Swept Source Optical Coherence Tomography Angiography: Characteristic Findings in Type 3 Macular Neovascularization.

We report a typical illustration of Swept source OCT-Angiography (SS-OCT-A) findings in type 3 macular neovascularization(MNV) or retinal angiomatous proliferation (RAP). This is a case of a 70-year-old Caucasian male patient presenting with an exudative type 3 neovascular age-related macular degeneration. En face SS-OCT-A could non-invasively detect a tiny perifoveal circular "clew-like" high-flow neovascular lesion, visible in the deep capillary plexus, the outer retina and communicating with the choriocapillaris, with a perilesional dark halo and associated to no-flow macular cysts in the deep capillary plexus slab. En face SS-OCT-A could also highlight the presence of a telangiectatic capillary dilation in the superficial capillary plexus appearing to be at the origin of the retinal neovascularization. Cross-sectional SS-OCT-A showed an intra-retinal vertical high vascular flow within the hyper-reflective neovascular lesion, with a typical hyperreflective "kissing sign" and associated to subretinal and intraretinal fluid. In conclusion, en face OCT-A is useful tool to diagnose type 3 MNV or RAP non-invasively and associated cross-sectional OCT-A scan is very helpful highlighting the linear vascular high-flow within the retinal neovascularization.

INTRODUCTION

Type 3 macular neovascularization (MNV), also called retinal angiomatous proliferation (RAP), is a subtype of neovascular age-related macular degeneration (AMD) that is characterized by retinal-retinal or retinal-choroidal anastomosis (1) infiltrate the neurosensory retina, and communicate with the retinal circulation in what has been referred to as a retinal-choroidal anastomosis (RCA.

Optical coherence tomography angiography (OCT-A) is a relatively new imaging technique allowing non-invasive high-resolution visualization of retinal and choroidal vasculature. It showed great interest detecting noninvasively choroidal neovascularization, including type 3 MNV ((2 ,3) )also known as retinal angiomatous proliferation, have been well described clinically, as well as with fluorescein angiography (FA.Our aim is to report a typical illustration of Swept source OCT-A (SS-OCT-A) findings of type 3 MNV in a patient with exudative neovascular AMD .

CASE PRESENTATION

A 7O-year-old Caucasian male patient presenting to ophthalmology emergency unit complaining about blurred vision and metamorphopsia in his left eye. Best-corrected visual acuity was 0.3 in his left eye.

En face SS-OCT-A (DRI OCT Triton, Topcon, Japan)could non-invasively detect a tiny perifoveal circular "clew-like" high-flow neovascular lesion, visible in the deep capillary plexus (DCP), the outer retina (OR) and communicating with the choriocapillaris (CC) with a perilesional dark halo and associated to no-flow macular cysts in the DCP. En face SS-OCT-A could also highlight the presence of a telangiectatic capillary dilation in the superficial capillary plexus (SCP) appearing to be at the origin of the retinal neovascularization. The lesion size was 0.07 mm 2 . Cross-sectional SS-OCT-A showeda distinctive vertical intra-retinal high vascular flow within the hyper-reflective neovascular lesion, with a typical hyperreflective "kissing sign" and associated to subretinal and intraretinal fluid ( figure 1 ) ).

Figure 1 : Swept Source OCT-A of type 3 macular neovascularization

En face OCT-A: Telangiectatic capillary dilation in superficial capillary plexus (blue circle).Small circular “clew-like” high-flow vascular lesion in deep capillary plexus, outer retinaand choriocapillaris slabs (yellow arrows) + perilesional dark halo (red arrowhead).No-flow macular cysts in deep capillary plexus (green arrowheads).

Cross-sectional OCTA: “Kissing sign” with vertical high-flow within the hyper-reflective lesion (orange arrow). Subretinal and intraretinal fluid

Patient was treated with 3 monthly intravitreal injections of anti-vascular endothelial growth factor (Bevacizumab) and then followed and treated on a "Treat & Extend" regimen.

DISCUSSION

We reported a case of exudative type 3 MNV secondary to AMD. SS-OCT-A could easily and non-invasively detect the tiny neovascular lesion with precise high definition images, without using the gold standard invasive fluorescein angiography and avoiding any risk of anaphylactia.

Dansingani et al. (2) also known as retinal angiomatous proliferation, have been well described clinically, as well as with fluorescein angiography (FA first described in 2015 the interest of OCT-A detecting Type 3 MNV (RAP) in 2 patients with neovascular AMD.

Kuehlewein et al. (4) studied 29 eyeswith active type 3 MNV using spectral domain OCT-A and found a 34% sensitivitydetectingthis neovascular lesion. However, Ahmed et al .(3) found a 81.8% sensitivity detecting type 3 MNV, using swept source OCT-A with a great interest for this particular technology.

Our case showed a typical illustration of OCT-A findings in type 3 MNV. En face SS-OCT-A could detect a highglow vascular “clew-like” vascular lesion at the level of DCP and OR and communicating with the CC. Associated cross-sectional OCT-A scan showed a linear vertical flow within the hyper-reflective neovascular lesion and a typical hyperreflective “kissing sign” (5).

In Dansingani et al. study (2) also known as retinal angiomatous proliferation, have been well described clinically, as well as with fluorescein angiography (FA, a careful and precise manual segmentation could highlight a complex of high-flow dilated capillaries in the DCP, not detectable on classical dye-using angiography, suggesting the potential origin of the neovascular lesion.Kuehlewein et al. (4) detected a connection between the DCP and small intraretinal neovascular complexes using OCT-A. Telangiectasia adjacent to type 3 MNV was recently described as one of the early features of RAP (6) .

In our case, en face SS-OCT-A automated segmentation could also highlight the presence of a telangiectatic capillary dilation in the SCP appearing to be at the origin of the retinal neovascularization and the supporting the hypothesis of the retinal origin of a category of type 3 MNV.

In conclusion, en face OCT-A is useful tool to diagnose type 3 MNV orRAP non-invasively. In our cases, it could identify tiny intraretinal neovascular complex in a case RAP secondary to AMD. Cross-sectional OCT-A was very helpful, highlighting the linear vascular high-flow within the retinal neovascularization.

This case was presented as a poster at “MACULART” meeting 2019 in Paris. Its abstract has been posted online on 2019.maculart-meeting.com.