Abstract
BackgroundThe eye is well known to be sensitive to clearly high doses (>2 Gy) of ionizing radiation. In recent years, however, cataracts have been observed in populations exposed to lower doses. Interventional cardiologists are repeatedly and acutely exposed to scattered ionizing radiation (X-rays) during the diagnostic and therapeutic procedures they perform. These "low" exposures may cause damage to the lens of the eye and induce early cataracts, known as radiation-induced cataracts. The O'CLOC study (Occupational Cataracts and Lens Opacities in interventional Cardiology) was designed to test the hypothesis that interventional cardiologists, compared with an unexposed reference group of non-interventional cardiologists, have an increased risk of cataracts.Method/DesignThe O'CLOC study is a cross-sectional study that will include a total of 300 cardiologists aged at least 40 years: one group of exposed interventional cardiologists and another of non-interventional cardiologists. The groups will be matched for age and sex. Individual information, including risk factors for cataracts (age, diabetes, myopia, etc.), will be collected during a telephone interview. A specific section of the questionnaire for the exposed group focuses on occupational history, including a description of the procedures (type, frequency, radiation protection tool) used. These data will be used to classify subjects into "exposure level" groups according to cumulative dose estimates. Eye examinations for all participants will be performed to detect cataracts, even in the early stages (lens opacities, according to LOCS III, the international standard classification). The analysis will provide an estimation of the cataract risk in interventional cardiology compared with the unexposed reference group, while taking other risk factors into account. An analysis comparing the risks according to level of exposure is also planned.DiscussionThis epidemiological study will provide further evidence about the potential risk of radiation-induced cataracts at low doses and contribute to cardiologists' awareness of the importance of radiation protection.Trial RegistrationNCT01061463
Highlights
The eye is well known to be sensitive to clearly high doses (>2 Gy) of ionizing radiation
The radiation protection standards formulated by the United States National Council on Radiation Protection (NCRP) and the International Commission on Radiological Protection (ICRP)
Reports of lens opacities related to environmental exposure come from the Hiroshima and Nagasaki survivors [5,6,7], from children living in the contaminated territories of Chernobyl [8], and residents of (60)Cocontaminated buildings in Taiwan [9]
Summary
The sensitivity of the lens of the eye to high doses of ionizing radiation (IR) is well known, considerable uncertainty surrounds the relation between radiation dose and cataracts. With a prevalence of 23% in the exposed group [13] vs approximately 10% in an unexposed group [33], 123 individuals in each group would be necessary Combining all this information, we estimated that the inclusion in our study of 150 subjects in each group would ensure a statistical power of 80% to test our hypothesis of a significant excess of lens opacities of different cataract types and stages in interventional cardiologists. The results should be available by 2011 and we will publish our findings, whether they are positive, negative, significant, or not significant
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