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M. Lago, C. Feitosa–Santana, M. Nishi, M.F. Costa, A.Q. Simões, D.F. Ventura; Luminance and Chromatic Constrast Sensitivity in Patients Intoxicated by Mercury Vapor: Evolution in Two Years . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5359.
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© ARVO (1962-2015); The Authors (2016-present)
To perform longitudinal assessment of luminance and chromatic contrast sensitivity functions (CSF) in a 2–year period (2002 – 2004) in patients with occupational mercury vapor intoxication.
The study was conducted in 22 patients (mean age=40.43 years; 15 men) intoxicated by chronic exposure to mercury vapor for 9.2 years (mean) in fluorescent lamp industries, away from the work place for 6.2 years (mean) and in 11 age–matched controls. Inclusion criteria were medical diagnosis of mercury intoxication, bc Snellen VA >20/30, and absence of known ophthalmological pathologies. All subjects were tested monocularly in a darkened room. CSFs were measured with a computerized psychophysical test (Psycho for Windows v. 2.36, Cambridge Research Systems), with a VSG 2/4 graphic board and a Sony FD Trinitron monitor, calibrated with a CS1000 Minolta spectrophotometer. The luminance CSF was measured with horizontal sinusoidal gratings at 3, 6, 12 and 18 cpd. Chromatic CSFs were determined with R/G and B/Y horizontal sinusoidal gratings of 0.7 and 2 cpd, after equiluminance correction. The u'v' (CIE 1976) chromaticity coordinates of the stimuli were: D6500: 0.198, 0.468; Red: 0.258, 0.454; Green: 0.133, 0.469; Blue: 0.210, 0.397 and Yellow: 0.188, 0.551. Average luminance was 34 cd/m2. A non–parametric statistical analysis (Mann–Whitney Rank Sum test with a= 0.05) was performed.
The luminance CS thresholds measured in 2002 and in 2004 in the patients were statistically different (p<0.001) from the controls at all tested frequencies. The same was true for the chromatic red–green and blue–yellow CS thresholds (p<0.001). When we compared thresholds of the 2002 and 2004 patient groups, CSs of the latter were higher at all spatial frequencies, except at 12 cpd in the luminance CS function and at 0.7 cpd in the red–green CS function. This increase in CS was statistically significant.
Our data allow us to conclude that chronic exposure to mercury vapor caused long term losses in luminance and chromatic contrast sensitivities. However, these losses were reduced by a small but significant amount two years after the first measurement.
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