Topographic Fundus Autofluorescence Patterns in MEWDS: Clues to Differentiate Primary Disease from Secondary MEWDS...

To characterize topographic fundus autofluorescence (FAF) patterns in Primary Multiple Evanescent White Dot Syndrome (MEWDS) and assess their value as diagnostic clues for differentiating Primary MEWDS from Secondary MEWDS and ocular syphilis.

In this retrospective observational single-centre study, patients diagnosed with MEWDS between July 2014 and April 2026 at a tertiary ocular immunology unit were reviewed. Demographic, clinical, and multimodal imaging data were collected. FAF was used for lesion distribution pattern classification. Secondary MEWDS cases from our cohort were analyzed together with previously reported cases identified through a targeted literature review.

Eighteen eyes of 17 patients were classified as Primary MEWDS. Four FAF distribution patterns were identified: diffuse, peripapillary, placoid-like, and peripheral sectorial. The diffuse pattern was the most frequent presentation. Localized patterns showed clinically relevant overlaps with Acute Idiopathic Blind Spot Enlargement/Acute Zonal Occult Outer Retinopathy-spectrum disease, Acute Syphilitic Posterior Placoid Chorioretinitis, and infectious Secondary MEWDS. Secondary MEWDS was identified in 17 eyes of 13 patients and occurred in association with infectious uveitis, non-infectious uveitis, and other retinal conditions. Syphilis-associated Secondary MEWDS cases consistently showed a peripheral sectorial distribution.

Distinct FAF distribution patterns may provide practical diagnostic clues in MEWDS presentations. Diffuse FAF involvement appears most typical of Primary MEWDS, whereas placoid-like and peripheral sectorial patterns should prompt exclusion of infectious etiologies, particularly ocular syphilis. Recognition of these patterns may help guide targeted systemic investigation and improve diagnostic confidence in atypical MEWDS presentations.