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PubMed2003

Assessment of visual functions following prenatal exposure to organic solvents.

Prenatal exposure to organic solvents has been previously associated with increased risk of color vision deficits and reduced visual acuity in young children. These findings prompted us to evaluate visual functioning in solvent-exposed infants using more sensitive non-invasive visual evoked potential (VEP) techniques. VEP techniques are described in the context of an ongoing prospective longitudinal cohort study of infants exposed to organic solvents in utero. VEPs are recorded via three active electrodes fitted over the occipital cortex while infants view changing visual stimuli. The sweep VEP is used to assess contrast detection and visual acuity by presenting sinusoidal gratings that "sweep" across a range of contrasts and spatial frequencies. Transient VEPs are used to assess responses to equiluminant chromatic- and luminance-modulated sinusoidal gratings presented in pattern onset-offset format. A single case study is presented showing abnormal chromatic responses and reduced contrast sensitivity in a 2.5-year-old boy following prenatal exposure to perchloroethylene (PCE). These VEP techniques therefore appear promising for the clinical assessment of visual toxicity in pediatric populations.

Child, Preschool↗
PubMed1987

Equilibrium hue judgements of dichromats.

It is generally held that protanopes and deuteranopes see only regions of blues and yellows in the visible spectrum, with an achromatic point, called the neutral point, separating these regions. Considerations of a zone model of color vision for the dichromatic observer led us to predict that a reduced form of red/green discrimination would allow equilibrium blue judgements to be made by protanopes. We show that protanopes can make equilibrium blue determinations with as much reliability as they make neutral point settings. Our results indicate that protanopes but not deuteranopes are able to rely on a reduced form of red/green discrimination in the short wavelength part of the spectrum. Protanopes describe wavelengths longer than the neutral point as yellow. Between the neutral point and equilibrium blue, different wavelengths are described as having varying aspects of blue and green; and short of equilibrium blue they appear reddish blue. For dueteranopes, the spectrum longer than the neutral point appears yellow, and short of it, blue. The results of our experiments showing that the protanopic equilibrium blue is invariant with intensity variations, as it is in the trichromat, add support to the idea of a reduced form of red/green discrimination for protanopes. Our results also allow the evaluation of various models of protanopia.

Color Perception↗
PubMed1994

Eye movement abnormalities in carriers of blue-cone monochromatism.

PURPOSE: Although impaired color vision and ERG changes have been detected in carriers of blue-cone monochromatism (BCM), no eye movement abnormalities have been identified. Quantitative eye movements of three obligate carriers of BCM were analyzed. METHODS: Horizontal and vertical eye movements of three obligate carriers of two families with BCM with visual acuity of 20/20 or better were recorded using the magnetic search coil technique. Subjects were examined fixing in primary and eccentric gaze and during horizontal and vertical smooth pursuit at 20 degrees, 40 degrees, and 80 degrees per second. RESULTS: All carriers displayed fixation instability. In two subjects, fine-amplitude upbeat, jerk-type nystagmus was detected. Reduced pursuit gain was found in the carriers. The third subject had small downbeat nystagmus. CONCLUSION: Abnormal eye movements are described for the first time in carriers of BCM. The nystagmus is clearly distinct from congenital or latent nystagmus and is similar to the nystagmus reported in BCM. Because all carriers had excellent visual acuity, in BCM, nystagmus is intrinsic to the disease and can appear independently of the visual defect.

Adult↗
PubMed1997

Evaluation of a significantly shorter version of the Farnsworth-Munsell 100-hue test in patients with three different optic neuropathies.

