Profound Vision Loss With Minimal Retinal Findings: A Case of Microvascular Ischemia Unraveled by Multimodal Imaging

An 80-year-old woman presented with sudden, profound vision loss in her left eye. Initial fundus examination showed only mild disc hyperemia, a few retinal hemorrhages, and venous dilation, findings insufficient to explain the severity of visual loss on their own. Optical coherence tomography (OCT) revealed hyperreflective bands in the inner nuclear layer consistent with paracentral acute middle maculopathy (PAMM), while en face OCT angiography demonstrated a fern-like perivenular pattern. A relative afferent pupillary defect (RAPD) was also noted at the 48-hour follow-up. Given the clinical-imaging discrepancy, fluorescein angiography, performed at the 48-hour follow-up, showed delayed arterial and venous filling, macular capillary dropout, and late optic disc leakage. Fundus autofluorescence revealed marked hypoautofluorescence in ischemic regions. Despite initial apparent anatomical resolution, vision remained poor, and the RAPD persisted. On the last follow-up, retinal atrophy had developed. Systemic evaluation identified previously undiagnosed atrial fibrillation, implicating microembolic retinal ischemia as the likely etiology. No emboli were visualized, but imaging suggested occlusion of small-caliber retinal vessels. No visual recovery was observed at follow-ups. To our knowledge, reports linking fern-like PAMM to newly discovered atrial fibrillation with this degree of vision loss are uncommon. This case underscores that profound vision loss may result from microvascular ischemia in the absence of overt fundus signs. It highlights the importance of multimodal imaging and cardiovascular assessment in unexplained acute visual loss.