Ipsilateral Recurrence of Optic Disc Drusen–Associated Anterior Ischemic Optic Neuropathy in a 15-Year-Old Boy

A 12-year-old healthy boy was seen at the Department of Ophthalmology, Rigshospitalet, in February 2017, due to a history of sudden painless loss of visual field in his left eye. The best-corrected visual acuity was 20/20 in both eyes. Pupils were equal, round, and reactive to light without a relative afferent pupillary defect. Color vision (Ishihara plates) testing showed no dyschromatopsia. Visual fields showed minor superior and inferior defects in both eyes as well as a dense inferior nasal defect in the left eye (Fig. 1A, upper 2 panels). The anterior segment was unremarkable in both eyes. The left optic nerve head was edematous with a central hemorrhage and a hemorrhage at the upper pole, and the right optic nerve head was elevated without hemorrhage (Fig. 1B, upper 2 panels). Bilateral optic disc drusen (ODD) were identified using enhanced depth imaging optical coherence tomography (EDI-OCT) (1), which also identified peripapillary hyperreflective ovoid mass-like structures, which are an unspecific marker of axonal crowding in the optic nerve head (Fig. 1C, upper 2 panels). Peripapillary OCT showed bilateral retinal nerve fiber layer thickening at Day 0, most pronounced on the left side (Fig. 1D, upper 2 panels). B-scan ultrasound showed a highly echogenic focus in both optic nerve heads, consistent with ODD (Fig. 2A). After excluding tumors of the orbit and brain using computed tomography (Fig. 2B) and MRI (not shown), a diagnosis of bilateral ODD with left ODD–associated anterior ischemic optic neuropathy (ODD-AION) was made. At 1-month, 8-month, and 24-month follow-up visits, the boy had no complaints, and no significant changes in the clinical features were seen, apart from a progressive left segmental optic atrophy and corresponding peripapillary retinal nerve fiber layer thinning (Fig. 1, third panel from above) as well as a left mild afferent pupillary defect detectable at 8-month and 24-month follow-up visits.FIG. 1.: A. Automated 30° visual field testing of the right eye (RE) showed superior and inferior defects at Day 0 and onward. In the left eye (LE), a dense inferonasal scotoma was seen at Day 0 in addition to superior and inferior defects. The visual field of the LE was stable at 8 months, but a significant worsening was seen at 27 months. This remained stable at 28.5 months. B. Fundus photographs showing pseudopapilledema on the RE, disc edema with a central hemorrhage and a hemorrhage at the upper pole in the LE at Day 0, segmental disc atrophy in the LE at 8 months, segmental disc swelling and hyperemia in the LE at 27 months, and a near-complete disc atrophy in the LE at 28.5 months. C. Enhanced depth imaging optical coherence tomography (OCT) shows optic disc drusen (red arrows) and peripapillary hyperreflective ovoid mass-like structures (yellow arrows) in both eyes. D. Peripapillary OCT shows retinal nerve fiber layer (RNFL) thickening in the RE and the LE at Day 0. In the LE, the RNFL thickness is reduced at 8 months, whereas it is slightly increased at 27 months and significantly reduced at 28.5 months.FIG. 2.: A. Ultrasound B-scan showed an echogenic focus in the right (upper panel) and the left (lower panel) optic nerve head, consistent with optic disc drusen (red arrows). B. Computed tomography scan showed hyperdensities at the optic nerve heads, consistent with optic disc drusen (red arrows).At 27 months after debut, the boy was seen due to sudden blurred vision in his left eye and intermittent sensations of pressure/tightness behind the eyes, in particular the left eye. The best-corrected visual acuity was 20/20 in both eyes, and the intraocular pressures were normal. Visual fields showed a pronounced superior arcuate scotoma, an almost complete inferior, altitudinal scotoma, a segmental swelling and hyperemia of the left optic nerve head on ophthalmoscopy, and a peripapillary retinal nerve fiber layer thickness segmentally slightly increased corresponding to the disc edema (Fig. 1, fourth panel from above). A moderate left afferent pupillary defect was noted. The right eye remained stable. The findings were compatible with an ipsilateral recurrence of ODD-AION in the left eye. At follow-up after 28-and-a-half months, optic atrophy was now near-complete (Fig. 1B, lower panel). ODD are acellular, calcified deposits located in front of the lamina cribrosa in the optic nerve head of up to 2% of the population (2). On OCT, ODD are always located above the lamina cribrosa, have a signal-poor core, often have a hyperreflective margin, and sometimes are seen as conglomerates of smaller ODD with internal reflectivity within the signal-poor core (1). ODD can lead to elevation of the disc and blurring of the disc margin, causing concern for papilledema, especially in children in whom ODD usually are not yet visible on the optic disc surface (3). The prevalence of ODD is estimated at 0.2%–2% in adults and 0.37%–1% in children (4). ODD are usually asymptomatic and discovered incidentally during a routine ophthalmological examination. The central visual acuity is in general well preserved. However, ODD are often associated with slowly progressive visual field defects (5). Young children with ODD usually present with elevated optic discs because of buried ODD (Fig. 1B and C, upper panel), which are located deeply in the optic nerve head tissue (3). ODD normally become superficial and thereby are visible on ophthalmoscopy, later in childhood (6). Severe complications of ODD in children include hemorrhages, choroidal neovascular membrane, nonarteritic AION (NA-AION), and retinal vascular occlusions (7). NA-AION is characterized by a sudden loss of function due to an interruption in the blood flow to the anterior part of the optic nerve, the presence of optic disc edema initially, optic disc–related visual field defects, and no evidence of neurologic or any other systemic, ocular, or optic nerve disease (8). NA-AION occurring in an eye with ODD is called ODD-AION. ODD are most likely a risk factor for development of AION and not just a coincidental coexistence (9). Patients with ODD-AION are younger, and they seem to have a more favorable visual outcome than patients with NA-AION (10). EDI-OCT of the optic nerve head is suggested in all cases of AION in younger patients, especially children, to detect deeply buried ODD not visible on ophthalmoscopy and perhaps the cause of the ischemic event. Bilateral simultaneous or sequential AION has been described to occur more frequently in patients with ODD-AION than in those with NA-AION (10). An ipsilateral recurrence of NA-AION is rare and is seen in only 6.4% of all patients with AION (8,10). To the authors' knowledge, an ipsilateral recurrence of ODD-AION has not been previously described in the literature, making this case unique and demonstrating the importance of follow-up, even years after diagnosis. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: M. Al-Bakri, A.-C. Larsen, L. Malmqvist, and S. Hamann; b. Acquisition of data: M. Al-Bakri, A.-C. Larsen, L. Malmqvist, and S. Hamann; c. Analysis and interpretation of data: M. Al-Bakri, A.-C. Larsen, L. Malmqvist, and S. Hamann. Category 2: a. Drafting the manuscript: M. Al-Bakri, A.-C. Larsen, L. Malmqvist, and S. Hamann; b. Revising it for intellectual content: M. Al-Bakri, A.-C. Larsen, L. Malmqvist, and S. Hamann; Category 3: a. Final approval of the completed manuscript: S. Hamann.