Ophthalmic Surgery, Lasers and Imaging Retina

Instruments/Devices/Technology 

Anatomic Localization of Type 1 and Type 2 Macular Neovascularization Using Swept-Source OCT Angiography

Elie H. Motulsky, MD, PhD; Fang Zheng, MD; Yingying Shi, MD; Giovanni Gregori, PhD; Philip J. Rosenfeld, MD, PhD

Abstract

BACKGROUND AND OBJECTIVE:

Swept-source optical coherence tomography angiography (SS-OCTA) and different boundary-specific segmentation strategies were used to distinguish type 1 macular neovascularization (MNV) from type 2 MNV in eyes with exudative age-related macular degeneration (AMD).

PATIENTS AND METHODS:

Eyes with exudative AMD were enrolled in a prospective study. Segmentation strategies included a slab from the outer retina (OR) to the choriocapillaris (CC) for the entire MNV, a slab from the retinal pigment epithelium (RPE) to the CC for the type 1 MNV, and a slab from the OR to the RPE for the type 2 MNV.

RESULTS:

In 13 eyes, SS-OCTA B-scans and en face images using different segmentation strategies were able to identify type 1 and type 2 components of the MNV.

CONCLUSION:

In eyes with exudative AMD, SS-OCTA imaging and commercially available boundary-specific segmentation strategies were used to distinguish between type 1 and type 2 MNV.

[Ophthalmic Surg Lasers Imaging Retina. 2018;49:878–886.]

Abstract

BACKGROUND AND OBJECTIVE:

Swept-source optical coherence tomography angiography (SS-OCTA) and different boundary-specific segmentation strategies were used to distinguish type 1 macular neovascularization (MNV) from type 2 MNV in eyes with exudative age-related macular degeneration (AMD).

PATIENTS AND METHODS:

Eyes with exudative AMD were enrolled in a prospective study. Segmentation strategies included a slab from the outer retina (OR) to the choriocapillaris (CC) for the entire MNV, a slab from the retinal pigment epithelium (RPE) to the CC for the type 1 MNV, and a slab from the OR to the RPE for the type 2 MNV.

RESULTS:

In 13 eyes, SS-OCTA B-scans and en face images using different segmentation strategies were able to identify type 1 and type 2 components of the MNV.

CONCLUSION:

In eyes with exudative AMD, SS-OCTA imaging and commercially available boundary-specific segmentation strategies were used to distinguish between type 1 and type 2 MNV.

[Ophthalmic Surg Lasers Imaging Retina. 2018;49:878–886.]

Introduction

In exudative age-related macular degeneration (AMD), macular neovascularization (MNV) has been classified into type 1, type 2, and type 3 neovascularization based upon its anatomic location in the macula using dye-based angiography and optical coherence tomography imaging.1,2 Type 1 MNV, previously referred to as occult neovascularization in dye-based angiography, resides between Bruch's membrane (BM) and the retinal pigment epithelium (RPE). Type 2 MNV, previously known as classic neovascularization, is found between the RPE and the neurosensory retina. With the development of optical coherence tomography angiography (OCTA), it is now possible to identify MNV based on both its anatomic location on cross-sectional B-scans and its flow characteristics.3,4 Although spectral-domain OCTA (SD-OCTA) can image both type 1 and type 2 MNV, several studies have shown that swept-source OCTA (SS-OCTA) is better at identifying the type 1 component of MNV, which is located under the RPE.5,6 This is primarily due to the swept-source OCT technology and its use of a longer laser wavelength of 1,050 nm, which has less sensitivity roll-off and better penetration through the RPE. As a result, SS-OCTA imaging provides better visualization of the sub-RPE neovascularization.5,6 Often, SS-OCTA preset segmentation strategies can demonstrate whether a neovascular lesion is present or absent, but even then, the clinician should interact with the instrument and move the boundaries to optimize visualization of the neovascularization.7 However, given the different characteristics of type 1 and type 2 neovascular lesions, it is possible to use boundary-specific slabs that follow the appropriate anatomical boundaries to obtain en face images that can visualize the two components of a mixed neovascular lesion. This paper not only explores the instrument's capability in generating these boundary-specific slabs, but also explains to the clinician the slab segmentation strategy to better visualize the entire MNV, as well as the separate type 1 and type 2 components of the lesion.

