Background: To study basal epithelial cell (BEC), sub-basal nerve plexus (SBN) and Langerhans cell (LC) density in patients with type 2 diabetes mellitus (T2DM) with corneal punctate epitheliopathy (CPE) and to assess their association with time to healing of CPE. Methods: Retrospective study of in vivo confocal microscopy (IVCM) in 160 eyes from 160 patients with T2DM diagnosed with CPE due to a single cause. Key exclusion criteria included multiple-causes for CPE or treatment with autologous serum. A total of 149 eyes from 149 gender-age-and aetiolgy-matched patients with CPE without T2DM comprised the control group. Electronic records were reviewed for demographic features, history of T2DM and aetiology of CPE. Density of BEC, SBN and LC were compared between the two groups. Results: The healing time in days for CPE with different aetiologies in the T2DM and control groups were as follows: dry eye (21.56 +/- 2.41; 7.00 +/- 2.19; P = 0.001); meibomian gland dysfunction (26.42 +/- 6.04; 9.21 +/- 2.55; P = 0.001); cataract extraction (38.00 +/- 19.62; 25.83 +/- 11.49; P = 0.043); drug induced (53.19 +/- 18.83; 41.86 +/- 23.87; P = 0.018) and exposure (38.25 +/- 14.13; 29.00 +/- 13.67; P = 0.026). LC density was 38.70 +/- 9.65 cells/mm(2) in the T2DM group compared with 25.53 +/- 3.54 cells/mm(2) in the controls (P = 0.001). SBN density was 11.76 +/- 1.69 mm/mm(2) in the T2DM group compared with 20.92 +/- 1.43 mm/mm(2) in the controls (P = 0.001). BEC density in the T2DM group was 4982 +/- 1178 cells/mm(2) compared with 5739 +/- 394 cells/mm(2) in the control group (P = 0.018). Age and duration of T2DM had no relationship with healing time (multiple linear regression, P = 0.618; P = 0.787). The density of LC in the T2DM group showed a negative correlation with SBN density (r = 0.350; R-2 = 0.1225; P = 0.034). The density of SBN in the T2DM group showed a positive correlation with BEC density (r = 0.427; R-2 = 0.1823; P = 0.008). The density of BEC in the T2DM group showed a negative correlation with healing time (r = 0.931; R-2 = 0.8668; P = 0.001). Conclusions: Utilising IVCM, we have demonstrated increased LC and decreased SBN in patients with T2DM and CPE. Both may be related to lower BEC density and nuclei enhanced reflection. Furthermore, decreased BEC density may lead to delay in cornea epithelium healing in the T2DM group compared with controls. An immune-mediated response may play a role in delayed wound closure in patients with T2DM.