Background  Age-related cataracts associated with type 2 diabetes are becoming increasingly prevalent in clinical settings, with significant postoperative anterior segment complications after phacoemulsification surgery, such as corneal edema and exacerbation of dry eye syndrome. The study of its pathophysiological changes is not comprehensive.

Objective To explore the effects of type 2 diabetes on the subepithelial nerve fiber layer, corneal stromal cells, and endothelial cell layer of the cornea in patients with age-related cataracts undergoing phacoemulsification surgery.

Methods The study was conducted from May to October in 2023 at the Ophthalmology Department in the First Medical Center of our hospital. The patients were divided into the diabetes group and the control group. In vivo confocal microscopy (IVCM) was used to capture images of the central cornea before the surgery, and at 1 week, 1 month, and 3 months after the surgery to assess the corneal layers. Then Image J plugin Neuron J was used to measure the length of corneal subcutaneous nerve fibers (CNFL), count the number of main and branch nerve fibers in confocal microscopy images, and obtain the density of nerve fibers (CNFD), nerve fiber branching density (CNBD), and anterior stromal cell density (AKD), posterior stromal cell density (PKD), and endothelial cell density (ECD). The differences in preoperative corneal indicators between two groups, in preoperative and postoperative indicators at 1 week, 1 month, and 3 months, and the changes between the different time points were compared.

Results There were 13 male patients and 14 female patients in the diabetes group (27 cases, 32 eyes), with an average age of 70.34±8.99 years; and 10 male patients and 20 female patients in the control group (32 cases, 36 eyes), with an average age of 69.86±7.84 years. No statistically significant differences were found in gender, age, and intraoperative ultrasound energy between the two groups. (P>0.05). The fasting blood glucose and HbA1c in the diabetes group were significantly higher than those in the control group (P<0.001). The preoperative CNFD in the diabetes group was significantly lower than that in the control group (P=0.01), and there was no statistical difference in the other two groups' corneal indicators before surgery (P>0.05); CNFD, CNBD, and CNFL in the two groups were significantly lower than those before operation, and at 1 week and 1 month after operation (multiple correction P<0.013), and CNFD in the diabetes group was significantly lower than that in the control group at 1 week and 1 month after operation (P<0.05), while there was no statistical difference in CNBD and CNFL between the two groups after operation (P>0.05). There was a significant interaction between two groups of LC at different groups and time points (P<0.05), LC in the two groups increased significantly at 1 week and 1 month after surgery compared with that before surgery (multiple correction P<0.013), and LC in the diabetes group were significantly higher than that in the control group at 1 week and 1 month after surgery (P<0.05). AKD, PKD and ECD in the two groups were significantly lower than those before surgery, and at 1 week, 1 month and 3 months after surgery (multiple correction P<0.013), and AKD in the diabetes group was significantly lower than that in the control group at 1 week and 1 month after surgery (P<0.05). There was no statistical difference between the two groups in PKD and ECD after surgery (P>0.05).

Conclusion Patients with type 2 diabetes experience more severe damage to the corneal nerve and cell layers after undergoing phacoemulsification surgery. The subepithelial nerve fibers recover well after 3 months of surgery, while the stromal and endothelial cell layers recover slowly. The anterior stromal cell layer is significantly affected by blood sugar. Diabetic patients must be aware of the potential occurrence of postoperative corneal complications. Extending the use of medications for assisting in corneal repair after surgery will be particularly necessary.