Acute zonal occult outer retinopathy (AZOOR) is typified by acute loss of 1 or more zones of outer retinal function associated with photopsia, minimal funduscopic changes, and abnormal ERG findings; unilateral disease is more common at first, but 1 or both eyes may be affected. Patients are typically young, myopic women who present with acute unilateral visual disturbances not infrequently associated with a mild vitritis (50%), apparently normal results on funduscopic examination, and visual acuity in the 20/40 range. Electrophysiological studies may demonstrate a consistent pattern of dysfunction, not only at the photoreceptor–RPE complex but also at the inner retinal level. Essentially, this consists of a delayed 30-Hz–flicker ERG and a reduction in the EOG light rise, which when present with classic symptomatology may be helpful diagnostically, obviating extensive neurologic evaluation. Visual field defects include enlargement of the blind spot and paracentral inferior, superior, and temporal defects with no corresponding retinal defect. Results of mfERG show decreased response from the blind spots and other visual field defects with corresponding loss or irregularity of the inner/outer segment line on OCT, suggesting that photoreceptor outer segment dysfunction and/or degeneration are the primary lesions in AZOOR. During the early stages of the disease, FA findings may be entirely normal, showing only a prolonged retinal circulation time. However, with disease progression, diffuse areas of hyperfluorescence and hypofluorescence and window defects corresponding to zones of RPE derangement become common. FAF imaging may be particularly useful in observing patients with AZOOR as it reveals conspicuous areas of central hypoautofluorescence corresponding to RPE and choriocapillary atrophy; peripheral hyperautofluorescence is seen at the border of the expanding lesion due to the presence of lipofuscin-laden cells that presage RPE cell death (Fig 6-50).
With extended follow-up, the majority of patients develop bilateral disease, with recurrences in approximately one-third. Similarly, the funduscopic appearance varies with the stage of the disease, ranging from initial subtle RPE changes with depigmentation in areas of visual loss to vessel attenuation, late pigment migration, and focal perivenous sheathing. Visual field abnormalities typically stabilize in approximately three-quarters of patients and partially improve in about 25%. Visual acuity remains in the 20/40 range in 68% of patients; however, legal blindness has been reported in as many as 18% with long-term follow-up.
Cancer-associated retinopathy and retinitis pigmentosa should be considered in the differential diagnosis of AZOOR. It is unclear whether treatment with systemic corticosteroids or IMT alters the disease course or visual outcome.
The considerable similarities between AZOOR and other white dot syndromes—namely, MEWDS, MCP, OHS, PIC, acute macular neuroretinopathy, and acute idiopathic blind spot enlargement syndrome—have led some investigators to group these entities together in the so-called AZOOR complex of diseases. Although an infectious etiology has been postulated, systemic autoimmune disease has been observed in 28% of patients, supporting the notion that these diseases are of an inflammatory etiology and arise in patients with a common non–disease-specific genetic background, possibly triggered by some exogenous agent.
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