Multiple Evanescent White Dot Syndrome (MEWDS) is a rare, temporary inflammatory condition that affects the outer layers of the retina. It is part of a group of eye conditions known as white dot syndromes. MEWDS is characterized by the sudden appearance of small white spots on the retina, which are often subtle and can be difficult to detect during a routine eye exam.
Recognizing Multiple Evanescent White Dot Syndrome
Individuals with MEWDS often experience a sudden, painless decline in vision or blurriness, usually affecting only one eye. Other common symptoms include blind spots (scotomas), flashing lights (photopsias), and sometimes an enlarged blind spot.
The condition predominantly affects young to middle-aged healthy women, with a ratio of affected females to males of approximately 5:1. While it most commonly presents in one eye, it can, in rare instances, affect both eyes.
A characteristic finding during an eye examination is an orange-yellow, granular appearance of the fovea. Small, grayish-white lesions, about 100-200 micrometers in size, may also be observed at the level of the retinal pigment epithelium and outer retina. These lesions are typically found in the posterior pole of the eye, outside the fovea.
Understanding the Origins of MEWDS
The cause of MEWDS is an idiopathic condition. However, it is believed to be an inflammatory chorioretinopathy, involving inflammation of both the choroid and the retina.
Around half of individuals affected by MEWDS report experiencing a flu-like illness or an upper respiratory infection shortly before the onset of their eye symptoms. These viral illnesses are considered potential triggers, though MEWDS can also occur without such a preceding event. Some reports have linked MEWDS to specific viral infections like Epstein-Barr virus and hepatitis A, as well as certain vaccinations.
The condition affects the outer retina and photoreceptors. Inflammation in these layers leads to visual disturbances. This impact on the photoreceptors can be observed through specialized imaging, showing structural disruptions.
Diagnosing and Managing MEWDS
MEWDS is diagnosed based on clinical findings and advanced imaging techniques. During an eye exam, the characteristic subtle white dots on the retina may be observed. These lesions are often small and can be challenging to see without specialized equipment.
Optical Coherence Tomography (OCT) is a common imaging test that reveals focal attenuation, or thinning, of the photoreceptor inner segment ellipsoid band. Fundus autofluorescence (FAF) can show hyperautofluorescent lesions, which are areas of increased light emission, around the posterior pole, even when the white dots are not clearly visible on direct examination. Fluorescein angiography (FA) may show early hyperfluorescence that extends into the later phases of the imaging.
MEWDS is a self-limited disease, resolving on its own without specific treatment. In most cases, the visual symptoms improve over several weeks to a few months. Corticosteroids are rarely considered, and only in severe or persistent cases, as the condition generally resolves spontaneously.
Outlook and Long Term Vision
The prognosis for individuals diagnosed with MEWDS is generally favorable, with most patients experiencing excellent visual recovery. Vision and visual fields typically return to their baseline within a few weeks to months after the onset of symptoms.
While rare, some patients may experience a persistent enlarged blind spot, photopsias, or dyschromatopsia (difficulty with color vision). Recurrence of MEWDS is uncommon, occurring in about 10% of patients, but it can happen. Despite these possibilities, MEWDS is largely considered a benign condition with a good long-term visual outcome for the majority of affected individuals.