[IONIZING RADIATION AND THE RISK FOR CATARACT AND LENS OPACITIES].

INTRODUCTION: The lens of the eye is among the most sensitive organs to ionizing radiation in the human body. The cataract is the earliest documented side effect of ionizing radiation, first reported in lab animals in 1897, only a year after the discovery of X-rays, and in 1906 among human radiation technicians. However, the exact mechanisms underlining this pathology have yet to be uncovered. In particular, the question as to whether radiation-induced cataract is a deterministic event, meaning a threshold dose must be exceeded in order for it to develop, still remains. Recent epidemiological studies, performed on populations exposed to lower radiation doses than those previously perceived cataractogenic, have led the International Commission on Radiological Protection (ICRP) in April 2011 to reduce its eye dose threshold for cataract induction from 2 Gy to 0.5 Gy, and the occupational annual dose limit from 150 mSv to 20 mSv/year. However, the ICRP have yet to support a stochastic effect (linear non-threshold) for radiation- induced cataract, although suggested by several studies. In this article, we review the current knowledge on radiation-induced cataract, including the speculated mechanism for its development, evidence for genetically predisposed populations, and the main recent epidemiological studies.