Magnetic Resonance Imaging, or MRI, is a sophisticated medical tool that generates detailed diagnostic images of organs and tissues using a powerful magnet and radio waves, not X-rays. Because the machine creates an intense magnetic field, any metallic objects brought near it can become hazardous. This requirement makes the question of wearing contact lenses during a scan a frequent concern before a procedure.
Why Contacts Are a Concern During MRI Scans
The powerful magnetic field generated by the MRI scanner is the central reason for caution regarding contact lenses. The concern relates directly to the materials used in manufacturing certain lenses, particularly the pigments. While most standard soft, clear contact lenses are made from non-metallic hydrogel or silicone hydrogel polymers, not all lenses have the same composition. The primary issue arises with colored, cosmetic, or prosthetic contact lenses. These lenses often contain tints or dyes that may incorporate metallic elements, such as the pigment iron oxide. Iron oxide is a ferromagnetic material that can interact strongly with the magnetic field.
If the components are ferromagnetic, the strong magnetic field can exert a force on these trace metallic elements. This interaction could cause the lens to vibrate or move slightly on the surface of the eye. This potential movement creates a physical and diagnostic issue for the patient and the imaging quality. The presence of any metallic fragment, even minute impurities, drives conservative safety protocols.
Understanding the Risks of Wearing Contacts
When a lens containing ferromagnetic material is exposed to the MRI’s magnetic field, two main negative outcomes are possible: physical harm and image degradation. The primary physical risk is localized heating of the lens and surrounding ocular tissue. The rapid switching of magnetic fields and radiofrequency energy induces currents in metallic components, causing them to warm up. This thermal effect can cause a burning or stinging sensation on the cornea. Discomfort or irritation can make it impossible for a patient to remain perfectly still, which can render images unusable and require a repeat procedure.
The second risk is the creation of image artifacts, often called magnetic susceptibility artifacts. The presence of metal, even in trace amounts, distorts the local magnetic field. This distortion appears on the final image as a dark void or signal loss, which can obscure the anatomy of interest. If the MRI is performed on the head, orbits, or brain, this artifact can compromise the diagnostic quality of the scan, potentially leading to a misdiagnosis.
Essential Preparation Before Your Scan
Given the potential for both patient discomfort and image interference, the safest and most standard recommendation is to remove all contact lenses before entering the MRI suite. This practice eliminates the risk entirely, regardless of the lens type, brand, or age. Patients should bring their contact lens case and solution with them to the facility so they can store their lenses immediately before the procedure.
Alternatives for Vision Correction
For patients who rely on corrective lenses for vision, there are simple and practical alternatives. The most straightforward approach is to wear eyeglasses right up until the moment of the scan. Since standard eyeglasses cannot be worn inside the narrow bore of the MRI machine, they must be removed just before entering the scanning room. Patients who are unable to see without correction for the duration of the scan may consider using daily disposable contact lenses on the day of the appointment. These lenses can be worn up to the scan and then safely discarded immediately afterward. It is always wise to discuss any difficulty with vision correction or lens removal with the MRI technologist prior to the scan.