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PubMed2001

Effects of maternal occupational exposure to organic solvents on offspring visual functioning: a prospective controlled study.

BACKGROUND: Previous studies in adults and animals with high level exposure to organic solvents suggested impairments in visual functioning. The objective of this pilot study was to examine the effects of maternal occupational exposure to organic solvents during pregnancy on offspring color vision and visual acuity, the development of which may be especially vulnerable to organic solvent exposure. METHODS: We conducted a prospective cohort study of 32 offspring of women who were exposed occupationally to organic solvents during pregnancy compared with 27 nonexposed children. Monocular and binocular color vision and visual acuity were assessed using the Minimalist Test and the Cardiff Cards, respectively. Children with known hereditary color vision loss were excluded. RESULTS: Solvent-exposed children had significantly higher error scores on red-green and blue-yellow color discrimination, as well as poorer visual acuity compared with the control group. Exposure index (an estimated measure of exposure intensity) was not significantly related to color discrimination or visual acuity score. Despite excluding all children with a known family history of color vision loss, clinical red-green color vision loss was found among 3 of the 32 exposed children compared with none of the matched controls. CONCLUSIONS: These preliminary findings suggest that occupational exposure to organic solvents during pregnancy is associated with an increased risk of color vision and visual acuity impairment in offspring. The importance of routine visual function screening in risk assessment after prenatal exposure to chemicals warrants further attention.

Adult↗
PubMed1998

Cortical color blindness is not "blindsight for color".

Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to "blindsight" for color or an instance of "covert" processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to chromatic contrast and motion in equiluminant displays. Moreover, visually evoked cortical potentials can still be elicited in response to chromatic stimuli. We suggest that these demonstrations reveal intact residual processes rather than the operation of covert processes, where proficient performance is accompanied by a denial of phenomenal awareness. We sought evidence for such covert processes by conducting appropriate tests on achromatopsic subject M.S. An "indirect" test entailing measurement of reaction times for letter identification failed to reveal covert color processes. In contrast, in a forced choice oddity task for color, M.S. was unable to verbally indicate the position of the different color, but was surprisingly adept at making an appropriate eye movement to its location. This "direct" test thus revealed the possible covert use of chromatic differences.

Blindness, Cortical↗
PubMed1999

Color science and spectrum inversion: a reply to Nida-Rümelin.

Martine Nida-Rümelin (1996) argues that color science indicates that behaviorally undetectable spectrum inversion is possible and raises this possibility as an objection to functionalist accounts of visual states of color. I show that her argument does not rest solely on color science, but also on a philosophically controversial assumption, namely, that visual states of color supervene on physiological states. However, this assumption, on the part of philosophers or vision scientists, has the effect of simply ruling out certain versions of functionalism. While Nida-Rümelin is quite right to search for empirical tests for claims about the nature of visual states, philosophical issues remain pivotal in determining the correctness of these claims.

Color Perception↗
PubMed2000

Ineffability of qualia: a straightforward naturalistic explanation.

In this paper I offer an explanation of the ineffability (linguistic inexpressibility) of sensory experiences. My explanation is put in terms of computational functionalism and standard externalist theories of representational content. As I will argue, many or most sensory experiences are representational states without constituent structure. This property determines both the representational function these states can serve and the information that can be extracted from them when they are processed. Sensory experiences can indicate the presence of certain external states of affairs but they cannot convey any more information about them than that. So, format- or code-conversion mechanisms that link different systems of representation (linguistic and perceptual) to each other will fail to extract any relevant information from sensory experiences that could be coded in language. They only way to establish specific roles for sensory experiences in communication and the organization of behavior is to attach to them, by associative links, words, or other behavioral responses. If a sensory experience has no linguistic label associated to it in a particular subject, then no linguistic description can token, or activate, that state in the subject. In other words, no linguistic description can cause a subject to undergo an unlabeled perceptual state. On the contrary, complex, or syntactically structured perceptual states can be built up, on the basis of descriptions, by mechanisms of constructive imagination (conceived here as one sort of format conversion). It is this difference between complex and unstructured representational states that gives us an understanding of the phenomenon we call the ineffability of qualia.

Color Vision Defects↗
PubMed1998

Reversible color vision loss in occupational exposure to metallic mercury.

Color vision was evaluated in twenty-one mercury exposed workers and referents matched for sex, age, tobacco smoking, and alcohol habits. The Lanthony 15 Hue desaturated panel (D-15 d) was applied. In the workers, mean urinary Hg (HgU) was 115+/-61.5 microg/g creatinine; in all but one the values exceeded the biological limit (BEI) proposed by the American Conference of Governmental Industrial Hygienists. A dose-related subclinical color vision impairment was observed in Hg-exposed workers compared to the referents. Just after the survey, working conditions were improved. Twelve months later the workers were reexamined. Mean HgU was 10.0 microg/g creatinine and in no subjects was the BEI exceeded. Color perception was significantly improved compared to the first examination and, furthermore, no differences were observed between exposed workers and referents. The results add evidence that the color vision loss observed during the first part of the study was related to Hg exposure and, moreover, show that this effect is reversible. These data indicate that metallic Hg can induce a reversible impairment in color perception. This suggests that color vision testing should be included in studies on the early effects of Hg. The possibility of applying the D-15 d as an early effect index in the biological monitoring of Hg exposed workers should also be entertained.

Adult↗
PubMed1993

G6PD haplotypes spanning Xq28 from F8C to red/green color vision.

