Dry cleaning workers are exposed to organic solvents like perchlorethylene (perc). This can affect the Central Nervous System (cns), provoke neurotoxicity and associate to neuro-visual alterations related to the visual contrast sensitivity function (csf) and the loss of color vision. Objective: To determine the deficits of contrast sensitivity (csf) by spatial frequency in a group of dry cleaning workers exposed to occupational levels of perc and its relation to the neurotoxic symptoms. Materials and methods: A case and control study in 40 dry cleaning workers and in 35 regular people with no exposure to perc was done in Bogota, Colombia. The csf was evaluated using psychophysical methods; the spatial frequencies studied were 0.5, 1.0, 2.0, 4.0, 8.0 and 16.0 cpd. Neurotoxicity was evaluated with the modified questionnaire Q16. Results: Significant differences were observed in cs above 1.0cpd (p < 0.05). The Spearman correlation showed a significant negative relation between the punctuation of the modified version of the Q16 questionnaire and the spatial frequencies2.0, 4.0 and 8 cpd (Spearmanp Rho < 0.05) in the cases. The Mann Whitney U test showed significant differences between cases and controls for the modified Q16 questionnaire (p <0.05). Conclusion: the csf was significantly lower in those exposed to perc for the spatial frequencies above 1.0 cpd. The presence of neurotoxic symptoms in dry cleaning workers is associated with losses in csf in medium and high spatial frequencies.

<em><strong>Objective</strong><em> To modify the neurotoxic symptoms questionnaire (Q16) and assess its repeatability and comparability. <em><strong>Materials and Methods</strong><em> A group of 100 participants ranging from the ages of 18 to 40, with an education level equivalent to high school or technical college, similar to the education level of dry-cleaners in Bogotá was used to validate the questionnaire in sydney, Australia. Three test questionnaires and a demographic information questionnaire were presented to participants. The modified Q16 was applied twice in order to evaluate repeatability. <em><strong>Results</strong><em> sixty males and forty females participated in the study. Cronbach’s Alpha was applied in order to analyze the reliability of the Q16 modified with a Likert scale, getting an internal consistency of 0.887. The paired t test was applied in order to evaluate repeatability, obtaining significant differences in two questions with p=0.027 and p=0.020 values, respectively. Comparing the results of the Likert scale scores with the original, a direct link was observed between them. <em><strong>Conclusions</strong><em> The modified Q16 provides more answer choices, closer to reality, internal consistency and repeatability. The modified Q16 may be a better option to assess neurological symptoms