Age-controlled correlation between blood HbA1c level and thicknesses of ten retinal layers on macular OCT volume scans

Abstract

Purpose : The blood HbA1c level is a commonly used index to diagnose diabetes and to measure the long-term glycemic control for diabetic patients. Here, we study the age-controlled relationship between HbA1c and ten retinal layers segmented from spectral domain optical coherence tomography (OCT) macular volume scans in a large population-based study in Leipzig, Germany.

Methods : From the population-based, age and sex stratified LIFE-Adult study, all eyes of participants with reliable Spectralis SD-OCT (Heidelberg Engineering, Heidelberg, Germany) macular volume scans (97 horizontal B-scans with 512 A-scans each; reliability criterion: B-scan quality ≥ 20 dB) and available blood HbA1c level were included. Thicknesses of the following ten retinal layers were extracted from the OCT machine (Figure 1A): retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), inner segment (IS), inner-outer segment junction (IS-OS), outer segment (OS) and retinal pigmented epithelium layer (RPE). For each of the 49,664 A-scans of each layer, a partial Pearson correlation with HbA1c removing all variance explained by age was calculated. P-values were adjusted for multiple comparisons by the false-discovery method.

Results : 17,599 eyes of 8,893 participants were included (see Figure 1B and 1C for demographics). The age-controlled correlation of each A-scan is visualized in Figure 2. GCL and IPL showed a negative correlation (red) in parafoveal and perifoveal areas and a positive correlation (blue) in more peripheral areas, while RNFL exhibited an extensive negative correlation. The outer layers did not exhibit a fovea-featured pattern, but were negatively correlated in ONL, IS and IS-OS. Excluding all 1561 eyes of 787 participants treated with antidiabetic medication at the time of the study did not change the correlation patterns.

Conclusions : Retinal layers thicknesses and blood HbA1c level exhibited specific correlation patterns which differ between inner and outer layers. Generally, thinner RNFL, GCL, IPL, ONL, IS and IS-OS are associated with higher HbA1c. Blood HbA1c level can be reflected in the retina in pre-clinical or early stage diabetes patients, as indicated by our findings in our large sample of subjects without diabetic medication.

This is a 2020 Imaging in the Eye Conference abstract.