Quantitative and Qualitative Characteristics of Retinal Vasculature Shadowing on Enface Swept Source Oct, in Healthy Subjects and Diabetic Macular Edema

Background: To evaluate the characteristics of retinal vascular shadowing, viewed through en face swept source optical coherence tomography (SS-OCT) imaging in normality and diabetic macular edema (DME). Design: Prospective case series conducted at Shaare Zedek Medical Center. Participants or Samples: 34 eyes of 17 healthy subjects and 30 eyes of 16 diabetic patients. Methods: Collected data included demographics, Snellen chart measured visual acuity, current HBA1C levels, previous laser treatments and swept source OCT measured central retinal subfield thickness. SS-OCT en face images were generated and flattened at three planes: ganglion cell layer (GCL), inner plexiform layer (IPL), retinal pigment epithelium (RPE). The largest vessel was identified at the RPE level, retrieved at the GCL and IPL layers and its diameter measured. The deepest plane in the choroid at which shadow of this vessel could be identified was then measured from the RPE. Main Outcome Measures: Diameter of the largest vessel, depth of the vascular signal. Results: DME mostly affected the vascular shadow at the IPL level. At this plane, the measured vessel of the largest vessel was significantly reduced in DME (93.3 ± 33.5 vs. 115.9 ± 2.54 microns; p<0.01). A trend was found between DME and reduction of depth of the vascular signal (retrieved at 120.0 ± 74.2 microns below the RPE in diabetic eyes vs. 148.7 ± 92.1 microns in eyes of healthy patients aged more than 55 years; p=0.07). Conclusions: DME impacts vascular shadowing, over and under the RPE.