|Year : 2020 | Volume
| Issue : 3 | Page : 234-243
Emerging retinal diseases and newer terminologies in spectral domain optical coherence tomography
Divya Alex, Anantharaman Giridhar, Mahesh Gopalakrishnan, Shivam Madan, Swati Indurkhya, Swati Haridas, Sailesh Kumar, Dinesh Rungta
Department of Vitreoretinal Services, Giridhar Eye Institute, Kochi, Kerala, India
|Date of Submission||22-Jul-2020|
|Date of Acceptance||27-Jul-2020|
|Date of Web Publication||23-Dec-2020|
Dr. Divya Alex
Department of Vitreoretinal Services, Giridhar Eye Institute, Ponneth Temple Road, Kadavanthra, Kochi - 682 020, Kerala
Source of Support: None, Conflict of Interest: None
The retina practice has changed in such a way that diagnosis is incomplete without an optical coherence tomography (OCT) image. This article gives a brief update on the emerging spectrum of retinal diseases and newer terminologies in the spectral domain OCT to keep pace with the rapid advancements in the field of imaging.
Keywords: Emerging retinal diseases, newer terminologies, spectral-domain optical coherence tomography
|How to cite this article:|
Alex D, Giridhar A, Gopalakrishnan M, Madan S, Indurkhya S, Haridas S, Kumar S, Rungta D. Emerging retinal diseases and newer terminologies in spectral domain optical coherence tomography. Kerala J Ophthalmol 2020;32:234-43
|How to cite this URL:|
Alex D, Giridhar A, Gopalakrishnan M, Madan S, Indurkhya S, Haridas S, Kumar S, Rungta D. Emerging retinal diseases and newer terminologies in spectral domain optical coherence tomography. Kerala J Ophthalmol [serial online] 2020 [cited 2022 Dec 3];32:234-43. Available from: http://www.kjophthal.com/text.asp?2020/32/3/234/304537
| Introduction|| |
Introduced by researchers at Massachusetts Institute of Technology in the early 1990s, optical coherence tomography (OCT) has allowed ophthalmologists to see the eye from a different perspective. With the latest improvements in imaging, spectral-domain OCT (SD-OCT) allows unrivaled details of the retina and choroid. SD-OCT acts as an optical biopsy, and is used in the diagnosis and follow-up of various retinal and choroidal diseases involving the macular region.
In 2014, at International Nomenclature OCT (INOCT) Panel, Staurenghi et al. proposed a nomenclature system for normal anatomic landmarks in SD-OCT and the panel suggested a consensus regarding the most proper terminology [Figure 1].
|Figure 1: Nomenclature for normal anatomic landmarks seen on spectral domain-optical coherence tomography images proposed and adopted by the international nomenclature for optical coherence tomography panel|
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| International Nomenclature Optical Coherence Tomography Definitions of the Normal Anatomic Landmarks in Spectral Domain-Optical Coherence Tomography|| |
Moving from within the vitreous toward the outer layers of the globe, SD-OCT detects neurosensory retina resting between two layers of extreme hyperreflectivity. The first layer is at the vitreoretinal interface and the retinal nerve fiber layer. The second lay corresponds to the retinal pigment epithelium (RPE) – Bruch's membrane complex. The INOCT agreed on the adequate nomenclature for the outer retinal bands depending on the reflectivity of the layer.
The external limiting membrane band (ELM) - is located at the boundary between the cell bodies (nuclei) and the inner segments (IS) of the photoreceptors and comprises clusters of junctional complexes between the Müller cells and the photoreceptors.
Myoid zone (MZ) - the hyporeflective region between ELM and ellipsoid zone (EZ) corresponds to the innermost segment of photoreceptors. The reduced reflectivity of this zone is due to the lower packing density of mitochondria.
EZ - the hyperreflective region adjacent to the MZ is the interface between inner and outer photoreceptors (previously referred as IS-outer segments [OS] junction). They are packed with mitochondria and have the potential for high reflectivity.
The interdigitation zone (IZ) - corresponds to the contact cylinder represented by the apices of the RPE cells that encase the cone OS. This layer was previously referred to as cone outer segment tips/Verhoeff's membrane, or rod outer segment tips, and it is not always distinguishable from the underlying RPE layer.
