Reduced Corneal Nerve Fiber Density in Type 2 Diabetes by Wide-Area Mosaic Analysis

PURPOSE. To determine if corneal subbasal nerve plexus (SBP) parameters derived from wide-area depth-corrected mosaic images are associated with type 2 diabetes. METHODS. One hundred sixty-three mosaics were produced from eyes of 82 subjects by laser-scanning in vivo confocal microscopy (IVCM). Subjects were of the same age, without (43 subjects) or with type 2 diabetes (39 subjects). Mosaic corneal nerve fiber length density (mCNFL) and apical whorl corneal nerve fiber length density (wCNFL) were quantified and related to the presence and duration of diabetes (short duration < 10 years and long duration >= 10 years). RESULTS. In mosaics with a mean size of 6 mm(2) in subjects aged 69.1 +/- 1.2 years, mCNFL in type 2 diabetes was reduced relative to nondiabetic subjects (13.1 +/- 4.2 vs. 15.0 +/- 3.2 mm/mm(2), P = 0.018). Also reduced relative to nondiabetic subjects was mCNFL in both short-duration (14.0 +/- 4.0 mm/mm(2), 3.2 +/- 3.9 years since diagnosis) and long-duration diabetes (12.7 +/- 4.2 mm/mm(2), 15.4 +/- 4.2 years since diagnosis; ANOVA P = 0.023). Lower mCNFL was associated with presence of diabetes (P = 0.032) and increased hemoglobin A1c (HbA1c) levels (P = 0.047). By contrast, wCNFL was unaffected by diabetes or HbA1c (P > 0.05). Global SBP patterns revealed marked degeneration of secondary nerve fiber branches outside the whorl region in long-duration diabetes. CONCLUSIONS. Wide-area mosaic images provide reference values for mCNFL and wCNFL and reveal a progressive degeneration of the SBP with increasing duration of type 2 diabetes.