We tested the hypothesis that a subset of the Farnsworth-Munsell 100-hue test (FM-100) would be a sensitive, specific, and practical means of monitoring color vision in patients with chronic optic nerve disorders. We retrospectively analyzed the records of 1,113 patients affected with optic neuritis (ON), Graves' ophthalmopathy with suspected optic neuropathy, or idiopathic intracranial hypertension with suspected optic neuropathy (IIH). One hundred six records of patients showed that an FM-100 had been performed (23 ON, 46 Graves', 37 IIH). Forty additional patients were studied prospectively (11 ON, 17 Graves', 12 IIH). The sensitivity and specificity of all possible 21 chip subtests were compared against the same statistics for the entire test. We found that for these three optic nerve disorders, a test consisting of chips 22-42 had nearly the same sensitivity and specificity as the entire test when compared with the clinical diagnosis. At 90% specificity, the ratio of sensitivities of the short version to the original version of the test were IIH, 53%/45%; optic neuritis, 85%/79%; and Graves', 67%/70%. The majority of the clinical value of the test can be achieved in one fourth of the original examination time.

Adult↗
PubMed1993

Impact of new and emerging instrumentation in optometry.

Traditional tests of vision emphasize visual acuity, visual fields, and testing for hereditary color vision defects. New instrumentation for testing vision has proliferated due to advances in our knowledge of the visual system, the availability of new technologies, the introduction of computers into practice, and the expanded scope of optometric practice. Each is discussed in relation to the subsequent symposium papers by other authors.

Color Perception↗
PubMedDate not supplied

[A multifactorial etiologic approach to diabetic dyschromatopsia. Study of 100 diabetics].

Diabetic dyschromatopsia is frequent and is a true complication of diabetes mellitus. Causative factors other than retinopathy have been suggested, but they remain unclear. We have explored the color vision of 100 diabetics aged 16 to 65 (88 insulin-dependent, 12 non-insulin dependent) with Lanthony's D15 desatured panel. Degenerative complications were looked for, especially by fundoscopy and electrophysiological exploration of peripheral nerves using specific scoring. 73% of the diabetics had dyschromatopsia. Dyschromatopsia was significatively more frequent when retinopathy was present (26 out of 30 diabetics with retinopathy versus 47/70 without). We explain the absence of a strict parallelism between dyschromatopsia and retinopathy by the intervention of other factors. Whereas the equilibration of the diabetes was not different between the groups with or without dyschromatopsia, patient age, microalbuminuria, blood pressure and alcohol intake were higher in patients with dyschromatopsia. The greater prevalence of peripheral neuropathy in patients with dyschromatopsia, confirmed by electrophysiology, and independently from the existence of retinopathy, is an indicator of the existence of neuronal disease, whose level remains to be determined. Our results are the indispensible preliminary step to a study of the respective importance of these pathogenic factors.

Adolescent↗
PubMed1987

[Evaluation of the desaturated Panel D-15. II: Comparison between the desaturated Panel D-15 and Farnsworth 100-hue tests].

The color vision was examined in 319 subjects in a comparative manner by means of the desatured Panel D-15 and Farnsworth 100-hue test used as reference test. The results expressed by scoring, were as follows: 1) a strong correlation (r = 0.80) was evidenced between the 2 tests; 2) the probable scores of the desaturated Panel D-15 were predicted from the 100-hue scores, by means of a suitable regression equation; thus allowing the calculation of norms of the desaturated Panel D-15 by reference to the well-established norms according to age of the 100-hue test; 3) the normal or pathological character of the scores of the desaturated Panel D-15 was infered from these norms, and was in good agreement with the scores of 100-hue test (K = 0.68); 4) the normal or pathological character of the qualitative patterns of the desaturated Panel D-15 was also infered from the scores; so: the minor errors were normal from 30 years old patients; a single diametral error is normal; 3 or 4 diametral errors are normal from 65 years old patients.

Adolescent↗
PubMed2005

Autosomal dominant cone dystrophy caused by a novel mutation in the GCAP1 gene (GUCA1A).

