Acute, Idiopathic Blind Spot Enlargement Syndrome

Newcomb, Robert D. OD, MPH, FAAO

Case Report

An otherwise healthy 12-year-old boy was evaluated for an enlarged blind spot in his left eye. Neither optic nerve edema/neuritis nor a retrobulbar mass explained this finding. Consultation with a neuro-ophthalmologist over a period of 14 months resulted in a diagnosis of acute, idiopathic blind spot enlargement syndrome, a rare and poorly understood ocular condition. To the author’s knowledge, this is the youngest case ever reported.

College of Optometry, The Ohio State University, Columbus, Ohio

Received August 24, 1999; revision received December 30, 1999.

Article Outline

A 9-year-old white male patient (JS) was first examined in the Binocular Vision and Pediatrics (BVP) Clinic at The Ohio State University College of Optometry on July 25, 1994. He had been referred by an optometrist in private practice who suspected mild refractive amblyopia OS and recommended appropriate vision therapy at the College for this condition.

At the initial examination, his chief complaints were blurred distance vision, horizontal diplopia at near, and occasional headaches without glasses. His medical history was unremarkable, and he was taking no medications at the time of his examination. His refractive status was OD +0.50 sphere 20/20 and OS +2.00 sphere 20/20–2. Ductions and versions were smooth and full OU, and the cover test with correction in place showed orthophoria at far and 8 exophoria at near. His accommodative amplitudes were 17 D OD, OS, and OU with good facility (5 cycles in 30 seconds). He demonstrated good fusion (i.e., he saw four dots) at testing distances of 20 feet and 40 cm with the Worth Dot test. His external and slit lamp examinations were normal OU except for mild inferior superficial punctate keratitis OS. His pupils were equal, round, and reactive to light and accommodation; intraocular pressure was 16 mm Hg in each eye. The dilated fundus examination revealed a 0.25 cup/disc ratio with clear media and normal retinal periphery and posterior pole in each eye; his visual fields were full by confrontations in each eye. The diagnoses at that time were (1) simple anisometropic hyperopia and (2) mild refractive amblyopia OS. He was advised to get new glasses for full-time wear and to return for a progress check in 1 month.

Over the next 6 months, JS was seen six times in the BVP clinic for vision therapy related to his mild refractive amblyopia OS; however, his best corrected visual acuity OS never did improve beyond 20/20–1.

On June 6, 1995, at age 10, he returned for his annual eye examination. At that time, he reported no blur, diplopia, or headaches; his comprehensive eye examination on that day revealed no change in either his visual or ocular health status. He was advised to continue wearing his glasses and to return in 1 year for another comprehensive eye examination. The patient was next seen on April 28, 1998, when he was 12 years old. On this visit, he reported a dark area temporally OS, and his left visual field had been blurry for the preceding month. He reported no flashes or floaters or previous trauma. His medical history was still unremarkable. He was taking no medications, but did report having a hay fever allergy. His refractive status and corrected visual acuities were unchanged from the previous examination, as were his binocular vision and accommodative tests. His external, pupil, slit lamp, and dilated fundus examinations were also all unchanged from the previous visit. Tonometry was 13 mm Hg OD and 15 mm Hg OS. His confrontation visual field was full OD but showed a suspected temporal loss OS; although the Humphrey 76 point screening test showed 75/76 points seen OD, it revealed only 71/76 points seen OS. Based upon his recent symptoms and a suspected temporal visual field loss OS, he was referred to the OSU College of Optometry Diagnosis and Management of Ocular Disease (DMOD) clinic on the following day.

On April 29, 1998, he reported no change in his visual symptoms. His best corrected visual acuities were 20/20 OD and 20/25 OS, and he had a 1+ afferent pupillary defect and a positive red cap desaturation test in his left eye (OD = 100; OS = 75). His Humphrey 24–2 threshold visual field test was normal OD, but showed an inferiorly enlarged blind spot OS (Fig. 1). With suspected diagnoses of either early retrobulbar neuritis or a mass OS, JS was referred to a neuro-ophthalmologist.

Nine days later, on May 8, the patient was examined by a neuro-ophthalmologist, who wrote “perimetry shows relative enlargement of the left blind spot, but there is no abnormality of peripapillary retina or of the discs themselves” (Fig. 2). He did not order a fluorescein angiography study, but he did order a magnetic resonance imaging (MRI) scan of the orbits. When the results of the MRI scan proved to be normal, he advised no treatment except for monitoring the condition in 1 month.

At his next neuro-ophthalmology appointment on June 12, his corrected visual acuities were stable but his enlarged blind spot OS was worse and now extended more superiorly (Fig. 3). Color vision measured 10/11 OD and 8/11 OS with the AO HRR plates, and a small, left, relative afferent pupillary defect was present. Tonometry, slit lamp, and ophthalmoscopy findings were normal, as before. At this point, the neuro-ophthalmologist suggested the most likely diagnosis would be acute, idiopathic blind spot enlargement syndrome (AIBES), and again advised no treatment other than monitoring in 2 months.

On August 21, 1998, our patient was seen for the third time by the neuro-ophthalmologist who recorded improved OS color vision and a smaller OS visual field loss that was more confined to the inferior temporal quadrant (Fig. 4). The suspected diagnosis of AIBES was re-established, and the patient was advised to return in 3 months for monitoring.

