Colour vision impairment and alcohol consumption

The relationship between alcohol intake and colour discrimination capacity was examined among 136 persons of whom 16 were undergoing treatment in a detoxification centre. Current weekly alcohol consumption (or prior to treatment for those in the centre) was obtained with a detailed questionnaire, which divided week and weekend drinking into types of alcohol (beer, wine, spirits). Alcohol consumption varied from 0-5824 g/week; median: 266 g/week. Qualitative and quantitative assessment of acquired dyschromatopsia was obtained with a colour arrangement test, the Lanthony D-15 desaturated panel. In all age categories, the prevalence of dyschromatopsia increased with alcohol intake. Moreover, all the heavy drinkers (greater than 751 g/week) presented a certain degree of dyschromatopsia, whether or not they were undergoing treatment for alcoholism in a detoxification centre. Colour loss was primarily in the blue-yellow range; however, 4 of the 16 persons from the detoxification centre presented complex dyschromatopsia patterns including red-green loss. This raises the question of possible progressive deterioration. Multiple regression analysis showed that colour vision loss was significantly related to both age (p less than 0.001) and alcohol intake (p less than 0.01). These results underline the importance of taking into account the contribution of alcohol consumption in studies on acquired dyschromatopsia.     

Does occupational exposure to organic solvents affect colour discrimination?

This review assesses the evidence regarding the effects of occupational exposure to organic solvents on colour discrimination and investigates exposure-response relationships and reversibility. This review also considers the current state of knowledge of the possible mechanisms underlying changes in colour vision, and the human health significance of any reported changes. Among the commonly used organic solvents, styrene has been investigated the most thoroughly. Studies of styrene-exposed workers in Germany, Italy and Japan provide a sufficiently consistent body of evidence to support a robust conclusion that styrene does cause an impairment of colour discrimination relative to age-matched controls. Generally, the impairment of colour discrimination observed in styrene-exposed workers tends to be of the tritan (blue-yellow) type, although some cases of red-green impairment have also been found. The limited information available on exposure-response relationships indicates that the effects on colour discrimination would not be expected at 8-hour time weighted average (8 h TWA) exposures <20 ppm, although a precise threshold cannot be determined. The data on reversibility are limited and inconclusive. The results from the most rigorous study in which this aspect was investigated point to a reversibility of effects after a 4-week exposure-free period, whereas results from a study with limitations suggest a persistence of effect. The effects of toluene, tetrachloroethylene or mixed solvent exposure have also been investigated, although the information available is generally less reliable than for styrene. For toluene, it can be confidently concluded that this solvent does not have an acute effect on colour discrimination, even when exposures are relatively high (50-150 ppm 8 h TWA, and 290-360 ppm 30 minutes TWA). However, studies are inconclusive on whether long-term or repeated exposure to toluene can cause a persistent impairment of colour discrimination. There are few studies that have specifically investigated the effects of tetrachloroethylene on colour discrimination. Among these studies, none has examined the potential for any acute effects of this solvent vapour. A large-scale study in Japanese workers showed no effects of long-term exposure to tetrachloroethylene concentrations in the region of 12-13 ppm. However, the test methodology used was relatively insensitive to changes in colour discrimination, hence the results do not provide reassurance for an absence of subtle effects. A study in Italian dry-cleaners suggested a slight impairment of colour discrimination relative to controls, associated with relatively low exposures to tetrachloroethylene (mean 8 h TWA exposure approximately 6 ppm). The studies concerning the effects of mixed solvent exposure on colour discrimination are based on workers exposed to solvents in paints and lacquers, workers from the printing and petrochemical industries, people working in or living near to microelectronics factories and children exposed to solvents prenatally. However, these studies are subject to design limitations or methodological irregularities, such that no conclusions regarding the effects of mixed solvent exposure on colour discrimination can be drawn. Overall, the only credible evidence for an effect of solvents on colour discrimination derives from the studies on styrene. Because of limitations in the data for other solvents it is not possible to determine whether the evidence for styrene reflects a generic property of solvents. The mechanisms of styrene-induced effects on colour discrimination have not been properly investigated and can only be the subject of speculation. One conclusion that can be drawn is that pathological changes to the ocular system, such as changes to the lens, are unlikely to be involved. This is because there is an absence of convincing evidence for such changes from medical examinations conducted in epidemiological studies of solvent-exposed workers. Also, it seems unlikely that effects on colour discrimination are a nonspecific consequence of more generalised CNS depression, given that styrene-induced effects on colour discrimination appear to occur below the threshold for narcotic effects. The effects of styrene on colour discrimination are subtle and involve an impairment of the ability to discriminate accurately between closely related shades of the same colour rather than 'colour blindness'. There is no valid basis for using colour discrimination as a marker for other forms of solvent-induced neurotoxicity.     