PURPOSE: To describe the clinical features and genetic analysis of a family with an autosomal dominant cone dystrophy (adCD). METHODS: Selected members of a family with an autosomal dominant cone dystrophy underwent ophthalmic evaluation. Blood samples were obtained, genomic DNA was isolated, and genomic fragments were amplified by PCR. Linkage to locus D6S1017 was established. DHPLC mutational analysis and direct sequencing were used to identify a mutation in GUCA1A, the gene encoding the guanylate cyclase activating protein 1 (GCAP1). RESULTS: Of 24 individuals who are at risk of the disease in a five generation family, 11 members were affected. Clinical presentations included photophobia, color vision defects, central acuity loss, and legal blindness with advanced age. The disease phenotype was observed in the second and third decades of life and segregated in an autosomal dominant fashion. An electroretinogram performed on one proband revealed profoundly subnormal and prolonged photopic and flicker responses, but preserved scotopic ERGs, consistent with a cone dystrophy. Mutational analysis and direct sequencing revealed a C451T transition in GUCA1A, corresponding to a novel L151F mutation in GCAP1. Like the E155G mutation, this mutation occurs in the EF4 hand domain, a region of GCAP1 critical in conferring calcium sensitivity to the protein. The leucine at this position is highly conserved among vertebrate guanylate cyclase activating proteins. CONCLUSIONS: A novel L151F missense mutation in the EF4 high affinity Ca2+ binding site of GCAP1 is linked to adCD in a large pedigree. The cone dystrophy in this family shares clinical and electrophysiologic characteristics with other previously described adCD caused by mutations in GUCA1A.

Adult↗
PubMed1999

Visual impairment and REP-1 gene mutations in Japanese choroideremia patients.

Choroideremia (CHM), an X-linked recessive hereditary disease, is an intractable chorioretinal dystrophy. The rate of disease progression of CHM reportedly shows considerable variability. A number of mutations involving the gene that codes for Rab escort protein-1 (REP-1) have been detected in CHM patients. We have analyzed REP-1 gene mutations of Japanese CHM patients. The present study was designed to investigate the clinical variability and the genotype to phenotype relationship in 15 Japanese CHM patients referred to the Department of Ophthalmology of Juntendo University Hospital. The clinical investigation of visual acuity, visual field, color vision and refraction revealed inter-individual variability. Mutation analyses of the REP-1 gene revealed 10 types of mutations in 13 patients from 11 families, including an insertion, small deletions, nonsense mutations and an A to CC mutation. In 13 CHM patients with detectable REP-1 gene mutations, no relationship of genotype to phenotype was detected. At present, we consider the REP-1 genotype to be an unreliable prognostic factor for counseling of CHM patients. In two patients from one family, no mutations were detected in coding regions of the REP-1 gene. These patients may have intron mutations of the REP-1 gene, not detectable by the techniques employed in this study, or other causative genes. Both were observed to have somewhat slower disease progression than the other 13 patients. More advanced analyses are necessary to answer questions regarding the genotype-phenotype relationship in CHM patients.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Tubby-like protein 1 homozygous splice-site mutation causes early-onset severe retinal degeneration.

PURPOSE: To characterize the disease expression of an autosomal recessive human retinal degeneration associated with a mutation in TULP1 (tubby-like protein 1), a gene with currently unknown function. METHODS: Homozygotes and heterozygotes from an extended Dominican kindred with a TULP1 splice-site gene mutation (IVS14+1,G-->A) were studied clinically and with visual function tests. Sequence analysis of TULP1 was also performed in unrelated patients with severe retinal degeneration from a North American clinic population. RESULTS: Homozygotes had nystagmus, visual acuity of 20/200 or worse, color vision disturbances, bull's eye maculopathy, and peripheral pigmentary retinopathy. Younger patients had a relatively wide extent of kinetic visual fields; older patients had only peripheral islands. No rod function was measurable by psychophysics in any of the patients; markedly reduced cone function was detectable across the visual field of younger patients and in the remaining peripheral islands of older patients. Rod and cone electroretinograms (ERGs) were not detectable using standard methods; microvolt-level cone ERGs were present in some patients. Heterozygotes had normal visual function. No putative pathogenic sequence changes in TULP1 were observed in North American patients with comparably severe retinal phenotypes, mainly in the diagnostic category of Leber congenital amaurosis. CONCLUSIONS: This TULP1 splice-site mutation in homozygotes causes early-onset, severe retinal degeneration involving macular and peripheral cones and rods. The constellation of phenotypic findings suggests that the TULP1 gene product is critically important for normal photoreceptor function and may play a role in retinal development.