The patient was examined by his neuro-ophthalmologist three more times over the next 10 months (on October 23, 1998, January 28, 1999, and June 24, 1999). During this period of time, his color vision and relative afferent pupillary defect returned to normal, and his enlarged blind spot significantly improved but did not totally return to normal size (Figs. 5, 6, and 7). After his last visit on June 24, 1999, his visual ordeal of 15 months had finally resolved, and he was dismissed from the care of his neuro-ophthalmologist and advised to have routine annual eye examinations by his primary care optometrist.

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Table 1 lists several eye diseases in which idiopathic enlargement of one or both blind spots has been reported. 1, 2 Most of these conditions have other ocular signs and visual symptoms that aid the optometrist in making at least a tentative diagnosis of the disease process. This patient, however, had no other findings associated with an enlarged blind spot in his left eye.

In 1977, Miller first described a very interesting neuro-ophthalmological condition in which young and otherwise healthy adults presented with unilateral optic disc edema and a corresponding enlarged blind spot but no other ocular abnormality. In his report of eight patients between the ages of 25 and 35, all had normal visual acuity, color vision, and pupillary responses, and all recovered fully without any medical intervention over a period of 4–8 mo. He termed the condition “the big blind spot syndrome.”3

In 1988, Fletcher et al. reported on a series of seven patients, ages 25 to 39, who had unilateral blind spot enlargements without optic disc edema and with normal visual acuity (except for one patient with amblyopia) and normal color vision; most (5 of 7) had normal pupillary responses. All of the patients who were available for follow-up evaluations showed spontaneous regression of the enlarged blind spot within 3 months. These investigators termed the condition “acute, idiopathic blind spot enlargement” (AIBSE) syndrome. 4

Seven months after that article was published, Hamed et al. proposed that patients with AIBSE represented a subset of those with multiple evanescent white-dot syndrome (MEWDS), 5 a mysterious retinal disorder that had been described just 4 years earlier by Jampol et al. 6 In 1989, Hamed et al. published an article that described 2 female patients, one 18 years old and the other 15 years old, who had enlarged blind spots even after their documented MEWDS had resolved. 7 MEWDS has been reported to be a variant of posterior uveitis that involves the retinal pigment epithelium and eventually the overlying photoreceptors. Although the exact cause of MEWDS is unknown, some experts have hypothesized that it may be a result of secondary a subclinical viral infection, because some patients have reported that flu-like symptoms preceded their visual symptoms. 8

In 1991, Khorram et al. reported three cases of blind spot enlargement as a manifestation of multifocal choroiditis. All of their patients had reduced visual acuity as a presenting symptom, and all regained normal acuity and regression of the transient blind spot enlargement after being treated with oral corticosteroids. 9 Also in 1991, Singh wrote in Ophthalmology :

Rather than considering acute idiopathic blind spot enlargement to be a subset of multiple evanescent white dot syndrome, we propose that multiple evanescent white dot syndrome is one of several conditions characterized by blind spot enlargement. We have found that various diseases affecting the peripapillary retina, including some that are not classifiable, can cause blind spot enlargement without visible optic nerve or retinal involvement. 10

In 1993, Gass proposed a new term, acute zonal occult outer retinopathy (AZOOR), which he suggested could be used to describe a new group of retinopathies of unknown cause. 11 The common pathological finding was asymmetric and patchy photoreceptor dysfunction as measured with full-field electroretinograms. All patients who were studied had the following clinical characteristics: (1) rapid visual field loss, (2) photopsia, and (3) no (or minimal) visible ophthalmoscopic signs.

He suggested that clinical entities such as MEWDS, AIBES, acute macular neuroretinopathy, and multifocal choroiditis, or pseudo-presumed ocular histoplasmosis syndrome, may all have a common cause but may be diagnosed clinically at various stages in the natural course of the disease processes. Support for this hypothesis can be found in other cases of AIBSE reported in the literature by Callanan and Gass, 12 Rehman and Woon, 13 and Pece et al. 14 Interestingly, Pece et al. performed both fluorescein angiography and indocyanine green angiography on their patient and concluded that the hypofluorescent spots scattered throughout the posterior pole seen with indocyanine green angiography were evidence of inflammation in the entire choroid and not just the optic nerve head.

Not all patients with AIBSE experience a complete recovery of vision. In 1992, Cooper and Lesser reported a 39-year-old woman with bilateral AIBSE in whom visual symptoms and enlarged blind spots persisted for more than 6 years. 15 In 1995, Jacobson et al. suggested that

the spectrum of disease manifestations of AZOOR includes some retinopathies that have not only an acute but also a chronic phase. We speculate that this chronic phase of the disease represents the natural history of damaged photoreceptors after their recovery or lack thereof from one or more acute phases.16

Table 2 lists several eye diseases reportedly associated with the mysterious eye disease known as AZOOR. 11

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Whenever a patient presents with an enlarged blind spot—either unilaterally or bilaterally—the optometrist must hope for the best but plan for the worst. Most patients with enlarged blind spots will have associated subjective and/or objective clinical data that will help the optometrist make at least a tentative diagnosis. However, when all other subjective and objective clinical data are negative [as in this case], a tentative diagnosis of AZOOR—which includes AIBES—must be considered.

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I gratefully acknowledge the expertise and cooperation of Avrom D. Epstein, MD, in the care of our mutual patient.

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16. Jacobson SG, Morales DS, Sun XK, Feuer WJ, Cideciyan AV, Gass JD, Milam AH. Pattern of retinal dysfunction in acute zonal occult outer retinopathy. Ophthalmology 1995; 102:1187–98.

acute; idiopathic blind spot enlargement syndrome (AIBES); acute zonal occult outer retinopathy (AZOOR); neuro-optometry; visual field testing

© 2000 American Academy of Optometry