Acute zonal occult outer retinopathy presenting as optic neuritis

Abstract

Acute zonal occult outer retinopathy (AZOOR) is an outer retinal disorder characterized by the acute loss of visual functions. Herein, we report a case of AZOOR presenting features mimicking optic neuritis. A 17-year-old healthy male reported fogginess in the right eye for 2 weeks. His best-corrected visual acuity was 20/20 in both eyes. Results of a color vision test and pupillary reaction were unremarkable. Funduscopic examination revealed a subtle hyperemic disc surrounded by hyperpigmentation in the right eye. Visual field examination confirmed an enlarged blind spot in the affected eye. Fundus autofluorescence imaging revealed zonal hyperautofluorescence around the optic disc. Fluorescein angiography showed optic disc staining and a window defect in the retinal pigment epithelium. Optical coherence tomography demonstrated loss of the ellipsoid line at the corresponding hyperautofluorescent region. All these characteristics indicated a diagnosis of AZOOR. However, the prolonged P100 wave observed through visual-evoked potential examination, hyperintensity T2 signal at the retrobulbar optic nerve through magnetic resonance imaging, and mild hyperemic optic disc along with optic disc staining through fluorescein angiography resemble the characteristics of optic neuritis. Because the clinical features of AZOOR are similar to those of optic neuritis, ophthalmologists should be able to differentiate between these two diseases to achieve a timely and correct diagnosis.

Keywords: Autofluorescence; acute zonal occult outer retinopathy; optic neuritis; optical coherence tomography.

Figure 1

Funduscopic examination at presentation showed a mild change in peripapillary pigmentation and a hyperemic optic disc in the right eye, (a) fundus image of the left eye was unremarkable, (b) visual field examination revealed blind spot enlargement in the right eye, (c) normal visual field was recorded in the left eye, (d) fluorescein angiography showed a window defect in the retinal pigment epithelium at the corresponding area of hyperautofluoresence and optic disc staining at the mid-to-late phase, (e) fluorescein angiography in the left eye was unremarkable, (f)

Figure 2

(a) Fundus autofluorescent imaging revealed peripapillary hyperautofluoresence in the right eye at presentation. (b) Fundus autofluorescent image of the right eye at the 6-month follow-up revealed no changes in hyperautofluoresence compared with that at presentation. Normal fundus autofluorescence was observed in the left eye at presentation (c) and at the 6-month follow-up, (d) optical coherence tomography showed loss of the ellipsoid line in the right eye at presentation, (e) optical coherence tomography at the 6-month follow-up showed no further loss of the ellipsoid line in the right eye, (f) optical coherence tomography in the left eye was unremarkable at presentation (g) and at the 6-month follow-up (h)

Figure 3

Visual evoked potential examination showed a significant delayed P100 component in the right eye (a). Electrooculography showed a mildly decreased Arden ratio in the right eye (b)

Figure 4

Magnetic resonance imaging showed an increased T2 signal in the retrobulbar optic nerve (a). (b) No contrast enhancement was found at the T1 mode

Figure 5

Electroretinogram showed slight reduction in the amplitude of the photopic and scotopic waves in the right eye compared with the left eye