Patients and Methods

Patients with exudative AMD were enrolled in a prospective SS-OCTA imaging study at the Bascom Palmer Eye Institute. The institutional review board of the University of Miami Miller School of Medicine approved the study, and patients signed an informed consent in order to participate. The study was performed in accordance with the tenets of the Declaration of Helsinki and was compliant with the Health Insurance Portability and Accountability Act of 1996.

SS-OCTA imaging was performed using the PLEX Elite 9000 instrument (Carl Zeiss Meditec, Dublin, CA), with a central wavelength of 1,050 nm, a scan rate of 100,000 A-scans per second, and the FastTrac motion correction system. The 3 mm × 3 mm and 6 mm × 6 mm scan patterns were used for visualizing MNV. The 3 mm × 3 mm scan pattern consists of 300 A-scans in each horizontal B-scan and 300 different B-scans, where B-scans are repeated four times at every given location. The 6 mm × 6 mm scan pattern consists of 500 A-scans in each horizontal B-scan and 500 different B-scans, where B-scans are repeated twice at every given location.

Three different boundary slabs were used to visualize the entire MNV and then the type 1 and type 2 components separately. The entire MNV was visualized using a slab extending from the outer retina (OR) to the choriocapillaris (CC), or more precisely from the outer plexiform layer (OPL) to 8 µm beneath BM. This was previously referred to as the ORCC slab.7 The type 2 component of the MNV was visualized using a slab extending from the OR to the RPE. The type 1 component was identified by using a slab extending from the RPE to the CC boundary. Retinal projection artifacts were removed using a previously published algorithm that is now included with the instrument.8 Although preset boundaries were used as the initial step in visualizing the MNV and its components, optimal visualization of the neovascular lesion required subtle adjustments to the thickness and position of the boundaries, image brightness, and image contrast. All B-scan and en face flow and structure images were generated directly from the SS-OCTA instrument.

Results

Thirteen eyes from 13 patients with exudative AMD and MNVs containing both type 1 and 2 components identified on cross-sectional OCT B-scans were imaged and visualized using the aforementioned strategy. The ORCC slab identified the entire MNV, whereas the RPE to CC slab identified the type 1 component, and the OR to RPE slab identified the type 2 component. In this report, we show five representative cases in Figures 1 through 5. In these figures, the first row shows the different en face flow images, the second row shows the en face structural image from each slab, the third row shows B-scans with superimposed segmentation lines and color-coded flow, and the fourth row shows the same B-scans without any segmentation or flow overlays. The first column shows the type 1 component using the RPE to CC slab, the second column shows the type 2 component using the OR to RPE slab, and the third column shows the entire MNV using the ORCC slab.

Case 1: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a left eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Figure 1.

Case 1: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a left eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Case 2: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a left eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of type 1 neovascular component. The bright blue solid line indicates the location of the B-scan below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and boundaries corresponding to the en face images in A and B. The red color represents flow above the RPE and the green color represents flow below the RPE. The segmentation boundaries represented by a dotted yellow line with the upper boundary following the retinal pigment epithelium (RPE) and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation lines. (H) Horizontal structural B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation lines corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer and the lower boundary following BM. (L) Horizontal structural B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Figure 2.

Case 2: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a left eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of type 1 neovascular component. The bright blue solid line indicates the location of the B-scan below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and boundaries corresponding to the en face images in A and B. The red color represents flow above the RPE and the green color represents flow below the RPE. The segmentation boundaries represented by a dotted yellow line with the upper boundary following the retinal pigment epithelium (RPE) and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation lines. (H) Horizontal structural B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation lines corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer and the lower boundary following BM. (L) Horizontal structural B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Case 3: 6 mm × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the RPE and the green color represents flow below the retinal pigment epithelium (RPE). Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing a RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Figure 3.

Case 3: 6 mm × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the RPE and the green color represents flow below the retinal pigment epithelium (RPE). Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing a RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Case 4: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing a RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Figure 4.

Case 4: 3 mm × 3 mm swept-source optical coherence tomography angiography (SS-OCTA) scan of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing a RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Case 5: 6 mm × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) imaging of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Figure 5.

