Participants and Their Diagnoses

Patients were recruited from the practices of 6 retina specialists (K.B.F., L.A.Y., J.S.D., N.W., D.S., G.Q.). Patients were included if they exhibited a neurosensory detachment on cross-sectional OCT with hyperreflective material in the subretinal space, in the context of AMD, myopic macular degeneration, pachychoroid spectrum disease, or retinal dystrophy. Eyes with non-AMD diagnoses were retained for study if they harbored types of SHRM that might be seen in AMD (eg, vitelliform lesion in Best disease) or that can occur with AMD in “overlap” conditions.

Clinical charts and multimodal imaging data were reviewed including fundus photography, fluorescein angiography, fundus autofluorescence, and OCT, all of which had been performed as clinically indicated.

Fluorescein angiographic appearances of “choroidal” neovascular lesions were recorded in terms of the original descriptions of “occult” and “classic” patterns, but type 1, type 2, and type 3 lesions themselves were defined and classified anatomically using both fluorescein angiography and cross-sectional OCT.

Subretinal fibrosis was identified by the fundus biomicroscopy finding of an elevated mound of yellow-white tissue with late staining and minimal leakage on fluorescein angiography. Subretinal hyperreflective exudation was recognized on cross-sectional OCT in association with neovascularization as previously described. Acquired vitelliform lesions were defined as subfoveal accumulations of yellow-white material exhibiting moderate to intense hyperautofluorescence and were described in terms of their amorphous and granular components.

All patients had undergone OCTA of the study eye. Patients for whom gradable OCTA images were unavailable owing to media opacity or poor fixation were excluded. Multimodal images and OCT and OCTA segments of SHRM foci in included patients were sent to one of the authors (K.K.D.) for grading and classification.

Imaging

Imaging devices used were as follows: TRC-50IX fundus camera (Topcon Corporation, Tokyo, Japan), Spectralis HRA+OCT scanning laser ophthalmoscope (Heidelberg Engineering, Heidelberg, Germany), and RTVue XR “Avanti” (Optovue, Fremont, California, USA).

The RTVue XR is a spectral-domain OCT device that employs a split-spectrum amplitude-decorrelation algorithm for angiographic processing. Horizontal and vertical raster patterns are combined to correct eye movement artifacts in post-processing. The viewing software performs automated tissue boundary detection to assist in segmenting retinal and choroidal layers for en face projection. Four preset curve pairs are offered (superficial, deep, outer retina, choriocapillaris), as well as a “flat” line pair with slant adjustment. In cross-sectional mode, the viewing software offers the option of overlaying thresholded (“all-or-nothing” encoded) flow signals on structural reflectance scans, enabling point-to-point correlation between cross-sectional structural, cross-sectional angiographic, en face structural, and en face angiographic views.

Since a SHRM focus represents, in geometric terms, a “space-occupying lesion” its presence violates the assumptions regarding lamellar tissue arrangement on which automated segmentation algorithms rely. To interpret scans with segmentation errors, each SHRM focus was studied using multiple preset boundary curves, with manual adjustment of the anteroposterior positions of those curves. Lesions were also “scrolled through” to build up a mental 3-dimensional image of each lesion. OCTA imaging artifacts were described using recently published nomenclature.

Optical Coherence Tomography Angiography Outcome Measures

Each SHRM focus was examined for intrinsic flow that could be demonstrated in both cross-sectional scans with angiographic overlays and in en face views. In cross-section, the presence of a flow signal at the level of the RPE could be interpreted as intrinsic rather than projected if there was no corresponding flow signal in the inner retina along the same A-scan axis. Furthermore, to qualify SHRM definitively as vascularized, the en face morphology of its (intrinsic) flow signature had to differ from that of the retinal circulation, distinguishing it from projection artifact.

Additionally, each SHRM focus was examined systematically from anterior to posterior aspects using en face planes to study projection characteristics. The anterior surface was studied to determine whether it produced a well-resolved projection of the flow signature of the overlying retina. The projection onto the anterior surface of the SHRM was compared qualitatively with the projection of the retinal circulation onto the surrounding unmasked RPE, and graded “strong” (comparable, eg, Figure 4 ), “weak” (attenuated or reduced detection), absent, or ungradable. Projection of the retinal microvasculature through SHRM onto the RPE was similarly assessed, and weak retina-RPE projection was attributed to SHRM opacity.

