X-rays can cause cataracts, but this effect depends largely on the dose and duration of exposure. The lens of the eye is particularly sensitive to ionizing radiation like X-rays, and when exposed to sufficient levels, the radiation can damage the lens cells, leading to opacification or clouding known as cataracts. This damage may not be immediately visible and can develop months or even years after exposure.
The lens is made up of transparent cells that focus light onto the retina. When X-rays penetrate the eye, they can disrupt the normal structure and function of these lens cells by damaging their DNA and proteins. This damage accumulates over time, causing the lens to lose its clarity and become cloudy, which impairs vision. The severity of cataract formation increases with the radiation dose received by the lens.
Historically, cases of cataracts were observed in physicists and workers exposed to neutron radiation and X-rays during the early development of particle accelerators and radiological equipment. These occupational exposures demonstrated that even relatively low doses of radiation, if repeated or prolonged, could induce cataracts. The threshold dose for radiation-induced cataracts is estimated to be around 5 sieverts (Sv) for a single exposure, but lower doses over multiple exposures can also cause cataracts, sometimes at doses as low as a few sieverts cumulatively.
In medical settings, X-rays are used diagnostically at much lower doses than those known to cause cataracts. For example, routine dental or chest X-rays deliver doses far below the threshold that would harm the lens. However, healthcare workers who are repeatedly exposed to low-dose X-rays over long periods, such as radiology technicians or interventional cardiologists, may have a higher risk of lens damage if proper protective measures are not used. Prolonged low-dose exposure can affect not only the lens but also other parts of the eye, such as the cornea and tear film.
Radiation-induced cataracts are classified as a nonstochastic effect, meaning they have a threshold dose below which the effect is unlikely to occur. Above this threshold, the likelihood and severity of cataracts increase with dose. This contrasts with stochastic effects like cancer, where any dose carries some risk. The damage to the lens is cumulative and progressive, often worsening over time after the initial exposure.
Protective measures such as leaded glasses or shields are essential for individuals who work with or around X-rays regularly. These reduce the dose to the lens and help prevent cataract formation. In clinical practice, the benefits of diagnostic X-rays generally outweigh the minimal risk of cataracts, especially when exposure is limited and controlled.
In summary, X-rays can cause cataracts by damaging the lens cells through ionizing radiation. The risk depends on the dose and frequency of exposure, with high or repeated doses increasing the chance of cataract development. Routine diagnostic X-rays pose minimal risk, but occupational exposure without protection can lead to lens opacities and vision impairment over time.