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PubMed1995

Variation in color matching and discrimination among deuteranomalous trichromats: theoretical implications of small differences in photopigments.

Individual differences in abnormal color vision are well known. A fundamental unresolved problem is the great variation in color vision even among those classified as having the same color-vision defect. Several physiological hypotheses have been proposed to account for this variation but little consideration has been given to how (and how much) color matching and discrimination are affected by the posited physiological mechanisms. Advances in molecular genetics have renewed interest in this problem, which is at the foundation of the relation between genotype and phenotype. We report here theoretical Rayleigh ranges (chromatic discrimination) and quantal matches for deuteranomalous trichromats with photopigments in the red/green range that vary in their separation and optical density. The results show there is relatively little loss of discrimination with pigments of normal optical density separated by as little as 2-3 nm. With pigments separated by 4 nm or less, however, optical density can strongly influence discrimination when varied independently in the two types of cone. Moderately lower (or higher) optical density in only one cone-type affects discrimination by altering the shape of the cone's relative spectral sensitivity function. The lack of correlation between Rayleigh-match midpoint and range, which is reported in the literature, may be accounted for by independent variation in pigment separation and optical density.

Color Perception↗
PubMed1994

The molecular genetics and evolution of primate colour vision.

Until recently, the genetic basis of colour vision could only be inferred from measuring the colour vision of family groups. However, in the past few years the sites of the genes for visual pigments have been located and sequenced. The genes that specify the opsins for the rod and short-wavelength cone pigments are located on the third and seventh chromosomes, respectively. In Old World primates the genes for the middle- and long-wavelength pigments are located on the q arm of the X chromosome in a head-to-tail array. The close sequence similarity of the two genes on the X chromosome leads to a high frequency of unequal inter- and intragenic recombination leading to gene deletion or the creation of hybrid genes. In New World primates there is only a single locus on the X chromosome for a middle- to long-wavelength cone pigment. However, three alleles can occur at this locus and each codes for a slightly different cone pigment. As a result there are three types of male dichromat and three types of female dichromat and trichromat in each species. Colour vision in New World primates might be an intermediate stage between the uniform dichromacy of non-primate mammals and the uniform trichromacy of Old World primates. Alternatively, colour vision in New World primates might be an adaptation to allow a wide variety of colour-vision types within a single family group.

Alleles↗
PubMed1992

Evaluation of the visual system in multiple sclerosis: a comparative study of diagnostic tests.

In 22 patients with clinically definite multiple sclerosis (MS) who were without visual symptoms and had a visual acuity of at least 1.0 in both eyes at the time of measurement, the following tests were performed to detect subclinical lesions in the visual system: visual evoked potential (VEP), contrast sensitivity test (CS), flight of colours test (FOC), colour vision test (Ishihara plates) (CV) and the pupillary light reflex (PLR). VEP was abnormal in 81.8%, CS in 72.7%, FOC in 36.4%, CV in 31.8%, and PLR in 52.3% of the patients. VEP and CS together were most sensitive: combining these techniques subclinical lesions of the visual system were detected in 90.9% (20/22) of these asymptomatic patients.

Adult↗
PubMed1980

A model for colour vision defect.

The Unique Green phenomenon whereby the wavelengths of light which are judged neither blue-green nor yellow-green show a distinct genetic polymorph. Amongst the males there is a clear bimodality whereas there is a near normal distribution amongst the females. The classification of the types of person so produced breeds true apparently in the X-chromosome. This phenomenon now having been confirmed is impossible to fit into the strict Walraven model of colour vision without modification. The modification that would be used is discussed and it is shown that a number of other difficulties within the Walraven model model can also be resolved.

Color Perception↗
PubMed2005

New intraocular lens technology.

PURPOSE: To review the current status of phakic intraocular lenses (IOLs), intraocular treatment of presbyopia, and IOLs that filter some blue light. DESIGN: Review of current information on the subject from numerous sources. METHODS: Medline search and Internet search engines on the topics of phakic IOLs, presbyopia or multifocal IOLs, and blue light and macular degeneration. RESULTS: An iris fixated phakic IOLs is now approved in the United States (US). There are concerns for corneal endothelial stability and late dislocation. Other approaches include anterior chamber fixation with concerns of corneal endothelial stability and pupil elongation, and posterior chamber fixation with concerns of cataract formation, IOL dislocation, and pigment dispersion. Intraocular treatment of presbyopia includes monovision, multifocal, and accommodative IOLs. Which approach is superior today is still not clear. There are IOLs designed to block some blue light to potentially lessen the risk of age-related macular degeneration (ARMD). While there is presumptive evidence of this, no definitive study shows such a correlation. Color perception issues are unlikely to be a problem. While decreased scotopic vision has been proposed, there is no study that proves this is an issue of clinical significance. CONCLUSIONS: The IOL field is dynamic with many new choices. Phakic IOLs and treatment of presbyopia will be an increasingly important part of ophthalmology; however, there are important unresolved issues. With better evidence that blue light is an important variable in ARMD, such an approach could rapidly become the standard.

