Chernobyl offers insight into cataract formation

Thirty years ago today, the meltdown at Chernobyl Nuclear Power Plant spewed a plume of radioactive material into the air of northern Ukraine, Russia and Belarus. Some 1,000 square miles around the plant was sealed off from public access, allowing the flora and fauna to recover without human interference. Though a disaster for the  environment, the area became an ideal laboratory to study the long-term effects of radiation exposure, including cataracts.

In 2000, researchers from the University of South Carolina and the French National Center for Scientific Research (CNRS) began studying the inhabitants of the Chernobyl exclusion zone to further examine the development of cataracts following exposure to ionizing radiation.

"As a starting point for our studies of animal populations, we took our cue from the medical literature--one of the first effects observed was the presence of cataracts in the eyes of people exposed to energy from atomic bombs," said lead American investigator Tim Mousseau in a press release. "And we found that both birds and rodents show elevated frequencies and degree of cataracts in their eyes in the more radioactive areas. Nowadays, we see higher rates of cataracts in flight crews who spend a lot of time in airplanes, which expose them to extra radiation. And people who work in radiology fields are more likely to show increased prevalence and degree of cataract formation in their eyes."

Acute exposure leads to clouding because dividing cells such as lens epithelium are most susceptible to radiative damage. Cells dividing at the equator are highly exposed, and when hit with ionizing radiation fail to migrate correctly from the anterior to the center, congregating instead in the posterior and blocking light.

Continued, low-level exposure is thought to impact the eye differently. Mousseau and colleagues showed in a recent meta-analysis that the chronic exposure experienced by animals in the Chernobyl area induces cataracts and other diseases via oxidative stress, which has also been proposed as a causative mechanism in humans.

Yet although initial die offs and abnormalities were severe, wildlife populations are now flourishing despite high levels of lingering radiation. The authors reveal that some organisms have adapted physiologically to the exposure by increasing production of the intracellular antioxidant glutathione (GSH). They found that birds in regions with higher radiation within the exclusion zone actually had higher GSH levels, resulting in better body condition and less DNA damage.

Concurrently, new research has illuminated the link between antioxidants and cataracts in humans.

The Chernobyl disaster serves as a sobering reminder on the dangers of radiation, but now we can use the data it provides to prevent and develop treatments for diseases of the eye and beyond.