The team examined 22 licensed commercial fishermen and state employees who had worked in such waterways. For controls, the team examined 21 watermen and state employees who worked in the ocean, where Pfiesteria cannot survive. Eleven of those in the control group reported exposure to a fish kill or to fish with lesions that could not have been caused by Pfiesteria . One subject in each group had had symptoms of EAS in the past, but neither subject had significant and current neuropsychologic impairment when examined. The team found no pattern of abnormalities in these evaluations, with one exception.
Neurotoxins can affect vision, including the ability to detect visual patterns.
But certain chemicals, drugs, alcohol, and several developmental and degenerative conditions can have the same effect. Moreover, scientists have not determined whether visual contrast sensitivity is affected by known dinoflagellate toxins. The researchers point out that there is no evidence that a relationship exists between potential environmental exposure to Pfiesteria or related toxic dinoflagellates and a reduction in visual contrast sensitivity, but that such reduced sensitivity should be considered in future studies to assess whether it might act as a marker of toxic dinoflagellate exposure.