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PubMed2002

Y-chromosomal red-green opsin genes of nocturnal New World monkey.

The X-chromosomal locality of the red-green-sensitive opsin genes has been the norm for all mammals and is essential for color vision of higher primates. Owl monkeys (Aotus), a genus of New World monkeys, are the only nocturnal higher primates and are severely color-blind. We demonstrate that the owl monkeys possess extra red-green opsin genes on the Y-chromosome. The Y-linked opsin genes were found to be extremely varied, in one male appearing to be a functional gene and in other males to be multicopy pseudogenes. These Y-linked opsin genes should offer a rare opportunity to study the evolutionary fate of genes translocated to the Y chromosome.

Animals↗
PubMed2004

Cone inputs in macaque primary visual cortex.

To understand the role of primary visual cortex (V1) in color vision, we measured directly the input from the 3 cone types in macaque V1 neurons. Cells were classified as luminance-preferring, color-luminance, or color-preferring from the ratio of the peak amplitudes of spatial frequency responses to red/green equiluminant and to black/white (luminance) grating patterns, respectively. In this study we used L-, M-, and S-cone-isolating gratings to measure spatial frequency response functions for each cone type separately. From peak responses to cone-isolating stimuli we estimated relative cone weights and whether cone inputs were the same or opposite sign. For most V1 cells the relative S-cone weight was <0.1. All color-preferring cells were cone opponent and their L/M cone weight ratio was clustered around a value of -1, which is roughly equal and opposite L and M cone signals. Almost all cells (88%) classified as luminance cells were cone nonopponent, with a broad distribution of cone weights. Most cells (73%) classified as color-luminance cells were cone opponent. This result supports our conclusion that V1 color-luminance cells are double-opponent. Such neurons are more sensitive to color boundaries than to areas of color and thereby could play an important role in color perception. The color-luminance population had a broad distribution of L/M cone weight ratios, implying a broad distribution of preferred colors for the double-opponent cells.

Action Potentials↗
PubMed2006

Random wiring in the midget pathway of primate retina.

The present study addresses the questions of how topographically organized neuronal populations are connected, and whether there is anatomical evidence for color-selective wiring in retinal pathways for red-green color vision. The connectivity of OFF midget bipolar and OFF midget ganglion cells was studied in the peripheral retina of dichromatic ("red-green color blind") and trichromatic ("color normal") marmosets (Callithrix jacchus). Midget bipolar cells were identified immunohistochemically. Midget ganglion cells were retrogradely labeled from the lateral geniculate nucleus and photofilled. Comparable results were obtained from all retinas studied. Between 3 and 16 bipolar terminals converge onto each ganglion cell. Nearly all bipolar terminals investigated show regions of colocalization (areas of presumed synaptic contacts) with ganglion cell dendrites. This contact area makes up approximately 14% of the axon surface area for a typical midget bipolar cell. The output from individual midget bipolar axons is often shared between midget ganglion cells so that, on average, <70% of the axon terminal area of a midget bipolar cell shows overlap with the dendritic field of a given midget ganglion cell. We conclude that there is no morphological evidence of red-green color selectivity in the connections between midget bipolar and midget ganglion cell mosaics. Furthermore, the results suggest that convergence is based on local interactions between axons and dendrites rather than cell-by-cell recognition between members of each mosaic.

Animals↗
PubMed2003

Optic neuropathy following an altitude exposure.

This case report describes a 20-yr-old man who presented with retro-orbital pain and blurred vision in his left eye 3 wk after an altitude exposure in a hypobaric chamber. He was found to have significant deficits in color vision and visual fields consistent with an optic neuropathy in his left eye. The patient was diagnosed with decompression sickness and treated with hyperbaric oxygen with a U.S. Navy Treatment Table VI. All signs and symptoms resolved with a single hyperbaric oxygen treatment but recurred. A head MRI revealed a left frontoethmoid sinus opacity. A concomitant sinusitis was diagnosed. The patient had full resolution of symptoms after a total of four hyperbaric oxygen treatments and antibiotic therapy at 6-wk follow-up. Although a para-infectious etiology for this patient's optic neuropathy cannot be excluded, his history of altitude exposure and significant, rapid response to hyperbaric oxygen treatment strongly implies decompression sickness in this case.

