiform gyri, with preserved color imagery. Our findings, in conjunction with previous cases in the literature, are consistent with a single neural network for color processing in which a disconnection of internal activation from stored color representations produces impaired color imagery with preserved color perception, whereas a disconnection of visual input to these representations produces achromatopsia with preserved color imagery.

Cerebral Infarction↗
PubMedDate not supplied

What do color blind children really see? Guidelines for clinical prescreening based on recent findings.

Recent research on classical red-green blind observers has shown that complete dichromacy may be present only under conditions where the viewing angle is small. For viewing angles greater than about 4 degrees, both rods and an anomalous cone have been shown to underlie a weak form of trichromacy. The conditions for rod or anomalous cone mediation of this trichromacy have also been shown to depend on the overall viewing luminance. These data taken together prompt a rethinking of the classical view of red-green dichromacy and lead to new considerations of the color discrimination performance of dichromatic candidates. In this paper we review the recent research on the presence of trichromatic abilities in classical dichromats and we relate these findings to the needs of the clinician, especially in the screening of young children.

Child↗
PubMedDate not supplied

Early detection of glaucomatous damage. II. Changes in the appearance of the optic disk.

Once we understand that an increase in the size of the optic disk cup is due to loss of optic nerve fibers combined with some physical tissue rearrangements, it is quite clear that cupping begins as soon as nerve loss begins. Methods to detect cupping are more sensitive to the earliest glaucoma damage than are present field testing methods. This conclusion is supported by large clinical studies and histological demonstration of nerve fiber loss prior to field loss in eyes with abnormal cups, asymmetric cupping, or nerve fiber layer abnormalities. While automated perimetry is likely to increase the sensitivity of detection, better test methodologies are needed to combine with the objectivity of computer-assisted machines. Disk hemorrhages, nerve fiber layer defects, and color vision abnormalities are early signs of damage, supporting the conclusion that damage is present before field loss. A number of other methods await further testing to determine their effectiveness. The idea that the disease glaucoma is defined by a certain visual field finding on the Goldmann perimeter is not valid if we define glaucoma as an eye with a history of elevated IOP and optic nerve damage. While such field loss is a convenient means of defining a particular stage of damage in glaucoma, there are clearly earlier stages of damage, whether we can always detect them or not. No patient should be told that he or she does not have glaucoma, but rather has ocular hypertension, based on a particular visual field finding. As testing and examination methods improve, so, hopefully, will our ability to determine whether damage is present. As this occurs, we will be better enabled to select most rationally those patients who will benefit from therapy. The idea that field testing is relatively insensitive to the earliest glaucoma damage might lead the skeptic to conclude that perimetry is not worth the trouble. This review has indicated that none of our present methods, ophthalmoscopic, psychophysical or otherwise, is perfect. But to omit using any of them (especially field testing) does a great disservice to the glaucoma patient. The greatest usefulness of the new automated instruments is that adequate field testing is now available in a cost-effective form to every ophthalmic office. We need to strive for better detection and follow-up of glaucoma damage to prevent needless blindness.

Color Perception Tests↗
PubMedDate not supplied

Acquired dyschromatopsia in glaucoma.

Recent studies have suggested that the recognition of blue-yellow color vision deficits may have some predictive value in determining which ocular hypertensives are at risk of developing glaucoma and in monitoring the progress of the disease in glaucoma patients. This article reviews current theories of normal color vision and the differences that may occur in glaucoma, outlining methods of color vision testing and interpretation, and summarizing the results of recent studies.

Adaptation, Physiological↗
PubMedDate not supplied

Ophthalmologic manifestations of Alzheimer's disease.

Alzheimer's disease is a progressive neurologic disorder which may present with visual disturbance before the diagnosis is clearly established. Central acuity and visual field are initially normal. Alzheimer patients may show anomalies of color vision, spatial contrast sensitivity, susceptibility to visual masks, fundus examination, ocular motility, higher cortical visual function, visual evoked potential, and pattern electroretinogram. Pathologic analysis has shown abnormalities at all levels of the visual axis from retinal ganglion cell to associative visual cortex. Correlations between the visual abnormalities of Alzheimer's disease and corresponding neuroanatomic substrates are discussed.

Adult↗
PubMedDate not supplied

Optic disc pallor: a false localizing sign.

A 20-year-old pregnant woman was referred with bilateral mild visual acuity loss and optic disc pallor. Because of profound color vision deficits out of proportion to her acuity loss, an abnormality of the cone photoreceptors was suspected. An electroretinogram confirmed the diagnosis of a cone dystrophy and precluded further costly and invasive testing. Cone dystrophy should be considered in the differential diagnosis of any patient with bilateral, nonrefractive visual loss, especially if color vision is disproportionately affected, even with a normal retinal appearance and no significant family history.

Adult↗