Association Between Corneal Changes and Retinal Oximetry in Diabetes Mellitus

Abstract

Purpose

Diabetes mellitus (DM) causes different corneal changes that are associated with the severity of diabetic retinopathy. To identify the pathophysiological reasons for this, corneal tomography and optical densitometry (COD) were combined with retinal oximetry.

Methods

Patients with DM and healthy subjects were included in this pilot study. Spatially resolved corneal thickness and COD were assessed using the Pentacam HR (Oculus). The pachymetry difference (PAC_Diff) was calculated as an indicator of an increase in the peripheral corneal thickness. Oxygen saturation (SO₂) of the retinal vessels was measured using the Retinal Vessel Analyzer (Imedos Systems UG). Subsequently, the associations between corneal and retinal parameters were analyzed.

Results

Data from 30 patients with DM were compared with those from 30 age-matched healthy subjects. In DM, arterial (P = 0.048) and venous (P < 0.001) SO₂ levels were increased, and arteriovenous SO₂ difference was decreased (P < 0.001). In patients, PAC_Diff was higher than that in healthy subjects (P < 0.05), indicating a stronger increase in peripheral corneal thickness. The COD was reduced in DM (P = 0.004). The PAC_Diff of concentric rings with a diameter of 4 mm (r = −0.404; P = 0.033) to 8 mm (r = −0.522; P = 0.004) was inversely correlated with the arteriovenous SO₂ difference. Furthermore, PAC_Diff 4 mm was negatively associated with arterial SO₂ (r = −0.389; P = 0.041), and the COD of the peripheral corneal areas correlated positive with arterial SO₂ (COD total 10–12 mm: r = 0.408; P = 0.025).

Conclusion

These associations might indicate a common pathogenesis of corneal and retinal changes in DM, which could be caused by reduced oxygen supply, mitochondrial dysfunction, oxidative stress, and cytokine effects.

Plain Language Summary

Retinal changes are particularly important for ophthalmologists in the management of diabetes mellitus. These are primarily consequences of diabetic vascular changes that can lead to a lack of oxygen. However, there is also evidence of significant changes in the cornea of patients with diabetes. In the present study, the associations between changes in corneal thickness profile, optical density of the cornea, and oxygen saturation of retinal vessels in diabetes mellitus were demonstrated for the first time. Therefore, this study could contribute to clarifying the possible causes of corneal changes in patients with diabetes.

Keywords:

• diabetes mellitus
• retinal oximetry
• corneal optical densitometry
• pachymetry
• retinal vessel analyzer
• pentacam HR

Data Sharing Statement

The dataset analyzed in this study is available from the corresponding author upon reasonable request.

Statement of Ethics

This study adhered to the tenets of the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of the University Hospital Carl Gustav Carus, Dresden, TU Dresden, Germany (EK 424102016 and EK 91032013). Before enrolment, all participants were informed of the study purpose, methods, and data analysis, and informed consent was obtained from all participants.

Disclosure

The authors declare no conflicts of interest in this work.