Acute Idiopathic Blind Spot Enlargement (AIBSE) syndrome is a subclinical peripapillary retinopathy first reported by Fletcher et al. in 1988. The initial report described seven cases presenting with photopsia and steeply bordered scotomas centered on the blind spot, despite normal fundus examination.
AZOOR is an unexplained outer retinal disorder that predominantly occurs in young women with myopia, presenting with acute vision loss and visual field defects accompanied by photopsia in one or both eyes. AIBSE represents part of this spectrum.
Sex: More common in women (men can also be affected)
Race: Tends to be more common in Caucasians
Refraction: Higher incidence in patients with moderate to high myopia
The relationship between AIBSE and MEWDS has been debated, and it has been suggested that AIBSE may be a late-stage manifestation of MEWDS. However, its tendency to be confined to the peripapillary retina is considered a distinguishing feature from MEWDS and other PICCPs 1).
QHow is AIBSE different from MEWDS and AZOOR?
A
AIBSE is part of the AZOOR spectrum and is also considered to overlap with MEWDS. However, it tends to be confined to dysfunction of the peripapillary retina, does not present with white spots, and does not show progressive visual field or electroretinogram deterioration as seen in AZOOR, which are clues for differentiation. The diagnosis remains under debate 1)2).
Acute-onset scotoma: A scotoma with steep borders centered on the blind spot appears unilaterally.
Photopsia: The most common positive visual phenomenon. Patients report spiral movements within the scotoma, colored lights, or a sensation like a “flash afterimage.”
Color vision abnormality: Dyschromatopsia (qualitative color vision abnormality) may be observed.
Intraocular findings: In some cases, intraocular inflammation, nonspecific RPE changes, peripapillary subretinal gray-white changes, and peripapillary vascular changes are observed.
In a 39-year-old female case reported by Ishihara et al. (2023), the left eye showed 1+ vitreous cells, 0.5+ vitreous haze, mild optic disc edema, and perivascular sheathing. Fluorescein angiography revealed moderate diffuse vasculitis and disc leakage, which was the first report of AIBSE complicated by retinal vasculitis2).
Immunologic triggers: Viral illnesses (e.g., influenza) and vaccinations (e.g., MMR vaccine) have been suggested as possible triggers.
Preceding infection: In the case by Gunasagaran et al. (2022), a mild respiratory illness preceded the onset by 3 weeks 1). MEWDS is also known to be preceded by flu-like symptoms.
Risk factors are as follows.
Young women
White people
Moderate to high myopia
AZOOR is often associated with autoimmune diseases (such as Hashimoto’s disease and multiple sclerosis), and in the AZOOR spectrum including AIBSE, attention should be paid to these complications.
QCan AIBSE develop after a cold?
A
It has been suggested that viral diseases may act as an immunological trigger for AIBSE, and case reports have documented preceding respiratory illness before onset1). However, many cases occur without prior infection, and a causal relationship has not been established.
Diagnosis is made by combining multiple examination modalities. In cases with normal fundus but visual field abnormalities, differentiation from optic neuritis is particularly important.
Functional Tests
Automated perimetry (HVF): The cornerstone of diagnosis. It confirms enlargement of the blind spot (scotoma with steep borders).
Multifocal electroretinography (mfERG): Waveform reduction around the fovea corresponding to blind spot enlargement is useful for diagnosis. Reduction of mfERG consistent with the visual field defect location is a decisive diagnostic finding.
Full-field electroretinography (ff-ERG): Amplitude may be reduced. In the case reported by Ishihara et al. (2023), ff-ERG showed reduced a-wave amplitude in both eyes2).
Imaging Tests
OCT: In the acute phase, loss of regularity of the ellipsoid zone (EZ) and interdigitation zone (IZ), and temporary discontinuity of the external limiting membrane (ELM) are observed. In mild cases or during the recovery phase, only the IZ may be abnormal.
OCTA (Optical Coherence Tomography Angiography): Coarsening of the choriocapillaris has been reported, which is useful as a diagnostic aid1).
Optic neuritis: Most commonly misdiagnosed because it presents with normal fundus and visual field abnormalities. Negative MRI and different mERG findings from optic neuritis help in differentiation.
Infectious diseases and systemic vasculitis: Screening for syphilis, Lyme disease, tuberculosis, sarcoidosis (ACE, lysozyme), SLE, and ANCA-associated vasculitis is recommended as exclusion tests1)2).
QHow can we differentiate from optic neuritis?
A
In AIBSE, fundus findings are often normal, and MRI findings are also negative, making it difficult to differentiate from optic neuritis. If mERG shows a reduction in peripapillary amplitude corresponding to visual field abnormalities, it suggests outer retinal damage rather than optic neuritis, providing diagnostic evidence for AIBSE. When visual field abnormalities cannot be explained by fundus findings, it is important to consider the possibility of AZOOR in the differential diagnosis and perform further examination if necessary.
