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Short sight is an eye opener for workers in pneumatic caissons

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Construction workers operating in great depth pneumatic caissons should be monitored carefully by occupational health services for signs of short sight, concludes an ophthalmological study in Japan.

Among 12 caisson workers aged 22–57 years, nine stated their distance vision was blurred and three of them had eye pain or itching Eight actually had short sight, and seven were considered to have short sight of late onset.

The researchers estimated the time to onset of symptoms as 4–30 work sessions (346–2407 minutes) and the total period of exposure to oxygen during that time as 18–44 sessions (1269–3833 minutes, total oxygen exposure 5628–17 745 UPTD (unit of pulmonary toxicity dose). On re-examination six months later short sight had resolved in most men and increased in one. The researchers calculated the workers were exposed to partial pressure of oxygen of 1.2–1.5 atmospheres absolute pressure (ATA), lower than routinely used in hyperbaric oxygen treatment.

The workers had been working for 11 weeks maintaining machinery in the caisson, working for 29–119 minutes at 4.15–4.75 ATA, 4 days a week (men × sessions = 524) before having a thorough eye examination. All except three were examined again six months after the job had finished.

Great depth engineering is a new method whose use is spreading rapidly with the demands of large scale civil engineering projects. Under Japanese law workers in high pressure environments must be monitored for medical conditions, but eye problems have not been mentioned before.