Adult↗
PubMed1976

Adverse effects of the drugs most frequently administered to the elderly--Part II.

The uncertainties associated with identificatin of adverse drug reactions are numerous. These effects which involve the eyes and vision constitute an important group but they are inadequately described and classified in most reports. Vague statements of visual disturbances, blur, changes in color vision, or difficulties in reading are indicated in many articles. Both parts of this report provide a listing of potential adverse effects, systemic and ocular. The drug groups included in part II are the antipsychotics, antianxiety drugs, antidepressants, antiparkinson drug and a miscellaneous group.

Aged↗
PubMed1975

Large optic nerve glioma with normal vision.

When the diagnosis of optic glioma is made, the visual loss is most often mildly or profoundly impaired. We report the details of the unusual situation where central visual acuity, visual fields, and color vision were normal at the time a large optic nerve glioma was demonstrated in a young boy. To our knowledge, this is the first case report containing ophthalmologic, neuroradiologic, surgical, and histologic details illustrating the rare association of normal vision and an optic glioma.

Child↗
PubMed2001

Ocular side effects possibly associated with isotretinoin usage.

PURPOSE: To evaluate reported ocular side effects associated with isotretinoin usage. METHODS: One thousand seven hundred forty-one case reports received from spontaneous reporting systems, data from the Drug Safety Section of Roche Pharmaceuticals, and the world's literature were evaluated using the World Health Organization Causality Assessment Guide of Suspected Adverse Reactions. RESULTS: Thirty-eight different signs or symptoms of ocular abnormalities associated with isotretinoin usage have been classified as "certain," "probable/likely," "possible," "unlikely," or "conditional/unclassifiable." CONCLUSION: Adverse ocular side effects secondary to isotretinoin that are "certain" include abnormal meibomian gland secretion, blepharoconjunctivitis, corneal opacities, decreased dark adaptation, decreased tolerance to contact lens, decreased vision, increased tear osmolarity, keratitis, meibomian gland atrophy, myopia, ocular discomfort, ocular sicca, photophobia, and teratogenic ocular abnormalities. Those that are "probable/likely" are decreased color vision (reversible) and permanent loss of dark adaptation. Those that have a "possible" association include permanent keratoconjunctivitis sicca. Suggested guidelines for ocular examination for patients on isotretinoin are given.

Adolescent↗
PubMed2002

A rationale for the structure of color space.

The colors perceived by humans in response to light stimuli are generally described in terms of four color categories (reds, greens, blues and yellows), the members of which are systematically arrayed around gray. This broadly accepted description of color sensation differs fundamentally from the light that induces it, which is neither 'circular' nor categorical. What, then, accounts for these discrepancies between the structure of color experience and the physical reality that underlies it? We suggest that these differences are based on two related requirements for successful color vision: (1) that spectra be ordered according to their physical similarities and differences; and (2) that this ordering be constrained by the four-color map problem.

Animals↗
PubMedDate not supplied

The cone/horizontal cell network: a possible site for color constancy.

Color vision is spectrally opponent, suggesting that spectrally opponent neurons, such as the horizontal cells in fish and turtle retinae, play a prominent role in color discrimination. In the accompanying paper (Kraaij et al., 1998), it was shown that the output signal of the horizontal cell system to the cones is not at all spectrally opponent. Therefore, a role for the spectrally opponent horizontal cells in color discrimination seems unlikely. In this paper, we propose that the horizontal cells play a prominent role in color constancy and simultaneous color contrast instead of in color discrimination. We have formulated a model of the cone/horizontal cell network based on measurements of the action spectra of the cones and of the feedback signal of the horizontal cell system to the various cone types. The key feature of the model is (1) that feedback is spectrally and spatially very broad and (2) that the gain of the cone synapse strongly depends on the feedback strength. This makes the synaptic gain of the cones strongly dependent on the spectral composition of the surround. Our model, which incorporates many physiological details of the outer retina, displays a behavior that can be interpreted as color constancy and simultaneous color contrast. We propose that the horizontal cell network modulates the cone synaptic gains such that the ratios of the cone outputs become almost invariant with the spectral composition of the global illumination. Therefore, color constancy appears to be coded in the retina.

