Understanding Diabetes’ Effects on the Cornea

Diabetes affects corneal endothelial cells in patients that are older, as well as those who have suffered with the disease for at least 10 years and have high glycated hemoglobin (A1C), a new study shows. The results, published in Scientific Reports, point to the need for patients with diabetes to undergo regular corneal endothelial examinations.

Patients with type 2 diabetes (T2D) exhibited significantly lower endothelial cell density (ECD), higher variation in endothelial cell size (CV), and greater central corneal thickness (CCT) compared with a control group. Differences were larger for those with longstanding diabetes and A1C greater than or equal to 7%.

The corneal endothelium is a single layer of cells that plays a major role in maintaining the optical transparency of the cornea. Chronic hyperglycemia from T2D can lead to micro- and macro-vascular disorders and can affect almost all ocular structures, including the cornea. It is unclear why diabetes damages the endothelium, but osmotic damage due to excessive sorbitol accumulation and oxidative damage due to glycation end-product accumulation are among the reasons proposed, the authors said.

For patients with T2D, monitoring corneal endothelial cells is critical, the researchers said. The number of cells can decrease with surgical trauma, including from cataract surgery. Preoperative cell dysfunction can lead to greater damage postoperatively. Loss of corneal endothelial cells postoperatively can cause corneal failure, highlighting the importance of considering cell transplantation. During Descemet membrane endothelial keratoplasty (partial-thickness cornea transplant), there is a high probability of failure when the donor has diabetes because endothelial cells are firmly attached to the posterior stroma.

For all ages, diabetes and control group findings were significantly different, the study showed. The ECD and percentage of hexagonal cells were significantly lower in the diabetes group than in the control group (P=.023 and P=.030, respectively) while the group with diabetes exhibited higher CV and thicker CCT.

The ECD, CV, hexagonality, and CCT of the group of patients with diabetes for at least 10 years were significantly different from the control group. Only CV and CCT were significantly different, however, for those with diabetes for less than 10 years.

ECD, CV, and CCT were significantly different from the control group for those in the high A1C group, while only CV and CCT were significantly different in groups with lower A1C.

For the group of patients aged 60 and older ECD, CV, and hexagonality of the diabetes and control groups were significantly different. For those 50 and older, only CCT showed a significant difference.

The authors sought to conduct a large-scale study as most previous ones included samples of less than 100 cases, leading to variability in results. Also, few focused on the impact on corneal endothelial cells by age group.

The current study included 511 patients with T2D (1022 eyes) and 900 controls (1799 eyes). Participants were analyzed using a noncontact specular microscope and a Pentacam Scheimpflug camera.

Reference

Kim YJ and Kim TG. The effects of type 2 diabetes mellitus on the corneal endothelium and central corneal thickness. Sci Rep. Published online April 15,2021. doi:10.1038/s41598-021-87896-3