Focal Functional and Microstructural Changes of Photoreceptors in Eyes with Acute Zonal Occult Outer Retinopathy

Abstract

Purpose: Acute zonal occult outer retinopathy (AZOOR) is characterized by an acute zonal loss of outer retinal function with minimal ophthalmoscopic changes in one or both eyes. We present a patient with AZOOR whose ultrastructural and functional findings were followed for 8 months. Case: A 22-year-old woman developed an acute central scotoma in her right eye. Her best-corrected visual acuity (BCVA) was 0.5 OD and 1.2 OS. The ophthalmoscopic examinations, fluorescein angiography, and full-field electroretinograms (ERGs) were normal in both eyes. The amplitudes of the multifocal ERGs (mfERGs) were attenuated in the area corresponding to the scotoma. Spectral domain optical coherence tomography showed an absence of both the inner and outer segment (IS/OS) line of the photoreceptors and the cone outer segment tip (COST) line between the IS/OS line and the retinal pigment epithelium. These changes were seen in the area corresponding to the scotoma. One month later, the scotoma disappeared and the BCVA improved to 1.2 OD. The mfERGs increased to almost the same amplitude as the fellow eye. The IS/OS line became discernible but the COST line was still absent. The ophthalmological findings of the right macula remained normal during the 11-month follow-up period. Conclusions: Our findings indicate that the selective loss of the IS/OS and the COST lines is probably the morphological alterations corresponding with the reduced BCVA and the mfERGs in the areas of the visual field defects in the acute phase of AZOOR. But in the recovery phase, only the abnormality of the COST line is a subclinical sign for the disease. These findings should be important in understanding and evaluating the pathological mechanism in other outer retinal diseases.

Optical coherence tomography imaging in uveitis

“…The authors suggested that the cone photoreceptor OS dysfunction could be initially reflected by the indistinctiveness of the OS/RPE (COST) line and the absence of foveal bulge and that abnormalities in the IS/OS junction may follow these changes in the more advanced stages. So et al [133] also reported loss of the OS/RPE (COST) line in acute phase AZOOR. In the acute phase, selective loss of the IS/OS and the OS/RPE (COST) lines corresponded with reduced visual acuity and mfERG potentials in areas of visual field defects.…”

“…Loss of photoreceptor bodies (ONL) and outer segments with corresponding visual field defects as well as reduced visual acuity and mfERG potentials [127][128][129][130][131] Peripapillary IS/OS junction line defects in eyes with blind spot enlargement [130] Loss of the IS/OS junction line at the junctional areas between preserved and severely damaged retina [130] Thinning of inner nuclear layers [130] Indistinctiveness of OS/RPE (COST) line and absence of foveal bulge [132,133] Normal choroidal thickness [131] Recovery phase…”

Paraneoplastic and non-paraneoplastic retinopathy and optic neuropathy: Evaluation and management

“…Some experts feel that AZOOR is a unique entity that may be more precisely defined by multimodal imaging: 1) autofluorescence, demonstrating characteristic zonal degeneration of the outer retina and RPE, typically beginning around the nerve and progressing to the periphery, and 2) high-definition spectral domain OCT, showing zonal or annular loss of the photoreceptor layer and IS/OS complex. 81,143,184,199,263,267 5.2.…”

Changes in Optical Coherence Tomography Findings in Acute Zonal Occult Outer Retinopathy

“…Initially, minimal or no fundus changes occur, but enlarged blind spots, abnormalities on electroretinograms (ERGs) and permanent visual field loss often occur in this slowly progressing form of retinal pigment epithelium degeneration [1, 2]. Optical coherence tomography (OCT) images from eyes with AZOOR show a loss or irregularity of the photoreceptor inner segment/outer segment (IS/OS) line in areas corresponding to reduced multifocal ERG (mfERG) responses and visual field defects [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. Recently, the cone outer segment tip (COST) line has been recognized as a thin, highly reflective line located between the IS/OS junction and the retinal pigment epithelium [16].…”

“…Recently, the cone outer segment tip (COST) line has been recognized as a thin, highly reflective line located between the IS/OS junction and the retinal pigment epithelium [16]. To our knowledge, there are few reports in the literature describing the abnormalities of the COST line in AZOOR [8]. However, there are several detailed reports about AZOOR patients who showed subjective and objective improvements in visual function [4, 8, 9, 10, 11, 12, 13, 14, 15].…”