Abstract
This study evaluated cataracts in wild boar exposed to chronic low-dose radiation. We examined wild boar from within and outside the Fukushima Exclusion Zone for nuclear, cortical, and posterior subcapsular (PSC) cataracts in vivo and photographically. Plausible upper-bound, lifetime radiation dose for each boar was estimated from radioactivity levels in each animal’s home range combined with tissue concentrations of 134+137Cesium. Fifteen exposed and twenty control boar were evaluated. There were no significant differences in overall prevalence or score for cortical or PSC cataracts between exposed and control animals. Nuclear (centrally located) cataracts were significantly more prevalent in exposed boar (p < 0.05) and had statistically higher median scores. Plausible upper-bound, lifetime radiation dose ranged from 1 to 1,600 mGy in exposed animals, with no correlation between dose and cortical or PSC score. While radiation dose and nuclear score were positively associated, the impact of age could not be completely separated from the relationship. Additionally, the clinical significance of even the highest scoring nuclear cataract was negligible. Based on the population sampled, wild boar in the Fukushima Exclusion Zone do not have a significantly higher prevalence or risk of cortical or PSC cataracts compared to control animals.
Highlights
The lens of the eye is one of the most sensitive tissues to ionizing radiation[1,2], making cataracts an excellent indicator of long-term tissue effects from low-dose radiation exposure
Thirty eyes from 15 wild boar within the Fukushima Exclusion Zone (FEZ) and four eyes from two boar outside the FEZ were evaluated from Japan. (Fig. 1) Due to a lack of sufficient control animals collected from Japan, 36 eyes of 18 wild pigs from uncontaminated areas of the Savannah River Site (SRS) in Aiken, South Carolina were evaluated
Wild boar within the Fukushima Exclusion Zone did not have a significantly higher prevalence or score of cortical or posterior subcapsular (PSC) cataracts compared to control animals
Summary
The lens of the eye (intraocular lens) is one of the most sensitive tissues to ionizing radiation[1,2], making cataracts an excellent indicator of long-term tissue effects from low-dose radiation exposure. The LOCS (lens opacity classification system) compares opacifications within the lens to a set of standard images, providing a score for lesions within different parts of the lens This system was developed in an attempt to standardize cataract evaluations and is commonplace in clinical and research settings. While other advanced imaging modalities provide more objective means of cataract evaluation, LOCS is universally available, usable in a field setting, and requires no special equipment[24,25]. Modalities such as histology are useful for identifying cataractous changes within the lens, but require sampling of the exact cross-section of the lesion, making this an impractical survey method. A similar evaluation in avian species[33] lacked ophthalmologist involvement and incorrectly identified cataracts as opacities that may be obscuring the visibility of the iris, an ocular structure anatomically located in front of the lens
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