Abstract
Purpose :
To evaluate changes in retinal nerve fiber layer (RNFL), ganglion cell/inner plexiform layer (GC/IPL) and choroidal thickness (CT) in type 1 diabetic patients using enhanced-depth imaging spectral-domain optical coherence tomography (EDI-OCT).
Methods :
Patients with type 1 diabetes mellitus and no macular edema were recruited for this cross-sectional study. Exclusion criteria included refractive error ≥5.00 diopters and/or other retinal diseases, as well as history of previous cardiovascular events or chronic kidney disease. All patients underwent a complete ophthalmologic examination, including automatic segmentation of the retinal layers using EDI-OCT (Cirrus 4000. Zeiss) and manual measurement of the CT using the software’s caliper tool, at three different points: subfoveal, 1000µm nasal and temporal from the subfoveal line.
Results :
514 eyes of 257 patients were included in the study. Mean age was 45±11 years, 54.1% were female, mean diabetes duration was 20.3±10.8 and mean HbA1c was 7.4±1.0. No signs of diabetic retinopathy (DR) were observed in 54.9% of the patients, and the rest were classified into mild DR (62.1%), moderate DR (12.5%), severe DR (13.4%) and proliferative DR (7.3%). Patients with DR were older (p=0.001) and had previous cataract surgery more frequently (p=0.001). Patients with proliferative DR showed thicker RNFL (Figure 1), but these differences were only statistically significant in the temporal subfield (p=0.020). GCL/IPL thickness significantly decreased with the worsening of the DR severity. Similarly, CT is inversely correlated to DR worsening, except for the proliferative stage when choroid is thicker than in patients without DR (Figure 2).
Conclusions :
Large controversy exists in the literature, and contradictory results have been published, regarding the role of the choroid in the pathophysiology of DR and macular edema. We report a decrease in CT with increasing severity of DR, but a significant increase in proliferative DR patients. This could be explained by the overexpression of VEGF in proliferative eyes with subsequent choroidal vasodilation and increased blood flow and thickness of this layer. Our study also shows a significant thinning of the GCL/IPL in eyes with more severe DR, suggesting a potential neurodegenerative damage of the retina even in early stages of DR.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.