BACKGROUND Phototoxic maculopathy most likely results from longer exposure to light from sources such as the sun, welding arcs, tungsten halogen lamp filaments or operation microscopes. The value of the multifocal ERG for the evaluation of functional defects in this rare entity has not been described to date. METHODS We describe the case of a 38-year-old male patient who presented to his local ophthalmologist with bilateral loss of vision and acute ocular pain after having worked for two hours at an electric welding arc. A foveal lesion was found in both eyes, resulting in a bilateral reduction of visual acuity. Nine months later, the patient underwent examination and further investigations at the university eye clinic in Tübingen. Visual field defects on both sides could be detected with automatic threshold perimetry. Using the multifocal ERG with a central element of 2 degrees diameter, a central defect was detected only for the right eye. CONCLUSIONS In rare cases, a photic maculopathy can result from exposure to light during arc welding. It can be masked in the first days by a phototoxic keratitis. Multifocal ERG and automatic perimetry are useful tools for the detection and quantification of the functional defects.