Polypoidal choroidal vasculopathy (aneurysmal Type 1 choroidal neovascularisation)
Chapter 4.6 of the book AMD: an overview of clinical forms, by Mayer Srour, David Sayag. Text intended for healthcare professionals.
Type 1 neovascularisation
PART 6: Polypoidal choroidal vasculopathy (aneurysmal Type 1 choroidal neovascularisation)
(aneurysmal Type 1 choroidal neovascularisation)
Part 6: Polypoidal choroidal vasculopathy
Polypoidal choroidal vasculopathy (PCV) was first described by Yannuzzi in 19821. It is an abnormal, branching vascular network in the inner choroid, associated with aneurysmal vascular dilatations, which can cause serous detachment of the retinal pigment epithelium (RPE) and sometimes a true haemorrhagic picture. PCV is more prevalent in Asian populations than in Caucasian populations. It is usually discovered at an earlier age than AMD.
PCV is most often idiopathic, but may also be secondary to exudative AMD, a myopic staphyloma, CSCR/DRE (central serous chorioretinopathy/diffuse retinal epitheliopathy), or a naevus’. More recently, Freund has included PCV within the pachychoroid spectrum (Figure
and renamed it « aneurysmal Type 1 neovascularisation »*.
NON-NEOVASCULAR PACHYCHOROID NEOVASCULAR PACHYCHOROID
Pachychoroid Peripapillary CRSC acute/C Pachychoroid Polypoidal vasculopathy Pigment Pachychoroid neovasculopathy | (PCV) Epitheliopathy SD (PPS)
(PPE)
AutoFluo Localised RPE alterations Localised RPE alterations +/- Gravitational tract Non-specific Non-specific
Type 1 CNV
Absence of flow BVN +/- Polyps
C: chronic. RPE alterations: alterations of the retinal pigment epithelium. Pm: Papillomacular. SRD: Serous retinal detachment. CNV: Choroidal neovascularisation. A: Angio. PED: Pigment epithelial detachment. V: Vascularised. ICG: indocyanine green angiography. BVN: Branching Vascular Network.
Diagnosis
Fundus examination
On fundus examination, PCV may be suspected when there is a PED with lipid exudates, often associated with subretinal haemorrhage. Red-orange, spherical lesions may also be seen beneath the RPE, more or less prominent, of varying size, single or multiple (Figure 2).
Drusen, RPE alterations and areas of geographic atrophy are absent or rare. PCV may be located retrofoveolar, juxtafoveolar, extrafoveolar, peripapillary and even peripheral, and its location differs between populations. In Caucasians, lesions are often extrafoveolar with a strong peripapillary tropism (23 to 68%). In Asian populations, the location of polyps is variable, with central retrofoveolar involvement in nearly 30% of
Type 1 choroidal neovascularisation
some Chinese populations. Less commonly, polypoidal dilatations may be located in the peripheral retina and fall within the scope of haemorrhagic exudative chorioretinopathies. Patients are often asymptomatic, and the lesions may be discovered incidentally. The course is often spontaneously favourable. In the case of major haemorrhage, the differential diagnosis with a tumour may arise.
A pigment epithelial detachment (PED) is visible (green circle), often associated with exudates (yellow arrow) and subretinal haemorrhages (red arrow).
Fluorescein angiography (FA) and indocyanine green angiography (ICG)
Fluorescein angiography is not very specific for PCV. It shows progressive staining of the aneurysmal dilatations, with little leakage in the late phase, and hyperfluorescence of the branching vascular network (BVN), very often associated, which is difficult to distinguish from the polyps (Figure 3). Polypoidal lesions are often masked by haemorrhages and blend into the hyperfluorescence of the PEDs.
ICG is the key examination for diagnosing PCV: it shows the polyps as rounded hyperfluorescent lesions from the early phases, which may persist in the late phase or show a wash-out phenomenon (Figure 4). The BVN is visible from the early phases, with polyps within it or at its edge, forming a late « hyperfluorescent lesion ». Choroidal hyperpermeability is also seen on ICG. ICG is an essential examination in the follow-up of PCV, as it shows the disappearance or attenuation of polyp hyperfluorescence after treatment. Pulsatile filling of the polyps may sometimes be seen and would be a risk factor for rupture and haemorrhage.
Progressive hyperfluorescence of the aneurysmal dilatations, with little leakage in the late phase, and hyperfluorescence of the branching vascular network that is difficult to distinguish from the polyps.
The polyps appear as rounded hyperfluorescent lesions (red arrows) from the early phases, which may persist in the late phases or show a wash-out phenomenon (red circle). The polyps are accompanied by the BVN (green arrow), which is visible from the early phases, with polyps within it or at its edge, forming a late « hyperfluorescent lesion ».
