MRI Safety of Iron Oxide-Containing Pigments in Keratopigmentation

To evaluate the magnetic resonance imaging (MRI) safety of iron oxide-containing pigments previously used in femtosecond laser-assisted keratopigmentation (KTP).

Twelve pigment formulations were initially screened using MRI to identify the most magnetically reactive sample. Standardized pigment amounts equivalent to clinical use were measured with a precision microbalance. Temperature changes were monitored with fiber optic thermometry in porcine corneas with and without pigment after femtosecond laser tunnel creation during a standard MRI protocol. Pigment motility was assessed by suspending impregnated filter paper in MRI-safe glass jars and observing potential movement within the bore. MRI sequences were analyzed for image distortion.

No measurable temperature increase was observed in pigment-containing or control porcine corneas during MRI exposure. No pigment movement was detected; the impregnated filter paper remained stable without displacement, deflection, or torque. MRI revealed a localized signal at the pigment site, causing mild distortion limited to the corneal region, with no interference in adjacent or posterior ocular structures.

Iron oxide-containing pigments (Biotic Phocea, France) used in KTP did not cause heating, motility, or clinically significant imaging artifacts during MRI. Although localized corneal signal distortion was noted, it did not hinder the visualization of deeper eye tissues. These findings support the safety of MRI in patients with prior KTP using iron oxide pigments, including those who had initial pigments implanted.