Visual impairment on dentists related to occupational mercury exposure

A detailed assessment of visual function was obtained in subjects with low-level occupational mercury exposure by measuring hue saturation thresholds and contrast sensitivity functions for luminance and chromatic modulation. General practice dentists (n = 15) were compared to age-matched healthy controls (n = 13). Color discrimination estimated by the area of Mac Adam ellipses was impaired, showing diffuse discrimination loss. There was also reduction of contrast sensitivity for luminance and chromatic (red-green and blue-yellow) modulation, in all tested spatial frequencies. Low concentrations of urinary mercury (1.97 ± 1.61 μg/g creatinine) were found in the dentists group. Color discrimination as well as contrast sensitivity function, assessed psychophysically, constitutes a sensitive indicator of subtle neurotoxic effect of elemental mercury exposure.     

Effects of high doses of toluene on color vision

High exposure to toluene may cause optic neuropathy and retinopathy, both associated with dyschromatopsia. Another solvent, ethanol, is known to induce acute blue-yellow dyschromatopsia. This study investigated the acute effects of high doses of toluene on color vision. Eight male printshop workers were examined before and after cleaning printing containers with pure toluene. After cleaning, concentrations of toluene in blood were between 3.61 and 7.37 mg/l. Color vision was tested with the Farnsworth panel D-15 test, the Lanthony desaturated panel D-15 test, and the Standard Pseudoisochromatic Plates part 2. For control of possible acute effects, eight workers of a metal-working factory without any neurotoxic exposure were tested according to the same procedure. Acute exposure to toluene did not cause impairment of color vision. However, statistical power is limited due to the small number of exposed subjects. Color vision of the printshop workers tested before cleaning was slightly impaired (statistically not significant) when compared with unexposed subjects.     

Associations between platelet monoamine oxidase-B activity and acquired colour vision loss in a fish-eating population

Platelet monoamine oxidase-B (MAO-B) has been considered a surrogate biochemical marker of neurotoxicity, as it may reflect changes in the monoaminergic system in the brain. Colour vision discrimination, in part a dopamine dependent process, has been used to identify early neurological effects of some environmental and industrial neurotoxicants. The objective of this cross-sectional study was to explore the relationship between platelet MAO-B activity and acquired colour discrimination capacity in fish-consumers from the St. Lawrence River region of Canada. Assessment of acquired dyschromatopsia was determined using the Lanthony D-15 desaturated panel test. Participants classified with dyschromatopsia (n=81) had significantly lower MAO-B activity when compared to those with normal colour vision (n=32) (26.5+/-9.6 versus 31.0+/-9.9 nmol/min/20 microg, P=0.030)). Similarly, Bowman's Colour Confusion Index (CCI) was inversely correlated with MAO-B activity when the vision test was performed with the worst eye only (r=-0.245, P=0.009), the best eye only (r=-0.188, P=0.048) and with both eyes together (r=-0.309, P=0.001). Associations remained significant after adjustment for age and gender when both eyes (P=0.003) and the worst eye (P=0.045) were tested. Adjustment for heavy smoking weakened the association between MAO-B and CCI in the worst eye (P=0.140), but did not alter this association for both eyes (P=0.006). Adjustment for blood-mercury concentrations did not change the association. This study suggests a relationship between reduced MAO-B activity and acquired colour vision loss and both are associated with tobacco smoking. Therefore, results show that platelet MAO-B may be used as a surrogate biochemical marker of acquired colour vision loss.     

