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B.V. Worgul, Y.I. Kundiev, N.M. Sergienko, R.E. Shore, V.V. Chumak, P.M. Vitte; Dose Related Incidence of Radiation Cataract in a Six Year Follow-up of a Cohort of the Chernobyl Clean-up Workers . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4241.
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Purpose: We are currently 6 years into a longitudinal study of cataract prevalence and incidence in a cohort of radiation-exposed Chernobyl clean-up workers (Liquidators) with the following objectives. 1) To determine whether radiogenic cataract is a stochastic or a deterministic, process. 2) To determine the risk of radiation-induced cataracts among Liquidators as a function of dose. 3) To determine the effect of known confounders on cataractogenic risk from radiation exposure. The overall goal is to resolve long-standing issues regarding radiation risk to the eye and the adequacy of current guidelines for those at risk. Methods: From the records of 32,826 Ukrainian Liquidators available to our study group, 11,797 with doses ranging from background to over 1000 mSv were chosen for enrollment. Of those, 11,290 remain in the program. There were numerous criteria for the selection not least of which were cataract confounder determinability and the confidence that a high certainty could be placed on existing or retrospective dosimetry of the cohort. Each member of the entire cohort to date has received two complete ophthalmic exams (median interval of two years). Results: The risk following relatively high doses was large; for instance, the best estimates of the relative risk after a 1000 mSv lens dose were 3.5-fold for incident Stage 1 superficial cortical cataracts and 2.6-fold for all Stage 1 incident cataracts. The analyses of the cataract prevalence data showed similarly large relative risks. At the other end of the dose scale, our findings of elevated relative risks for a variety of lens opacity endpoints in the range of 100-200 mSv argues against a dose threshold. It should be noted that 4000 mSv is the currently recognized allowable career eye dose limit for those at risk Conclusions: The data demonstrate radiation cataracts appear following doses far lower than has been presumed and are clearly consistent with the absence of a dose threshold for radiation cataract development. Given that all national and international risk standards for ocular exposure are predicated on a threshold, and one that is relatively high, the current risk guidelines for ocular radiation safety require reassessment.
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