Acute Macular Neuroretinopathy: New Insights into Pathogenesis and Association with Retinal Capillary Ischemia

Abstract

 

Purpose

 

To report novel multimodal imaging findings in acute macular neuroretinopathy (AMN) which implicate an underlying ischemic pathogenesis. A simple classification system is proposed to reflect the location of SD-OCT lesions in AMN that affect the outer plexiform layer (OPL)/inner nuclear layer (INL) junction of the inner macula (Type 1) versus the OPL/outer nuclear layer (ONL) region of the outer macula (Type 2).

 

Methods

 

Retrospective observational case series reviewing clinical and imaging data from 8 patients (10 eyes) with AMN. All patients demonstrated classic parafoveal, dark grey, wedge-like lesions with NIR reflectance and characteristic abnormalities with SD-OCT imaging that were classified as Type 1 or 2 in relation to the location of the lesion above (Type 1) or below (Type 2) the OPL.

 

Results

 

Of the 8 patients, 5 were female and 3 were male, averaging 46.8 years in age (range, 21-65). Seven of the individuals were Caucasian, and the other was African American. The retinal lesions were unilateral in all but 2 cases. Visual acuity (VA) in the affected eyes at the time of presentation ranged from 20/15 to 20/30. After an average follow-up of 9.5 weeks (range, 3-30), VA ranged from 20/20 to 20/30. Five eyes (4 patients) had Type 1 lesions and 5 eyes (4 patients) had Type 2 lesions. While Type 1 lesions lead to thinning of the INL, Type 2 lesions resulted in thinning of the ONL. Type 2 lesions were always associated with significant outer macular defects including attenuation of the inner segment/outer segment (IS/OS) and outer segment/retinal pigment epithelium (OS/RPE) bands, whereas Type 1 lesions failed to disrupt the integrity of the IS/OS junction.

 

Conclusions

 

The diagnosis of AMN has vastly improved with the integration of multimodal imaging. Two types of AMN lesions may be seen with SD-OCT occurring above and below the OPL: Type 1. Hyperreflective bands in the OPL/INL region with subsequent INL thinning, and Type 2. Hyperreflective bands in the OPL/ONL region with subsequent ONL thinning. Type 2 lesions may be associated with concomitant defects of the IS/OS band. We propose that each of these lesions may be explained by occlusion of the superficial capillary plexus (SCP) (Type 1) or deep capillary plexus (DCP) (Type 2) located in the innermost and outermost portion of the INL respectively immediately adjacent to each corresponding lesion type.

 

 

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 688 retina