Animals↗
PubMedDate not supplied

Cone contributions to the photopic spectral sensitivity of the zebrafish ERG.

Microspectrophotometry studies show that zebrafish (Danio rerio) possess four cone photopigments. The purpose of this study was to determine the cone contributions to the zebrafish photopic increment threshold spectral-sensitivity function. Electroretinogram (ERG) b-wave responses to monochromatic lights presented on a broadband or chromatic background were obtained. It was found that under the broadband background condition, the zebrafish spectral-sensitivity function showed several peaks that were narrower in sensitivity compared to the cone spectra. The spectral-sensitivity function was modeled with L - M and M - S opponent interactions and nonopponent S- and U-cone mechanisms. Using chromatic adaptation designed to suppress the contribution of the S-cones, a strong U-cone contribution to the spectral-sensitivity function was revealed, and the contributions of the S-cones to the M - S mechanism were reduced. These results show that the b-wave component of the ERG receives input from all four cone types and appears to reflect color opponent mechanisms. Thus, zebrafish may possess the fundamental properties necessary for color vision.

Adaptation, Physiological↗
PubMed2005

Color architecture in alert macaque cortex revealed by FMRI.

The contribution that different brain areas make to primate color vision, especially in the macaque, is debated. Here we used functional magnetic resonance imaging in the alert macaque, giving a whole brain perspective of color processing in the healthy brain. We identified color-biased and luminance-biased activity and color-afterimage activity. Color-biased activity was found in V1, V2, and parts of V4 and not in V3a, MT, or other dorsal stream areas, in which a luminance bias predominated. Color-biased activity and color-afterimage activity were also found in a region on the posterior bank of the superior temporal sulcus. We review anatomical and physiological studies that describe this region, PITd, and postulate that it is distinct from areas V4 and TEO. When taken together with single-unit studies and lesion studies, our results suggest that color depends on a connected ventral-stream pathway involving at least V1, V2, V4, and PITd.

Animals↗
PubMed1985

Differentiation between recently resolved optic neuritis and central serous retinopathy. Use of tests of visual function.

A test battery was performed on 13 patients with resolved central serous retinopathy and on 13 patients with resolved optic neuritis to see whether the tests would help to distinguish between the two conditions. We found that the most useful discriminators were the relative afferent pupillary defect, followed by the visual evoked potential latency and the critical flicker frequency. The total error score on the Farnsworth-Munsell 100-Hue Test and the nature of the color vision defect were not helpful in separating the two diseases.

Adult↗
PubMed2006

Color naming deficits and attention-deficit/hyperactivity disorder: a retinal dopaminergic hypothesis.

BACKGROUND: Individuals with Attention-Deficit/Hyperactive Disorder (ADHD) have unexplained difficulties on tasks requiring speeded processing of colored stimuli. Color vision mechanisms, particularly short-wavelength (blue-yellow) pathways, are highly sensitive to various diseases, toxins and drugs that alter dopaminergic neurotransmission. Thus, slow color processing might reflect subtle impairments in the perceptual encoding stage of stimulus color, which arise from hypodopaminergic functioning. PRESENTATION OF HYPOTHESES: 1) Color perception of blue-yellow (but not red-green) stimuli is impaired in ADHD as a result of deficient retinal dopamine; 2) Impairments in the blue-yellow color mechanism in ADHD contribute to poor performance on speeded color naming tasks that include a substantial proportion of blue-yellow stimuli; and 3) Methylphenidate increases central dopamine and is also believed to increase retinal dopamine, thereby normalizing blue-yellow color perception, which in turn improves performance on the speeded color naming tasks. TESTING THE HYPOTHESIS: Requires three approaches, including:1) direct assessment of color perception in individuals with ADHD to determine whether blue-yellow color perception is selectively impaired; 2) determination of relationship between performance on neuropsychological tasks requiring speeded color processing and color perception; and 3) randomized, controlled pharmacological intervention with stimulant medication to examine the effects of enhancing central dopamine on color perception and task performance IMPLICATIONS OF HYPOTHESIS: If substantiated, the findings of color perception problems would necessitate a re-consideration of current neuropsychological models of attention-deficit/hyperactivity disorder, guide psycho-education, academic instruction, and require consideration of stimulus color in many of the widely used neuropsychological tests.