Photoreceptor disruption can be visualized on OCT as the loss of integrity or absence of the outer retinal layers: The ELM, EZ, and IZ. Disruptions of these layers on OCT have been shown to correlate with worse visual acuity and retinal sensitivity in many retinal diseases.
| Enhanced Depth Imaging|| |
The near-infrared 800 nm light source that is used in conventional OCT systems is scattered by the photoreceptor layer, and as a result, the signal reflected from the choroid is weak. Superior quality choroidal imaging can be obtained with a slight modification in conventional OCT systems with a longer wavelength of light, giving a low signal-to-noise ratio (Swept-source) and an improved high-quality eye-tracking ability, better image averaging capability as used in enhanced depth imaging (EDI). Morphological and vascular analyses of the choroid have been revolutionized with the advent of EDI. Studies have found the mean subfoveal choroidal thickness in healthy eyes to be 287 ± 76 mm using EDI. The variants are better known as leptochoroid and pachychoroid [Figure 2].
|Figure 2: Enhanced depth imaging showing better delineation of the sclero-choroidal boundary (red triangles) (a) Spectral domain-optical coherence tomography of a healthy retina revealing a normal choroidal thickness. (b) Spectral domain-optical coherence tomography of a pathological myopic eye with choroidal neovascular membranes revealing extremely thin choroid (Leptochoroid). Note the reduced choroidal thickness further away from the macula (c) spectral domain-optical coherence tomography of an eye with polypoidal choroidal vasculopathy showing a diffusely thick choroid (Pachychoroid) with compression of choriocapillaris and dilated vessels at Haller's layer|
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Leptochoroid is defined as extreme choroidal thinning in SD OCT. In Greek, Lepto means thin or fine. It is a new clinical entity characterized by geographical hyperpigmented fundus centered in the macula, with surrounding relative hypopigmented fundus and associated with decreased choroidal thickness. Leptochoroid is not specific to high myopia. Spaide described an entity of age-related choroidal atrophy (ARCA) affecting older individuals with a myopic error of 6 diopters, mean age being 80.6 years, mean choroidal thickness being 69.8 mm, and mean visual acuity being 20/40. Eyes with ARCA may demonstrate extreme leptochoroid; however, they have a discrete appearance from eyes with high myopia. ARCA is characterized by a tessellated fundus appearance and rarefaction of the choroidal vessels under the macula, whereas highly myopic eyes with extreme leptochoroid have prominent choroidal vasculature instead of rarefaction of the choroidal vessels. In addition, eyes with ARCA may have reticular pseudodrusen. These two entities suggest that choroidal thickness alone is not a reliable indicator of visual function.
The term pachy originates from the Greek, which means thick. Pachychoroid is a relatively novel concept describing a phenotype characterized by focal or diffuse choroidal thickening, attenuation of the choriocapillaris overlying dilated choroidal vessels in the Hallers layer (pachyvessels) and associated with progressive RPE dysfunction and neovascularization. Several clinical manifestations have been described to reside within the pachychoroid disease spectrum, including central serous chorioretinopathy (CSCR), pachychoroid pigment epitheliopathy (PPE), pachychoroid neovasculopathy, polypoidal choroidal vasculopathy/aneurysmal type 1 neovascularization, focal choroidal excavation (FCE) and peripapillary pachychoroid syndrome (PPS). Newer entities are discussed.
| Pachychoroid Pigment Epitheliopathy|| |
The term PPE was first introduced by Warrow et al. The clinical appearance of the pigment epitheliopathy included mottling of the RPE, irregular areas of RPE elevation termed “drusenoid RPE lesions” with the absence of soft drusen [Figure 3]. Since none of the eyes had manifested neurosensory detachment, PPE was considered a forme fruste of CSCR. Indocyanine green (ICG) shows increased choroidal hyperpermeability as mid-phase hyperfluorescence that co-existent with the areas of RPE disturbances. These patients were often misdiagnosed with pigmentary age-related macular degeneration (AMD), pattern dystrophy, or retinal pigment epithelitis. However, PPE is usually asymptomatic and usually found in the fellow eyes of CSCR. RPE elevation with microbreak appearance can be a prerunner to subretinal fluid (SRF) formation later on. It was subsequently observed that patients with PPE could go on to develop type one neovascularization, with or without aneurysmal (polypoidal) lesions, without necessarily developing CSCR.