Type 1 choroidal neovascularisation
SD-OCT
The diagnosis of PCV can be strongly suspected on the basis of OCT. Polyps appear as dome-shaped elevations of the RPE containing one or more hyper-reflective rings with a hyporeflective centre. The BVN produces a flat, irregular elevation of the RPE (double layer sign) corresponding to two highly reflective layers (the RPE layer and a layer beneath the RPE). In the case of exudation, serous retinal detachments, intraretinal cystoid spaces or retinal thickening may be seen. Swept-source or EDI imaging usually shows a pachychoroid (>300 µm) associated with « pachyvessels »* (Figure 5).
The polyps appear as a steep-sloped, or « ogival », PED, sometimes adjacent to a serous PED. The « double layer sign » is present, together with a thick choroid.
OCT-A
OCT-A remains disappointing for the time being in visualising polyps. By contrast, the BVN, which is characterised by linear blood flow, is well detected by OCT-A. Polypoidal lesions appear in most cases as round hypodense structures without flow or as round hyperdense structures (between 17% and 45% of cases depending on the series 4) with flow, sometimes surrounded by a hypodense halo. This absence of signal within the polyp does not mean that there is no blood flow, but rather that the characteristics of the blood flow do not meet the detection criteria of OCT-A (Figures 6 and 7). This lack of detection may be explained by signal attenuation due to the RPE, or because the flow characteristics are undetectable (flow too slow, flow circulating only at the periphery of the polyp, or hyalinisation of the polyp with obstruction of the lumen). Consequently, with current technology, OCT-A cannot replace ICG in the assessment and detection of PCV’.
OCT-A at the level of the choriocapillaris shows the abnormal choroidal network as a hyperdense lesion with flow (green arrow). The polypoidal lesion appears as a round hypodense structure without flow (red arrow) and the neovessel as a hyperdense structure with flow (yellow arrow).
Some authors have proposed classifying PCV into different subtypes>® according to ICG and OCT appearances. A distinction is made between Type 1 PCV, or « polypoidal neovascularisation », in which there is a draining network (the BVN) and a feeder vessel, the choroid is thinner, lesions are large and the response to anti-VEGF is favourable (Figure 7). On the other hand, there is Type 2 PCV, or « idiopathic PCV », with no or only a discreet BVN, a small lesion and a thicker choroid (Figure 8). Recently, an American team proposed a new name for PCV: aneurysmal Type 1 choroidal neovascularisation°. However, there is no consensus on these subclassifications and names.
Top left and top right: fluorescein angiography and ICG images.
Middle left and right, and bottom: OCT-A with flow mapping (segmentation passing through the polyps and the BVN). The polypoidal lesion appears as a round hyperdense structure with flow (red arrow) and the BVN appears as a hyperdense lesion with flow (green arrow).
Part 6: Polypoidal choroidal vasculopathy
Colour fundus photograph
Autofluorescence _Fluorescein angiography ICG angiography
SD-OCT
Colour fundus photograph (A) showing a haemorrhagic serous detachment between the optic disc and the macula. Autofluorescence image (B) showing hypo-autofluorescence in the areas of serous retinal detachment (SRD). Fluorescein angiography (C) showing late-phase leakage from the polypoidal detachment. ICG angiography (D) showing late hypercyanescence of the polyp. SD-OCT (E) showing a hyper-reflective polypoidal elevation, hyper-reflective white dots and a macular SRD.
Conclusion
For the diagnosis of PCV, ICG remains the gold standard and can be useful for follow-up. The OCT appearance is highly suggestive of PCV, and the current resolution of OCT-A is not sufficient to replace ICG in PCV. Finally, the diagnosis of AMD should be reassessed with ICG if the therapeutic response is insufficient, in order to detect the presence of PCV. B-scan OCT, en face OCT and OCT-A complement the angiographic work-up to distinguish the BVN from polypoidal lesions and to assess neovascular activity by showing the extent of intra- and subretinal exudation.
References
- 1. Yannuzzi LA. Idiopathic polypoïdal choroïdal vasculopathy. Macula Society Meeting 1982 ; Miami, Florida, USA. 2. Gallego-Pinazo R, Dolz-Marco R, Gémez-Ulla F et al. Pachychoroïd Diseases of the Macula. Med Hypothesis Discov Innov Ophthalmol. 2014;3(4) :111-5. 3. Dansingani KK, Gal-Or O, Sadda SR et al. Understanding aneurysmal Type 1 neovascularization (polypoïdal choroïdal vasculopathy) : a lesson in the taxonomy of ’expanded spectra’ - a review. Clin Exp Ophthalmol. 2018;46(2) :189-200. 4. Srour M, Querques G, Semoun O, et al. Optical coherence tomography angiography characteristics of polypoïdal choroïdal vasculopathy. Br J Ophthalmol. 2016;100(11) :1489-1493 5. Kawamura A, Yuzawa M, Mori R et al. Indocyanine green angiographic and optical coherence tomographic findings support classification of polypoïdal choroïdal vasculopathy into two types. Acta Ophthalmol. 2013;91 :e474-e481. 6. Tanaka K, Nakayama T, Mori R et al. Associations of complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) genotypes with subtypes of polypoïdal choroïdal vasculopathy. Invest Ophthalmol Vis Sci. 2011;52:7441-7444.