Long-term complications of sulfur mustard poisoning: retinal electrophysiological assessment in 40 severely intoxicated Iranian veterans

BACKGROUND The eye is one of the most sensitive organs to sulfur mustard (SM) [C4H8Cl2S], and preliminary symptoms of exposure usually become evident in the eyes. In this study we aim to evaluate the possible long-term retinal electrophysiologic complications of SM poisoning in Iranian veterans during Iran-Iraq war (1980-1988). METHODS In a cross-sectional study forty Iranian veterans who were exposed to mustard gas during the Iran-Iraq war (1980-1988) were included. All the cases underwent complete ocular exam and retinal electrophysiological evaluation, including electroretinography (ERG) and electrooculography (EOG). Data was analyzed using SPSS software. The normal distribution was checked using the Shapiro-Wilk test. Comparison of electrophysiologic values with maximum standard levels was performed using one-sample Student t-test and test of significance was one-tailed. RESULTS Foreign body sensation (70%), dry eye (50%), photophobia (30%), lacrimation (20%) and pain sensation (10%) were among the common symptoms. ERG showed significant reduced amplitude in rod response, maximal combined response, oscillatory potentials, cone response and 30 Hz flicker waves compared to normal values (p < 0.05). Implicit time of b-wave rod response ERG recording was significantly decreased (p < 0.05). Implicit time of cone response b-wave was within normal limits. In EOG, Arden ratio did not decrease (total average of 2.311 and 2.48 in right and left eyes, respectively). CONCLUSION Delayed toxic effects of SM poisoning in the veterans were observed in the retina, but not in the retinal pigment epithelium layer. As the retina is a neural tissue, long-term effects of SM on neural tissues are presumed.