Adolescent↗
PubMedDate not supplied

[Dyschromatopsia: manifestation or epiphenomenon in the course of diabetic neuropathy].

We performed a study in 92 diabetic patients (76 Type 1 and 16 Type 2) without retinopathy to determine the relation between diabetic dyschromatopsia and neuropathy, which has been evoked in previous studies. Color vision was explored with Lanthony's desaturated D 15 panel. Peripheral nervous function was explored with an electrophysiological score which has been beforehand validated. Moreover evoked visual potentials were performed in 38 diabetic subjects in order to determine whether dyschromatopsia was related to an impairment of central optic pathways. Fifty-one among the 92 diabetic subjects had a blue-yellow dyschromatopsia. Among the recorded parameters, only peripheral nervous impairment was significantly more frequent in the group with dyschromatopsia than in the group without. Ten among 38 diabetics had impairment of the evoked visual potentials. Frequency of alteration of evoked visual potentials was not different between the group with and the group without dyschromatopsia. Our results confirm the relationship between dyschromatopsia and the alteration of the nervous function in diabetic subjects. In return, lack of significant modification of evoked visual potentials among diabetic patients with dyschromatopsia and the blue-yellow axis of dyschromatopsia are in opposition with a direct neurological origin of dyschromatopsia. We therefore evoke a common process in the beginning of the diabetic dyschromatopsia and of peripheral neuropathy.

Adolescent↗
PubMed2001

Digital vision theory: Boolean logic model.

Guild (1932) stated the general requirements for processing signals in color vision system and a digital format of his paradigm is developed in this paper. The disk structure generates the digital receptor pulse. The input modalities form sets, linked by intersections, joins, and complement junctions. The synapses are elements in these junctions. Complex synapses form junctions to create Boolean logic processing. A computer program using these Boolean logic functions calculates: Light and dark adaptation responses; Color matching and spectral coordinate functions; Chromatic adaptation; Color shift responses; and Dynamic neural responses. These calculations compare favorably with the experimental data. The processing criteria for signals in the vision system are given by Guild (1932). The analysis in this paper uses his criteria to develop a model of the vision system. A computer program simulates the digital processing of signals from the external photon source to the neural output signals from the ganglion cells in the inner-plexiform layer. The responses are compared with the responses of actual vision systems.

Color Perception↗
PubMed1988

The relationship between hue discrimination and contrast sensitivity deficits in patients with diabetes mellitus.

In an attempt to elucidate more fully the pathophysiologic basis of early visual dysfunction in patients with diabetes mellitus, color vision (hue discrimination) and spatial resolution (contrast sensitivity) were tested in diabetic patients with little or no retinopathy (n = 57) and age-matched visual normals (n = 35). Some evidence of visual dysfunction was observed in 37.8% of the diabetics with no retinopathy and 60.0% of the diabetics with background retinopathy. Although significant hue discrimination and contrast sensitivity deficits were observed in both groups of diabetic patients, contrast sensitivity was abnormal more frequently than hue discrimination. However, only 5.4% of the diabetics with no retinopathy and 10.0% of the diabetics with background retinopathy exhibited both abnormal hue discrimination and abnormal contrast sensitivity. Contrary to previous reports, blue-yellow (B-Y) and red-green (R-G) hue discrimination deficits were observed with approximately equal frequency. In the diabetic group, contrast sensitivity was reduced at all spatial frequencies tested, but for individual diabetic patients, significant deficits were only evident for the mid-range spatial frequencies. Among diabetic patients, the hue discrimination deficits, but not the contrast sensitivity abnormalities, were correlated with the patients' hemoglobin A1 level. A negative correlation between contrast sensitivity at 6.0 cpd and the duration of diabetes also was observed.