Occupational exposure to different levels of mixed organic solvents and colour vision impairment

Mixed organic solvents have a broad range of applications in industry. Occupational exposure to organic solvents has been shown to be associated with colour vision impairment. The study was designed to determine the impact of chronic occupational exposure to organic solvent mixtures on colour vision of car industry painters. 408 workers of assembly location and 2 different paint locations of a car manufacturing company were included in the study. The workers were studied in three groups. The first group consisted of those working in the assembly location with no exposure to organic solvents. The second and third groups included those working in the new and old paint locations, exposed to organic solvents at lower and higher levels than the permissible level, respectively. The Lanthony D-15 desaturated (LD-15) test was used for screening acquired colour vision impairment. The frequency of acquired colour vision impairment was 44.28% for workers of the old paint location, 29.31% for workers of the new paint location, and 3.90% for workers of the assembly location, indicating a significant difference (p < 0.001). The results of logistic regression indicated there was a significant relationship between colour confusion index (CCI) and exposure to organic solvents (p < 0.001) for the old and new paint locations. We suggest that chronic occupational exposure to organic solvents at higher and even lower levels than the permitted levels may lead to acquired colour vision impairment. It is recommended that LD-15 test would be implicated in the early diagnosis of nervous system disorders in workers exposed chronically to organic solvents.     

Colour vision loss among disabled workers with neuropsychological impairment

Test performance on a neurobehavioural battery was examined with respect to acquired colour vision loss among patients with a history of neurotoxin exposure. The study group included 14 men and 7 women with clinically diagnosed neuropsychological impairment (mean age: 41.3 ± 8.1 years; mean educational level: 13.4 ± 1.4 years). Verbal and visual ability, memory and psychomotor function were assessed with the California Neuropsychological Screening Battery. Colour vision was assessed with the Lanthony D-15 desaturated colour arrangement panel. Acquired dyschromatopsia was present in 17 patients (80.9%), 11 of whom manifested patterns of Type II colour vision loss. Simple regression analysis of neuropsychological test performance with respect to colour vision loss, using age-adjusted Z-scores, revealed significant relationships (p≤0.05) solely for tests which rely heavily on the visual system. Significant differences in visual task test scores were also observed with the type of dyschromatopsia (Kruskal-Wallis, p≤0.05). These findings suggest that poor performance on visual tasks and colour vision loss may both result from damage to neuro-ophthalmic pathways or that loss of integrity of the peripheral visual pathways may affect visual task performance. The authors propose that visual testing should be incorporated into neurobehavioural test batteries.     

Colour vision defects in occupational chronic solvent encephalopathy

Occupational chronic solvent encephalopathy (CSE) is associated with a number of neurobehavioural disorders including defects of visual perception. The purpose of this study was to characterize colour vision defects in CSE patients. Colour vision was tested in bright illumination with the Farnsworth-Munsell 100-hue test in workers who had CSE due to occupational exposure to common industrial solvents. Before assessing colour vision, the subjects' ocular health and visual functions were evaluated. On the basis of this evaluation, 36 subjects with healthy eyes were selected and their colour vision was tested monocularly. The colour vision performance of the patient group was, statistically, significantly inferior to that of a control group matched by age at a group level. A mixed form of reduced colour sensitivity was found in 42% (n=15/36) of the cases, affecting the entire range of Munsell hues. No association was found between the length and intensity of exposure and colour vision performance. Our results show that CSE patients can have significantly impaired colour discrimination ability, although their eyes are healthy and their other visual functions are normal. This may indicate toxic damage to higher level visual processing, possibly the colour selective regions of the cerebral cortex.     

Color vision and occupational toluene exposure.

