Visual contrast sensitivity as a diagnostic tool.

In “Possible Estuary-Associated Syndrome: Symptoms, Vision, and Treatment,” Shoemaker and Hudnell (1) advocated use of the visual contrast sensitivity (VCS) test as a biomarker to diagnose possible estuaryassociated syndrome (PEAS) and to assess response to their proposed treatment regimen. However, the use of VCS as a diagnostic test for PEAS (and subsequent treatment of PEAS with cholestyramine) is not supported by a careful examination of the existing evidence. These points should be clarified. Shoemaker and Hudnell (1) made indirect reference to my work (2) in citing Hudnell’s publication that suggested a statistical association between VCS deficits in estuary watermen and hours spent at fish kills (3). In this paper Hudnell et al. (3) used our medical data and their vision data, but reached some conclusions that are not wholly supported by the original historical data. For example, Hudnell et al. (3) ruled out the possibility that observed VCS deficits could be due to known neurotoxicants such as solvents or metals, on the basis of our occupational and environmental history responses. These responses were qualitative only and were not sufficiently detailed to distinguish between gasoline poured into a fuel tank (reported by most fishermen) and that used as hand-cleaner (reported by some fishermen). The history elicited did not fully document exposure to other specific and potentially neurotoxic substances that might be found in estuaries, such as hydrogen sulfide from decaying organic materials. [These omissions have been addressed in the current cohort studies in North Carolina (4).] Hudnell et al.’s alternative hypothesis (3), that the VCS deficits may be