Adult↗
PubMed2005

Organization of the human trichromatic cone mosaic.

Using high-resolution adaptive-optics imaging combined with retinal densitometry, we characterized the arrangement of short- (S), middle- (M), and long- (L) wavelength-sensitive cones in eight human foveal mosaics. As suggested by previous studies, we found males with normal color vision that varied in the ratio of L to M cones (from 1.1:1 to 16.5:1). We also found a protan carrier with an even more extreme L:M ratio (0.37:1). All subjects had nearly identical S-cone densities, indicating independence of the developmental mechanism that governs the relative numerosity of L/M and S cones. L:M cone ratio estimates were correlated highly with those obtained in the same eyes using the flicker photometric electroretinogram (ERG), although the comparison indicates that the signal from each M cone makes a larger contribution to the ERG than each L cone. Although all subjects had highly disordered arrangements of L and M cones, three subjects showed evidence for departures from a strictly random rule for assigning the L and M cone photopigments. In two retinas, these departures corresponded to local clumping of cones of like type. In a third retina, the L:M cone ratio differed significantly at two retinal locations on opposite sides of the fovea. These results suggest that the assignment of L and M pigment, although highly irregular, is not a completely random process. Surprisingly, in the protan carrier, in which X-chromosome inactivation would favor L- or M-cone clumping, there was no evidence of clumping, perhaps as a result of cone migration during foveal development.

Color Perception↗
PubMed2005

Clinical and genetic features of Hungarian achromatopsia patients.

PURPOSE: To describe the clinical features and molecular genetic findings in a collection of Hungarian achromatopsia patients. METHODS: Twelve patients with congenital achromatopsia from nine Hungarian families were analyzed in this study. The patients underwent standard ophthalmological examination including detailed full-field electroretinography and color vision testing. In two patients, dark adaptation and spectral luminosity tests were also performed. PCR/RFLP analysis and DNA sequencing was applied for mutation screening of CNGA3 and CNGB3. Heterologous minigene expression was used to evaluate transcript splicing of a new intronic mutation in CNGB3. RESULTS: Mutations in CNGA3 were present in four families and mutations in CNGB3 in the remaining five families, including mutations known from Western European patient samples and two new CNGB3 mutations: c.112C>T/Gln38X and c.1663-5T>G. Heterologous expression in COS7 cells shows that the latter induces a splicing defect through the activation of a cryptic splice site 4 bases upstream of the genuine splice site. The patients presented with a clinical picture typical for congenital achromatopsia and there was no significant difference in the phenotype of subjects with either CNGA3 or CNGB3 mutations based on standard ophthalmological examination. However, we assume residual cone function in a subject homozygous for the Phe547Leu mutation in CNGA3 based on prior detailed psychophysical testing (i.e., dark adaptation and spectral luminosity). CONCLUSIONS: Mutations in CNGA3 and CNGB3 account for achromatopsia in Hungarian patients including known mutations and a few new CNGB3 mutations. While standard ophthalmological examination revealed a phenotype of complete achromatopsia, we show that thorough psychophysical testing can help to identify subjects with some minute cone function.

Adult↗
PubMed2004

The Nagel anomaloscope: its calibration and recommendations for diagnosis and research.

