Microperimetric assessment of the two optical coherence tomography subtypes of acute macular neuroretinopathy

Background: This study evaluates the morpho-functional alterations associated with acute macular neuroretinopathy (AMNR).

Design: Prospective observational case series study carried out at the University Vita-Salute, Scientific Institute San Raffaele.

Participants: Five out of six eyes (three patients) showed the typical features of AMNR.

Methods: The patients underwent an ophthalmological examination, including best-corrected visual acuity (BCVA) measurement, electroretinogram and electroculogram (ERG/EOG), multifocal electroretinogram (mfERG), infrared reflectance, short wavelength and near-infrared-fundus autofluorescence (SW-FAF/NIR-FAF), spectral-domain optical coherence tomography (SD-OCT) and microperimetry.

Main outcome measure: Microperimetric alterations in the two SD-OCT subtypes of AMNR.

Results: The BCVA was 20/20 in all patients. ERG and EOG were normal; mfERG revealed a generally reduced response with a more reduced signal in the areas corresponding to the macular lesions. SD-OCT demonstrated two different patterns of retinal alterations. In case 1, SD-OCT revealed a hyperreflective, plaque-like band at the junction of the outer plexiform layer (OPL) and the inner nuclear layer (INL), extending into the INL (type 1 lesion). In cases 2 and 3, SD-OCT disclosed a hyperreflectivity of the OPL associated with outer nuclear layer thinning and disruption of the outer segment/retinal pigment epithelium junction (type 2 lesion). Microperimetry revealed a wide scotoma involving the entire macular area in all eyes, including the unaffected eye of case 1. The reduction in retinal sensitivity was greatest in type 1.

Conclusions: SD-OCT confirms that AMNR may occur in different patterns. Microperimetry demonstrated that functional alterations are also discernible in apparently uninvolved areas. Both examinations are extremely valuable in characterizing the changes associated with AMNR.