Purpose: To explore areas of poor retinal capillary blood flow seen on OCT angiography (OCTA) in sickle cell patients, using adaptive optics scanning light ophthalmoscopy (AOSLO) vascular imaging.

Methods: Ten sequential 3x3 mm parafoveal OCTA full layer scans were obtained per eye utilizing a commercial spectral domain OCT system (Avanti RTVue-XR; Optovue, Fremont, CA), and were used to identify regions of interest (ROIs) with intermittent or constant nonperfusion near the foveal avascular zone (FAZ). AOSLO vascular imaging was performed on these ROIs to characterize dynamic features of abnormal blood flow. AOSLO employed quad detection in the nonconfocal channels, allowing visualization of contrast at an arbitrary angle. 

Results: We studied 11 eyes of 11 patients (mean age 33, range 23-44; 8 females, 3 males; 6 right eyes, 5 left eyes). Nine patients had hemoglobin SS (HbSS) disease, 8 with nonproliferative sickle cell retinopathy (SCR) and 1 with proliferative SCR. One patient had HbSC disease with proliferative SCR. One patient had sickle cell trait with proliferative SCR. Ocular and systemic treatment histories varied. We found evidence of abnormal blood flow on OCTA and AOSLO in all patients imaged. AOSLO vascular imaging of ROIs identified by OCTA revealed peristaltic slowed forward flow and red blood cell (RBC) rouleaux formation, and intravascular sludging and stasis. AOSLO vascular imaging was able to image a single sickled cell flowing through a capillary segment. In areas of poor blood flow, the capillary wall on AOSLO often appeared dilated and congested with a lumpy-bumpy contour.

Conclusions: AOSLO vascular imaging revealed in vivo that areas of intermittent and constant nonperfusion imaged by OCTA were due to abnormal RBC flow. Combining OCTA with AOSLO vascular imaging provided a clearer picture of some of the vascular anomalies of sickle cell disease, and may be useful for characterizing response to emerging therapeutic approaches.

Dynamic Visualization of Abnormal Parafoveal Blood Flow in Sickle Cell Patients Using OCTA and AOSLO Vascular Imaging

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