Clinical Implications of Suspended Scattering Particles in Motion Observed by Optical Coherence Tomography Angiography

Abstract

The objective of this study was to investigate the relationship between suspended scattering particles in motion (SSPiM) in optical coherence tomography angiography (OCTA) and treatment response in diabetic macular edema (DME). We retrospectively reviewed the medical records of patients diagnosed with DME who had undergone intravitreal injection. The optical density ratio (ODR) of the intraretinal cyst and the numbers of hyperreflective foci from OCT images and SSPiM from OCTA images were compared, and their association with treatment response was analyzed. Forty-five eyes from 45 patients were included in this study. Twenty-four patients were treated with anti-vascular endothelial growth factor, and 21 patients were treated with a steroid. Binary logistic regression model showed that SSPiM in OCTA images was associated with hyperreflective foci numbers (P = 0.038) and mean ODR of the intraretinal cyst (P = 0.006). Linear regression model showed that SSPiM in the inner nuclear layer was related to treatment response (P = 0.006). SSPiM on OCTA images is related to the poor structural response to treatment in DME.

Figure 1

A patient with diabetic macular edema who underwent intravitreal triamcinolone injection. (A) Fundus photograph. (B) Optical coherence tomography (OCT) image. There is an intraretinal cyst with hyperreflective foci. (C) OCT image with optical coherence tomography angiography (OCTA) signal of the intraretinal cyst. (D) OCT image before treatment of an intraretinal cyst 0.07 mm² in size. (E) OCT image one month after intravitreal triamcinolone injection; the largest intraretinal cyst remains and is 0.09 mm² in size. Small intraretinal cysts without OCTA signal have disappeared. (F) OCTA image including inner nuclear layer (INL) with suspended scattering particles in motion (SSPiM) before treatment (arrow). (G) OCTA image including outer nuclear layer (ONL) before treatment without SSPiM. (H) OCTA image including INL after treatment with decreased SSPiM (arrow). (I) OCTA image including ONL after treatment without SSPiM.

Figure 2

A patient with diabetic macular edema who underwent intravitreal ranibizumab injection. (A) Fundus photograph. (B) Optical coherence tomography (OCT) image. There are several intraretinal cysts. (C) OCT image with optical coherence tomography angiography (OCTA) signal; the intraretinal cysts do not show OCTA signal. (D) OCT image before treatment; the largest intraretinal cyst size is 0.15 mm². (E) OCT image one month after intravitreal triamcinolone injection; the intraretinal cysts have disappeared. (F) OCTA image including inner nuclear layer (INL) without suspended scattering particles in motion (SSPiM) before treatment. (G) OCTA image including outer nuclear layer (ONL) without SSPiM before treatment. (H) OCTA image including INL after treatment without SSPiM. (I) OCTA image including ONL including ONL after treatment without SSPiM.

Figure 3

A patient with diabetic macular edema who underwent intravitreal triamcinolone injection. (A) Fundus photograph. (B) Optical coherence tomography (OCT) image. There are several intraretinal cysts. (C) OCT image with optical coherence tomography angiography (OCTA) signal. The largest intraretinal cyst (arrow) has OCTA signal, while other intraretinal cysts do not have OCTA signal (arrowhead). (D) OCT image before treatment; the largest intraretinal cyst is 0.04 mm² in size. (E) OCT image one month after intravitreal triamcinolone injection; the largest intraretinal cyst size is 0.02 mm², a reduction of 48.14%. (F) OCTA image including inner nuclear layer (INL) with suspended scattering particles in motion (SSPiM) before treatment (arrow). (G) OCTA image including outer nuclear layer (ONL) without SSPiM before treatment. (H) OCTA image including INL with decreased SSPiM after treatment (arrow). (I) OCTA image including ONL without SSPiM after treatment.