Journal Article↗
PubMed1986

Neurosyphilis and retrobulbar neuritis in a patient with AIDS.

A 33-year-old homosexual patient with acquired immune deficiency syndrome (AIDS) developed sudden unilateral loss of vision. Slit-lamp and funduscopic examination of the affected eye was completely within normal limits. The patient, however, had a Marcus Gunn pupil, decreased color vision, and a large central scotoma on visual field examination. This was consistent with retrobulbar optic neuritis. Laboratory investigation revealed a highly positive serum and cerebrospinal fluid venereal disease reaction level (VDRL). A diagnosis of neurosyphilis was made, and the patient was treated with ten days of intravenous penicillin therapy. Ophthalmologists should be aware that many patients with AIDS have also been exposed to syphilis. Regardless of their clinical presentation, all AIDS patients should be examined and tested for syphilis and treated as is necessary.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Considerations in evaluation and treatment of the child with low vision.

Habilitation of infants and children with visual impairments should be based on a thorough understanding of their visual capabilities and limitations. Comprehensive evaluation of visual function includes measurement of visual acuity, contrast sensitivity, visual field, color vision, adaptation, visual sphere, accommodation, and oculomotor functions. It is best completed through a team approach that uses therapists, special educators, and physicians. A complete evaluation also includes examination of the effect of other motor functions on the use of vision. Nearly all aspects of a child's vision can be measured in play situations with tests that are easy to use. However, further education of nonphysician team members in refractive errors, optics, and function of optical devices may be necessary to ensure an accurate and thorough evaluation.

Adaptation, Ocular↗
PubMed2000

[Simple retinal detachment: computer reconstruction of visual perception during the first month after surgery].

Visual function during the first month following ab externo surgery for retinal detachment with raised macula has been inadequately investigated. We present through pictures the patient's perception of his visual function after surgical intervention consisting of cryotherapy, draining, scleral buckling, and gas. The patient used image processing software to modify the pictures seen by the nonoperated eye in order to reproduce his visual perception with the operated eye. Results show the relation between visual perception and clinical examination. When the surgical procedure is undergone early, visual recovery only requires a few days and color vision returns quickly. Hyalitis and gas perception prevails at first, then visual acuity increases progressively and efficiently.

Color Perception↗
PubMed1982

Wavelength-discrimination behavior in the grasshopper Phlaeoba.

The grasshopper Phlaeoba sp. has ocular filters that are arranged in discrete retinal bands. These filters modify the spectra of some of its photoreceptors, all of which are apparently filled with the same resident photopigment. The receptor response differences produced by the ocular filters provide a potential basis for wavelength discrimination. Behavioral tests of wavelength discrimination in Phlaeoba were therefore run; they confirmed earlier qualitative findings that indicated that Phlaeoba can discriminate between visual stimuli on the basis of wavelength cues and quantitatively showed that the behavioral preference is proportional to the receptor spectral difference. Tests of animals with indistinct retinal bands indicated that wavelength discrimination was reduced in this variant but was still quantitatively related to the receptor spectra. These data suggest that the filter-mediated color vision hypothesis applies in the case of Phlaeoba.

Animals↗
PubMed1983

Pupillary defects in amblyopia.

We examined the pupils of 55 amblyopic subjects to determine whether a pupillary defect could be detected in the amblyopic eye. We found relative afferent pupillary defects in 45 of the subjects; these defects were equal to or larger than 0.3 log unit (that is, easily visible) in 29 subjects. The pupillary defect was always in the amblyopic eye, but it could not be correlated with the severity or the cause of the amblyopia, with visual-evoked potential abnormalities, or with color vision defects.

Adolescent↗