Contrast sensitivity in organic-solvent-induced chronic toxic encephalopathy

This is a study of visual contrast sensitivity in a series of subjects with previously diagnosed occupational organic-solvent-induced chronic toxic encephalopathy. Contrast sensitivity was measured for 16 subjects using the Vistech VCTS 6500 chart. The results were compared with age-stratified normal data. Six of the 16 subjects (37.5%) recorded abnormal contrast sensitivity results. Monocular abnormalities were found for two (33%) of these subjects. Statistically significant abnormalities in contrast sensitivity were observed at the intermediate spatial frequencies of three cycles per degree (cpd; P < .0005), 6 cpd (P < .025), and 12 cpd (P < .01). We conclude that contrast sensitivity is abnormal in some cases of occupational organic-solvent-induced chronic toxic encephalopathy. Intermediate spatial frequency channel neurones in the visual system may be more vulnerable to solvent toxicity than those of low or high spatial frequency. Contrast sensitivity testing may be a useful adjunct in the diagnostic process for this disease. Further research involving larger numbers of subjects is recommended.