Studies on chronic carbon disulfide poisoning

Summary Direct ophthalmoscopic/color fundus photographic examinations and the Prednisolone Glucose Tolerance Test (PGTT) were performed in 214 male carbon disulfide workers, three times in 5 years. The purpose of the follow-up study was to determine the following: (1) the effects of exposure cessation on the course of retinopathy; (2) a prognosis for retinopathy in workers continuously exposed for years; (3) a reasonable maximum length of service at exposure sites, for which equal or shorter exposure duration would not cause retinopathy under present Japanese working conditions; (4) the relationship between changes in glucose tolerance and the course of retinopathy.During the five-year period of study, 56 workers were transferred from exposure to non-exposure work and 31 were not examined. Thus, the subjects completely followed-up numbered 183(85.5%) and fell into two groups: still-exposed and removed from exposure.Results can be summarized as follows: (1) Progression to a more developed stage of retinopathy occurred in 23.1% of the 134 still-exposed group members. (2) Among the 80 removed group members, the prevalence of progression was 13.7%, but no progressed case was found in workers with a short duration of past exposure (10 years or less). (3) Disappearance or improvement to a milder stage of retinopathy occurred in 1.5% of the still-exposed and in 11.3% of the removed group members. In the latter, these changes occurred much sooner after exposure cessation. Even in workers exposed for a long duration, retinopathy either disappeared or improved after cessation. (4) Mean blood-glucose values at both one and two hours (during PGTT) were higher in workers with retinopathy than in those without retinopathy. However, data regarding any relationship between changes of glucose tolerance and the course of retinopathy were not obtained during the study.Finally, similarities in the clinical pictures of chronic carbon disulfide poisoning and diabetes are discussed.