BACKGROUND: The Nagel anomaloscope Model I is the definitive clinical instrument for classifying phenotypic variations in X-linked color-vision disorders. Its system of classification is based on the Rayleigh equation: the relative amounts of red and green primary lights required to match a yellow primary. Our aim was to characterize how changes in mains voltage and ambient temperature influence the wavelength and intensity of each primary and alter the Rayleigh matches of normal and anomalous trichromats. METHODS: A Nagel Model I anomaloscope was calibrated in wavelength and intensity while varying the temperature of its prism housing and the mains voltage. Three normal, three protanomalous and three deuteranomalous trichromats made Rayleigh matches at various temperatures and voltages. RESULTS: The intensities of the green and red primaries show an exponential growth with mains voltage. Additionally, the wavelengths and intensities of all three primaries change with prism housing temperature. As a result, the R-G match midpoints of normal and anomalous trichromats shift with increasing mains voltage, and more markedly with increasing prism housing temperature, to higher R-G settings. CONCLUSIONS: Rayleigh matches obtained with the Nagel I anomaloscope are sensitive to changes in voltage supply and prism housing temperature, arising largely from thermal effects of the internal light sources. However, the instrument may still be safely used for diagnostic and research purposes provided that: (1) a stable voltage supply is used; (2) it is kept at a constant temperature; and (3) the match midpoint of the reference population has been established under identical conditions.

Biomedical Research↗
PubMed2002

Estimates of L:M cone ratio from ERG flicker photometry and genetics.

Estimates of L:M cone ratio for males with normal color vision were derived using the flicker-photometric electroretinogram (ERG). These were obtained by best fitting ERG spectral sensitivity functions to a weighted sum of long (L)- and middle (M)-wavelength-sensitive cone spectral absorption curves. Using the ERG, measurements can be made with extremely high precision, which leaves variation in the wavelength of maximal sensitivity (lambda(max)) of the cone photopigments as the major remaining source of inaccuracy in determining the ratio of cone contributions. Here that source of inaccuracy was largely eliminated through the use of individualized L-cone spectral absorption curves deduced from L-pigment gene sequences. The method was used on 62 normal males as part of an effort to obtain a true picture of how normal variations in L:M cone ratio are distributed. The percentage of L cones in the average eye was 65%L [where %L = 100 X L / (L+M)]. There were huge individual differences ranging from 28%-93%L, corresponding to more than a 30-fold range in L:M ratio (0.4-13). However, the most extreme values were relatively rare; 80% of the subjects fell within +/-15 %L of the mean, corresponding to a 4-fold range in L:M ratio (1-4). The method remedies major weaknesses inherent in earlier applications of flicker photometry to estimate cone ratio; however, it continues to depend on the assumption that the average L cone produces a response with an identical amplitude to that of the average M cone. A comparison of the ERG results with the distribution of cone ratios estimated from cone pigment messenger RNA in cadaver eyes indicates that the assumption generally holds true. However, there may be a small number of exceptions in which individuals have normally occurring (but relatively rare) amino acid substitutions in one of their pigments that significantly affect the physiology of the cone class containing that pigment, so as to reduce the amplitude of its contribution to the ERG. Consistent with this possibility, extreme cone contribution ratios were found to be associated with atypical L-pigment amino acid combinations.

Adolescent↗
PubMed1997

Identification of a gene within the tandem array of red and green color pigment genes.

The tandem array of color pigment genes on chromosome Xq28 contains nested exons of a distinct gene. This gene (termed TEX28) is composed of five exons that span almost the entire distance between the protein-coding regions of the color pigment genes and a transketolase-related gene. Although most of the TEX28 gene is repeated within the color pigment gene array, the exclusion of exon 1 from the array is predicted to restrict transcription to a single copy of the gene. The TEX28 gene encodes a polypeptide of 410 amino acid residues. This polypeptide does not display significant homology with any known proteins in public databases. Transcripts of the gene (1.8 kb) were detected in testes, but not in any other tissue examined. Color vision disorders that result from the deletion of color pigment genes should be reappraised for associated phenotypes that may derive from disruption of the TEX28 gene.

Amino Acid Sequence↗