Rising Incidences of MEWDS Amid COVID-19 Infections and Vaccinations

COVID-19 News: Understanding Multiple Evanescent White Dot Syndrome (MEWDS).
Multiple Evanescent White Dot Syndrome (MEWDS) is a rare type of eye condition i.e., posterior uveitis, characterized by the presence of numerous pale whitish dots in the posterior pole and midperiphery of the retina. These dots, as indicated by the syndrome's name, are transient and may not be present during a patient's consultation. MEWDS belongs to a group of inflammatory chorioretinopathies known as white dot syndromes, which are marked by multiple, discrete, white lesions located at the deeper levels of the retina or choroid. Although MEWDS is typically self-limited, some patients may experience persistent blind spot enlargement, and about 10% of cases may recur. Despite these challenges, the prognosis for patients with MEWDS is generally favorable.
 
Symptoms and Demographics
MEWDS primarily affects healthy middle-aged females between the ages of 15 and 50, with women being four times more likely to develop the condition than men. Approximately 30% of patients report a preceding viral infection. Symptoms include an acute, painless, unilateral change in vision, with patients noticing blurred vision, photopsias (flashes of light), dyschromatopsia (color vision defects), or a temporal or paracentral scotoma (blind spot). While MEWDS usually affects one eye, rare cases of bilateral involvement have been documented, often presenting asymmetrically.
 
Clinical Findings and Disease Course
During an eye examination, MEWDS manifests as flat, multifocal, grey-white lesions ranging from 100 to 200 microns, primarily located outside the fovea in the posterior pole. A distinctive feature of MEWDS is an orange-yellow fovea with granularity. Other possible findings include optic disc edema, mild vitritis (posterior vitreous cells), mild anterior chamber flare, a relative afferent pupillary defect, and an enlarged blind spot. Rarely, sheathing of retinal veins and superficial retinal hemorrhages may be observed.
 
Pathogenesis and Treatment
The exact cause of MEWDS remains unknown, although a viral prodrome is frequently reported. Imaging techniques such as Indocyanine Green Angiography (ICGA) and Spectral-Domain Optical Coherence Tomography (SD-OCT) suggest that the disease is linked to vaso-occlusive issues in the choriocapillaris, leading to transient ischemia in the outer retina and reversible damage to the photoreceptors' outer segments. Since MEWDS is self-limiting, almost all patients recover good visual acuity within three to nine weeks without treatment. Symptoms like photopsias and scotomata gradually resolve, and the lesions typically disappear, sometimes leaving behind mild pigment mottling or chorioretinal scarring.
 
Impact of COVID-19 on MEWDS Incidence
The COVID-19 pandemic has significantly influenced the incidence and course of various diseases, including MEWDS. A study that is covered in this COVID-19 News report, conducted in Korea by researchers from Onnuri Eye Hospital and Konyang University College of Medicine, compared the incidence of MEWDS before and during the pandemic. The pre-COVID-19 group included patients diagnosed from March 11, 2017, to March 10, 2020, while the post-COVID-19 group covered diagnoses from March 11, 2020, to March 10, 2023. The results showed a significant increase in MEWDS cases during the pandemic. Before the pandemic, 0.011% of hospital visits were due to MEWDS, compared to 0.030% during the pandemic, indicating a notable rise (p = 0.029, B = 2.756).
 
Demographic and Clinical Features
The study evaluated 8 and 20 patients for the pre-COVID-19 and post-COVID-19 groups, respectively, diagnosing 6 and 14 patients with MEWDS in each group. The mean ages were 36.5 years and 37.58 years in the pre- and post-COVID-19 groups, respectively, with no significant differences in visual acuity at presentation or follow-up. The time to improvement and complication rates were also similar between the groups. However, the post-COVID-19 group included a higher proportion of male patients and exhibited a wider age range, potentially indicating that COVID-19 and vaccination might influence the incidence and demographics of MEWDS.
 
MEWDS and COVID-19 Infections
Two patients in the post-COVID-19 group developed MEWDS following a COVID-19 infection. One case involved a 13-year-old boy who presented with blurred vision and was subsequently diagnosed with COVID-19. Another case involved a 36-year-old man who developed a scotoma after contracting COVID-19, despite having been vaccinated a year earlier. These cases align with previous reports suggesting that viral infections can trigger MEWDS.
 
MEWDS Following COVID-19 Vaccination
The oldest patient in the post-COVID-19 group, a 78-year-old man, developed MEWDS after receiving a COVID-19 booster vaccine. This case adds to the growing body of evidence linking MEWDS to vaccinations. Similar findings have been reported in other studies, suggesting that the immune response triggered by vaccines can sometimes lead to ocular inflammation.
 
Complications and Recurrences
Two patients in the post-COVID-19 group developed complications. One case involved a 40-year-old woman who developed macular neovascularization (MNV) nine months after MEWDS diagnosis, successfully treated with anti-vascular endothelial growth factor (VEGF) injections. Another case involved a 23-year-old woman who developed bilateral, sequential MEWDS accompanied by bacillary layer detachment (BALAD) and subretinal fluid. These complications, while rare, underscore the complex interplay of factors influencing MEWDS during the pandemic.
 
Conclusion
The COVID-19 pandemic has led to a significant increase in the incidence of MEWDS, likely due to increased viral transmission and vaccine use. The demographic and clinical features of MEWDS have also become more diverse. Although the exact mechanisms remain unclear, it is evident that COVID-19 and related vaccinations play a role in the pathogenesis and manifestation of MEWDS. Further research with larger sample sizes and multicenter studies is needed to fully understand these relationships and improve patient outcomes.
 
The study findings were published in the peer reviewed journal: Scientific Reports.
https://www.nature.com/articles/s41598-024-63255-w
 
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