To investigate corneal transparency alteration in patients with type 2 diabetes and its influencing factors.

A case-control study was conducted.A total of 52 patients with type 2 diabetes mellitus (DM) (104 eyes) and 23 age-matched healthy controls (46 eyes) were enrolled as DM group and normal control group in the Second Affiliated Hospital of Anhui Medical University from October 1, 2020 to October 30, 2021.Patients with DM were further divided into non-diabetic retinopathy (non-DR) and DR groups according to their fundus conditions.Corneal densitometry (CD) was evaluated using the Pentacam.According to its built-in program, the cornea was divided into anterior, intermediate, and posterior layers and subdivided into 0-2 mm, >2-6 mm, >6-10 mm, and >10-12 mm annular regions with the corneal apex as the center of the circle.Pentacam automatically calculated the CD value of each corneal layer and region as well as the total CD value.The influencing factors of total CD value in diabetes group were analyzed by a multivariate linear regression analysis model.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of the Second Affiliated Hospital of Anhui Medical University (No.YX2023-129[F1]).Written informed consent was obtained from each subject before any medical examination.

The total CD value of diabetes group was 20.24±3.10, which was significantly higher than 18.79±3.31 of normal control group (t=-2.583, P=0.011).The CD values of the anterior layer, intermediate layer, 0-2 mm, and >2-6 mm regions were significantly higher in diabetes group than in normal control group (all at P<0.05).The CD values in the anterior layer were higher in non-DR and DR groups than in normal control group, and the CD values and total CD values in the middle and posterior layers were higher in non-DR group than in normal control group and DR group, and the differences were statistically significant (all at P<0.05).The CD values in the 0-2 mm and >2-6 mm regions were significantly higher in non-DR group than in normal control group, and the CD value in the >6-10 mm annular region was significantly higher in non-DR group than in DR group and normal control group (all at P<0.05).Multivariate linear regression analysis showed that age and glycosylated hemoglobin (HbA1c) level were the main influencing factors for the increase in CD values in diabetic patients (β=0.266, P<0.001; β=0.423, P=0.003).

The decrease of corneal transparency precedes the appearance of DR in patients with diabetes.Poor control of HbA1c level in diabetic patients may cause the decline of corneal transparency.

Diabetes mellitus; Diabetic retinopathy; Cornea; Densitometry; Pentacam