Biomedical Technology↗
PubMed2005

Explantation of an AcrySof Natural intraocular lens because of a color vision disturbance.

PURPOSE: To describe a patient who complained of color vision disturbance after implantation of a clear intraocular lens (IOL) in one eye and a yellow IOL in the other. DESIGN: Interventional case report. METHODS: A 50-year-old woman complained of binocular imbalance and "yellow vision" in her left eye after implantation of a visible blue light-filtering yellow IOL. A clear IOL had been implanted in her right eye 1 month before. She requested explantation of the yellow IOL. RESULTS: The yellow IOL was exchanged for a clear one, which resolved the unbalanced color vision. CONCLUSIONS: Patients may be intolerant of the color disturbance that results when dissimilarly colored IOLs are implanted. It is advisable to avoid this practice.

Acrylic Resins↗
PubMed2006

Genetics of variation in human color vision and the retinal cone mosaic.

Variation in human color vision is mainly caused by one common polymorphism (Ser180Ala) in the L pigment, and to the frequent presence of hybrid genes that encode pigments with various spectral properties. Both recombination and gene conversion between the highly homologous L and M pigment genes have generated wide variation in genotype and color vision phenotype. The S, M and L cones are distributed randomly in the central retina. Unlike S cones, M and L cones vary widely in number within the central retina. Determining the number of the three classes of cone and their special distribution in the living retina has significantly advanced the ability to correlate the cone mosaic in normal and color-defective subjects with the color vision phenotype. The transcription factors NR2E3, TRbeta2 and RXRgamma play crucial roles in establishment of the retinal cone mosaic during eye development.

Animals↗
PubMedDate not supplied

Predicting glaucomatous sensitivity loss using perimetric color saturation test.

PURPOSE: To predict future glaucomatous sensitivity loss using a perimetric color saturation test (PCST) that measures the color saturation discrimination threshold for six hues (red, yellow, green, green-blue, blue, and purple) at 9 degrees in horizontal and 3 degrees in vertical extrafoveal points. METHODS: This new test was carried out on 31 patients (31 eyes) with early glaucoma or ocular hypertension. The sensitivity loss at the four points approximately 9.5 degrees apart from the fixation point was prospectively evaluated annually for 3 years using the Humphrey Field Analyzer (HFA) program central 30-2. The initial results of PCST and the total deviation (TD) in the follow-up HFA results were compared. RESULTS: Twenty-seven patients (27 eyes) were followed up for 3 years. The color saturation threshold for six hues was correlated with the TD of HFA results at 108 points in the 27 eyes. The TD was -4 dB or better at the baseline measurement in 91 out of the 108 points. The averaged TD in the second and the third year in the follow-up period decreased below -4 dB in 10 of these 91 points, which were categorized as progression points in relation to the 81 nonprogression points. In the initial PCST, only the saturation threshold for purple was higher in the progression points when compared with the nonprogression points (P=.0004, Mann-Whitney U-test). CONCLUSION: Future sensitivity loss is most likely at the points where the threshold of color saturation discrimination is increased for purple in eyes with early glaucoma or ocular hypertension.

Adult↗
PubMed2004

Impairments of colour vision induced by organic solvents: a meta-analysis study.

The impairment of colour discrimination induced by occupational exposure to toluene, styrene and mixtures of organic solvents is reviewed and analysed using a meta-analytical approach. Thirty-nine studies were surveyed covering a wide range of exposure conditions. Those studies using the Lanthony Panel D-15 desaturated test (D-15d) were further considered. From these for 15 samples data on colour discrimination ability (Colour Confusion Index, CCI) and exposure levels were provided, required for the meta-analysis. In accordance with previously reported higher CCI values for the exposed groups, the computations yielded positive effect sizes for 13 of the 15 samples, indicating that in the great majority of the studies the exposed groups showed inferior colour discrimination. However, the meta-analysis showed great variation in effect sizes across the studies. Possible reasons for inconsistency among the reported findings are discussed. These pertain to exposure-related parameters, as well as to confounders such as conditions of test administration and characteristics of subject samples. Those factors vary considerably among the studies and might have greatly contributed to divergence in measured colour vision capacity, thereby obscuring consistent effects of organic solvents on colour discrimination.

Color Perception↗
PubMed2005

Individual differences among grapheme-color synesthetes: brain-behavior correlations.

Grapheme-color synesthetes experience specific colors associated with specific number or letter characters. To determine the neural locus of this condition, we compared behavioral and fMRI responses in six grapheme-color synesthetes to control subjects. In our behavioral experiments, we found that a subject's synesthetic experience can aid in texture segregation (experiment 1) and reduce the effects of crowding (experiment 2). For synesthetes, graphemes produced larger fMRI responses in color-selective area human V4 than for control subjects (experiment 3). Importantly, we found a correlation within subjects between the behavioral and fMRI results; subjects with better performance on the behavioral experiments showed larger fMRI responses in early retinotopic visual areas (V1, V2, V3, and hV4). These results suggest that grapheme-color synesthesia is the result of cross-activation between grapheme-selective and color-selective brain areas. The correlation between the behavioral and fMRI results suggests that grapheme-color synesthetes may constitute a heterogeneous group.