We examined the relationship between acquired color vision loss and exposure to toluene and total hydrocarbons among 125 male workers. Seventy-two toluene-exposed printers were compared with 34 workers from the same photogravure plant with ambient background exposure, and with 19 workers from a bookbinding plant located in the same town (nonexposed). Environmental mean toluene exposure level at workstation was estimated from individual 8-h sampling. Historic exposure data from the last 30 years were used to construct two cumulative exposure indices, one for toluene and one for total hydrocarbons. Airborne toluene levels were overall lower than the current Threshold Limit Value (TLV) of 50 ppm. Color vision was assessed by the Lanthony D-15 desaturated panel. Color vision loss was quantitatively established by the Color Confusion Index (CCI) and classified by type of acquired dyschromatopsia according to Verriest's classification. CCI was positively related to current airborne toluene levels, and cumulative exposure indices for toluene and total hydrocarbons (.18< or =r< or =.35). Odds ratios of acquired dyschromatopsia were significant for current airborne toluene, toluene, and total hydrocarbon past exposure (1.27 [1.02-1.58], 1.21 [1.04-1.39], 1.15 [1.02-1.31], respectively). In conclusion, this study suggests that the Lanthony D-15 desaturated panel detects early neurotoxic effects among workers exposed to toluene.     

Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil

We evaluated vision loss in workers from fluorescent lamp industries (n = 39) who had retired due to intoxication with mercury vapour and had been away from the work situation for several years (mean = 6.32 years). An age-matched control group was submitted to the same tests for comparison. The luminance contrast sensitivity (CSF) was measured psychophysically and with the sweep visual evoked potential (sVEP) method. Chromatic red–green and blue–yellow CSFs were measured psychophysically. Colour discrimination was assessed with the Farnsworth–Munsell 100-hue test, Lanthony D-15d test and Cambridge Colour Vision Test. Patient data showed significantly lower scores in all colour tests compared to controls (p < .001). The behavioural luminance CSF of the patients was lower than that of controls (p < .001 at all frequencies tested). This result was confirmed by the electrophysiologically measured sweep VEP luminance CSF except at the highest frequencies—a difference that might be related to stimulus differences in the two situations. Chromatic CSFs were also statistically significantly lower for the patients than for the controls, for both chromatic equiluminant stimuli: red–green (p < .005) and blue–yellow (p < .04 for all frequencies, except 2 cycles per degree (cpd), the highest spatial frequency tested) spatial gratings. We conclude that exposure to elemental mercury vapour is associated with profound and lasting losses in achromatic and chromatic visual functions, affecting the magno-, parvo- and koniocellular visual pathways.     

DNA adducts and strand breaks in workers exposed to vapours and aerosols of bitumen: associations between exposure and effect

To study the associations between exposure to vapours and aerosols of bitumen and genotoxic effects, a cross-sectional and cross-shift study was conducted in 320 exposed workers and 118 non-exposed construction workers. Ambient air measurements were carried out to assess external exposure to vapours and aerosols of bitumen. Hydroxylated metabolites of naphthalene, phenanthrene and pyrene were measured in urine, whereas (+)-anti-benzo[a]pyrene-7,8-diol-9,10-epoxide ((+)-anti-BPDE), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8oxodGuo) and DNA strand breaks were determined in blood. Significantly higher levels of 8-oxodGuo adducts and DNA strand breaks were found in both pre- and post-shift blood samples of exposed workers compared to those of the referents. No differences between exposed workers and referents were observed for (+)-anti-BPDE. Moreover, no positive associations between DNA damage and magnitude of airborne exposure to vapours and aerosols of bitumen could be observed in our study. Additionally, no relevant association between the urinary metabolites of PAH and the DNA damage in blood was observed. Overall, our results indicate increased oxidative DNA damage in workers exposed to vapours and aerosols of bitumen compared to non-exposed referents at the group level. However, increased DNA strand breaks in bitumen workers were still within the range of those found in non-exposed and healthy persons as reported earlier. Due to the lack of an association between oxidative DNA damage and exposure levels at the workplaces under study, the observed increase in genotoxic effects in bitumen workers cannot be attributed to vapours and aerosols of bitumen.     

Effects of chlordiazepoxide upon successive red-green discrimination responses in Japanese monkeys,Macaca fuscata

Monkeys were trained on a successive go/no-go type red-green discrimination task for food following intramuscular saline. After reaching a 90% correct criterion, they were injected with 20 mg/kg of chlordiazepoxide (CDP) and then tested on the same successive task or on the simultaneous red-green discrimination task. CDP was found to disrupt waiting (no-go) response on the successive discrimination task, without affecting discrimination itself as shown by their perfect results on the simultaneous discrimination task. The result is interpreted in terms of the drug's disinhibitory effects.     

