Abstract

The lens of the eye is highly sensitive to radiation.

The International Commission on Radiological Protection (ICRP) estimates that in case of acute exposure, radiogenic lens opacities (cataracts) are triggered above a threshold dose in the order of magnitude of 0.5 – 2 Gy or, respectively, in case of long-term exposure of 5 – 6 Gy.

The national and international radiological protection bodies have recognised the lens’s particular radiation sensitivity and introduced specific limit values for the lens. For example, paragraph 55 of the German Radiation Protection Ordinance sets a limit value for the lens of the eye (organ dose) of 150 mSv/year for occupational exposure and 15 mSv/year for people under 18 years of age.

Recent epidemiological studies have focussed especially on Hiroshima and Nagasaki atomic bomb survivors, Chernobyl clean-up workers, and radiologic technologists in the U.S.

Here, the lowest measured/reconstructed radiation doses were in the range of 5 – 100 mGy.

According to these studies, there is a high probability that the threshold dose is < 0.8 Gy.

In various studies, an increase in the cataract rate was observed after radiation exposure of around 0.5 Gy and relative hazard ratios of around 1.5 were observed after exposure to 1 Gy.

In the light of the current data situation, the Commission on Radiological Protection recommends:

• That the provisions of the German Radiation Protection Ordinance (StrlSchV) and the German X-ray Ordinance (RöV) on the protection of the lens be brought into line with the latest scientific findings.
• Examination of the lens should be included as appropriate in the medical monitoring of people occupationally exposed to radiation, if there is potentially high lens exposure.
• Recent experimental results point to a paradigm shift in the assessment of the risk of radiation-induced cataracts. For that reason, research strategies must also be adopted in Germany to develop a basic understanding of the mechanisms underlying radiation-induced cataract. In this context, systematic analysis of genetic predisposition to higher sensitivity to radiation-induced cataract must be promoted, along with clinical/epidemiological research which studies the dose-effect relationship between radiation exposure and cataract formation quantitatively on the basis of independent observation.

The Commission on Radiological Protection adopted the recommendation “Radiation-Induced Cataracts” with scientific founding in the 234th meeting on 14 May 2009.