Earlier Diagnosis of Peripheral Neuropathy Using A Simple sCreening Tool (ACT)

This study is looking at people with diabetes (type 1 and type 2 diabetes) to see how well a short questionnaire, called the ACT, can identify nerve damage in the feet and legs (also known as peripheral neuropathy). The investigators will compare the ACT questionnaire to other commonly used tools (the DN4 and Michigan Neuropathy Screening Instrument) and to an eye-test that detects small nerve fibers in the eye (called corneal confocal microscopy, or CCM). The main goal is to find out if the ACT questionnaire is accurate in detecting nerve damage and painful nerve damage caused by diabetes. The investigators will also look at whether changes in blood sugar levels, measured with a continuous glucose monitor (Freestyle Libre 3 and iCan), are linked to nerve pain and small nerve fiber damage.

This a cross-sectional cohort study in patients with diabetes with the aim of assessing the validity and diagnostic accuracy of the ACT questionnaire in identifying peripheral neuropathy (PN) in patients with diabetes and explore underlying mechanisms for nerve damage. The primary endpoint is to validate the ACT tool in identifying diabetic painful neuropathy against the DN4 questionnaire, Michigan Neuropathy Screening Instrument (MNSI) and in relation to underlying small nerve fibre damage (CCM). And the secondary endpoints include the investigation of the association between glycemic indices using continuous glucose monitoring (CGM- Freestyle Libre 3 and iCan) with neuropathic pain (ACT/DN4/MNSI) and small nerve fibre damage (CCM). Participants will attend 3 visits and the following will be assessed: * Visit 1(baseline): Consent, screening, CCM, ACT, MNSI, DN4, CGM (Freestyle Libre 3). * Visit 2 (14-days follow-up): CGM (freestyle Libre 3), ACT, MNSI, DN4 * Visit 3 (between 1-6 months): CGM (iCan)