Irreversible color vision losses in patients with chronic mercury vapor intoxication

Abstract

This longitudinal study addresses the reversibility of color vision losses in subjects who had been occupationally exposed to mercury vapor. Color discrimination was assessed in 20 Hg-exposed patients (mean age = 42.4 +/- 6.5 years; 6 females and 14 males) with exposure to Hg vapor during 10.5 +/- 5.3 years and away from the work place (relative to 2002) for 6.8 +/- 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 +/- 35.4 mug/g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 (Ventura et al., 2005), but at the time of the follow-up tests, in 2005, this value was 1.4 +/- 1.4 microg/g creatinine for patients compared with 0.5 +/- 0.5 microg/g creatinine for controls (different group from the one in Ventura et al. (2005)). Color vision was monocularly assessed using the Cambridge Colour Test (CCT). Hg-exposed patients had significantly worse color discrimination (p < 0.02) than controls, as evaluated by the size of MacAdam's color discrimination ellipses and color discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. (2005) and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation (Ventura et al., 2005) and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, color vision impairment remains irreversible.

Métodos utilizados na avaliação psicofísica da visão de cores humana

“…Usando o CCT, Ventura e colaboradores (2003c) (Delahunt et al, 2004), parkinsonianos (Regan et al, 1998), sujeitos expostos ao consumo de álcool (Castro et al, 2009), usuários de cloroquina (Ventura et al, 2003c), neuropatia óptica hereditária de Leber ( Ventura et al, 2005( Ventura et al, , 2007a, pacientes com esclerose múltipla (Moura et al, 2008), com a distrofia muscular de Duchenne , intoxicados por mercúrio (Canto-Pereira et al, 2005;Feitosa-Santana et al, 2008;Rodrigues et al, 2007;Ventura et al, 2005). Também tem sido utilizado em pesquisas em ciência básica, como a avaliação da ausência de somação binocular, olho dominante e efeito da aprendizagem na discriminação de cores (Costa et al, 2006), aparência de cores para dicromatas (Brettel, Viénot, & Mollon, 1997), variações na mistura e discriminação de cores entre tricromatas e deuteranômalos, além de inspirar a criação de sistemas que usam o mesmo tipo de disposição do estímulo em mosaico para o estudo da discriminação do sistema visual humano (Figura 2) (Knoblauch, Vital-Durand, & Barbur, 2001;Rodrigues et al, 2007).…”

Comparison of color discrimination in chronic heavy smokers and healthy subjects

“…A visual percept may consist of stimuli that vary over the space (spatial contrast), time (temporal contrast) or direction of motion, and vary in luminance (achromatic) and chromaticity (saturation and hue color) [9][10][11] . Thus, chromatic contrast involves chromaticity differences, which can be expressed by the distance in the CIE 1976 uniform chromaticity scale diagram and assessed by the size of MacAdam ellipses on the Cambridge Color Test (CCT), for example 12,13.…”

Preliminary Findings on the Effects of Occupational Exposure to Mercury Vapor Below Safety Levels on Visual and Neuropsychological Functions

“…[5][6][7][8][9][10] Nevertheless, there is no clear knowledge of the level of exposure at which Hg vapor causes adverse effects. Visual impairment has been found in subjects with very low urinary Hg concentration, such as children exposed to inorganic Hg in their living environment 11 and dentists exposed to inorganic Hg because of the manipulation of dental amalgam in their work environment.…”