Clinical Research Directory

Inclusion Criteria: Age ≥18 and ≤82 years * Diagnosed with 1) type 1 diabetes (for at least 5 years) or 2) type 2 diabetes * The Toronto consensus criteria will be used for a case definition of DPN where patients have to have at least probable DPN (31). Diagnosis of DPN is confirmed with abnormal DPN Check. Painful DPN will be defined using the grading system for neuropathic pain (50) and will be in line with IASP's definition of neuropathic pain, i.e., "pain caused by a lesion or disease of the somatosensory system" (The Toronto consensus criteria). * TCNS score \> 5 * Eligible patients with painful DPN must have a pain intensity of at least 4 on an 11-point numerical rating scale (NRS, 0-10) for at least 3 months on at least semi-daily basis and no severe pain other than pain due to neuropathy (the pain intensity will be based on the pain the patients experience while on current pain treatment, if any). * Stable pain medication for \> 1 month prior to inclusion. Exclusion criteria Exclusion Criteria: * Concomitant neurological (neurodegenerative disorders, migraine, epilepsy, stroke, tumor) or clinically significant psychiatric illness * Neuropathy or neuropathic pain due to other causes than diabetes (vitamin B12 deficiency, prior treatment with neurotoxic chemotherapy, chronic alcohol abuse, spinal stenosis, etc.) * Change in current pain treatment during treatment (paracetamol is allowed as rescue medicine) * Prior or current excessive alcohol use (\>14 or \>21 units/week for women and men, respectively) or illegal substance abuse * Positive urine hCG test result indicating pregnancy * Morphine use \>20mg/day * Blindness or severely impaired vision * The investigator finds the patient unfit for the study (e.g. due to use of alcohol or drugs, mental incapacity, unwillingness, or language barrier precluding adequate understanding or cooperation or presence of any condition that in the investigators' opinion may lead to poor adherence to study protocol).