Functional and high-resolution retinal imaging monitoring photoreceptor damage in acute macular neuroretinopathy

HIGH-RESOLUTION IMAGING OF THE OUTER RETINA IN TYPE 2 ACUTE MACULAR NEURORETINOPATHY

PURPOSE

The purpose of this study was to investigate the outer retinal changes in a patient with type 2 acute macular neuroretinopathy (AMN).

METHODS

A 35-year-old White woman complaining of a unilateral blind spot was imaged using various retinal imaging modalities including clinical optical coherence tomography (OCT), OCT-angiography, fundus fluorescein angiography, and adaptive optics (AO).

RESULTS

Fundus examination revealed multiple paracentral reddish brown petaloid lesions in the symptomatic left eye, while the other eye was unremarkable. Clinical OCT showed areas of hyperreflectance at the outer plexiform layer/outer nuclear layer complex with a disrupted inner/outer segment junction, which are characteristic features of type 2 AMN. AO imaging further revealed either shortening or absence of cone outer segments within the AMN lesions attributing to the darker features observed in the en face images from fundus photography and scanning laser ophthalmoscopy.

CONCLUSION

The AO findings indicate that the petaloid lesions in type 2 AMN are caused by a combination of the shortening and absence of the outer segment in individual cone photoreceptors.

Structural Changes in Acute Macular Neuroretinopathy Revealed With Adaptive Optics Optical Coherence Tomography

This case report discusses using adaptive optics imaging in a patient with acute macular neuroretinopathy with retinal structural changes.

Case Report: Recurrent Acute Macular Neuroretinopathy-Monitoring Recovery with Multimodal Imaging

SIGNIFICANCE

Acute macular neuroretinopathy (AMN) is a rare, nonprogressive condition affecting the outer retina that can be diagnosed clinically using widely available multimodal imaging techniques. This case report presents an exceedingly rare same-eye recurrence of AMN and describes the characteristic imaging findings of this unique, not fully understood clinical entity.

PURPOSE

The following report provides a detailed account of recurrent AMN from 4 hours of symptom onset to 4 months with repeat multimodal imaging captured at different visits. This report also devotes some discussion to the current understanding of its pathophysiology, associations, management, and imaging characteristics.

CASE REPORT

A 32-year-old woman with unilateral recurrent AMN was monitored frequently with various multimodal imaging from 4 hours after onset of new scotoma to 4 months. The primary finding in the acute stage was a hyperreflective lesion of the outer nuclear and outer plexiform layers followed by disruption of underlying external limiting membrane, ellipsoid zone, and photoreceptors. This resolved into stable outer nuclear layer thinning and subtle disruption of the deeper layers after 1 week. Fundus photography revealed a red-brown petaloid lesion adjacent to the fovea, and optical coherence tomography angiography revealed subtle decreased perfusion of the choriocapillaris layer throughout follow-up.

CONCLUSIONS

Acute macular neuroretinopathy is a rare nonprogressive condition of the outer retina most often affecting otherwise healthy young female individuals and is most associated with recent flu-like illness and oral contraceptives. The underlying mechanism of AMN remains unknown, but modern imaging techniques have elucidated the disease locus to be choroidal and/or deep capillary plexus. It is important for eye care providers to recognize AMN as a clinical entity distinct from other retinal conditions that require different management.

[Acute macular neuroretinopathy: En face OCT description, case series]

Acute macular neuroretinopathy (AMN) is a rare disease characterized by involvement of the outer retinal layers of the macula. The diagnosis of AMN is based on multimodal imaging, combining infrared reflectance (IR) imaging and optical coherence tomography with B-scan analysis (OCT-B). The en face OCT is a tomographic image processing technique, integrating data from entire A-scans to create a frontal retinal image of the desired area. Structural en face OCT imaging appears to be effective in delineating AMN lesions, using segmentation between the outer plexiform line and the ellipsoid line. In the future, analysis of the various modalities of a single OCT acquisition may be sufficient to diagnose AMN.

DIRECTIONAL VARIABILITY OF FUNDUS REFLECTANCE IN ACUTE MACULAR NEURORETINOPATHY: EVIDENCE FOR A CONTRIBUTION OF THE STILES-CRAWFORD EFFECT

PURPOSE

To document directional reflectivity of fundus lesions in a case of acute macular neuroretinopathy.

METHODS

Case report. Clinical and imaging data from a patient with acute macular neuroretinopathy were reviewed. Imaging comprised infrared scanning laser ophthalmoscopy, optical coherence tomography and flood-illumination adaptive optics images acquired through different entry pupils in the cardinal directions (approximately 2° eccentricity).

