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Catarina A Neves, EVICR.net - ECR-RET-2010-02 Study Group; Retinal layer location of increased retinal thickness in eyes with subclinical and clinical macular edema in diabetes type 2. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4706.
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© ARVO (1962-2015); The Authors (2016-present)
To identify the layer location of increased retinal thickness (RT) in eyes with subclinical and clinical macular edema in diabetes type 2 using SD-OCT Cirrus (Carl Zeiss Meditec, Dublin, CA, USA) and semi-automated segmentation of retinal layers.
194 type 2 diabetic patients/eyes with mild nonproliferative diabetic retinopathy (NPDR) (ETDRS levels 20/35) enrolled in the ECR-RET-2010-02 study (ClinicalTrials.gov Identifier: NCT01145599) were examined with Cirrus SD-OCT at the baseline visit. Eyes were classified as presenting subclinical macular edema (62 eyes) or clinical macular edema (12 eyes) based on SD-OCT central subfield (central 1000µm; CSF) and DRCR.net standards (i.e., RT >260µm and ≤290µm in women and >275µm and ≤305µm in men, or RT ≥290µm in women and ≥305µm in men, respectively). Automated segmentation of the retinal layers on OCT was performed in these two groups using an in-house developed segmentation tool based on the IOWA reference algorithm followed by human grader verification and correction as needed. RT of 7 retinal layers was calculated (RNFL, GCL+IPL, INL, OPL, ONL, IS+OS and RPE) and compared between groups and with a control group of 86 healthy eyes.
From the 194 type 2 diabetic eyes with mild NPDR, 62 were classified as presenting subclinical macular edema and 12 as having clinical macular edema. When comparing the different retinal layers thickness with normal controls, the highest increases in RT were found in the INL (41.0% increase in subclinical macular edema and 90.5% in the clinical macular edema). Increases were also found in the neighbouring layers (GCL+IPL: 8.9% and 36.6%, OPL: 26.2% and 55.5%, for the subclinical and clinical macular edema groups, respectively). Less increase was found in the ONL (8% for both groups) and no changes were found in the IS+OS and RPE complex.
The increase in RT occurring in diabetic eyes with subclinical and clinical macular edema is predominantly located in the INL but extends to a lesser degree to the GCL+IPL and OPL indicating that it is probably due to extracellular fluid accumulation originating from the deep retinal vascular capillary net and not from any specific neuronal or glial cell swelling.
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