|Figure 3: a) Foveal section spectral domain-optical coherence tomography of an eye with pachychoroid pigment epitheliopathy showing irregular retinal pigment epithelium with patchy loss of ellipsoid, pachyvessels, and thick choroid. (b) Spectral domain-optical coherence tomography of an eye with pachychoroid neovasculopathy (PCN) showing a hyperreflective double layer sign, subretinal and intraretinal fluid, pachyvessels, and pachychoroid. (c) Optical coherence tomography-angiography detecting an entangled branching vascular network with peripheral anastomosis (d) Indocyanine green showing the branching vascular network. Both corresponding to the level of PCN|
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| Pachychoroid neovasculopathy (PCN/PNV)|| |
Pang and Freund described the evolution of type one neovascularization in eyes over backdrop changes consistent with PPE, and coined the term PNV. Characteristic features of PNV include the presence of type 1 neovascularization, which appears on OCT as a shallow irregular separation of the RPE from Bruch's membrane, which appears as “double layer sign (DLS)” overlying pachyvessels. The presence of hyporeflectivity in DLS is a crucial marker of chronic CSCR, whereas hyperreflectivity in DLS distinctly correlated with PCN and polypoidal choroidal vasculopathy, indicative of underlying neovascular tissue complex. The presence of neovascularization can be confirmed by detection of leakage on FA, typically in the form of late leakage with undetermined origin, and a corresponding late staining “plaque” on ICGA. With the advent of OCT angiography (OCTA), the diagnosis of PCN is more straightforward. OCTA reveals a tangled filamentous branching vascular network (BVN) with a flow signal corresponding to the DLS. The sensitivity of OCTA in detecting a BVN is more than that of ICG [Figure 3].
| Peripapillary Pachychoroid Syndrome|| |
PPS was described by Phasukkijwatana et al. as a distinct variant of the pachychoroid disease spectrum, in which maximal choroidal thickness occurs close to the optic nerve rather than subfoveally. These patients typically present with nasal macular intraretinal and/or SRF and crowded disc and occasional optic nerve edema [Figure 4]. Peripapillary choroidal congestion with a compartment-like effect on the peripapillary region was proposed as an etiologic mechanism. The association of PPS with choroidal folds, short axial length, and hyperopia indicated similarities with Uveal Effusion syndrome (UES). Serous macular detachments diffuse granular intense hyperfluorescence in early and late ICGA as usually seen only in UES and makes it distinct. It is important to recognize this clinical entity, which can be confused with posterior uveitis and neuro-ophthalmologic disorders to avoid unnecessary interventions.
|Figure 4: (a and b) Spectral domain-optical coherence tomography enumerating the features of peripapillary pachychoroid syndrome. Note the nasal intraretinal schisis (red asterisk) with maximum choroidal thickness nasally near the optic nerve head (ONH) (white triangle). (c) Spectral domain-optical coherence tomography imaging of a nonconforming focal choroidal excavation where the photoreceptor tips are detached from the underlying retinal pigment epithelium, with a hyporeflective cleft (green asterisk). (d) Spectral domain-optical coherence tomography imaging of a conforming focal choroidal excavation, where the photoreceptor tips are in direct contact with the retinal pigment epithelium|
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| Pachydrusen|| |
Coined by Spaide, Pachydrusen is a relatively new entity characterized by yellowish-white Sub-RPE drusenoid deposits in patients with the thick choroid [Figure 5]. The various locations described for the pachydrusen are in the posterior pole sparing the macula, peripapillary area, and near arcades, while the distribution pattern can be solitary, scattered, or clustered having a better-defined outer border. Choroidal morphology under pachydrusen showed increased Haller's layer thickness with attenuation of choriocapillaris. Whether the occurrence of these changes is a causal or resultant phenomenon needs to be elucidated.
|Figure 5: (a-d) Images showing various types of drusen. (a) Spectral domain optical coherence tomography imaging of soft drusen (red triangle) located below the retinal pigment epithelium. Mild disruption of the ellipsoid zone is visible. No signs of subretinal fluid or choroidal neovascular membranes. (b) large soft confluent drusen obscuring the foveal contour (c) Spectral domain optical coherence tomography demonstrating multiple reticular pseudodrusen as hyper-reflectance between the ellipsoid and retinal pigment epithelium (green triangle) in contrast to typical soft drusen (red triangles) which clearly reside below retinal pigment epithelium. (e) Spectral domain optical coherence tomography image showing the presence of subretinal hyperreflective membrane (SHRM, red asterisk) in type 2 classic choroidal neovascular membranes. (f) Spectral domain-optical coherence tomography image demonstrating a type 1 choroidal neovascular membranes with a fibrovascular pigment epithelial detachment (green asterisk) without SHRM|
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| Reticular Pseudo Drusen or Subretinal Drusenoid Deposits|| |
Subretinal drusenoid deposits (SDD) is unique from other subtypes of drusen by being located above the level of the RPE [Figure 5]. Although they can appear in individuals with no other apparent pathology, their highest rates of occurrence are in association with AMD. Reticular pseudodrusen are also documented in diseases such as Sorsby's fundus dystrophy, pseudoxanthoma elasticum, and acquired vitelliform lesions. They are found bilaterally, more in females and with increased age. On histological examination, RPD has been shown to have discrete compositions from typical drusen, suggesting different pathways of pathogenesis. SDD is thought to be a precursor lesion for Type 3 choroidal neovascular membranes (CNVM) or retinal angiomatous proliferation.
