Abstract
AimsTo establish the sequential changes by glycemic control in the mean thickness, volume and reflectance of the macular photoreceptor layers (MPRLs) and retinal pigment epithelium in patients with type 2 diabetes without diabetic retinopathy.MethodsThirty-one poorly controlled (HbA1c > 8.0%) patients with type 2 diabetes without diabetic retinopathy undergoing glycemic control and 39 control subjects with normal HbA1c levels (< 5.9%) underwent periodical full medical, neurological and ophthalmological examinations over 2 years. Glycemic variability was evaluated by standard deviation and coefficient of variation of monthly measured HbA1c levels and casual plasma glucose. 3D swept source-optical coherence tomography (OCT) and OCT-Explorer-generated enface thickness, volume and reflectance images for 9 subfields defined by Early Treatment Diabetic Retinopathy Study of 4 MPRLs {outer nuclear layer, ellipsoid zone, photoreceptor outer segment (PROS) and interdigitation zone} and retinal pigment epithelium were acquired every 3 months.ResultsGlycemic control sequentially restored the thickness and volume at 6, 4 and 5 subfields of outer nuclear layer, ellipsoid zone and PROS, respectively. The thickness and volume of outer nuclear layer were restored related to the decrease in HbA1c and casual plasma glucose levels, but not related to glycemic variability and neurological tests. The reflectance of MPRLs and retinal pigment epithelium in patients was marginally weaker than controls, and further decreased at 6 or 15 months during glycemic control. The reduction at 6 months coincided with high HbA1c levels.ConclusionGlycemic control sequentially restored the some MPRL thickness, especially of outer nuclear layer. In contrast, high glucose during glycemic control decreased reflectance and may lead to the development of diabetic retinopathy induced by glycemic control. The repeated OCT examinations can clarify the benefit and hazard of glycemic control to the diabetic retinopathy.
Highlights
Diabetic retinopathy, the leading cause of blindness in working-age individuals has been viewed traditionally as a microvascular complication in diabetes
Because the thickness of individual macular photoreceptor layer (MPRL), except for outer nuclear layer (ONL), and retinal pigment epithelium (RPE) is < 20 μm, and because optical coherence tomography (OCT) image quality depends on the instrument reliability and measurement variability [6], the excellent OCT repeatability is essential to measure the metrics of the individual layers of MPRLs and RPE
The current study aimed to investigate the impact of glycemic control and glycemic variability on the sequential changes in the metrics of individual MPRLs and RPE in type 2 diabetic patients without diabetic retinopathy using enface OCT
Summary
The leading cause of blindness in working-age individuals has been viewed traditionally as a microvascular complication in diabetes. The advent of the high-resolution spectral-domain and swept-source-optical coherence tomography (OCT) and image segmentation algorithms permit depth-resolved enface OCT imaging for viewing the retinal layers in the coronal plane, enabling to measure the metrics (spatial thickness, volume and reflectance) of individual macular photoreceptor layers (MPRLs) and retinal pigment epithelium (RPE) [1]. Studies on the impact of diabetes on the metrics of MPRLs and RPE using enface OCT had been cross-sectional [3] and inconsistent [4, 5]. Because the thickness of individual MPRLs, except for outer nuclear layer (ONL), and RPE is < 20 μm, and because OCT image quality depends on the instrument reliability and measurement variability [6], the excellent OCT repeatability is essential to measure the metrics of the individual layers of MPRLs and RPE. We measured the metrics of RPE, because RPE has the close functional and morphological relationship with MPRLs
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