Occupational Mercury Contamination Produces Loss of Color-and Contrast-Vision but no Effect in Full Field

Purpose: To assess the effect of mercury vapor exposure on visual function. Methods: Retired workers from a fluorescent lamp industry (n=24) were tested and compared to age-matched controls. Inclusion criteria were medical diagnosis of mercury contamination, with 20/20 Snellen VA and absence of known ophthalmological pathologies. Color vision was assessed with the following tests: FM-100 hue, Lanthony desaturated and Cambridge Colour Vision Test (Cambridge Research Systems Ltd). The sweep visual evoked potential system – sVEP (NuDiva2) using bipolar electrode placement was used to estimate contrast sensitivity. Full-field electroretinograms (ERG) were measured following the ISCEV protocol. All tests were performed monocularly in a darkened room. Results: Color vision loss was detected in 21/24 patients. Scores of patients ranged from 48 to 452 in the FM-100 test and from 152 to 302 in the Lanthony desaturated test and were statistically different from those of controls (p< 0.001). CCT ellipses of patients were significantly larger than those of controls in field 1 (p=0.02) and field 3 (p=0.01), but not in field 2 (p=0.07). Contrast sensitivity measured by the sVEP was reduced in all patients (n=14) relative to controls at the mid-frequency range - 0.8 (p