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CASE REPORT
Year : 2023 | Volume
: 37
| Issue : 1 | Page : 66-68
Blind spot enlargement: A differential diagnosis challenge
Aristotelis Karamaounas1, Anna M Sideri1, Anastasia Tsiogka2, Iordanis Georgiou2, Dimitrios Kourkoutas2, Petros Petrou1
1 Department of Ophthalmology, “G. Gennimatas” General Hospital of Athens, Athens, Greece
2 Department of Ophthalmology, 401 General Military Hospital of Athens, Athens, Greece
Correspondence Address:
Anastasia Tsiogka
Department of Ophthalmology, 401 General Military Hospital of Athens, 3 P. Kanellopoulou Street, Athens 11525
Greece
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/sjopt.sjopt_132_21
A 39-year-old woman, without any systemic or ocular history, presented with a paracentral scotoma in her right eye with normal visual acuity. Humphrey's visual fields showed a reversible enlargement of the right blind spot. The final diagnosis was acute idiopathic blind spot enlargement which was successfully treated with intravenous steroids. Although differential diagnosis of blind spot enlargement can be challenging, multimodal imaging with combination of visual field's assessment can help us make the right diagnosis.
Keywords: Acute idiopathic blind spot enlargement, multiple evanescent white dot syndrome, white dot syndrome
Optic disc consists mainly of ganglion cell axons without any blood vessels and photoreceptors. This physiological anatomic structure generates a visual scotoma known as a blind spot. A lot of rare diseases may cause enlargement of the blind spot.
Acute zonal occult outer retinopathy (AZOOR) was first described by Gass in his 1992 Donders Lecture to The Netherlands Ophthalmological Society.[1] In addition, it has been suggested that AZOOR may represent a spectrum of diseases, including multiple evanescent white dot syndrome (MEWDS), presumed ocular histoplasmosis, acute macular neuroretinopathy, multifocal choroiditis (MFC), punctate inner choroidopathy, acute annular outer retinopathy, AZOOR, and acute idiopathic blind spot enlargement (AIBSE).[1]
We herein present a case of a young woman with unilateral AIBSE in whom the recovery of the optical function in visual fields and the structural changes of the outer retina was documented using multimodal imaging over a period of 3 years.
Case ReportA 42-year-old woman was referred to our department, complaining of a relative paracentral scotoma in her right eye 10 days after experiencing temporal photopsia, without any visual acuity decrease. Her past medical and family history was unremarkable, and there was no history of a recent viral infection. Similarly, her past ocular history was without any findings, apart from a mild myopia (6D) in both eyes.
Snellen visual acuity was 10/10 in both eyes. Intraocular pressure of the right and left eyes was 12 mmHg and 14 mmHg, respectively. Anterior segment examination was unremarkable and dilated fundus examination revealed focal areas of grayish halo around the optic nerve head, without any optic disc swelling. The patient underwent a complete neuro-ophthalmic examination that was unremarkable. Humphrey's visual field (HVF) demonstrated an enlargement of the blind spot of the right eye with a mean deviation (MD) of − 4.58 dB, P <1%, and pattern standard deviation of 11.69, P < 0.5% [Figure 1]. Spectral-domain optical coherence tomography revealed loss of the ellipsoid zone and outer nuclear layer that extended from the peripapillary area to the parafoveal region. Increased peripapillary autofluorescence was seen in the right eye, and ultrasound examination was normal.
Figure 1: Humphrey's visual field examination of the right eye shows an enlargement of the blind spot enlargement with MD: −4.58 db. MD: Mean deviationFluorescent angiography revealed hypofluorescence in the early phases and hyperfluorescence in the late phases that correlated with the multiple punched-out lesions without optic disc staining [Figure 2]. Indocyanine green angiography demonstrated “choroidal silence” during all phases [Figure 3]. Multifocal electroretinogram (ERG) was normal. To exclude any autoimmune or infectious disease, an extensive laboratory and imaging workup was sent and all the examinations were normal.
