Acute Zonal Occult Outer Retinopathy: A Guide
Understanding AZOOR
AZOOR is a rare disease that affects the outer retina, the layer of tissue at the back of the eye responsible for detecting light. Specifically, it targets the photoreceptors (the cells that convert light into signals sent to the brain) and the retinal pigment epithelium, or RPE (a supportive layer beneath the photoreceptors). When these cells are damaged, parts of the visual field can go dark or distorted.
The condition was first described in 1993. It belongs to a family of conditions sometimes referred to as 'white dot syndromes' because they involve inflammation in the outer retina and can share overlapping features. However, AZOOR stands out because the back of the eye often looks normal or nearly normal during a routine examination, even when significant vision loss is present.
In AZOOR, the primary damage appears to occur at the level of the photoreceptors. These cells, known as rods and cones, are essential for vision. Rods help with dim-light and peripheral vision, while cones are responsible for color and central detail. When photoreceptors die or stop working properly, the RPE and the choroid (a blood vessel layer beneath the retina) may undergo secondary changes over time.
This pattern is similar to what happens in other photoreceptor diseases such as retinitis pigmentosa. The RPE and choroidal changes are believed to follow the loss of photoreceptors rather than cause it. Electroretinography, or ERG (a test that measures the electrical activity of the retina), consistently shows reduced signals from these damaged cells. In fact, ERG abnormalities were recorded in 99% of patients tested in one large review (ScienceDirect, 2010).
The exact cause of AZOOR remains unknown. Researchers have proposed two leading theories. The first suggests that a viral infection may trigger the condition. One study involving 51 patients found that 20% had a viral-like illness shortly before their AZOOR symptoms began (ScienceDirect, 2010). The second theory points to an autoimmune process, in which the body's immune system mistakenly attacks the photoreceptor cells.
These two theories are not mutually exclusive. It is possible that a viral infection could set off an abnormal immune response directed at the retina. However, no single virus or autoimmune antibody has been consistently identified as the definitive cause. Research is ongoing to better understand the mechanism behind this condition.
Who Is Affected and Risk Factors
AZOOR primarily affects young to middle-aged adults. The average age at presentation is approximately 36.7 years, though cases have been reported in individuals ranging from 12 to 85 years of age (ScienceDirect, 2010). The condition shows a strong female predominance, with a male-to-female ratio of approximately 1 to 3.2 (ScienceDirect, 2010). This means women are about three times more likely to be diagnosed with AZOOR than men.
A notable percentage of AZOOR patients also have an autoimmune disease affecting other parts of the body. One systematic review of 427 patients found that 27% had an extraocular autoimmune disease at the time of their AZOOR presentation (Wikipedia, citing systematic review data). Conditions such as Hashimoto thyroiditis, multiple sclerosis, and other autoimmune disorders have been reported in AZOOR patients. This association supports the theory that immune system dysfunction plays a role in the development of the condition.
Some patients report a flu-like or viral illness in the weeks before AZOOR symptoms appear. In one study, 20% of patients had experienced such an illness prior to presentation (ScienceDirect, 2010). While this does not prove that a virus directly causes AZOOR, it suggests that infections could act as a trigger in susceptible individuals. People who develop unusual visual symptoms after a viral illness should mention this history to their eye care provider.
AZOOR has been reported most frequently in white individuals, though it can affect people of any racial or ethnic background. It may occur in one eye or both eyes. Myopia, or nearsightedness, has also been noted as a possible associated factor in some case reports, though this link is not firmly established.
Signs and Symptoms
The most common symptom of AZOOR is photopsia, the perception of flashing or shimmering lights. Patients often describe these as 'shining' or 'glittering' lights that appear in their field of vision. The photopsia typically begins suddenly and may be persistent. This symptom is reported by the vast majority of AZOOR patients and is often the reason they first seek medical attention.
Many people with AZOOR experience a blind spot or an area of missing vision. The most frequently observed pattern is enlargement of the physiologic blind spot, the small area in each eye where the optic nerve connects to the retina. This enlarged blind spot was found in 75% of visual fields examined in one large review (ScienceDirect, 2010). Some patients may also develop peripheral vision loss or other irregular patterns of visual field defects.
Despite the concerning symptoms, many AZOOR patients retain relatively good central visual acuity. In one study, visual acuity was 20/40 or better in 74% of tested eyes (ScienceDirect, 2010). This means that many patients can still read and perform tasks requiring detailed central vision, even though their peripheral or paracentral vision may be affected. However, the degree of vision loss varies widely from person to person.
