Abstract
Purpose :
To characterize intracellular and extracellular retinal edema in minimal to moderate diabetic retinopathy (DR) through OCT-Leakage.
Methods :
In this retrospective cross-sectional study, 142 eyes from 142 patients (28% women) aged 52-88 years were imaged by spectral domain optical coherence tomography (SD-OCT) and color fundus photography. Using the 7 field ETDRS protocol, the eyes were grouped into three DR severity groups, levels 10 to 20 minimal, 35 mild and 43 to 47 moderate DR. DRCR.net standards for Cirrus SD-OCT were used to identify eyes with subclinical (SCME) and clinical macular edema (central involved macular edema - CIME). Retinal layer thicknesses were calculated using an in-house segmentation algorithm to assess the contributions of each individual layer to the overall thickness value. OCT-Leakage, a new algorithm to detect sites of low optical reflectivity (LOR) was applied to the full retina and to each retinal layer. Extracellular fluid was measured by the LOR area ratio, which stands for the fraction of the number of A-scans with LOR and the total number of A-scans, within the considered area.
Results :
The 142 eyes were divided into three severity groups, with 54 eyes in group 10-20, 54 eyes in group 35 and 34 eyes in group 43-47. Macular edema, either SCME or CIME, was present in 43% of eyes in group 10-20, 41% of eyes in group 35 and 38% in group 43-47. CIME was found in 7%, 7% and 12%, respectively for each group.
In eyes with macular edema, either SCME or CIME, increases in retinal thickness were significantly correlated with increases in the LOR ratios (INL: r=0.45, p<0.001; OPL: r=0.48, p<0.001). The edema was identified as predominantly intracellular (retinal thickness increase without corresponding increase in LOR ratio) in group 10-20 (65%) and extracellular (retinal thickness increase with corresponding increase in LOR ratios) in groups 35 (77%) and 43-47 (69%) (p=0.010).
Conclusions :
Retinal edema can occur at any time since the initial stages of diabetic retinal disease, independently of its severity, as eyes from diabetic patients in the initial stages of DR with different ETDRS retinopathy grading show similar prevalence of SCME and CIME. The INL is the more susceptible layer to increase in the occurrence of retinal edema. Retinal edema appears to be mostly extracellular except in the initial stages of the diabetic retinal disease where intracellular edema is predominant.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.