Figure 2: In the upper left fundus, photograph reveals multiple white lesions around the optic disc. Fluorescein angiography shows early hypofluorescence and late hyperfluorescence that correlated with the multiple punched-out lesions without optic disc staining
Figure 3: ICG angiography demonstrated choroidal silence since the early phases according to the retina lesions. ICG: Indocyanine green angiographyA diagnosis of AIBSE was made based on symptoms, clinical examination, and imaging findings. It was decided not to treat the patient. After 3 months, HVF revealed a decrease of the blind spot with a MD: −1.12 dB. The blind spot remained stable over a period of 3 years, but fundoscopy revealed areas of focal retinal atrophy at the same spots where the previous white lesions existed [Figure 4].
Figure 4: Right: 3-year follow-up right eye fundus photograph shows atrophic areas where the previous white lesions existed. Autofluorescence reveals hypoautofluorescent spots around the optic disc while the OCT macula remains unremarkable. OCT: Optical coherence tomography Discussion Blind spot enlargement is a rare finding in the visual field examination.[2] The term was used to describe several different entities. Idiopathic intracranial hypertension is the most common cause of blind spot enlargement, with approximately one-quarter of patients presenting with visual field defects. These findings occur mainly due to blind spot enlargement causing the displacement of the peripapillary retina and refractive changes due to significant optic nerve head swelling. Other common causes of blind spot enlargement are inflammatory or infectious diseases such as syphilis,[3] West Nile virus,[4] or rubella vaccination.[5] In these cases, blind spot enlargement corresponds to retinal and choroidal areas that appear abnormal in the fundus examination.
Differential diagnosis of blind spot enlargement includes neurosurgical emergencies that should be promptly assessed, such as extremely high blood pressure, extradural and subdural hematoma, cerebral abscess, papilledema, and bitemporal hemianopsia from a chiasmal lesion. In addition, patients with optic disc drusen, tilted disc, and peripapillary atrophy may also present with blind spot enlargement.[6]
For decades, the classification of the AZOOR complex diseases as well as the pathogenesis and treatment remains controversial due to similarities of symptoms and overlap of their clinical findings. AIBSE was for the first time described by Fletcher et al. in 1988.[7] Ten years later, Paul et al. stated that AIBSE is similar to MEWDS, except from the characteristic white dots which are usually absent.[8] The patients are usually young myopic females and present with unilateral blind spot enlargement and chorioretinal lesions without visual defects. These features make it difficult to assign a specific diagnosis without the help of multimodal imaging and close monitoring of the natural history of the disease for years.
Yannuzzi in his 2013 Charles L. Schepens Lecture to the American Academy of Ophthalmology suggested that AIBSE could in fact be a clinical sign of three different rare entities: MEWDS, MFC, and AZOOR. He also proposed that the deferential diagnosis is challenging at first, but observation of the clinical progression would likely reveal the following: regression of the blind spot enlargement, which corresponds with the diagnosis of MEWDS; persistence of the blind spot enlargement with peripapillary atrophy, which would lead to MFC; or finally, persistence and/or progression of the blind spot enlargement, which is characteristic for AZOOR.
AIBSE is a disease of the outer retina, and therefore, it shares many similarities with MEWDS. Patients usually develop multifocal active retinal lesions around the optic disc that later take the form of atrophic or discolored lesions. The etiology of AIBSE and the related syndromes is unknown. Unlike MEWDS, recovery in visual fields in patients with AIBSE does not occur. Regarding the treatment of these diseases, the use of steroids remains a debate among uveitis specialists.[4] Finally, in most cases, symptoms of MEWDS and AIBSE are reversible without treatment after weeks or months.
In our case, multimodal imaging played a key role in the diagnosis of AIBSE, since patient symptoms and findings from clinical examination could point toward a specific diagnosis. This is common, especially in cases of blind spot enlargement due to inflammatory disease. In addition, multiple functional tests such as HVFs and multifocal ERGs were performed to assess the existence of visual defects. Observation is important in accurate patient counseling, and serial imaging could be used to provide prognostic information of the natural history of the disease.[9]
In conclusion, the classification of AIBSE and AZOOR complex diseases remains controversial. Our case provides evidence of functional recovery of vision in a patient diagnosed with AIBSE. Through multimodal imaging, we were able to diagnose this challenging case and monitor the anatomic and functional changing.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
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Conflicts of interest
There are no conflicts of interest.
References
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