Zweifel et al., have proposed a three-stage classification for SDD using the amount of hyperreflective material visible on SDOCT and the level of distortion to the ellipsoid layer. Stage 1 is defined by the diffuse deposition of granular hyperreflective material between the RPE and the EZ. Stage 2 represents the progression of material accumulation between the RPE and EZ, forming small mounds and large enough to distort the contour of the EZ. In stage 3, SDD takes on a conical shape, in contrast to the gently rounded appearance of stage 2 lesions, and punch through the ellipsoid boundary.
| Focal Choroidal Excavation|| |
FCE is a concavity in the choroid occurring without any adjacent scleral abnormality or ectasia and normal-appearing overlying retina. Origin of FCE can be congenital posterior malformation or acquired. FCE is now considered as a distinct entity in pachychoroid spectrum. FCE lesions could represent the scarring of choroidal connective tissue from a previous inflammatory process. Presumably, scar contraction could draw the choroid and RPE toward the sclera producing FCE. Abnormal structure or configuration of the overlying RPE or Bruch's membrane in FCE may predispose to CNVM.
Two patterns of excavation have been described. In conforming FCE, the photoreceptor tips are in direct contact with the RPE, whereas in nonconforming FCE the photoreceptor tips appeared to be detached from the underlying RPE, and a hyporeflective cleft can be observed in the intervening space [Figure 4]. Nonconforming FCE can be misdiagnosed as SRF.
| Dome Shaped Macula|| |
It is the forward convex bulge of the macula that is observed in highly myopic eyes with or without posterior staphylomas, usually detected in vertical and horizontal OCT scans. Three dome-shaped macula (DSM) configurations have been described by Caillaux et al.:
- Horizontal oval-shaped dome (63%) – dome can be visible only in vertical OCT
- Vertical oval-shaped dome (16%) – dome can be visible only in vertical OCT
- Round dome (21%) – dome present on both horizontal and vertical OCT scans [Figure 6].
|Figure 6: The different configurations of dome-shaped macula. (a and b) Horizontal dome-shaped macula as seen only in vertical optical coherence tomography imaging. Note the ellipsoid zone disruption at the fovea and epiretinal membrane. (a) Horizontal optical coherence tomography fails to reveal the dome-shaped macula. (b) A vertical optical coherence tomography section across the fovea shows an inward protrusion of the macula due to dome-shaped macula. (c and d) Vertical dome-shaped macula revealed only in horizontal optical coherence tomography imaging. Vertical optical coherence tomography fails to show the dome-shaped macula. Both images show subretinal fluid indicative of dome-shaped maculopathy (c) Round dome as seen in both vertical and horizontal optical coherence tomography imaging|
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DSM was thought to be secondary to ingrowth of the choroid, but recent research indicates that the main problem is focal scleral thickening in the foveal area., One of the major complications in these patients is the loss of vision secondary to the SRF accumulation. DSM mimics CSCR and results in mismanagement and shows the importance of vertical OCT scan. The condition is usually managed conservatively due to conflicting evidence of treatment success using anti-vascular endothelial growth factor (VEGF) injections, oral spironolactone, and PDT.
| Subretinal Hyperreflective Material|| |
Subretinal hyperreflective material (SHRM) is a morphological feature identified on the SD-OCT as hyperreflective material located between neurosensory retina and RPE [Figure 5]. The range of SHRM seen in macular disease includes neovascular tissue, fibrin, exudates, vitelliform material, and hemorrhage. OCTA can distinguish vascular from avascular SHRM. OCTA reveals a strong intrinsic flow signal with an entangled network in a vascular SHRM.