Neurological and Neurophysiological Findings in Workers with Chronic 2,3,7,8‐Tetrachlorodibenzo‐p‐Dioxin Intoxication 50 Years After Exposure

The last eight survivors of 80 workers accidentally exposed to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) during production of herbicides based on trichlorophenoxyacetic acid in 1965–1967 in a chemical factory were followed. All were men, mean age 72.4 ± 1.3 years. Their current median TCDD blood level was 112 (46–390) pg/g lipids. Neurological examination revealed central nervous system impairment in all individuals and signs of polyneuropathy in 87.5%, which was confirmed by a nerve conduction study (NCS) in 75%. A Lanthony test demonstrated acquired dyschromatopsia in 87.5% of the patients, with deterioration of mean colour confusion index (CCI) from 1.52 ± 0.39 in 2010 to 1.73 ± 0.41 in 2016. Single‐photon emission computer tomography (SPECT) of the brain showed focal reduction of perfusion in various brain locations in all patients and worsening in six patients. Visual‐evoked potentials (VEP) was abnormal in 62.6% of individuals. Most patients complained of psychological problems. The neuropsychological test battery showed most positive impairments in the Trail Making Test evaluating processing speed (average level in the range of mild neurocognitive impairment), which correlated with mean CCI (p < 0.05). Conclusion: Fifty years after exposure, blood levels of TCDD are still 10 times higher than the general population. NCS, VEP, Lanthony test and SPECT findings deteriorated from examination of these patients in 2004 and in 2010. The total of abnormal tests per patient in 2016 is very high. Minor differences among patients and their reduced count may explain why the number of impairments in 2016 does not correlate with TCDD blood level.     

Colour vision and occupational toluene exposure: results of repeated examinations

Potential effects of human occupational exposures to toluene on colour vision were investigated in a follow-up study over 4 years with three repeated examinations. Colour vision was measured with the Lanthony desaturated colour vision test D-15d, and the colour confusion index (CCI) was calculated. The mean current exposures were 26+/-21 ppm for printers (high toluene level) and 3+/-4 ppm for end-processors (low toluene level). The mean exposure durations were 23+/-6 years for "long-time exposed" and 7+/-2 years for "short-time exposed" subjects. Repeated analyses (n=162) and multiple regressions (maximum available n=267) did not reveal significant effects of toluene with respect to intensity or duration of current or long-term exposure. Age and occupational qualification were significantly associated with CCI in both kinds of analysis, whereas alcohol consumption (carbohydrate-deficient transferrin, CDT) and smoking habits (cigarettes per day) were not. It is concluded that current industrial exposure limits of toluene provide sufficient protection against possible disturbance of colour vision.     

Ocular adverse effects of sildenafil

(1) Abnormal colour vision and brightness were two adverse effects of sildenafil observed during pre-marketing studies. Both effects are dose-dependent and reversible, and led to sildenafil being contraindicated in patients with hereditary degenerative retinal disturbances such as pigmentary retinitis. (2) Several cases of anterior ischaemic optic neuropathy have been reported since the marketing release of sildenafil. These are potentially serious adverse effects that can have permanent sequelae, such as a reduced field of vision.     

The effects of long-term occupational exposure to carbon disulphide on serum lipids.

No definite conclusion can be made from many epidemiological and clinical studies of lipid metabolism in workers exposed to carbon disulphide (CS2). The aim of our investigation was to study the serum lipid levels in workers exposed to different CS2 levels to establish possible exposure-response relationships. The first group, spinners, were exposed to high CS2 levels; the second group, workers in viscose production, to low CS2 levels; and the third group included non-exposed workers. As a part of a large examination, total and free serum cholesterol, total lipid and triglyceride levels were determined. Mean total lipid levels were similar in high and low CS2 exposed workers, but significantly lower in non-exposed workers. The total serum cholesterol mean levels were also similar in both groups, but significantly higher in the non-exposed group. Only serum triglyceride values were related to the CS2 levels: the most elevated were in the high exposed workers, somewhat lower in the low exposed, and the lowest in the non-exposed group. The finding is especially important as triglycerides are the most specific for developing atherosclerosis, which is often reported in workers with long-term exposure to carbon disulphide.     

