Abstract
Purpose: :
To describe the anatomical features of diabetic macular edema(DME) in spectral domain optical coherence tomography(SD-OCT) and its correlation with focal or diffuse leakage patterns in fluorescein angiography(FA).
Methods: :
60 eyes of 56 diabetic patients with clinically significant DME and acceptable FA and SD-OCT images were studied. The early/mid/late phase FA images were analyzed along with OCT thickness profile. The thickened retinal area was classified into typical focal leakage(leakage from microaneurysm(MA)), typical diffuse leakage(leakages from the capillary plexus), or combined/questionable leakage. Using the tracking system with combining of the confocal SLO and SD-OCT images, the leakage sources in FA were matched to the corresponding OCT images. Macular cystic changes were divided into macrocystoid and microcystic changes in FA. Correlations between FA patterns and corresponding OCT changes were analyzed.
Results: :
Typical focal macular edema(ME) shows fluid accumulation predominantly in the outer plexiform layer/outer nuclear layer(OPL/ONL). The leaking MAs come in contact with the synaptic portion of OPL(fluid conductivity barrier) or directly leak into the loose fiber portion of the OPL(Henle’s layer). Typical diffuse ME caused fluid collection predominantly in the inner nuclear layer(INL) and secondarily in the OPL/ONL. The deep capillary plexus is located between the two fluid barriers(inner plexiform layer(IPL) and synaptic portion of OPL), thus, diffuse leakages are frequently related with cystic changes in the INL being visible as late parafoveal microcystic patterns in FA. In the combined/questionable ME, partial sections consisting of cysts/swelling in the INL and much larger of prominent areas of cysts/swelling in the OPL are noticed. Central macrocysts are mainly located in OPL/ONL, but occasionally fuses with INL cysts towards the foveal center. Macrocysts show thinner dye pooling than parafoveal microcysts in late phase FA. In the fovea, the visibility of dye contrast was influenced by the extent of pigmentation anterior to the cyst.
Conclusions: :
Based on the concept of relative fluid conductivity barrier of the IPL and OPL, we could find a relationship between the anatomic location of the leaking source and where the fluid accumulates within the retinal layers in DME. Focal leakage from MAs resulted in fluid collection predominantly within the OPL/ONL. However, diffuse leakages resulted in fluid collection in both INL and OPL.
Keywords: diabetic retinopathy • imaging/image analysis: clinical • pathology: human