Abstract Aims/hypothesis Non-invasive in vivo corneal confocal microscopy is gaining ground as an alternative to skin punch biopsy to evaluate small-diameter nerve fibre characteristics. This study aimed to further explore corneal nerve fibre pathology in diabetic neuropathy. Methods This cross-sectional study quantified and compared corneal nerve morphology and microneuromas in participants without diabetes ( n =27), participants with diabetes but without distal symmetrical polyneuropathy (DSPN; n =33), participants with non-painful DSPN ( n =25) and participants with painful DSPN ( n =18). Clinical and electrodiagnostic criteria were used to diagnose DSPN. ANCOVA was used to compare nerve fibre morphology in the central cornea and inferior whorl, and the number of corneal sub-epithelial microneuromas between groups. Fisher’s exact tests were used to compare the type and presence of corneal sub-epithelial microneuromas and axonal swelling between groups. Results Various corneal nerve morphology metrics, such as corneal nerve fibre length and density, showed a progressive decline across the groups ( p <0.001). In addition, axonal swelling was present more frequently ( p =0.018) and in higher numbers ( p =0.03) in participants with painful compared with non-painful DSPN. The frequency of axonal distension, a type of microneuroma, was increased in participants with painful and non-painful DSPN compared to participants with diabetes but without DSPN and participants without diabetes (all p ≤0.042). The combined presence of all microneuromas and axonal swelling was increased in participants with painful DSPN compared with all other groups ( p ≤0.026). Conclusions/interpretation Microneuromas and axonal swelling in the cornea increase in prevalence from participants with diabetes to participants with non-painful DSPN and participants with painful DSPN. Graphical Abstract