Type 2 Diabetes and the Inner Layer of the Cornea: What a Review of 22 Studies Found

Type 2 diabetes can affect more than the retina. A systematic review and meta-analysis published in 2026 in Frontiers in Endocrinology looked at the cornea’s inner cell layer, the endothelium, across different stages of diabetic retinopathy and lengths of disease.

How the review was done

The authors followed PRISMA and MOOSE guidelines (PROSPERO CRD420261473313) and searched five databases from inception through July 15, 2026. They included cross-sectional studies that compared endothelial cell density (ECD), the coefficient of variation (CV, a measure of cell-size irregularity), and the percentage of hexagonal cells (HEX) in people with type 2 diabetes versus controls, or between diabetes subgroups. Twenty-two studies, covering 5,878 eyes, were included. Quality was graded with an AHRQ checklist.

What they found

• Compared with controls, people with type 2 diabetes had significantly lower endothelial cell density, higher cell-size variation, and a lower percentage of hexagonal cells.
• Eyes with diabetic retinopathy had lower density, higher variation, and fewer hexagonal cells than diabetic eyes without retinopathy.
• There were no significant differences between proliferative and non-proliferative retinopathy.
• Diabetes lasting 10 years or more was associated with lower cell density and a lower percentage of hexagonal cells.

The authors cautioned that several of these estimates were sensitive to individual studies or to possible publication bias, so the results should be interpreted carefully. They suggested that a preoperative look at the endothelium may be beneficial in people with diabetes, especially those with retinopathy or a long duration of disease. This review did not study any specific corneal implant or surgical technique, and it does not mean that every person with diabetes will have a problem with the cornea. If you have diabetes and are being evaluated for eye surgery, it is reasonable to ask whether the endothelium has been checked.

Source: Corneal endothelial changes in type 2 diabetes mellitus: a systematic review and meta-analysis with subgroup comparisons by diabetic retinopathy status and disease duration (Frontiers in Endocrinology (PubMed), 2026). This article is an educational summary written by Khanna Vision Institute and is not a substitute for medical advice.