Case 5: 6 mm × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) imaging of a right eye with macular neovascularization (MNV). (A) En face SS-OCTA flow image of the type 1 neovascular component. The bright blue solid line indicates the location of the B-scans below. (B) En face structure image from the same slab used in A. (C) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in A and B. The red color represents flow above the retinal pigment epithelium (RPE) and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the RPE and the lower boundary following the Bruch's membrane (BM). (D) Horizontal B-scan without flow or segmentation lines showing RPE elevation at the location of type 1 MNV. (E) En face SS-OCTA flow image of the type 2 neovascular component. The bright blue solid line indicates the location of the B-scans below. (F) En face structure image from the same slab used in E. (G) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in E and F. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the outer plexiform layer (OPL) and the lower boundary following the RPE. (H) Horizontal B-scan without flow or segmentation lines showing intraretinal fluid and subretinal hyperreflective material (SRHM) corresponding to type 2 neovascular component. (I) En face SS-OCTA flow image of the entire MNV. The bright blue solid line indicates the location of the B-scans below. (J) En face structure image from the same slab used in I. (K) Horizontal B-scan with flow and segmentation boundaries corresponding to the en face images in I and K. The red color represents flow above the RPE and the green color represents flow below the RPE. Segmentation boundaries are depicted by dotted yellow line with the upper boundary following the OPL and the lower boundary following BM. (L) Horizontal B-scan without flow or segmentation lines showing both RPE elevation at the location of type 1 MNV and SRHM above RPE.

Case 1

An 86-year-old man diagnosed with dry AMD in the right eye and exudative AMD in the left eye presented with decreasing vision in the left eye. Best-corrected visual acuity (BCVA) was 20/40 in the right eye and 20/100 in the left eye. SS-OCTA imaging was performed to visualize the MNV (Figure 1). A slab with an upper boundary just under the RPE and a lower boundary located just under BM shows the type 1 component (Figures 1A–1D). On the SSOCTA instrument, this slab is obtained by using the RPE to RPE-fit segmentation boundaries. The en face flow image (Figure 1A) shows the flow signature of the type 1 component. In the cross-sectional B-scan images, the superimposed yellow doted lines indicate the segmentation boundaries that correspond to the en face image (Figure 1C; in these images, red corresponds to flow above the RPE and green corresponds to flow under the RPE). Of note, the type 1 component of the MNV is always associated with an elevation of the RPE above BM referred as double layer sign (Figure 1D). Using an upper boundary in the OR and a lower boundary following the top of the RPE, the type 2 component can be visualized (Figures 1E–1H). On the SS-OCTA instrument, this slab is obtained by using the OPL to RPE segmentation boundaries. The lower boundary following the RPE has been adjusted to rest just above the RPE. On the B-scan (Figures 1G and 1H), the type 2 component is represented by the red flow signature above the RPE. The entire MNV was identified using the ORCC slab, which extends from the OR to the CC (Figures 1I-1L). On the B-scan, the red color within the segmentation lines corresponds to the type 2 component, and the green color corresponds to the type 1 component (Figure 1K).

Case 2

A 66-year-old man diagnosed with exudative AMD in the right eye and dry AMD in the left eye presented with decreasing vision in the left eye. BCVA was 20/80 in the right eye and 20/20–2 in the left eye. The type 1 component of the MNV is visualized in Figures 2A–2D, the type 2 component of the MNV is shown in Figures 2E–2H, and the entire neovascular lesion is shown in Figures 2I–2L.

Case 3

A 70-year-old woman diagnosed previously with dry AMD in both eyes presented with decreasing vision in her right eye. BCVA was 20/200 in the right eye and 20/20 in the left eye. The type 1 component of the MNV is visualized in Figures 3A–3D, the type 2 component of the MNV is shown in Figures 3E–3H, and the entire neovascular lesion is shown in Figures 3I–3L.

Case 4

An 85-year-old man diagnosed with exudative AMD in both eyes presented with decreasing vision in his right eye. BCVA was 20/25 in the right eye and 20/200 in the left eye. The type 1 component of the MNV is visualized in Figures 4A–4D, the type 2 component of the MNV is shown in Figures 4E–4H, and the entire neovascular lesion is shown in Figures 4I–4L.

