Yes, radiation can cause cataracts. Both ionizing radiation (from X-rays, CT scans, and radiation therapy) and ultraviolet radiation from sunlight can damage the lens of the eye and lead to clouding over time. The current recognized threshold for ionizing radiation is 0.5 Gray of absorbed dose, though recent evidence suggests damage may begin at even lower levels.
How Radiation Damages the Lens
The lens of your eye is covered by a thin layer of actively dividing cells called lens epithelial cells. These cells are unusually vulnerable to radiation because, unlike most tissues in the body, the lens has no way to shed damaged cells. Old and injured cells simply get pushed toward the center and back of the lens, where they accumulate.
When ionizing radiation hits these cells, it causes DNA damage within about an hour of exposure. The cells attempt to repair themselves over the next 24 hours, but repair is often incomplete. Radiation also triggers oxidative stress, flooding cells with reactive molecules that damage proteins. Over time, these damaged proteins clump together and lose their transparency, creating the cloudy patches we call a cataract. Exposed cells can also enter a state of permanent shutdown called senescence, where they stop dividing but don’t die, contributing to the gradual breakdown of normal lens structure.
Ultraviolet light from the sun works through a related but distinct pathway. UVA and UVB rays generate free radicals in the lens, which modify lens proteins and break down the fatty molecules in cell membranes. This cumulative UV damage is one reason cataracts are more common in populations with high sun exposure.
What Radiation Cataracts Look Like
Radiation-induced cataracts have a characteristic pattern that distinguishes them from the most common age-related type. They almost always start as a posterior subcapsular cataract, meaning the clouding begins at the back surface of the lens, right at its center. This shows up initially as a fine granular opacity that gradually spreads outward toward the edges, eventually forming a plaque-like opacity.
This matters because posterior subcapsular cataracts tend to cause more noticeable vision problems earlier than other types. They sit directly in the path of light entering the eye, so even a small opacity can cause glare, difficulty reading, and trouble seeing in bright conditions. By contrast, the nuclear cataracts that develop with normal aging often progress more slowly and may go unnoticed for years.
Dose Thresholds and Latency
The International Commission on Radiological Protection recognizes 0.5 Gray as the threshold dose for radiation-induced cataracts. Above this level, the risk increases regardless of whether the dose was received all at once or accumulated over years. Recent research has identified lens changes at even lower doses, on the order of 1 Gray or below, raising questions about whether any true “safe” threshold exists.
The time between radiation exposure and cataract development varies significantly depending on the dose. Higher doses produce cataracts faster. In children who received craniospinal radiation for brain tumors at a median dose of 23.4 Gray, 28% developed cataracts within a median of about 28 months. For lower occupational exposures, cataracts may take a decade or more to become clinically significant. This delay is one reason radiation cataracts were historically underrecognized: by the time vision problems appeared, the connection to an earlier exposure was easy to miss.
Risk From Medical Imaging
A single head CT scan delivers a relatively small dose to the eye lens, and for most people, occasional diagnostic imaging poses minimal cataract risk. However, the cumulative effect of repeated scans is measurable. A large Canadian study found that cataract surgery risk increased by about 10% per 100 milliGray of lens dose when looking at outcomes three years after exposure. The Beaver Dam Eye Study in the United States found that people who reported having head CT scans had 45% higher odds of posterior subcapsular opacities compared to those who hadn’t.
Risk appeared to climb more steeply above 250 milliGray of cumulative dose, after which it rose in a roughly linear pattern. Below that level, the hazard ratios remained relatively flat. To put this in perspective, a single head CT delivers roughly 50 milliGray to the lens, so reaching the higher-risk zone would typically require multiple scans over time. A Taiwanese study of over 30,000 people found that those who had undergone at least one CT scan had a 76% higher risk of developing cataracts compared to those who hadn’t.
Occupational Exposure in Medical Workers
Healthcare workers who perform fluoroscopy-guided procedures face the most significant occupational risk. Interventional cardiologists, who stand near X-ray equipment for hours during catheter-based heart procedures, absorb scatter radiation to their eyes on a daily basis. A Brazilian study comparing interventional cardiologists to clinical cardiologists who don’t perform these procedures found stark differences: 33% of the interventional group had some degree of lens opacity, compared to 16% in the control group. Posterior subcapsular cataracts specifically were found in 13% of interventional cardiologists versus just 3% of their non-interventional peers. A meta-analysis found a cataract prevalence of 36% among interventional cardiologists, consistent with these results.
These findings prompted the ICRP in 2011 to dramatically lower its recommended occupational dose limit for the eye lens from 150 millisieverts per year to just 20 millisieverts per year, averaged over five years, with no single year exceeding 50 millisieverts.
Radiation Therapy and Cataract Risk
Patients who receive radiation therapy to the head, face, or brain face the highest cataract risk because the doses involved are far above occupational levels. In a study of 65 children treated with craniospinal irradiation for brain tumors, more than one in four developed cataracts, and six of those thirteen children required surgical intervention. The median time to cataract development was just over two years after treatment.
Adults treated with radiation for head and neck cancers, eye tumors, or as part of bone marrow transplant conditioning face similar risks. The likelihood depends on total dose, how many sessions the dose is divided into, and how much of the radiation field overlaps with the eyes. Modern radiation planning techniques can reduce lens exposure, but when the treatment target is close to the eyes, some exposure is often unavoidable.
Protective Measures That Work
For medical workers, leaded eyewear is the most effective frontline defense. Studies on neuroangiography procedures found that lead glasses reduced lens radiation exposure by a factor of about 5, cutting the dose per interventional procedure from roughly 169 microsieverts down to 33 microsieverts. When lead glasses are combined with ceiling-mounted lead shields, the reduction factor reaches 8 to 10.
For everyday UV-related cataract risk, sunglasses that block 99 to 100% of UVA and UVB rays provide meaningful protection, especially during peak sun hours. Wide-brimmed hats add another layer by reducing the amount of UV that reaches the eyes from above and around the edges of glasses.
If you’ve had significant radiation exposure, whether from medical treatment, occupational work, or repeated diagnostic imaging, regular eye exams with a dilated lens evaluation can catch posterior subcapsular changes early. Radiation cataracts are treated the same way as any other cataract: surgical lens replacement, which has a high success rate and is one of the most commonly performed surgeries worldwide.