Early central and peripheral corneal microstructural changes in type 2 diabetes mellitus patients identified using in vivo confocal microscopy

Abstract The aim of this study was to find early central and peripheral corneal microstructural changes in healthy subjects and type 2 diabetes mellitus (T2DM) patients with/without cornea fluorescein dot staining. This is a prospective case-control study of T2DM patients with/without cornea fluorescein dot staining. Age, sex, duration of diabetes, and serum glycosylated hemoglobin A1c (HbA1c) levels were recorded. Keratograph 5 M (K5 M) and in vivo confocal microscopy were performed on all subjects. The cornea was divided into 5 zones: central, superior, temporal, nasal, and inferior. Basal epithelial cell (BEC) density, the area of BEC, sub-basal nerve plexus (SBN) density, Langerhans cell (LC), and endothelial cell (EC) density were quantitatively analyzed. This study included a total of 87 individuals (28 males and 59 females; mean age, 62.30 ± 9.93 years) with T2DM, without (n = 48; T2DM group 1) and with (n = 39; T2DM group 2) cornea fluorescein staining, as well as 51 age- and sex-matched healthy subjects (18 males and 33 females; mean age, 61.53 ± 10.15 years). Ocular Surface Disease Index scores, Schirmer &Igr; test, tear meniscus height, the first breakup of tear film occurrence (NIKBUT-first), and the average time of all breakup incidents (NIKBUT-average) values were significantly lower for the T2DM groups than for the healthy group. The corneal sensations of all cornea positions in the T2DM groups were significantly different from the control group. The HbA1c in the T2DM groups showed a negative correlation with central BEC density (R = 0.348, P = .015; R = 0.91, P = .001); there was no correlation of HbA1c with BEC density in the control group. The BEC density, the area of BEC, SBN, and LC density of T2DM group 1 and T2DM group 2 were significantly different compared with the control group in all corneal positions (P < .001). The BEC density of T2DM group 2 was significantly different from T2DM group 1 in the central (P = .044) and inferior (P = .013) zones. The area of BEC in T2DM group 2 was significantly different from T2DM group 1 in inferior zone (P = .014) and other corneal positions showed was no significant difference (P > .05). The SBN density of T2DM group 2 was not significantly different from T2DM group 1 in all corneal positions (P > .05). The LC density of T2DM group 2 was significantly different from T2DM group 1 in the central (P = .006) and inferior (P = .006) zones. Although the LC density in the T2DM groups showed no significant difference in all corneal zones (P > .05), the LC density in the central zone was significantly lower compared with the peripheral zone in the control group (P = .001). The central ECs in the 3 groups were not significantly different (P > .05). LC induced an immune-mediated contribution to corneal nerve damage and may influence the early stages of BEC proliferation and differentiation in T2DM. BEC density was the reliable index for evaluating the early condition of diabetic corneal epitheliopathy. The BEC density of the central and inferior corneal zones was more sensitive.