ObjectiveTo compare the clinical characteristics of primary multiple evanescent white dot syndrome (MEWDS) and secondary MEWDS. MethodsA retrospective case-control study. A total of 27 patients 29 eyes diagnosed with MEWDS at the Eye Center of the Second Hospital of Hebei Medical University from January 2022 to January 2024 were enrolled in this study. All affected eyes underwent best corrected visual acuity (BCVA), fundus color photography, fundus autofluorescence (FAF), ultra-widefield FAF, fluorescein fundus angiography (FFA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT) examinations. Among them, 9 eyes (all primary MEWDS) were examined separately by ultra-wide-angle swept-frequency source OCT angiography (WF SS-OCTA). BCVA was measured using a standard logarithmic visual acuity chart and was converted to the logarithmic minimum angle of resolution (logMAR) visual acuity during statistics. Distribution patterns of MEWDS lesions were categorized into optic disc, macular, and sectoral based on ultra-widefield FAF. Based on whether it was complicated by other chorioretinal diseases or whether other chorioretinal diseases appeared before the resolution of MEWDS lesions, the affected eyes were divided into a primary MEWDS group and a secondary MEWDS group, comprising 14 cases 16 eyes and 13 cases 13 eyes, respectively. Among the 13 eyes in the secondary MEWDS group, 8 were complicated by multifocal choroiditis, 3 by punctate inner choroidopathy, and 2 by idiopathic choroidal neovascularization. The clinical and multimodal imaging features were compared between the two groups. Comparison of two sets of count data was performed using Fisher's exact probability test. ResultsThe mean logMAR BCVA was 0.20±0.17 in the primary MEWDS group and 0.44±0.19 in the secondary MEWDS group. The primary group comprised 10 eyes with the optic disc pattern and 6 with the macular pattern, whereas the secondary group had 2 and 11 eyes, respectively. An intact retinal pigment epithelium (RPE)-Bruch's membrane (BM)-choroidal capillary plexus (CC) complex was observed in 16 eyes and 13 eyes of the primary and secondary groups, respectively. The choroidal thickness was 229.00 (110.75) μm and 250.00 (117.50) μm in the primary and secondary groups, respectively. Statistically significant differences were observed between the two groups in logMAR BCVA (t=-3.64), distribution patterns of MEWDS lesions, and the number of eyes with intact RPE-BM-CC complex (P＜0.05). In contrast, no statistically significant differences were found in choroidal thickness, multimodal imaging features, or inflammatory scores (P＞0.05). WF SS-OCTA was performed in 9 eyes, the superficial capillary plexus, deep capillary plexus, outer retina and choriocapillaris layer appeared normal. En-face OCT at the layer of the outer retina showed hyperreflective dots and spots disseminated at the optic disc and posterior pole, corresponding roughly to spots on color fundus photography, hyperfluorescence in the early phase of FFA, hypofluorescence in the late phase of ICGA, hyperautofluorescence on ultra-widefield FFA and disruption of outer retina in OCT. ConclusionsThe RPE-BM-CC complex in primary MEWDS was intact and predominantly manifested in the optic disc pattern. In secondary MEWDS, the RPE-BM-CC complex was mostly incomplete and predominantly manifested in the macular pattern.
