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Julie You Kwon, Amir H Kashani, Guangui Liu, Fang Zheng, Andrew R Miller, Zhongdi Chu, Ruikang K Wang, Giovanni Gregori, Philip J Rosenfeld; Suspended Scattering Particles in Motion (SSPiM): A Feature of OCT Angiography in Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2017;58(8):937.
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© ARVO (1962-2015); The Authors (2016-present)
The appearance of intraretinal fluid (IRF) associated with hard exudates on optical coherence tomography angiography (OCTA) was previously described in diabetic retinopathy (DR) and retinal venous occlusion. In this report, we further characterize the appearance of IRF in OCTA images of diabetic macular edema (DME). We suggest that the appearance of these areas is more common than previously reported and consistent with suspended scattering particles in motion (SSPiM).
Patients with DME were imaged with either a prototype swept source OCT angiography (SS-OCTA) or a commercial spectral domain OCT angiography (SD-OCTA) instruments (Carl Zeiss Meditec, Dublin, CA). All OCTA images consisted of at least one 3x3mm image centered on the fovea of the study eye. OCTA en face images were used to identify the presence or absence of areas with increased OCTA signal intensities not associated with any retinal vasculature as described by Matsunaga D et al. and Kashani AH et al., 2015. These areas of increased OCTA signal intensity generally appeared as oval or circular regions on non-segmented, total retinal flow slabs (Fig 1) that were correlated with cross-sectional OCT scan. Patient demographics of sex, age, central retinal thickness (CRT) and DR stage were recorded.
Twenty-eight patients (36 eyes) with DME were imaged between Jan and Nov 2016. Mean age was 53 yrs; 68% were male. Mean LogMAR VA was 0.21 and CRT was 303 um. DR ranged from mild nonproliferative (NPDR) (3), moderate (12), severe (5) to proliferative DR (16). SSPiM correlated with hyperreflective pockets of IRF with or without hard exudates on cross-sectional SD-OCT (Fig 2). SSPiM lesions had anatomic preference for the edge of foveal avascular zone (FAZ) and the deep retinal plexus. Presence of SSPiMs did not appear to correlate with visual acuity.
We further characterize the unique appearance and anatomic position of areas with IRF that appear to have a flow signature on OCTA; we have use the term SSPiM to describe these areas. These areas of hypereflective IRF tend to localize around the FAZ and within the deep retinal plexus. We hypothesize that SSPiM is a unique feature of OCTA and represents movement of particulate material within IRF. The long term significance of this finding is under study.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1: En Face OCTA of SSPiM
Figure 2: Corresponding B-scan
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