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At least 1,423 records · Page 79Linked to original sources
PubMed2004

Evaluating the human X-chromosome pigment gene promoter sequences as predictors of L:M cone ratio variation.

Men with normal color vision vary widely in the ratio of long- (L) to middle-wavelength sensitive (M) cones. This variation provides opportunities to test models for the mechanism that produces L versus M cones during development. The L and M photopigment genes lie in a tandem array. Each gene has a promoter, and upstream of each array there is a genetic element, termed the locus control region (LCR), that is required for the expression of both L and M pigment genes. During development, for each cell that has been determined to be an L or M cone, it has been proposed that the LCR acts as a stochastic selector which chooses one gene from the array to be expressed. In this model, the L and M promoters compete for contact with the LCR in each photoreceptor. Theoretically, the promoter that, by chance, is the first to successfully form a stable and permanent complex with the LCR commits the cell to a lifetime of exclusive expression of its associated gene. Under this model, it has been suggested that nucleotide differences in the promoters influence their ability to compete in forming a complex with the LCR. Thus, normal variation in L:M cone ratio is predicted to be associated with nucleotide polymorphisms in the promoters. Here we tested this hypothesis by comparing the L and M promoter sequences for 73 males with normal color vision for whom L:M cone ratio estimates had been obtained previously. The M gene promoter sequences were found to be identical for all 73 males and the L gene promoters were identical for 71 out of the 73 males. Two males had mutations where in each case the L promoter differed by one nucleotide substitution compared to normal. Both of the males with promoter mutations had unusual cone ratios which is consistent with the growing body of evidence indicating that the relative ability of the promoters to form a complex with the LCR is a factor in determining cone ratio. However, the vast majority of cone ratio differences were not associated with any difference in the promoter sequence. To explain the high degree of cone ratio variation among normal males, the mechanism that determines whether a cone is L or M must involve genetic elements that have a high degree of genetic polymorphism in the normal population. The results presented here indicate that there are additional genetic components of the mechanism which remain to be identified and incorporated into the present hypotheses.

Base Sequence↗
PubMed1999

Dominant optic atrophy. Refining the clinical diagnostic criteria in light of genetic linkage studies.

OBJECTIVE: To describe the clinical findings and refine the clinical diagnostic criteria for dominant optic atrophy based on eight British families in which the diagnosis was confirmed by linkage analysis. DESIGN AND PARTICIPANTS: Case series; 92 subjects in 8 pedigrees had both eyes examined. INTERVENTION: Family members received a domiciliary examination based on best-corrected visual acuity, color vision using Ishihara and Hardy Richter Rand (HRR) plates, confrontation field testing using a red target, and optic disc evaluation using a direct ophthalmoscope. Genomic DNA was extracted from leukocytes or buccal mucosal cells and genotyped using 12 fluorescently labeled microsatellite markers from the region 3q27-q29. MAIN OUTCOME MEASURES: Subjects were classified clinically as definitely or possibly affected on the basis of the domiciliary examination before genetic analysis, and these results were compared with the haplotype analysis. RESULTS: Clinically, 43 subjects were identified as definitely affected, 4 as possibly affected, and 45 as unaffected. Visual acuity in affected subjects ranged from 6/6 to count fingers and declined with age. On genetic analysis, a haplotype was identified in each family, which was found in all definitely affected members but not in those regarded as unaffected. The four possibly affected individuals also bore the haplotype that segregated with the disease. CONCLUSIONS: Simple clinical tests are highly efficacious in diagnosing dominant optic atrophy. Contrary to accepted criteria, symptoms begin before the age of 10 years in only 58% of affected individuals. Visual acuity in affected subjects is highly variable. A mild degree of temporal or diffuse pallor of the optic disc and minimal color vision defects, in the context of a family with dominant optic atrophy, are highly suggestive of an individual being affected, even if the visual acuity is normal. This widens the generally accepted diagnostic criteria for this disease.

Adolescent↗
PubMed1997

Visual function and quality of life among patients with glaucoma.