SHRM has a clear role as a biomarker or prognostic factor in neovascular AMD management. The presence of foveal involving SHRM, well-defined SHRM borders, and thicker SHRM at baseline are associated with poor visual outcome after anti-VEGF therapy even though there is a reduction in the size of SHRM., SHRM in wet AMD should be differentiated from fibrin in CSCR. The thickness of the choroid and vacuole sign, will help to differentiate the same.
| Complete Retinal Pigment Epithelium and Outer Retinal Atrophy and Incomplete Retinal Pigment Epithelium and Outer Retinal Atrophy|| |
The classification of atrophy meeting recently proposed a consensus definition and nomenclature for SD-OCT defined geographical atrophy in the setting of AMD.
They defined complete retinal pigment epithelium and outer retinal atrophy (cRORA): (1) a region of choroidal hypertransmission of at least 250 μm in diameter, (2) a zone of attenuation or loss of the RPE of at least 250 μm in diameter, and (3) evidence of overlying photoreceptor degeneration (loss of the IZ, EZ, and ELM and thinning of the outer nuclear layer). Incomplete retinal pigment epithelium and outer retinal atrophy (iRORA) does not fulfill all three criteria for cRORA and typically demonstrate discontinuous hypertransmission, a present but irregular or interrupted RPE band, and interrupted photoreceptor degeneration [Figure 7].Complete Outer Retinal Atrophy (cORA) is defined by continuous absence of the EZ and interdigitation zone and severe thinning of the outer retina with an intact RPE band. Incomplete Outer Retinal Atrophy (iORA) demonstrates thinning of the outer retina, an intact RPE band, and no hypertransmission. Visual acuity will be worst in cRORA.
|Figure 7: (a) Spectral domain optical coherence tomography image demonstrating features of incomplete retinal pigment epithelium and outer retinal atrophy. Note the irregular loss of retinal pigment epithelium band, and interrupted photoreceptor degeneration and discontinuous reverse shadowing (enhanced visibility of choroid due to loss of retinal pigment epithelium). (b) Spectral domain optical coherence tomography image demonstrating features of complete retinal pigment epithelium and outer retinal atrophy. Note the complete absence of retinal pigment epithelium, ellipsoid zone, external limiting membrane band with thinning of outer nuclear layer, and continuous reverse shadowing|
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| Multilayered Pigment Epithelial Detachment|| |
In 2014, Freund et al. coined the term multilayered pigment epithelial detachment (PED) for organized layers of hyperreflective bands between the RPE monolayer and Bruch's membrane within vascularized PEDs. It is comprised fibrocellular tissue with contractile properties organized in a spindle-shaped configuration. Khan et al., noted the presence of a prechoroidal cleft in multi-layered PED and described as one component of a “triple-layer” sign: Sub-RPE neovascular tissue, the hyporeflective space, and the underlying choroid [Figure 8].
|Figure 8: (a-i) Serial spectral domain optical coherence tomography images are showing the evolution of multi-layered pigment epithelial detachment from an extralarge pigment epithelial detachment. Note the formation of neovascular tissue within the pigment epithelial detachment in layers (red asterisk) and pre choroidal cleft (Red Triangle) with triple-layer sign|
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Although the appearance of multilayered PED can be rather dramatic, these eyes maintain surprisingly good visual acuity, presumably because the neovascular and subsequent cicatricial process is confined to the sub-RPE space and the neovascular tissue may provide oxygenation or nutritional support to the outer retina and RPE, protecting against involution and geographic atrophy.
| Disorganization of Retinal Inner Layers|| |
Disorganization of retinal inner layers (DRIL) has been defined by Sun et al., as the lack of distinguishable boundaries between the ganglion cell– inner plexiform layer (IPL) complex, inner nuclear layer, and outer plexiform layer in the central 1000 μ in DME patients [Figure 9]. The development of DRIL is not specific to DME, it is a common response to retinal stress. DRIL is a negative predictive OCT biomarker. Centrally located DRIL and the extent of disruption were both associated with worse visual acuity. For each 100 μm increase in DRIL, there is a negative impact of approximately 6 letters, which is more than 1 line on the ETDRS chart. It has been hypothesized that the disorganization of the inner retina occurs when bipolar axons snap when their elasticity limit has been exceeded because of edema. It has also been suggested that DRIL represents the loss of bipolar, amacrine, or horizontal cells within the inner retinal layers. Recently, it has been found that DEX implant has the potential to ameliorate DRIL and is related to the architectural effect on the Muller cells.