The inner choroid was examined en face, directly beneath the SHRM lesion. After accounting for segmentation errors, the sub-SHRM choriocapillaris and inner Sattler layers were compared with the homogenous, physiological flow signature of the more peripheral choroid. Flow signal attenuation could be attributed to masking (shadow) or inner choroidal atrophy. The choriocapillaris was considered to be masked by the SHRM if it appeared hyporeflective on the en face structural OCT and if the outline of the shadow matched the en face silhouette of the SHRM.

All images were examined independently by 2 retinal specialists (K.K.D. and F.G.) and any discrepancies were resolved by the senior author (K.B.F.). The outcome measures described above are illustrated in the accompanying figures, which describe example cases of each.

Type 2 Neovascularization

Three eyes of 3 patients were identified with type 2 neovascularization. Each of these exhibited well-defined early hyperfluorescence on fluorescein angiography, and flow within the type 2 lesions was detected readily by OCTA in both cross-sectional overlay and en face views ( Figures 1 and 2 ).

Multimodal imaging of the left eye of a 73-year-old myopic patient with type 2 neovascularization. (Top left) Color photography shows a grayish subfoveal lesion with a lighter halo. The retinal pigment epithelium is hypopigmented. (Top middle) Arterial-phase fluorescein angiography shows hyperfluorescence of the subfoveal lesion. (Top right) Choroidal vessels are well visualized on near-infrared reflectance. (Second row, left) Cross-sectional optical coherence tomography (OCT) shows subretinal hyperreflective material with adjacent subretinal fluid. Dilated choroidal vessels are noted beneath the lesion. (Second row, right) En face OCT (3 mm × 3 mm) through the mid choroid shows dilated choroidal vessels looping beneath the neovascular lesion and coursing toward the inferotemporal vortex vein. (Bottom row, left) Cross-sectional OCT with angiographic overlay (red pixels) shows a strong flow signal at the level of the retinal pigment epithelium (RPE). En face OCT angiography through the subretinal lesion shows a strong, well-circumscribed flow signal. The presence of retinal projection and the absence of a choriocapillaris flow signal surrounding the lesion localizes the segmentation plane to the anterior surface of the RPE.

Multimodal imaging of the left eye of an 83-year-old patient with mixed (type 1 and 2) neovascularization, subretinal hemorrhage, and subretinal hyperreflective exudate. (Top row, left) Color and red-free photographs show subretinal hemorrhage with surrounding fibrin and/or exudate. (Top row, right) Early venous and late-phase fluorescein angiography shows well-circumscribed hyperfluorescence in a “classic” configuration with some late leakage. (Second and third rows) Optical coherence tomography (OCT) line scans through the subretinal lesion with angiographic overlay (red pixels, inset). Multiple levels of reflectivity are seen within the subretinal lesion corresponding with blood (red arrowhead), tissue (green arrowhead), and exudate (blue arrowhead). (Lower right) En face OCT angiography (3 mm × 3 mm) shows the flow signal of the subretinal lesion and its internal morphology.

Eye #1 featured a hypopigmented myopic fundus with a thin choroid (<115 μm) and subfoveal type 2 neovascularization. Enhanced infrared transmission was seen through the choroid, behind the neovascular lesion, on cross-sectional OCT. Deep en face OCTA segments showed marked projection of the flow signature of the type 2 lesion onto the sclera , but in spite of this depth of tissue penetration by the scanning infrared laser, flow within the lumina of dilated outer choroidal vessels could not be detected.

In Eye #2, with type 2 neovascularization anterior to a pigment epithelial detachment (PED) ( Figure 2 ), the proximity of the flow signal to the elevated RPE made it difficult, in both en face and cross-sectional viewing modes, to determine definitively whether the neovascular tissue was predominantly subretinal or sub-RPE. However, the en face morphology of the flow signature showed greater resemblance to type 2 than type 1 neovascularization when compared with previously published images. Fluorescein angiography was helpful, showing a “predominantly classic” configuration.

In each of the above cases, retinal projection, onto either the type 2 lesion or the RPE, could not be graded owing to the intense flow signature of the type 2 lesion itself, which appeared qualitatively to have saturated the detection threshold of the device.

