For radiation protection purposes, it has generally been assumed that there is a threshold of dose below which no non-cancer effects arise (Hildebrandt, 2010). Recent epidemiological studies and studies on radiation-induced cataracts in animals (Ainsbury, 2009; Shore, 2010) suggested that the dose threshold for the loss of eye lens function could be lower than previously considered or that there may be no dose threshold at all. Consequently, the ICRP report 118 (ICRP, 2012) revised an absorbed dose threshold to the eye lens of 0.5 Gy for cataracts instead of 2 Gy previously recommended. Although new dose thresholds and occupational dose limits have been set for radiation-induced cataract, the relationship between radiation dose and radiation effect is not clear in the low dose region.
The reduction of the occupational dose limit for the eye lens to 20 mSv per year will have implications for interventional cardiologists - the targeted population in this study - and for other health care professionals, as previous studies have shown that this dose limit can easily be exceeded for medical staff. Moreover, previous studies have already suggested an increased risk of lens opacities for this group [Vaño, 2010 and 2013; Ciraj-Bjelac, 2010; Jacob, 2013], but they have been unable to establish a dose-response relationship. This study will focus on establishing solid epidemiological evidence with strong dose estimation by producing the largest study on lens opacities in medical personnel so far, with more subjects than in all previous studies with interventional cardiologists combined. Further improvements will be based on proper eye lens dosimetry and state-of-the-art ophthalmological examinations providing objective and quantitative assessment of radiation induced lens opacities.