RESULTS

The patient reported acute bilateral paracentral scotoma revealing dark, wedge-shaped macular plaques which by optical coherence tomography were associated with focal loss of the visibility of the cone outer segment tip and inner/outer segment lines. Comparing scanning laser ophthalmoscopy images taken at different entry points in the pupil showed that macular plaques varied from hyporeflectance to isoreflectance. Cone counts by flood-illumination adaptive optics within plaques and optical coherence tomography features of the cone outer segment tip showed also a strong directional variability, peaking at near-normal values. Within each modality, fusion images showed that directional variability covered most of macular plaques.

CONCLUSION

The characteristic fundus abnormalities of acute macular neuroretinopathy may show a strong directional variability. Our findings suggest that the Stiles-Crawford effect may be an important factor in signs and symptoms of acute macular neuroretinopathy.

Dysflective cones: Visual function and cone reflectivity in long-term follow-up of acute bilateral foveolitis

Purpose

Confocal adaptive optics scanning laser ophthalmoscope (AOSLO) images provide a sensitive measure of cone structure. However, the relationship between structural findings of diminished cone reflectivity and visual function is unclear. We used fundus-referenced testing to evaluate visual function in regions of apparent cone loss identified using confocal AOSLO images.

Methods

A patient diagnosed with acute bilateral foveolitis had spectral-domain optical coherence tomography (SD-OCT) (Spectralis HRA + OCT system [Heidelberg Engineering, Vista, CA, USA]) images indicating focal loss of the inner segment-outer segment junction band with an intact, but hyper-reflective, external limiting membrane. Five years after symptom onset, visual acuity had improved from 20/80 to 20/25, but the retinal appearance remained unchanged compared to 3 months after symptoms began. We performed structural assessments using SD-OCT, directional OCT (non-standard use of a prototype on loan from Carl Zeiss Meditec) and AOSLO (custom-built system). We also administered fundus-referenced functional tests in the region of apparent cone loss, including analysis of preferred retinal locus (PRL), AOSLO acuity, and microperimetry with tracking SLO (TSLO) (prototype system). To determine AOSLO-corrected visual acuity, the scanning laser was modulated with a tumbling E consistent with 20/30 visual acuity. Visual sensitivity was assessed in and around the lesion using TSLO microperimetry. Complete eye examination, including standard measures of best-corrected visual acuity, visual field tests, color fundus photos, and fundus auto-fluorescence were also performed.

Results

Despite a lack of visible cone profiles in the foveal lesion, fundus-referenced vision testing demonstrated visual function within the lesion consistent with cone function. The PRL was within the lesion of apparent cone loss at the fovea. AOSLO visual acuity tests were abnormal, but measurable: for trials in which the stimulus remained completely within the lesion, the subject got 48% correct, compared to 78% correct when the stimulus was outside the lesion. TSLO microperimetry revealed reduced, but detectible, sensitivity thresholds within the lesion.

Conclusions and importance

Fundus-referenced visual testing proved useful to identify functional cones despite apparent photoreceptor loss identified using AOSLO and SD-OCT. While AOSLO and SD-OCT appear to be sensitive for the detection of abnormal or absent photoreceptors, changes in photoreceptors that are identified with these imaging tools do not correlate completely with visual function in every patient. Fundus-referenced vision testing is a useful tool to indicate the presence of cones that may be amenable to recovery or response to experimental therapies despite not being visible on confocal AOSLO or SD-OCT images.

Quantification of retinal layer thickness changes in acute macular neuroretinopathy

Purpose

To quantitatively evaluate retinal layer thickness changes in acute macular neuroretinopathy (AMN).

Methods

AMN areas were identified using near-infrared reflectance (NIR) images. Intraretinal layer segmentation using Heidelberg software was performed. The inbuilt ETDRS -grid was moved onto the AMN lesion and the mean retinal layer thicknesses of the central grid were recorded and compared with the corresponding area of the fellow eye at initial presentation and during follow-up.

Results

Eleven patients were included (mean age 26±6 years). AMN lesions at baseline had a significantly thinner outer nuclear layer (ONL) (51±21 µm vs 73±17 µm, p=0.002). The other layers, including inner nuclear layer (37±8 µm vs 38±6 µm, p=0.9) and outer plexiform layer (OPL) (45±19 µm vs 33±16 µm, p=0.1) did not show significant differences between the study eyes and fellow eyes. Adjacent to NIR image lesions, areas of OPL thickening were identified (study eye: 50±14 µm vs fellow eye: 39±16 µm, p=0.005) with corresponding thinning of ONL (study eye: 52±16 µm vs fellow eye: 69±16 µm, p=0.002).

Conclusions

AMN presents with characteristic quantitative retinal changes and the extent of the lesion may be more extensive than initially presumed from NIR image lesions.