Subretinal Fibrosis

Four eyes were identified with subretinal fibrosis based on multimodal imaging. In Eye #4 subfoveal fibrosis had occurred adjacent to a PED. OCTA showed a tangled neovascular network within the PED with a trunk vessel that branched and coursed anteriorly into the subfoveal scar ( Figure 3 ). Pathologic disruption of the anteroposterior OCT reflectivity profiles in this eye resulted in failure of automated segmentation, necessitating the use of an arbitrary flat tissue boundary, with slant adjustment for best visualization.

Multimodal imaging of the right eye of an 87-year-old patient with mixed (type 1 and 2) neovascularization attributable to age-related macular degeneration. (Top row) Color and red-free photographs show subfoveal fibrosis, with scalloped edges, and perifoveal subretinal hemorrhage. Horizontal cross-sectional optical coherence tomography (OCT) through the fovea shows a complex pigment epithelial detachment with multilayered reflectivity (red asterisks), subretinal hyperreflective material (SHRM; green asterisk), and a focus of subretinal fluid. A small focus within the SHRM exhibits reduced reflectivity (green circle). (Second row and below) Horizontal cross-sectional OCT line scan through the fovea (each at the same latitude) with thresholded angiographic overlay (red pixels) shows a flow signal both at the level of the retinal pigment epithelium (RPE) and anterior to the RPE, within the SHRM focus. (Lower right) Color-coded en face OCTA segments at 3 different depths, overlaid, show the presence of mature type 1 neovascular tissue composed of trunk vessels (red), communicating via an intermediate trunk vessel (green) with type 2 neovascular vessels in the more anterior segment (blue). Owing to failure of automated segmentation, flat segments were used on a slant to construct a 3-dimensional impression of the neovascular complex. As a result, scan areas peripheral to the complex are not meaningfully interpreted with the exception of a retinal venule, seen best in the red-free photograph, which anastomoses with type 1 vessels at the superotemporal border of the foveal avascular zone (yellow arrowhead).

OCTA did not show any flow intrinsic to subretinal fibrosis in the other 3 cases, but in Eye #6 ( Figure 4 ) and Eye #7 the smooth inner surface of the hyperreflective fibrotic lesion produced strong, well-resolved projection artifacts of the overlying retinal vessels with large decorrelation amplitudes represented by bright en face pixels. Although dense foci of subretinal fibrosis appeared to mask both the retina-RPE projection and the visualization of choriocapillaris in en face views, these observations were difficult to validate with reference to cross-sectional scans, which showed indistinct tissue topology at the level of the RPE owing to choriocapillaris atrophy.

Color photograph with optical coherence tomography (OCT) and OCT angiography (cross-sectional and en face segments) of the right eye of an 86-year-old patient with neovascular age-related macular degeneration. (Left and middle columns) Color photography and OCT show extrafoveal subretinal fibrosis with well-defined edges. (Third column) Cross-sectional angiographic overlay (lower right) shows flow signal (red pixels) to be most concentrated at the anterior aspect of the fibrotic lesion and to be geometrically coupled to the flow signal of the retinal circulation, lying along the same A-scan line. Unlike the fibrotic focus seen in Eye #2 ( Figure 2 ), this patient does not have detectable flow intrinsic to fibrosis at the level of the retinal pigment epithelial–Bruch membrane complex. En face segmentation of the fibrotic lesion (Upper right) shows that its flow signal is morphologically coupled to the retinal circulation, confirming that it is indeed a projection artifact.

Subretinal Hyperreflective Exudation and Subretinal Hemorrhage

Subretinal hyperreflective exudate was identified in 10 eyes of 9 patients and was associated with type 1 neovascularization (4 eyes) and with type 2 neovascularization (Eye #2, described above, Figure 2 ). Combined evaluation of structural and OCT angiographic data enabled exudation to be distinguished from type 2 neovascular tissue within a compound SHRM focus containing both lesion types.

In Eye #2 subretinal hyperreflective exudation was located within the foveal avascular zone and retinal projections were therefore ungradable. Where gradable, the strength of projection artifacts related to exudation was variable ( Table 2 ). Figure 5 summarizes the findings in the left eye of an 86-year-old patient with type 1 neovascular AMD and subretinal hyperreflective exudation (Eye #9). In this eye OCTA showed strong retina-SHRM projection and weak retina-RPE projection.

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