Brain Mapping↗
PubMed2005

The importance of individual differences in grapheme-color synesthesia.

In this issue of Neuron, Hubbard et al. show individual differences in how grapheme-color synesthetes perform on cognitive tasks. Importantly, these behavioral differences were correlated with fMRI measures. Such individual differences have important ramifications for synesthesia research. If individual differences are ignored, then synesthesia research will be characterized by erroneous conclusions and failures to replicate.

Brain↗
PubMed2007

The use of tinted contact lenses in the management of achromatopsia.

BACKGROUND: Achromatopsia is a congenital, autosomal recessively inherited condition in which cones are either defective or absent. Complete achromatopsia results from having only rods as functioning photoreceptors. Many people with achromatopsia have small amounts of residual cone function that may provide minimal color vision under special circumstances. Clinical findings associated with the condition include reduced visual acuity, nystagmus, a greater than normal incidence of high ametropia, and severe photophobia. The photophobia resulting from achromatopsia can be debilitating even in normal indoor illumination. Tinted contact lenses have been reported to reduce photophobia and improve visual function in these patients. CASES: Two cases are reported here. A 32-year-old man presented with reduced and stable visual acuity, complete color blindness, nystagmus, and debilitating photophobia. The second patient was a 23-year-old woman who presented with reduced and stable visual acuity, severely impaired color vision, rotary nystagmus, and significant photophobia. Both of these patients were fit with centrally tinted contact lenses. Although visual acuity did not improve measurably in either patient with tinted compared with clear lenses, both experienced a dramatic reduction in photophobia with the lenses. CONCLUSION: Tinted spectacle or contact lenses may be useful in relieving photophobia associated with a number of cone disorders, including achromatopsia. In addition to decreasing light sensitivity, tinted lenses have been reported to improve visual acuity, decrease the size of central scotomata, enlarge peripheral visual field, and enhance visibility of long wavelength stimuli in bright illumination.

Adult↗
PubMed2004

Identification of a protanomalous chimpanzee by molecular genetic and electroretinogram analyses.

We determined the structures of long (L)-wavelength-sensitive and middle (M)-wavelength-sensitive opsin gene array of 58 male chimpanzees and we investigated relative sensitivity to red and green lights by electroretinogram flicker photometry. One subject had protanomalous color vision, while others had normal color vision. Unlike in humans, a polymorphic difference in the copy number of the genes and a polymorphic base substitution at amino acid position 180 were not frequently observed in chimpanzees.

Animals↗
PubMed1985

The problem of patient compliance.

The problem of noncompliance is an increasing and vexing one. Major reasons for this dilemma include a growing skepticism concerning the ability and dedication of the health care industry, as well as a growing population of older people. A review of medical history reveals ancient attitudes toward compliance. There are special problems for special people, such as infants, children, adolescents, elderly persons, and those who are hostile or have a "sick" wish or "death" wish. Persons who require long-term therapy require special care. Child abuse and abuse of elderly persons may be involved. Problems of decreased visual acuity, color perception, and deafness must be dealt with on an individual basis. The responsibility of the physician, which includes nonobtrusive monitoring, is stressed. Consideration is given to the pharmaceutical industry and the role it can play to help mitigate the problem. In conclusion, anticipation of the problem and improved doctor-patient relationships will achieve desired results.

Attitude↗
PubMed2002

Fomepizole therapy for reversal of visual impairment after methanol poisoning: a case documented by visual evoked potentials investigation.

PURPOSE: To illustrate the safety and efficacy of fomepizole in a case of methanol poisoning with initial visual impairment. DESIGN: Interventional case report. METHODS: A 60-year-old man was admitted with blurred vision and changes in color perception 18 hours after ingesting 100 ml methanol. Fomepizole was chosen for antidotal therapy in combination with hemodialysis. Flash electroretinogram (fERG) and flash visual evoked potentials (fVEPs) examinations were obtained at the bedside 2 hours after admission and on days 1 and 8. The monocular pattern-reversal visual evoked potentials (pVEPs) were investigated on days 1 and 8. RESULTS: A complete reversal of visual impairment was achieved within 20 hours. An abnormal b-wave amplitude and an increased peak III latency at VEPs were present on admission and recovered within 24 hours. CONCLUSIONS: Fomepizole appeared safe and effective for a patient who had severe methanol poisoning presenting with visual impairment.

Alcohol Dehydrogenase↗
PubMed1981

Atrophy of myelinated retinal nerve fibers after acute optic neuropathy.

A 45-year-old man with extensive myelinated retinal nerve fibers had an attack of anterior ischemic optic neuropathy. Serial fundus photographs documented the loss of myelin. Visual acuity in the affected eye decreased to 6/90 (20/300) and color perception was markedly reduced. The visual fields in the affected eye showed dense superior and inferior arcuate scotomas and central depression. These findings were unchanged nine months later, but the areas of myelinated nerve fibers had become smaller.

Humans↗