MEWDS (multiple evanescent white dot syndrome): symptoms, diagnosis and recovery

The retina is the light-sensitive layer at the back of the eye. In MEWDS, small white or yellow-white spots appear at the level of the outer retina and the retinal pigment epithelium, which is the layer beneath the light-sensing cells. The condition was first described in 1984 as a one-sided disturbance of vision with white dots at the deep retina and a granular appearance of the fovea, the centre of the retina.

It belongs to a group of rare inflammatory eye conditions called white dot syndromes. The review describes it as an inflammatory condition linked to reduced blood flow in the choriocapillaris (the capillary layer beneath the retina), and notes that because the changes are transient it has been likened to a common cold of the retina. The word evanescent refers to the dots fading away, usually within weeks.

The review lists the specific symptoms as decreased or blurred vision, photopsia (flashes of light) and subjective scotomas, which are blind spots or patches of missing vision. The temporal (outer) part of the visual field is often affected. Symptoms usually affect one eye and may come on over a few days.

The severity varies. The review says the decrease in visual acuity and the visual field impairment can both be very variable, depending on the degree of choriocapillaris non-perfusion. The condition is not usually painful, which can make people delay seeking help.

New flashes of light, floaters, a shadow or curtain across the vision, sudden blurring or loss of vision in one eye should be assessed the same day. The NHS advice on the related condition uveitis is to ask for an urgent GP appointment or get help from NHS 111 for eye pain, sensitivity to light, changes in vision such as flashing or blurring, or very red eyes, and to go to A&E or call 999 if you cannot see.

In practice, high street optometrists, NHS urgent eye services and hospital eye casualty departments can examine the retina. Many symptoms that look like MEWDS turn out to be a retinal tear, optic nerve inflammation, other types of uveitis or migraine aura, and those need different treatment.

The cause is not known. The review describes the typical patient as a myopic woman aged 20 to 40 after a flu-like episode, and a case report lists a flu-like prodrome, a predisposition to young females, blurred disc margins and temporal scotomata among its associated clinical features. A viral trigger or an immune reaction has been suggested but not proven.

MEWDS is not infectious and does not result from anything a person did. It is not known to be inherited.

An ophthalmologist will examine the retina after dilating the pupil, test vision and the visual field, and look at the front of the eye for inflammation. The review says fundoscopic signs together with photopsia and scotomas are only diagnostic hints, and that the diagnosis is confirmed with imaging.

It highlights three findings seen with multimodal imaging: hypofluorescent areas on indocyanine green angiography, hyperautofluorescent areas on blue-light fundus autofluorescence, and loss or damage of the ellipsoid zone (the photoreceptor layer) on optical coherence tomography. A case report found that foveal granularity may be the most specific feature of MEWDS, with OCT able to localise the pathology to the outer retina. Because the white dots can fade within weeks, they may be absent if the eye is examined late.

The NHS notes for uveitis that GPs refer suspected eye inflammation to an ophthalmologist, who will usually see the person within 24 hours for that condition. For MEWDS the route is the same: a GP or optometrist refers to hospital eye services.

There is no proven treatment, and none is usually needed. The review says visual function is restored without treatment within 8 to 10 weeks and that the disease does not usually recur. A case report of MEWDS managed by observation describes a plan to observe the clinical course without ophthalmic intervention.

Follow-up appointments check that the retina and field of vision are returning to normal and that no other condition has been missed. The review describes incomplete visual recovery as an atypical feature, reports recovery to 0.0 logMAR or better in 80% of patients in one large series, and says recent large cohorts have shown both eyes involved in up to 10% of patients and recurrences in up to 14%. Anyone whose symptoms return should be seen again.

In practice, people are advised to avoid driving if their vision does not meet the legal standard, to take care with stairs and sport while a blind spot is present, and to return promptly if new symptoms appear.

Most people can reassure themselves that the vision returns, but the weeks of blurred vision and flashes can be unsettling. Reading, screen work and driving may be affected until the field recovers. Eye hospitals and charities such as the RNIB provide general information and support for sight problems, and your optometrist can help with temporary adjustments.

Because information on MEWDS in UK patient resources is limited, the sources below include international clinical literature. Treat any recommendation as general information and follow the advice of the eye team looking after you.