One of the most challenging aspects of AZOOR is that the back of the eye often appears normal during a standard examination. Fundus examination was unremarkable in 76% of eyes in one review (ScienceDirect, 2010). Fluorescein angiography, a test that uses dye to image blood vessels in the retina, also typically appears normal or shows only minimal changes. This disconnect between symptoms and clinical appearance is a hallmark of AZOOR and can lead to delayed diagnosis.
Diagnosis and Testing
Electroretinography (ERG) is the most important diagnostic test for AZOOR. This test measures the electrical responses of the photoreceptors and other retinal cells when stimulated by light. In AZOOR, ERG shows decreased amplitudes, meaning the retina's electrical output is reduced. ERG abnormalities were found in 99% of patients tested in one major review (ScienceDirect, 2010). Both full-field ERG and multifocal ERG (which maps responses across different areas of the retina) may be used.
Formal visual field testing, also called perimetry, maps out the areas of vision that are functioning and the areas that are not. In AZOOR, this test commonly reveals an enlarged blind spot or other characteristic patterns of visual field loss. Visual field testing is essential for documenting the extent of damage and for monitoring whether the condition is stable, improving, or worsening over time.
Optical coherence tomography, or OCT, is an imaging technique that creates detailed cross-sectional pictures of the retina. In AZOOR, OCT may reveal disruption of the ellipsoid zone (also called the IS/OS junction), which represents the junction between the inner and outer segments of the photoreceptors. This finding confirms damage at the photoreceptor level. In early or mild cases, OCT may appear normal, but changes often become visible as the condition progresses.
Fundus autofluorescence (FAF) imaging detects natural fluorescence from a pigment called lipofuscin in the RPE. In AZOOR, FAF often shows a characteristic line of increased autofluorescence at the border between healthy and affected retina. This 'trizonal' pattern, with zones of decreased, increased, and normal autofluorescence, can help a retina specialist identify the extent of damage and distinguish AZOOR from other conditions.
Because AZOOR is rare and can mimic other diseases, a retina specialist will typically perform a thorough evaluation to rule out similar conditions. These may include multiple evanescent white dot syndrome (MEWDS), multifocal choroiditis, and other white dot syndromes. Blood tests may also be ordered to check for autoimmune markers or signs of infection. A careful clinical history, combined with ERG and imaging results, is usually needed to arrive at a confident diagnosis.
Treatment Options
No treatment has been proven to definitively improve the visual outcome of AZOOR. However, systemic corticosteroids (oral steroid medications such as prednisone) are the most commonly used therapy. Some reports have shown visual improvement in patients treated with systemic steroids, particularly when treatment is started early in the course of the disease. However, results vary, and the benefits must be weighed against the side effects of long-term steroid use, which can include weight gain, elevated blood sugar, and bone thinning.
Intravitreal steroids, meaning steroid medications injected directly into the eye, have shown promise in stabilizing or improving AZOOR in some patients. Ozurdex (dexamethasone intravitreal implant) is one such treatment that has been used. In one reported case, a patient who did not improve with systemic corticosteroids experienced remarkable visual improvement after intravitreal injection of Ozurdex, with recovery of the disrupted photoreceptor layer seen on OCT imaging. Intravitreal triamcinolone acetonide and Iluvien (fluocinolone acetonide implant) have also been used in small case series, with results suggesting disease stability in treated eyes.
For patients who do not respond to corticosteroids or who cannot tolerate long-term steroid use, other immunosuppressive medications may be considered. In at least one reported case, adalimumab (an anti-tumor necrosis factor alpha monoclonal antibody) led to obvious improvement in a patient who had not responded to traditional immunosuppressive treatments. Nonsteroidal anti-inflammatory drugs (NSAIDs) and antimicrobial medications have also been tried, though no therapy has been proven more effective than another.
In some cases, a retina specialist may recommend careful monitoring without active treatment. This approach, called watchful observation, may be appropriate when symptoms are mild, the condition appears stable, or the risks of treatment outweigh the potential benefits. AZOOR can sometimes stabilize on its own, and some patients experience partial spontaneous improvement. Regular follow-up visits with ERG testing, visual field testing, and OCT imaging are essential during observation to detect any changes promptly.
What to Expect
The course of AZOOR is unpredictable. Some patients experience a single episode that stabilizes, while others may have recurrent episodes or gradual progression. In many cases, visual acuity remains relatively preserved even though visual field defects persist. Because 74% of tested eyes maintained 20/40 or better vision in one study (ScienceDirect, 2010), many patients can continue to perform most daily activities. However, the blind spots and visual field loss can affect tasks such as driving, reading in dim light, and navigating unfamiliar environments.