Gene frequency and type of colour blindness in Ethiopians

All 954 boys and 1064 girls attending two schools in north-western Ethiopia were tested in February 1988 for colour blindness using the Ishihara plates. A total of 40 colour blinds (4.2%) were found among males and 2 (0.2%) among females. There were 31 (3.2%) deutans and 9 (0.9%) protans among males. Both female colour blinds were deutans. This study confirms a previous observation on the gene frequency of colour blindness in this population. For the first time it also provides information on the frequency of this polymorphism in female Ethiopians, as well as types of red-green defects.     

Fertility of male workers of the italian mint

Fertility among workers exposed to metal fumes and solvents in the Italian mint (stampers, founders, and other technical workers) was compared to the reproductive experience of the administrative staff. Data on the reproductive history and time to pregnancy were collected by interview. For workers with children, data on the time to pregnancy (TTP) for the first pregnancy was assessed in relation to occupational risk factors. The groups with the highest prevalence of pregnancy delay beyond 6 months were stampers (21%) and those exposed to solvents (21.5%). Logistic regression did not show a significant association of these job exposures with pregnancy delay, but the power of the study to show an important difference was low. The data are not inconsistent with the hypothesis that male exposure to solvents and metal fumes is associated with an increase in the TTP.     

Antiangiogenic effect of silicate nanoparticle on retinal neovascularization induced by vascular endothelial growth factor

Angiogenesis-related blindness indicates the spectrum of retinal diseases that are caused by pathological angiogenesis, resulting in catastrophic vision loss. We aimed to demonstrate the antiangiogenic effect of silicate nanoparticles (SiNPs) on the retinal neovascularization. No direct toxicity of SiNPs was observed on retinal neuronal or endothelial cells, nor on the retinal tissue. Furthermore, intravitreal injection of SiNPs effectively reduced anomalous retinal angiogenesis in oxygen-induced retinopathy mice. SiNPs also effectively inhibited in vitro vascular endothelial growth factor (VEGF)-induced angiogenesis. Via suppression of VEGF receptor-2 phosphorylation induced by VEGF, SiNPs blocked ERK 1/2 activation. SiNPs could be an inhibitor of the potency and safety of retinal neovascularization that is mediated by VEGF and utilized in the treatment of angiogenesis-related blindness. FROM THE CLINICAL EDITOR: In this important preclinical study, silicate NP-s are studied to address retinal neovascularization, an important pathomechanism of different retinal diseases that could lead to catastrophic vision loss. The authors conclude that SiNP-s could be utilized as inhibitors of retinal neovascularization mediated by VEGF and propose future applications in the treatment of angiogenesis-related blindness.     

Effect of lead on the levels of some immunoregulatory cytokines in occupationally exposed workers

Lead (Pb) may affect humoral and cellular immunity, acting on lymphocytes as well as on granulocytes and monocytes. Cytokines and nitric oxide (NO) play a central role in the immune balance. In this study, plasma levels of nitrites and nitrates (NOx), IL2, IL4, IL6, IL10, TNF-alpha and INF-gamma, were measured in healthy workers with very low (Pb-B=3.2-18.0 microg/dL) and low (Pb-B=9.1-46.0 microg/dL) Pb-exposure compared to non-exposed workers. Low Pb-exposed workers (Pb-B=9.1 -46.0 microg/ dL) were found to have significantly higher plasma IL-10 levels, and tendentially higher plasma TNF-alpha levels compared to non-exposed workers. This is the first report of a significant increase of plasma IL-10 levels in Pb-exposed workers. Plasma IL-10 increase was influenced by blood Pb levels even after correction for main confounding factors. No difference was found in plasma NOx levels between Pb-exposed and non-exposed workers, which is in agreement with previous findings exclusively regarding groups in the general population. Low Pb-exposure can induce an increase of pro-inflammatory cytokines, such as TNF-alpha, with a consequent increase of other cytokines, such as IL-10, considered a T cell cross-regulatory factor, suggesting possible interference of Pb in the system of immunophlogosis.