This study determines the relation between visual field impairment, visual functioning, and global quality of life in patients with glaucoma. Binocular visual field impairment was calculated from simultaneous Esterman visual field testing using the Humphrey automated perimeter. Visual acuity impairment, defined with the American Medical Association's Guides to the Evaluation of Permanent Impairment; visual functioning, measured with the VF-14 and the field test version of the National Eye Institute-Visual Functioning Questionnaire; and global quality of life, assessed with the Medical Outcomes Study 36-Item Short Form Health Survey, were determined in 147 consecutive patients with glaucoma. None of the Medical Outcomes Study 36-Item Short Form Health Survey domains demonstrated more than a weak correlation with visual field impairment. The VF-14 scores were moderately correlated (r = -0.58). Of the National Eye Institute-Visual Functioning Questionnaire scales, peripheral vision (r = -0.60), distance activities (r = -0.56), and vision-specific dependency (r = -0.56) were moderately correlated with visual field impairment; vision-specific social functioning, near activities, vision-specific role difficulties, general vision, vision-specific mental health, color vision, and driving were modestly correlated with visual field impairment (r value between -0.32 and -0.55); visual pain was weakly correlated with visual field impairment; and general health and vision-specific expectations were not notably correlated with visual field impairment. Statistically adjusting for visual acuity weakened the correlations. The Medical Outcomes Study 36-Item Short Form Health Survey indicated that our patients with glaucoma were comparable with previously studied patients without severe systemic medical problems. However, the Medical Outcomes Study 36-Item Short Form Health Survey scores did not correlate with visual field impairment in our study. Based on the moderate correlation between binocular visual field impairment with the VF-14 and the National Eye Institute-Visual Functioning Questionnaire, these questionnaires may be useful among patients with glaucoma.

Adolescent↗
PubMed1982

Classification of complete and incomplete autosomal recessive achromatopsia.

We studied color vision in 32 patients with autosomal recessive achromatopsia. Color matching revealed complete achromatopsia (rod monochromasy) in ten patients (Group I) and incomplete achromatopsia in the remaining twenty-two patients. Amongst the incomplete achromats, were three groups distinguishable by their color matching. Patients in Group II were dichromats; their color matches were mediated by rods and MWS (middle-wavelength sensitive) cones. Patients in Groups III and IV were trichromats. Color matches of patients in Group III were mediated by rods, LWS (long-wavelength sensitive) cones and MWS cones. Group III patients showed no evidence of SWS (short-wavelength sensitive) cones. Color matches of patients in Group IV were mediated by rods, LWS cones and SWS cones; color matching did not reveal MWS cones.

Adolescent↗
PubMed2003

ERGs, cone-isolating VEPs and analytical techniques in children with cone dysfunction syndromes.

Photoreceptor and post-receptoral function in children with congenital and acquired cone disorders was measured by full-field electroretinogram (ERG) and transient visual evoked potentials (VEPs). Subjects were five rod monochromats (RM), five with cone dystrophy (CD), and 30 controls. Patients were diagnosed by clinical findings, ERGs, and standard color vision tests. VEP stimuli were check reversals and color grating onsets that stimulated each photoreceptor type (L-, M-, or S-cones) or post-receptoral pathways (L-M, white/black). VEP signal-to-noise ratios (S/N) were calculated by Fourier analysis of VEP epochs. All RM patients showed extinguished cone ERGs. A near normal S-cone VEP was recorded from a blue-cone rod monochromat without any signal from the L- or M-cone stimuli. Two other RM patients were classified as incomplete RM based on a low-level VEP signal from either L- or M-cone stimuli. CD patients had mildly to severely reduced ERGs and VEPs were abnormal to all cone-isolating stimuli. The VEP S/N ratio was not significantly correlated with the amount of rod contrast in the color stimuli. Color VEPs provide an objective assessment of macular cone function in children with cone dysfunction syndromes that is more sensitive to residual central cone function than standard full-field ERGs. VEP techniques may be useful in the early detection of cone loss in children, especially in children who do not tolerate ERG testing.

Adolescent↗
PubMed2004

Delayed regeneration of foveal cone photopigments in Vogt-Koyanagi-Harada disease at the convalescent stage.

