Apparatus, including a guidewire having a distal end, that is configured to be inserted into proximity with a nasal sinus of a patient, the guidewire having a lumen. The apparatus also includes an optic fiber, traversing the lumen, configured to illuminate the distal end, and a coil, wound around the optic fiber and located within the lumen at the distal end, configured to generate a signal in response to a magnetic field interacting with the coil. A processor is configured to receive the signal and to evaluate a location of the distal end in response to the signal.
