The Complementary Role of Optical Coherence Tomography and Fluorescein Angiography in Diagnosing and Monitoring Retinal Vascular Status in Susac Syndrome: Two Case Reports

Background and Clinical Significance: Susac syndrome is a rare autoimmune-mediated microangiopathy characterized by the triad of encephalopathy, branch retinal artery occlusion (BRAO), and sensorineural hearing loss. Due to its variable onset and protean manifestations, the syndrome is frequently misdiagnosed, potentially leading to delayed treatment and irreversible organ damage. Ocular involvement is common and often provides the first diagnostic clue. Multimodal imaging, particularly fluorescein angiography (FA) and optical coherence tomography (OCT) as well as optical coherence tomography angiography (OCT-A), enables the detection of both acute and chronic ischemic retinal changes. Their complementary application yields critical insights into disease activity, supports monitoring of relapses, and guides therapeutic strategies. Case Presentation: We describe two patients with Susac syndrome presenting with distinct ocular and neurological features. A 43-year-old male developed recurrent BRAOs in both eyes, documented by FA, OCT, and OCT-A, with preserved best-corrected visual acuity (BCVA) of 0.00 logMAR in both eyes (OU). OCT demonstrated progressive thinning of the retinal nerve fiber layer (RNFL) and inner retinal layers, consistent with sequelae of microinfarctions, while FA revealed focal arteriolar wall hyperfluorescence. Immunosuppressive therapy with corticosteroids and mycophenolate mofetil stabilized his condition. A 31-year-old female with a history of migraine and encephalopathy showed thinning of the RNFL and ganglion cell layer (GCL) with macular atrophy on OCT. FA demonstrated peripheral arteriolar wall hyperfluorescence and microaneurysms. Despite these structural alterations, visual acuity remained unaffected. Serial imaging initially demonstrated mild progression on OCT and OCT-A, followed by disease stabilization under systemic immunosuppressive therapy. Conclusions: These cases highlight the pivotal role of multimodal imaging in the early recognition and long-term monitoring of Susac syndrome. OCT provides a detailed assessment of retinal microinfarctions and chronic atrophy, while FA remains indispensable for detecting vascular leakage and disease activity. The complementary use of OCT, OCT-A, and FA enhances diagnostic accuracy, facilitates timely therapeutic interventions, and supports individualized management. Regular ophthalmological monitoring, including advanced imaging modalities, should be considered an essential component of care in Susac syndrome.