Sub-clinical thickening of the fovea in diabetes and its relationship to glycaemic control: a study using swept-source optical coherence tomography

Abstract

Background Accumulation of multiple pockets of fluid at the fovea, as a complication of poor blood glucose control in diabetes, causes impairment of central vision. A new ability to demonstrate a pre-clinical phase of this maculopathy could be valuable, enabling diabetic individuals to be alerted to the need to improve their glycaemic control. This study aimed to use swept-source optical coherence tomography (SS-OCT) to measure foveal thickness and macular volume in diabetic individuals without cystoid macular oedema, and in non-diabetic individuals, and relate these measures to participants’ glycaemic control. Methods Centre point thickness (CPT) and total macular volume (TMV) were measured using SS-OCT (DRI OCT Triton™, Topcon, Tokyo, Japan). Participants’ glycosylated haemoglobin (HbA1c) level was also assessed (A1cNow®+ System, PTS Diagnostics, Indianapolis, IN, USA). The diabetic (n = 27) and non-diabetic (n = 27) groups were matched for age (p = 0.100) and sex (p = 0.414), and HbA1c level differed between diabetic and non-diabetic groups (p < 0.0005). The diabetic group comprised type 1 (n = 7) and type 2 (n = 20) diabetic individuals who were matched for duration of diabetes (p = 0.617) and whose glycaemic control was similar (p = 0.814). Results Diabetic individuals had significantly higher CPT (t(37) = 3.859, p < 0.0005) than non-diabetic individuals. In the diabetic group, multiple linear regression analysis revealed a conspicuous relationship between CPT and HbA1c level (β = 0.501, t(21) = 3.139, p = 0.005): there was a 19-μm increase in CPT for each 1% increase in HbA1c level. This relationship was not present in the non-diabetic group (β = − 0.068, t(23) = − 0.373, p = 0.712). Conclusions SS-OCT is the only way to measure macular thickness in vivo. Diabetic individuals en bloc had higher CPT compared with non-diabetic individuals. Moreover, in the diabetic group, HbA1c level significantly predicted CPT. Our results suggest that, in diabetes, sub-clinical thickening may occur at the fovea before cystoid macular oedema becomes clinically evident. This could provide diabetic individuals with an early warning of disease progression and motivate them to improve control of their diabetes, with a view to avoiding the need of intra-vitreal injections with their attendant risks.

Measuring the foveal avascular zone in diabetes: A study using optical coherence tomography angiography

“…Test results were expressed as the percentage of total hemoglobin that was glycosylated in the sample. The method by which the A 1c Now®+ System assesses HbA 1c level has been described previously 21 , 22 .…”

The Retinal Nerve Fiber Layer Thickness Is Associated with Systemic Neurodegeneration in Long-Term Type 1 Diabetes

“…Recently, Zafar et al 48 showed that, per unit increase in percent HbA1c from 7076 participants with diabetes, the RNFL thickness in the inferior quadrant correspondingly decreased. Furthermore, subclinical thickening of the retina is positively associated with HbA1c levels, 51 indicating retinal edema/neurodegeneration in response to hyperglycemia. Thus, to minimize the confounding effect of hyperglycemia, we adjusted for HbA1c in our models.…”