Case 5

An 89-year-old man diagnosed with exudative AMD in both eyes presented with a decreasing vision in his right eye. BCVA was 20/20 in the right eye and 2/200 in the left eye. The type 1 component of the MNV is visualized in Figures 5A–5D, the type 2 component of the MNV is shown in Figures 5E–5H, and the entire neovascular lesion is shown in Figures 5I–5L.

Discussion

SS-OCTA imaging can identify the neovascular lesions. By using different slabs, we construct en face flow images corresponding to regions above or below the RPE that separate the type 1 and type 2 components of the lesion. Historically, the ability to unambiguously visualize the MNV and distinguish between the type 1 and type 2 components has depended on the use of fluorescein angiography (FA) and indocyanine green angiography (ICGA). Undoubtedly, SS-OCTA imaging is faster, safer, and more comfortable for the patient than dye-based angiography, and in our experience, this newest SS-OCTA technology appears to be as sensitive as dye-based angiography in detecting the neovascular lesions, especially the type 1 component.

A shortcoming of this report is the lack of dye-based angiographic imaging of these cases. However, in our clinical practice, we have found that FA and ICGA are no longer necessary for patient management when using SS-OCTA imaging. Although some might argue that dye-based angiographic studies are needed to validate the sensitivity of SS-OCTA, we feel such a study is unnecessary and ethically unjustified given the risks and discomfort of dye-based angiography. The ability of SS-OCTA to identify type 1 MNV even in the absence of exudation has already been shown by our group.9,10 To justify such a comparison study, there would need to be a clear benefit from the use of dye-based angiography and the belief that distinguishing type 1 and type 2 MNV alters patient management. We argue that if SS-OCTA imaging had been available before dye-based angiography, it would be unlikely that dye-based angiography would have ever been developed to image MNV in AMD. Moreover, although the ability to distinguish between type 1 and type 2 MNV is of historical and academic interest given the difference in their leakage properties and the prognosis of these lesions if left untreated, given the current use of vascular endothelial growth factor inhibitors to treat all exudative neovascular lesions in AMD, it is unlikely that there is any clinical significance in identifying these different lesion components. Nevertheless, further SS-OCTA studies following these mixed neovascular lesions might identify relevant features that someday might predict treatment response or long-term vision.

In this report, we describe a comprehensive strategy using three different slabs to assist clinicians in identifying MNV and its type 1 and type 2 components. Although type 3 neovascularization can be imaged using both en face and B-scan OCTA imaging, this feature of MNV has been described elsewhere and is beyond the scope of this report.11 It should be stressed that, at this time, it is important for clinicians to interact with the software since small adjustments are often needed to produce optimal images of the MNV. It is reasonable to assume that these imaging limitations will be overcome by future developments in the software that will allow a fully automated analysis of MNV and its components.

References

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Authors

From the Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami (EHM, FZ, YS, GG, PJR); and the Department of Ophthalmology, Tianjin Medical University General Hospital, Tianjin, China (FZ).

This study was supported by grants from Carl Zeiss Meditec (Dublin, CA); the Salah Foundation; an unrestricted grant from the Research to Prevent Blindness, New York, NY; and the National Eye Institute Center Core Grant (P30EY014801) to the Department of Ophthalmology, University of Miami Miller School of Medicine.

Drs. Gregori and Rosenfeld received research support from Carl Zeiss Meditec. Dr. Gregori and the University of Miami co-own a patent that is licensed to Carl Zeiss Meditec. Dr. Rosenfeld received additional research support from Genentech and Tyrogenex; is a consultant for Achillion Pharmaceuticals, Acucela, Boehringer-Ingelheim, Carl Zeiss Meditec, Cell Cure Neurosciences, Chengdu Kanghong Biotech, Ocunexus Therapeutics, Genentech, Healios K.K, Hemera Biosciences, F. Hoffmann-La Roche Ltd., Isarna Pharmaceuticals, Lin Bioscience, MacRegen Inc., NGM Biopharmaceuticals, Ocunexus, Ocudyne, Tyrogenex, and Unity Biotechnology; and has equity interest in Apellis, Digisight, and Ocudyne. The remaining authors report no relevant financial disclosures.

Address correspondence to Philip J. Rosenfeld, MD, PhD, Bascom Palmer Eye Institute, 900 NW 17th Street, Miami, FL 33136; email: prosenfeld@miami.edu.

Received: May 25, 2018
Accepted: October 02, 2018

10.3928/23258160-20181101-09

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