Title: Widefield en face optical coherence tomography to quantify the extent of paracentral acute middle maculopathy
Abstract: Paracentral acute middle maculopathy (PAMM) has been described as a hyperreflective band or plaque-like region on spectral-domain optical coherence tomography (SD-OCT) at the level of the inner nuclear layer (INL), which is straddled by the intermediate and deep retinal capillary plexuses.1Sarraf D. Rahimy E. Fawzi A.A. et al.Paracentral acute middle maculopathy: A new variant of acute macular neuroretinopathy associated with retinal capillary ischemia.JAMA Ophthalmol. 2013; 131: 1275-1287Crossref PubMed Scopus (276) Google Scholar, 2Chen X. Rahimy E. Sergott R.C. et al.Spectrum of retinal vascular diseases associated with paracentral acute middle maculopathy.Am J Ophthalmol. 2015; 160: 26-34.e21Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar PAMM has been reported to cause eccentric wedge-shaped lesions that extend to the edge of the foveal avascular zone.3Pecen P.E. Smith A.G. Ehlers J.P. Optical coherence tomography angiography of acute macular neuroretinopathy and paracentral acute middle maculopathy.JAMA Ophthalmol. 2015; 133: 1478-1480Crossref PubMed Scopus (36) Google Scholar Although these lesions resolve over time, patients are left with irreversible INL atrophy, resulting in a permanent paracentral visual field defect. PAMM can be idiopathic or secondary to local retinal vascular or systemic disease; more recent observations support a vaso-occlusive etiology.4Sridhar J. Shahlaee A. Rahimy E. et al.Optical coherence tomography angiography and en face optical coherence tomography features of paracentral acute middle maculopathy.Am J Ophthalmol. 2015; 160 (e1252): 1259-1268Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar En face OCT and OCT angiography are effective for the qualitative evaluation of these lesions with 3 distinct en face OCT patterns reported in PAMM: arteriolar, fern-like, and globular.4Sridhar J. Shahlaee A. Rahimy E. et al.Optical coherence tomography angiography and en face optical coherence tomography features of paracentral acute middle maculopathy.Am J Ophthalmol. 2015; 160 (e1252): 1259-1268Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar, 5Christenbury J.G. Klufas M.A. Sauer T.C. Sarraf D. OCT Angiography of paracentral acute middle maculopathy associated with central retinal artery occlusion and deep capillary ischemia.Ophthalmic Surg Lasers Imaging Retina. 2015; 46: 579-581Crossref PubMed Scopus (37) Google Scholar OCT angiography has shown signal abnormalities localized to the deep capillary plexus.6Khan M.A. Rahimy E. Shahlaee A. Hsu J. Ho A.C. En face optical coherence tomography imaging of deep capillary plexus abnormalities in paracentral acute middle maculopathy.Ophthalmic Surg Lasers Imaging Retina. 2015; 46: 972-975Crossref PubMed Scopus (15) Google Scholar However, en face OCT and OCT angiography images of PAMM reported so far have been limited to central 3 × 3 mm or 6 × 6 mm macular scans and documentation of the extent of PAMM up to and beyond the arcades has not been described. We describe the utility of widefield en face OCT in categorizing the extent of the INL hyperreflective lesions in PAMM beyond the central macular region. An 82-year-old female patient presented 2 days after noticing a bell-shaped scotoma in the superior aspect of her visual field. She had multiple cardiovascular risk factors including coronary artery disease, hypertension, and hyperlipidemia, as well as a history of lung cancer. On presentation, her corrected visual acuity was 20/25 OU. Carotid ultrasonography showed moderate stenosis (50%) in both internal carotid arteries, which was below the threshold for vascular intervention. A complete blood count, chemistry panel, and erythrocyte sedimentation rate were normal. Her dilated examination and fluorescein angiography were unremarkable (Fig. 1A, B). Near-infrared fundus autofluorescence showed mild hypoautofluorescence along the superotemporal branch retinal artery (Fig. 1C) and near-infrared reflectance imaging showed mild hyporeflectivity in the same area (Fig. 1D). Widefield OCT imaging (55 degrees, 16.1 mm scan width with 217 B scans, Heidelberg Spectralis HRA + OCT, Carlsbad, CA, USA) showed a hyperreflective, plaque-like band at the level of the INL, best visualized on vertical OCT B scans (Fig. 2A), consistent with PAMM. Widefield en face imaging at the level of the middle retina showed prominent confluent hyperreflective lesions (Fig. 2B, C, white arrows, extent marked by yellow boundary) along the superotemporal branch artery, corresponding to the INL lesions on the B scan. The pattern of this hyperreflective area on the en face image corresponded to her scotoma. The horizontal OCT B scan through the macula (Fig. 2D) did not show INL hyperreflectivity. Imaging of her left eye was unremarkable. The parafoveal macula, particularly the middle retinal layers, where a watershed-like region exists, has a high perfusion demand, whose supply is limited by structure, placing it at greatest risk for an ischemic insult.7Yu S. Pang C.E. Gong Y. et al.The spectrum of superficial and deep capillary ischemia in retinal artery occlusion.Am J Ophthalmol. 2015; 159 (e51–52): 53-63Abstract Full Text Full Text PDF PubMed Scopus (132) Google Scholar The fact that PAMM lesions are in the middle macula, and predominantly parafoveal, aligns with an ischemic etiology.8Nemiroff J. Kuehlewein L. Rahimy E. et al.Assessing deep retinal capillary ischemia in paracentral acute middle maculopathy by optical coherence tomography angiography.Am J Ophthalmol. 2016; 162 (e121): 121-132Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar Fluorescein angiography is insufficient to identify isolated loss of the deep capillary plexus and is typically normal in the area of the PAMM lesions. OCT localization of these lesions at the level of the INL and the typical wedge-shaped appearance suggests that they represent an ischemic insult of the adjacent intermediate and deep capillary plexuses.8Nemiroff J. Kuehlewein L. Rahimy E. et al.Assessing deep retinal capillary ischemia in paracentral acute middle maculopathy by optical coherence tomography angiography.Am J Ophthalmol. 2016; 162 (e121): 121-132Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar, 9Rahimy E. Sarraf D. Dollin M.L. Pitcher J.D. Ho A.C. Paracentral acute middle maculopathy in nonischemic central retinal vein occlusion.Am J Ophthalmol. 2014; 158 (e371): 372-380Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar Even in the absence of a true branch retinal artery occlusion, it is presumed that transient occlusion of a large retinal arteriole with rapid restoration of normal flow could induce ischemia in the watershed zone of the middle retina, while sparing the nerve fiber and ganglion cell layers, explaining the plaque-like arteriolar pattern seen on the en face OCT image. Widefield en face OCT is a useful tool to help with easier recognition of the unique presentation of PAMM in terms of inner nuclear layer hyperreflectivity as well as localization of its extent anterior to the major arcades, which is difficult with conventional fluorescein angiography and OCT.