Long-term follow-up is important for anyone diagnosed with AZOOR. A retina specialist will typically schedule regular visits to repeat ERG, visual field testing, and OCT imaging. These tests help determine whether the condition is stable, improving, or worsening. Changes in symptoms, such as new flashes of light or expanding blind spots, should be reported promptly. Because AZOOR can affect both eyes, the unaffected eye is also monitored at each visit.
Receiving a diagnosis of a rare eye condition can be stressful and isolating. Patients may feel anxious about the uncertainty of their prognosis. It is important to know that many people with AZOOR maintain functional vision and continue with their normal routines. Connecting with support groups for rare retinal diseases, working with low vision specialists if needed, and maintaining open communication with a retina specialist can all help manage the emotional and practical challenges of living with this condition.
Living With AZOOR
While there is no proven way to prevent AZOOR from progressing, general eye health practices are still important. Wearing sunglasses that block ultraviolet light, eating a diet rich in leafy greens and omega-3 fatty acids, and avoiding smoking are all steps that support overall retinal health. These measures do not treat AZOOR directly, but they help maintain the health of the remaining retinal cells.
If AZOOR has caused noticeable blind spots or peripheral vision loss, certain adaptations can make daily life easier. Using brighter task lighting for reading, positioning objects within the stronger areas of your visual field, and being extra cautious when crossing streets or changing lanes while driving are practical strategies. A low vision specialist can provide customized recommendations and assistive devices if the visual field loss is significant enough to affect daily functioning.
Research into AZOOR and related conditions continues. New imaging technologies and a better understanding of the immune system's role in retinal disease may lead to more targeted treatments in the future. Patients are encouraged to maintain regular visits with a retina specialist and to ask about any emerging therapies or clinical trials that might be relevant to their situation.
When to See a Retina Specialist
Certain symptoms require immediate evaluation. If you experience a sudden onset of flashing or shimmering lights, a new or expanding blind spot, a curtain or shadow over part of your vision, or sudden vision loss in one eye, see a retina specialist or go to the emergency room immediately. These symptoms can indicate AZOOR, retinal detachment, or other serious conditions that require prompt diagnosis and care.
If you have already been diagnosed with AZOOR, maintaining regular appointments with a retina specialist is essential. Even when the condition seems stable, periodic testing can detect subtle changes that might not be noticeable in daily life. Any new or worsening symptoms between scheduled visits should prompt an earlier appointment. Because AZOOR can be bilateral, both eyes should be evaluated at every visit, even if only one eye has been affected so far.
Questions and Answers
In most cases, no. A routine eye exam may not reveal any visible abnormalities because the back of the eye often looks normal in AZOOR patients. Specialized tests are needed to confirm the diagnosis. Electroretinography (ERG) is particularly important because it can detect reduced electrical activity in the retina even when imaging and examination appear unremarkable. Visual field testing, OCT, and fundus autofluorescence also play key roles in diagnosis.
AZOOR can be unilateral (affecting one eye) or bilateral (affecting both eyes). Some patients initially present with symptoms in one eye and later develop involvement in the second eye. Because of this possibility, a retina specialist will monitor both eyes during follow-up visits, even if only one eye is currently symptomatic. There is no reliable way to predict whether the second eye will become affected.
The course of AZOOR varies greatly among individuals. Some people experience a single episode that stabilizes, and their vision remains relatively unchanged afterward. Others may have recurrent episodes or slow progression. Many patients retain good central visual acuity even when visual field defects are present. Regular monitoring with a retina specialist is the best way to track any changes and adjust the treatment plan accordingly.
Because AZOOR is rare, large clinical trials are limited. However, researchers continue to study immunosuppressive therapies, intravitreal steroid implants, and biologic medications for inflammatory and autoimmune retinal conditions. A retina specialist can provide information about any current studies or emerging treatment options that may be appropriate for your specific situation. Staying in regular contact with a retina specialist is the best way to learn about new developments.
Given that approximately 27% of AZOOR patients have a coexisting autoimmune disease (systematic review data), many retina specialists will recommend blood tests to screen for common autoimmune conditions. Identifying an underlying autoimmune disorder can be important for your overall health and may also influence treatment decisions for your AZOOR. Discuss this option with your retina specialist, who may coordinate care with a rheumatologist or other appropriate specialist.