Optical Coherence Tomography Angiography in Type 1 Diabetes Mellitus. Report 4: Glycated Haemoglobin

Abstract

The purpose of this study was to evaluate specifically the relationship between glycated haemoglobin (HbA1c) levels and retinal optical coherence tomography (OCT) and OCT angiography (OCTA) parameters in type 1 Diabetes Mellitus (DM). A total of 478 type 1 DM patients and 115 controls were included in a prospective OCTA trial (ClinicalTrials.gov NCT03422965). Subgroup analysis was performed for controls, no diabetic retinopathy (DM-no DR) and DR patients (DM-DR), and HbA1c levels. OCT and OCTA measurements were compared with HbA1c levels (current and previous 5 years). DM-no DR patients with HbA1c levels >7.5% showed lower VD than DM-DR and controls (20.16 vs. 20.22 vs. 20.71, p < 0.05), and showed a significant correlation between HbA1c levels and FAZc (p = 0.04), after adjusting for age, gender, signal strength index, axial length, and DM disease duration. DM-DR patients with HbA1c > 7.5% presented greater CRT than DM-no DR and controls (270.8 vs. 260 vs. 251.1, p < 0.05) and showed a significant correlation between HbA1c and CRT (p = 0.03). In conclusion, greater levels of HbA1c are associated with OCTA changes in DM-no DR patients, and with structural OCT changes in DM-DR patients. The combination of OCTA and OCT measurements and HbA1c levels may be helpful to identify patients at risk of progression to greater stages of the diabetic microvascular disease.

Keywords: HbA1c; diabetic retinopathy; foveal avascular zone; glycated haemoglobin; macular thickness; oculomics; optical coherence tomography; optical coherence tomography angiography; perfusion density; vessel density.

Figure 1

Consolidated standard of reporting trials (CONSORT)-style flow diagram describing included and excluded patients and eyes in each individual OCTA analysis. (* 1 eye = ≥ 1 criteria for exclusion).

Figure 2

Glycated Haemoglobin (HbA1c) levels in study subgroups. Left: Actual HbA1c level at the retinal imaging timepoint (2017). Right: Mean HbA1c calculated from previous 5 years timepoints (2013 to 2017).

Figure 3

Optical coherence tomography angiography (OCTA) analysis by glycated haemoglobin (HbA1c) level subgroups in diabetes mellitus (DM) patients without and with diabetic retinopathy (DR). Left: OCTA parameter analysis in DM-no DR patients. Right: OCTA parameter analysis in DM-DR patients. (p = values are adjusted by age, sex, signal strength index, diabetes mellitus duration, and axial length).

Figure 4

Correlations between glycated haemoglobin (HbA1c) levels and structural optical coherence tomography (OCT) parameters in study subgroups. Left: Structural OCT parameters and actual HbA1c level at the retinal imaging timepoint (2017). Right: Structural OCT parameters and Mean HbA1c calculated from previous 5 years timepoints (2013 to 2017). (Numerical values represent the p-value of correlations, p-values are adjusted by age, sex, signal strength index, diabetes mellitus duration, and axial length).

Figure 5

Correlations between glycated haemoglobin (HbA1c) levels and optical coherence tomography angiography (OCTA) parameters in study subgroups. Left: OCTA parameters and actual HbA1c level at the retinal imaging timepoint (2017). Right: OCTA parameters and Mean HbA1c calculated from previous 5 years timepoints (2013 to 2017). (Numerical values represent the p-value of correlations, p-values are adjusted by age, sex, signal strength index, diabetes mellitus duration, and axial length).