Abstract
Purpose: :
To evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents in a group of gas station workers.
Methods: :
We tested 25 workers (20 male; age=36,4±8,9 years) and 25 controls with no history of chronic exposure to solvents (10 male; age=33,8±8,8 years). All participants had normal visual acuity and no ophthalmological complaints. Urinary concentrations of toluene (M=0,3±0,16g/g of creatinine) and xylene metabolites (M=0,1 g/g of creatinine), were within safe limits. Time of exposure was (M=9,6±6,2 years), used as indicators of the exposure. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field were assessed with automatic white-on-white 24-2 perimetry (Humphrey II-750i). mfVEP were assessed in three workers (Veris Science 5.2.4). Contrast sensitivity (Metropsis software) was measured with sine wave gratings of 0,2; 0,5; 1,0; 2,0; 5,0; 10,0 and 20,0 cpd. The groups were compared using the Mann-Whitney U test.
Results: :
In the CCT, there were significant differences for the area of the ellipse, elipticity and thresholds for the protan, deutan and tritan confusion axes (p<0,05). Significant differences between the groups were also found for the D15d (p<0,01) and for the automated perimetry results for the 9o, 15o and 21o eccentricity rings (p<0,05), MD and PSD (p<0,05). Each subject from the workers group showed at least 30 sectors of the visual field with significantly reduced amplitude (p<0,05) in the mfVEP when compared to normative data, while control group subjects had a maximum of 16 sectors of reduced amplitude. Significant correlation was found between time of work and deutan axis thresholds (π=0,59; p<0,05), indexes of the Lanthony D15d (π=0,52; p<0,05), perimetry results in the Fovea (π=-051; p<0,05) and at 3, 9 and 15 degrees of eccentricity (π=-0,46; p<0,05).
Conclusions: :
Losses in visual function were found for chronic exposure to organic solvents even at exposures within occupational safety limits. The visual changes found were extensive and diffuse.
Keywords: contrast sensitivity • color vision • electrophysiology: clinical