The most telomeric region of the human X chromosome within band Xq28 consists of a gene-rich region of about 3 Mb which contains the genes for coagulation factor VIIIc, glucose-6-phosphate dehydrogenase (G6PD), and red/green color vision. We have studied five polymorphic sites from this region, in a sample of normal people from the Cosenza province of Southern Italy. These sites, which span a distance of some 350 kb, are in strong linkage disequilibrium. Of the 32 possible haplotypes only 10 were found, and 4 of these account for 80% of all X chromosomes analyzed. In addition, we found that all G6PD-deficient people with the G6PD Mediterranean mutation belong to only two haplotypes. One of these (Med 1) is found only within a small subregion of the area investigated, west of the Appennine mountain range. Most remarkably, all Med 1 G6PD-deficient individuals also had red/green color blindness. The more frequent haplotype (Med 2) is the same in Calabria and in Sardinia, where it accounts for about 90% of the G6PD Mediterranean mutations, despite the fact that gene flow between the populations of Sardinia and Southern Italy must have been limited. These data do not enable us to determine whether the two types of G6PD Mediterranean have arisen through two separate identical mutational events or through a single mutational event followed by recombination. However, the data indicate relatively little recombination over an extended region of the X chromosome and they suggest that the G6PD Mediterranean mutation is recent by comparison to the other polymorphisms investigated.

Adult↗
PubMed1998

Human rod monochromacy: linkage analysis and mapping of a cone photoreceptor expressed candidate gene on chromosome 2q11.

We have performed linkage analysis in eight families with rod monochromacy, an autosomal recessively inherited condition with complete color blindness. Significant linkage was found with markers located at the pericentromeric region of chromosome 2. A maximum lod score of 5.36 was obtained for marker D2S2333 at theta = 0.00. Mapping of meiotic breakpoints localized the disease gene between markers D2S2187 and D2S2229. Homozygosity for a number of subsequent markers indicating identity by descent was found in two families and provides evidence for a further refinement of the locus proximal to D2S373. This defines an interval of approximately 3 cM covering the ACHM2 locus for rod monochromacy. Radiation hybrid mapping of the CNGA3 gene encoding the alpha-subunit of the cGMP gated cation channel in human cone photoreceptors resulted in a maximum lod score of 16.1 with marker D2S2311 combined with a calculated physical distance of 6.19cR10,000. Screening of the CEPH YAC library and subsequent STS mapping indicated the physical order cen-D2S2222-D2S2175-(D2S2187/D2S2311)-qtel ofmarkers on 2q11 and showed that the CNGA3 gene maps most closely to D2S2187 and D2S2311. These data indicate that the CNGA3 gene maps within the critical interval of the ACHM2 locus for rod monochromacy and thus is a candidate gene for this disease.

Chromosome Breakage↗
PubMed1981

Paradoxical pupil in congenital achromatopsia.

Children with congenital achromatopsia possess an interesting paradoxical pupillary constriction to darkness that has not been previously described. This paper describes three children in whom this paradoxical pupillary reaction was documented with infrared pupillometry. The literature on the pupil in achromatopsia is reviewed and a tentative testable model of the reaction is hypothesized.

Child↗
PubMed1987

Pattern dystrophy of the retinal pigment epithelium.

We describe six related patients presenting with an autosomal dominantly inherited pattern dystrophy of the retinal pigment epithelium, significantly abnormal electro-oculogram and minor colour vision abnormalities. There is a continuum of variable phenotypic expression within the pattern dystrophies of the retinal pigment epithelium.

Adolescent↗
PubMed1986

Computer analysis of Farnsworth-Munsell 100-hue test.

Color vision abnormalities indicated by the Farnsworth-Munsell 100-hue Color Vision Tests (FM-100) were analyzed by computer to better characterize and group congenital and acquired color vision disorders and to help establish statistically significant diagnostic criteria. Standard evaluation of the FM-100 is by axis and error score calculations. A method has been established for computer-averaging many tests from patients with the same color abnormalities determined by history, standard FM-100 and Nagel anomaloscope. The computer calculated an average error score and standard deviation for each of the 85 color caps. Every time a new patient was evaluated for color vision abnormality, his score was compared with averaged tests with common diagnoses, by calculating distance scores. The averaged test with the lowest distance score consistently tended to coincide with the diagnosis. An analysis of 130 FM-100 color tests found technician-calculated error scores to be incorrect, although usually minor, in 40% of the tests. The computer-calculated axes agreed well with the technician's estimates. The distance scores predicted the diagnosis accurately 89% of the time. Many errors were due to the small number of protanopes averaged and inability to distinguish trichromats from dichromats.

Color Perception Tests↗
PubMed1981

A case of incomplete achromatopsia of the deutan type.

A 45 year old man was studied who was previously diagnosed as a typical achromat. Increment spectral sensitivity measurements on white and several colored backgrounds showed that he possessed a rod system, a cone system sensitive in the short wavelength region (blue cones) and a cone system sensitive in the long wavelength region (red cones). This investigation shows that rather extensive testing is required to classify incomplete achromats.

Color Perception Tests↗
PubMed1987

Electrophysiological study of the pigmentfarbenamblyopie.

The spectral sensitivity of the rapid off-response in the electroretinogram is found to be abnormal in some cases of Pigmentfarbenamblyopie or congenital red-green color deficiency. We hypothesize that there exists a fragile cone mechanism in these cases which show an abnormality in spectral sensitivity of the rapid off-response.

Adolescent↗