PURPOSE: To evaluate the physiological characteristics of the macula in patients with Vogt-Koyanagi-Harada disease during the convalescent stage with specific reference to the kinetics of foveal cone photopigment regeneration. METHODS: Six eyes of three patients at the convalescent stage of Vogt-Koyanagi-Harada disease were studied. All the eyes had best corrected visual acuity of 1.0 or better and had had no recurrence of inflammation for at least 12 months after the last episode. Foveal cone densitometry (FCD), focal macular electroretinograms, color vision tests, two-color perimetry, and optical coherence tomography (OCT) were performed. RESULTS: No regeneration of cone photopigments was detected within the 7-minute testing time by FCD in all eyes at the first examination after the last episode. However, the other functional tests were normal, and the OCT-determined macular morphology was also normal. The regeneration kinetics of the foveal cone photopigment improved in three of six eyes at 36, 37, and 19 months after the last episode, whereas the other three remained delayed at 18, 18, and 49 months. CONCLUSIONS: These findings suggest that a disorder of the foveal cone photopigment regeneration, and its recovery, requires a significantly longer time than that of other macular functions in some patients with Vogt-Koyanagi-Harada disease.

Adult↗
PubMed1975

Recognition of traffic signals viewed through colored filters.

Experiments were carried out to provide an empirical basis for setting color standards for sunglasses. Nineteen individuals, ten with anomalous color vision, viewed traffic signals through a series of color filters. Limits on the apparent color shift for the amber and green signals as well as for D65 are presented on a 1931 CIE chromaticity diagram. Limits on the reduction in the apparent luminosity for each of the three signals are given in terms of the minimum transmittance of the lens for each signal.

Automobile Driving↗
PubMed1996

Visual impairment, visual functioning, and quality of life assessments in patients with glaucoma.

BACKGROUND/PURPOSE: To determine the relation between visual impairment, visual functioning, and the global quality of life in patients with glaucoma. METHODS: Visual impairment, defined with the American Medical Association Guides to the Evaluation of Permanent Impairment; visual functioning, measured with the VF-14 and the Field Test Version of the National Eye Institute-Visual Functioning Questionnaire (NEI-VFQ); and the global quality of life, assessed with the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), were determined in 147 consecutive patients with glaucoma. RESULTS: None of the SF-36 domains demonstrated more than a weak correlation with visual impairment. The VF-14 scores were moderately correlated with visual impairment. Of the twelve NEI-VFQ scales, distance activities and vision specific dependency were moderately correlated with visual impairment. Of the twelve NEI-VFQ scales, distance activities and vision specific dependency were moderately correlated with visual field impairment; vision specific social functioning, near activities, vision specific role difficulties, general vision, vision specific mental health, color vision, and driving were modestly correlated; visual pain was weakly correlated; and two were not significantly correlated. Correcting for visual actuity weakened the strength of the correlation coefficients. CONCLUSIONS: The SF-36 is unlikely to be useful in determining visual impairment in patients with glaucoma. Based on the moderate correlation between visual field impairment and the VF-14 score, this questionnaire may be generalizable to patients with glaucoma. Several of the NEI-VFQ scales correlate with visual field impairment scores in patients with a wide range of glaucomatous damage.

Adolescent↗
PubMed1992

Isoluminant stimuli may not expose the full contribution of color to visual functioning: spatial contrast sensitivity measurements indicate interaction between color and luminance processing.

Visual performance is greatly impaired when tested with heterochromatic isoluminant stimuli. It is thus concluded that the chromatic system contribution to many visual tasks is limited. We suggest that unless color and luminance are shown to be processed independently, such experiments do not demonstrate shortcomings of the chromatic system but rather the inadequacy of using isoluminant stimuli for isolating that system. We hypothesize that color vision has evolved not only to encode color per se but also to enhance luminance-based visual processing, so that for color information to be fully effective, luminance as well as chromatic variations should be present in the stimulus. The hypothesis was tested by studying the contribution of color to spatial vision. The human contrast sensitivity function (CSF) was studied using luminance, isoluminance (color) and combined luminance/color sinusoidal gratings. It is found that luminance contrast sensitivity is enhanced when luminance contrast is accompanied by color contrast and vice versa. The nature of the interaction is best described by an additive single analyzer model. Color opponent cells which respond to both chromatic and achromatic stimuli may be identified as the analyzer.

Color Perception↗