A 42-year-old diabetic patient with a unilateral decrease in visual acuity (VA) and a history of flashes and floaters was referred for suspected retinal detachment. Best-corrected visual acuity (BCVA) was 6/5 in the right eye and 6/36 in the left eye.
On examination, the patient had a left relative afferent pupillary defect (RAPD) and decreased colour vision. Dilated retinal examination showed no evidence of retinal detachment or diabetic retinopathy, and the optic disc appeared normal. The rest of the physical examination was unremarkable. A provisional diagnosis of atypical optic neuritis was made and further diagnostic tests ordered.
An optical coherence tomography (OCT) scan of the macula showed disruption of the ellipsoid zone.
A subsequent fluorescein angiogram (FA) showed early hyperfluorescence in multiple areas and late staining of the optic disc.
The patient was diagnosed with multiple evanescent white dot syndrome (MEWDS).
This condition belongs to a group of posterior uveitidies, known as the white dot syndromes.
MEWDS is a rare, inflammatory condition of the retina that is seen more commonly in younger females and tends to be unilateral. Patients may recall suffering from a viral illness (e.g. flu-like symptoms) prior to the onset of ocular symptoms, but this is not always the case.
As its name suggests, the characteristic finding with MEWDS is the presence of multiple small whitish/yellowish dots throughout the peripheral macula and around the optic nerve. Foveal granularity is another classic sign. Mild vitritis may be present, but the anterior chamber remains unaffected. Optic disc oedema and an RAPD are often observed.
OCT demonstrates disruption of the ellipsoid zone, while early hyperfluorescent lesions arranged in a wreath-like pattern are visible with FA.
MEWDS is self-limiting so no treatment is required. Baseline visual acuity typically returns within a few weeks or months. Recurrence is unusual. Scotomas, photopsia and dyschromatopsia may persist in rare cases. Lesions may be replaced by scar tissue.
Think of MEWDS in atypical optic neuritis
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