Ionizing radiation exposure has been demonstrated to increase the risk of developing cataracts in the eye’s lens.
This article answers some of the most frequently asked questions surrounding radiation induced cataracts — what they are, how they form, and how to protect yourself from developing this debilitating condition.
What Are Cataracts?
Cataracts are the main cause of blindness worldwide and the second most common visual impairment after uncorrected refractive errors. The most common cataract symptom is slow but continual vision loss, with the lens gradually getting foggier and foggier.
For some people, cataracts result in only slight vision impairment, but for many others, the fogginess increases, resulting in total opacification of the lens and blindness.
Other symptoms include heightened glare sensitivity, the appearance of starbursts or halos around lights, and double vision. An interesting consequence of this condition is that people with cataracts don’t get red eyes in photos taken with flash photography.
There are three types of cataracts:
- Cortical cataracts. These develop from pathologic changes in the cells of eye lens fiber.
- Nuclear cataracts. Similar to cortical cataracts, nuclear cataracts are caused by changes in lens fiber.
- Posterior subcapsular cataracts. Also called (PSCCs), this type of cataract arises from abnormalities in the germinative zone of the lens. Contributive factors include steroid use, lack of endogenous antioxidants, and — the topic of this article — exposure to ionizing radiation.
Are Cataracts Caused By Radiation?
There’s still a lot of work to be done concerning cataract pathogenesis. Cataracts can be caused by a host of influences, including environmental and genetic factors.
That said, one of the contributing factors that we have the most certainty about is radiation exposure, with strong evidence for radiation exposure inducing cortical cataracts and posterior subcapsular cataracts.
So while radiation isn’t the only factor that can cause cataracts, radiation exposure drastically increases the likelihood of developing cataracts.
How Much Radiation Exposure Can Cause Cataracts?
Traditionally, the threshold dose for radiation-induced cataracts has been 5 Sv.
However, recently, the International Commission on Radiological Protection has reduced its threshold dose to 0.5 Gy and recommended an occupational exposure limit of 20 mSv per year.
Some argue that new studies on occupational exposure to radiation are needed to determine if the threshold should be lowered to 0.5 Gy industry-wide.
For now, what we do know is that radiation dosages as low as 2 Gy have been shown to increase cataract risk in radiologic technologists.
How Do Radiation-Induced Cataracts Form?
The human eye is a unique structure with advanced refraction capabilities. Unfortunately for technologists and others working closely with radiation, the delicate systems in the eye that enable us to experience vision are also susceptible to radiation destruction.
As scatter radiation enters the eye, it impacts a transparent layer of epithelial cells on the interior of the eye’s lens. The radiation knocks electrons out of atoms in the lens’ cells, damaging cells and inhibiting division.
Unfortunately, the lens can’t clear damaged cells, so as radiation continues to destroy cells, they build up on the lens — blocking light and creating cataracts.
Which People Are Most At Risk For Radiation-Induced Cataracts?
The people most at risk for radiation caused by cataracts among the general public include commercial airline pilots, people with actinide exposure, astronauts, and especially radiologic technologists.
The Impact of Radiation on Radiologic Technologists’ Eyes
In a major study of over 37,000 American radiologic technologists, progressive cataracts developed for radiation doses as low as 2 Gy. For healthcare professionals exposed to higher levels (roughly 60 mGy), their risk of developing cataracts was an astounding 20% higher than those exposed to 2 Gy.
This study showed that for every increase of 1 Gy, radiologic technologists suffered a 2% increase in their odds of developing cataracts.
Additional studies have continued to demonstrate the need for healthcare personnel to wear protective eyewear that can block scatter radiation.
The Impact of Radiation on Patients’ Eyes
What about patients receiving diagnostic or therapeutic radiation exposure?
A study by Merriam and Focht of 233 radiation therapy patients found that 128 of these patients developed cataracts within 9 years of treatment. Like radiologic technologists, the lowest radiation dosage that induced cataracts was 2 Gy at a minimum treatment time of 3 weeks.
Another study of over 400 children treated with radiotherapy for skin hemangiomas found an increased risk of roughly 50% per Gy for posterior subcapsular and cortical cataracts. This and other studies have shown that the risk of radiation-induced cataracts is higher for younger populations.
While the average patient increases their cataract risk with medical radiation exposure, the situation is especially threatening for technologists who undergo x-rays as patients.
A 20-year prospective cohort study of US radiologic technologists found that technologists were more susceptible to radiation induced cataracts from non-occupational x-rays, with technologists who received >3 x-rays to the face and neck putting themselves at a hazard ratio of 1.25 for developing cataracts.
This increased risk of cataracts from personal x-rays is likely due to the cumulative effects of radiation. Whereas other injuries heal over time, radiation damage is extremely difficult to recover. As a result, radiation damage builds up with each new exposure. So while a standard neck x-ray may not inflict lasting damage on the average patient’s eyes, it can cause harm to radiologists who already have a fair amount of radiation damage in the cells of their eyes.
What Are the Treatment Options for Radiation-Induced Cataracts?
Fortunately for people who have already received radiation-induced cataracts, various treatment options can help treat cataracts help to restore clear vision to the eye.
With a 99% success rate, the most common treatment is clear cornea surgery, which includes lens aspiration with posterior capsulotomy, IOL implantation, and anterior vitrectomy.
One study of surgeries performed on victims of radiation induced cataracts found that visual prognosis was limited by the corneal complications of radiotherapy and by the initial tumor involvement of the macula.
How To Protect the Eyes From Radiation?
The most effective way to protect the eyes of radiologists from scatter radiation is to encourage the use of leaded eyewear.
Radiation Protective Eyewear From Barrier Technologies
Here at Barrier Technologies, our engineers, manufacturers, and partners are dedicated to developing the most powerful & comfortable x-ray protective eyewear available.
Our frames come from leading brands such as Oakley, Costa, and the Rudy Project and utilize Corning 0.75mm Pb Med-X® Glass lenses. We also offer anti-reflective and anti-fog lens coatings to ensure you can see clearly during lengthy procedures.
To learn more about how we deliver the highest glass lens attenuation in the industry, visit our leaded eyewear catalog or contact us today.