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IAEA Cataract study

RELID cataract study

IAEA activity on Retrospective Evaluation of Lens Injuries and Dose (RELID)

The lens of the eye is one of the radiosensitive tissues in the body. Radiation induced cataract has been demonstrated among staff involved with interventional procedures using X rays [ICRP 85; Vano et al., 1998]. A number of studies suggest there may be significant risk of lens opacities in populations exposed to low doses of ionizing radiation. These include those undergoing CT scans [Klein et al., 1993], astronauts [Cucinotta et al., 2001; Rastegar et al., 2002], radiologic technologists [Chodick et al., 2008] radiotherapy [Hall et al., 1999] besides data from atomic bomb survivors [Nakashima et al., 2006; Neriishi et al., 2007] and those exposed in Chernobyl accident [Day et al., 1995]

These observations have clear implications for those working in interventional rooms. Interventionalists and paramedical staff (nurses and to some extent radiographers) remain near the X ray source and within a high scatter radiation field for several hours a day during interventional procedures. During typical working conditions and if radiation protection tools are not routinely used, x-ray exposure to the eyes of interventional physicians and paramedical personnel working in interventional and catheterization laboratories can be high.

The cataract has so far been considered to be a deterministic effect with threshold. The International Commission on Radiological Protection (ICRP) and the U.S. National Council on Radiation Protection and measurements (NCRP) have published threshold values, for detectable opacities of 5 Sv for protracted exposures and 0.5 to 2 Sv for acute exposure.

The Commission has now reviewed recent epidemiological evidence and has issued a statement after its meeting on 21st April 2011.

According to this statement, the threshold in absorbed dose for the lens of the eye is now considered to be 0.5 Gy.Estimations indicate that cumulative lifetime occupational doses received by interventionalists and some paramedical staff may exceed these currently accepted international standards unless specific measures are taken.

In its 2007 recommendations [ICRP 2007], the ICRP stated that ‘‘new data on the radiosensitivity of the eye with regard to visual impairment are expected ... because of the uncertainty concerning this risk, there should be particular emphasis on optimization in situations of exposure of the eyes”. The most recent ICRP statement for tissue reactions continues to recommend that optimization should be applied in any exposure situation and for any category of exposure.

Subcapsular posterior lens changes, characteristic of radiation exposure with a dose-effect threshold significantly less than 1 Gy were recently reported in Chernobyl cleanup workers [Worgul et al., 2007]. These findings are inconsistent with the 2000 and 2007 International Commission on Radiological Protection (ICRP) threshold of 5 Gy for ‘‘detectable opacities’’ from protracted exposures [ICRP 2000, ICRP 2007]. However, these data agree with the new threshold of 0.5 Gy for detectable lens opacities that was recently proposed in the ICRP statement.

Unfortunately, the regular and appropriate use of the personnel monitoring device by interventionalists is largely lacking. In surveys conducted by the IAEA during various training courses, in which cardiologists from over 56 countries have participated, responses indicate that only 33-77% of interventional cardiologists utilize radiation badges routinely.

An international study called RELID(Retrospective Evaluation of Lens Injuries and Dose) was initiated by the IAEA in 2008. A number of eye testing examinations have been held.

The ICRP has issued a statement in April 2011 reducing dose limit for eye lens by almost 8 fold

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