AIBSE syndrome is a self-limiting disease, and recovery takes several months. Visual field abnormalities may resolve spontaneously, but some cases have poor visual prognosis.
Corticosteroids may be used in severe cases, but it is unclear whether recovery is due to spontaneous remission or the effect of steroids.
Case by Gunasagaran et al. (2022): Started with oral prednisolone 60 mg/day but discontinued after 2 weeks due to side effects. Subsequently, vision recovered spontaneously (visual acuity 6/6 after 5 months) 1).
Case by Ishihara et al. (2023): Started with oral steroids 60 mg/day and improved, but relapsed after self-discontinuation. Subsequently improved again with 3 cycles of high-dose IV pulse steroid therapy 2).
After 4 weeks: Most positive visual symptoms and peripapillary scotomas disappear.
3–4 months later: Visual field markedly improves along with improvement in ELM/EZ continuity.
Blind spot enlargement usually does not return to normal, and peripapillary scarring may remain.
Some patients have residual photopsia or visual field defects. Rarely recurs.
Cases have also been reported where diffuse or regional chorioretinal atrophy occurs over the long term.
QAre steroids effective for AIBSE?
A
There is no established evidence, and it is difficult to distinguish from natural recovery. However, in cases of retinal vasculitis complications reported by Ishihara et al. (2023), responsiveness to steroids has been confirmed, and there is room for consideration in cases with severe inflammation 2). Generally, observation without treatment is common.
Regarding the pathophysiology of inflammatory choriocapillaritis including AIBSE, two hypotheses have been proposed.
Hypothesis 1: Primary Choriocapillaritis
Primary choriocapillaritis is the primary lesion, and photoreceptors are secondarily damaged.
OCTA findings (hypoperfusion and coarsening of the choriocapillaris) support this hypothesis. In acute posterior multifocal placoid pigment epitheliopathy and related diseases, marked hypoperfusion of the choriocapillaris has been confirmed in active lesions1).
Hypothesis 2: Primary photoreceptoritis
Primary photoreceptoritis causes atrophy of the photoreceptor outer segments.
In this hypothesis, changes in the choriocapillaris are considered secondary1).
Recovery phase: Changes confirmed on OCT disappear after 3–4 months, and visual acuity improves.
In the AZOOR spectrum, autoimmune diseases (such as Hashimoto’s disease and multiple sclerosis) are often reported, suggesting involvement of autoimmune mechanisms.
7. Latest Research and Future Prospects (Research Stage Reports)
Gunasagaran et al. (2022) first objectively described “coarsening” of the choriocapillaris in the affected eye of a 31-year-old woman with suspected AIBSE using en-face OCTA1). This finding, confirmed as asymmetry compared to the healthy eye, supports the hypothesis of choriocapillaris inflammation. Moll-Udina et al. (2020) from Spain also reported clear hypoperfusion foci in the choriocapillaris layer on OCTA.
During the COVID-19 pandemic, when access to electrophysiological testing was limited, OCTA was reported to be useful as a diagnostic alternative tool 1).
First report of AIBSE complicated by retinal vasculitis
Ishihara et al. (2023) reported the first case of AIBSE complicated by retinal vasculitis2). A 39-year-old woman developed new blind spot enlargement and photopsia in her left eye about one year after the initial onset in her right eye. The response to steroids (reduction of blind spot and improvement of vasculitis) and the relapse after discontinuation followed by improvement after restarting IV pulse steroid therapy were unusual for AIBSE. The authors emphasized the importance of regular monitoring.
QHow does OCTA help in diagnosing AIBSE?
A
OCTA can visualize enlargement and hypoperfusion of the choriocapillaris on en-face images. Even when electrophysiological tests such as multifocal electroretinography are difficult to perform, OCTA may assist in diagnosis as evidence of choriocapillaritis 1). However, it is not currently included in the diagnostic criteria.
Gunasagaran HL, Waldie A, Xiao W, Moore P. Coarsening of choriocapillaris on optical coherence tomography angiography as a sign of acute idiopathic blind spot enlargement. Am J Ophthalmol Case Rep. 2022;26:101558.
Ishihara R, Khan Y, Halim MS, Akhavanrezayat A, Onghanseng N, Levin MH, Nguyen QD. Acute idiopathic blind spot enlargement syndrome (AIBSES) with retinal vasculitis. Am J Ophthalmol Case Rep. 2023;29:101760.
Zimmermann JA, Eter N, Biermann J. Acute Idiopathic Blind Spot Enlargement Syndrome-New Perspectives in the OCT Era. J Clin Med. 2022;11(18). PMID: 36142923.
Copy the article text and paste it into your preferred AI assistant.
Article copied to clipboard
Open an AI assistant below and paste the copied text into the chat box.