|Figure 9: Representative spectral domain optical coherence tomography images showing combinations of the presence or absence of disorganization of retinal inner layers in diabetic macular edema. The central 1 mm foveal area is enclosed in the white box|
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| Lamellar Hole Associated Epiretinal Proliferation|| |
Lamellar Hole associated epiretinal proliferation is the epiretinal proliferation arising from Muller cells seen in the degenerative lamellar macular hole (LMH). LMH can be tractional or degenerative [Figure 10]. Degenerative LMH has a “top hat” morphology and is associated with the presence of intraretinal cavitation, potentially affecting all retinal layers. A foveal “bump” of spared retinal tissue is frequently present, as well as outer retinal disruption. There won't be no visual benefit after surgery, despite anatomical improvement. Tractional LMH has a “moustache” appearance and is associated with the presence of Epiretinal or premacular membrane. These lesions present with a “schitic” morphology, with a sharp split located in the Henle's layer, which separates the inner and outer retina. Foveal photoreceptors are frequently spared and usually have better visual acuity.
|Figure 10: The features of both variants of the lamellar macular hole (a). Degenerative LMH (b)Tractional LMH|
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| Ectopic Inner Foveal Layers|| |
The chronic anteroposterior and centripetal traction caused by the epiretinal membrane (ERM) may induce the displacement and reorganization of the inner retinal layers, creating a continuous floor of inner retinal tissue extending from the inner nuclear layer (INL) and IPL across the central fovea and referred to as ectopic inner foveal layers [Figure 11]. Ectopic inner foveal layer formation represents an important sign of ERM progression and it is the keystone of a newly proposed SD-OCT staging scheme for idiopathic ERM. OCTA taken in Stage 3 ERM with ectopic inner foveal layers (EIFL) has shown significantly distorted or absent FAZ. EIFL is associated with reduced pre- and post-operative visual acuity. The thickness of EIFL has a negative correlation with visual outcome.
|Figure 11: (a-d) The four stages of the epiretinal membrane. Ectopic inner foveal layers marked between the red arrows in (c)|
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| Dengue-Induced Inflammatory, Ischemic Foveolitis and Outer Maculopathy|| |
Approximately 5%–8% of patients with dengue fever are at a risk of developing permanent visual loss due to posterior segment involvement. The dengue-induced inflammatory, ischemic foveolitis, and outer maculopathy (DIII-FOM) encompass pathological changes induced by ischemia and inflammation of predominantly the outer retina. Inflammatory insult is evidenced in SDOCT by the presence of vitreous cells, cystoid spaces in Henle's layer, “conical” foveal elevations, presence of outer plexiform and outer nuclear hyper-reflectivity and disruption of ELM, EZ and inter-digitation zone. Immune complex deposition in the deep capillary plexus may be the reason for retinal ischemia. Although the inflammatory insult is controlled by early initiation of corticosteroids, the recovery of ischemic insult is unclear, resulting in permanent scotoma.
| Acute Macular Neuroretinopathy and Paracentral Acute Middle Maculopathy|| |
Both lesions present with acute onset of paracentral scotomas. First described by Bos and Deutman, in 1975, acute macular neuroretinopathy (AMN) is a rare retinal disorder that typically affects a young healthy woman in their teens-30's. The classic funduscopic finding in AMN is the presence of single or multiple dark, well-defined, wedge-shaped intraretinal lesions pointing to the fovea, often in a flower petal arrangement. SD-OCT demonstrates band-like hyper-reflective plaques at the ONL/OPL junction indicating disruption of photoreceptor cell bodies and their axons., With the resolution of this ONL/OPL hyper-reflectivity, thinning of the ONL and EZ disruption occurs.
More recently, Sarraf et al. identified characteristic AMN lesions at the level of the INL, a novel SD-OCT finding referred to as paracentral acute middle maculopathy (PAMM) [Figure 12]. PAMM may be idiopathic and may even develop in young and healthy individuals with an otherwise normal ocular examination. If so, appropriate systemic workup to exclude systemic or cardiovascular risk factors is advisable. Although the visual prognosis is good, the complete resolution of scotomas never occurs in both lesions.
|Figure 12: (a) Spectral domain optical coherence tomography of paracentral acute middle maculopathy shows hyperreflective band-like lesion located above the outer plexiform layer in the paracentral macula (b) Multicolour fundus photograph showing wedge-shaped lesions at the macula with apex directing toward the macula. (c) Spectral domain optical coherence tomography of acute macular neuroretinopathy shows hyperreflective band-like lesion located at the junction of the outer plexiform and inner nuclear layer|
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