Interventional cardiologists and risk of radiation-induced cataract: Results of a French multicenter observational study☆
Introduction
The wider use of medical imaging involving X-rays as a diagnostic tool and during interventional procedures has led to steadily increasing exposure of medical staff to ionizing radiation, especially in interventional cardiology with fluoroscopically guided procedures [1]. Around 350,000 coronary angiographies and/or percutaneous transluminal angioplasties [2] and close to 100,000 electrophysiological procedures are performed annually in France. These procedures require X-ray use and expose interventional cardiologists to radiation, in particular to the eyes, with doses per procedures that can range from about 10 μSv (micro Sievert) to more than 1000 μSv [3], [4], [5] depending on the type of procedure and use of radiation protection equipment. The radiosensitivity of the eye lens to radiation is well known. Although it is commonly accepted that high exposure to ionizing radiation induce lens opacities [6], the current debate includes lower doses with occupational annual dose limit of 20 mSv/year [7], [8], which may be in the range of the occupational exposure of unprotected medical staff in catheterization laboratories.
According to their anatomic location, cataract, or presence of lens opacities, can be classified into three main types: nuclear, cortical and posterior subcapsular (PSC) (see Fig. 1). At early stage of cataract, lens changes consist of small dots and vacuoles which, over time, aggregate to form larger opacities. PSC cataract is the least common form, but relatively minor PSC opacities can induce great impact on vision because of its location along the lens visual axis. PSC cataract is commonly associated with ionizing radiation exposure, but some epidemiological studies suggested that the traditional view that PSC opacities are the only type of radiation-induced cataract may be broadened to other type of cataracts [9].
Excess risk of PSC cataract among interventional cardiologists was first suspected in the USA [10] and later observed in some exposed/unexposed studies performed in samples of cardiologist from Uruguay and Columbia [11], Malaysia [12], and from Helsinki [13], suggesting a risk of lens opacities at least twice that of unexposed groups. These studies presented, however, methodological limitations and only focused on PSC opacities whereas other types of cataract may be involved [14]. Moreover, this risk had never been studied in France where cardiologists' workload and radiation protection awareness may be different from previously studied populations.
In this context, the O'CLOC study [15] (Occupational Cataracts and Lens Opacities in interventional Cardiology) was performed in France to screen different types of lens opacities among interventional cardiologists from many French centers and quantify the risk of early cataract among them, compared to an unexposed control group.
Section snippets
Materials and methods
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Population characteristics
Of the 526 ICs invited by email or postal mail to participate, in a message specifying an age criterion ≥ 40 years, 131 answered positively and were interviewed by telephone (Fig. 2). For the unexposed group, all 1082 IRSN workers at Fontenay-aux-Roses were contacted by email and after frequency matching criteria for age and sex with the IC group, 128 were interviewed by telephone. A history of head CT scan was slightly more frequent among the 128 unexposed workers than the 131 ICs, but the
Discussion
This multicenter study is the first to investigate the prevalence and risk of lens opacities in a population of French ICs compared with an unexposed group and considering all three common types of lens opacities. Prevalence for nuclear and cortical lens changes was concordant with the frequency observed in reference population-based studies on early stages of cataract [17], and was similarly distributed between exposed and unexposed group. Relationship between radiation exposure and this kind
Conclusion
The O'CLOC study performed in France indicates that PSC opacities in the population of interventional cardiologists are a side effect of this specialty. These results reinforce those of previous smaller studies. The increasing number of young cardiologists in IC training programs means that more physicians are likely to be exposed in the years to come and reinforces the need for radiation protection rules for medical personnel. Increasing cardiologists' awareness of the need for radiation
Acknowledgments
We are grateful to the cardiologists and IRSN volunteers who participated in the O'CLOC Study for their commitment and cooperation, and to Alexandre Bertrand who was in charge of recruitment and interviews of the participants. We thank all ophthalmologists involved in the study and in particular Dr Julien Bullet who performed eye examinations for IRSN workers.
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Clinical Trial Registration Information — URL: http://www.clinicaltrials.gov. Unique identifier NCT01061463.