Pachychoroid disease: review and update

Abstract

The pachychoroid disease spectrum is a phenotype characterized by alterations in choroidal vasculature which result in outer retinal and choriocapillaris damage and visual loss. The presence of pachyvessels is one of the key features of the pachychoroid phenotype. Recent imaging studies suggest that pachyvessels may form because of choroidal venous congestion in one or more quadrants. The formation of intervortex anastomosis may function as a compensatory mechanism to dissipate the increased venous pressure, while outflow obstruction has been hypothesized to occur at the site of the vortex vein exiting the sclera. This review aims to summarize recent imaging findings and discuss evolution in the understanding of pathogenesis of the pachychoroid disease spectrum. We have summarized notable treatment trials in central serous chorioretinopathy and polypoidal choroidal vasculopathy and included an update of the current diagnostic and management strategies of the entities that are part of the pachychoroid disease spectrum.

Fig. 1. Examples of imaging findings related to choroidal alterations in the pachychoroid disease spectrum.

Figure 1a shows the presence of pachyvessels which appear as prominent choroidal veins with large caliber crossing the horizontal watershed on indocyanine green angiography (ICGA). Areas of reduced filling are indicated by white arrows (a). This eye is also imaged with OCT (b) and en face 12 × 12 mm OCTA (c, d). Presence of subretinal fluid and pachyvessels within a thickened choroid can be observed in (b). c The pachyvessels can be observed with en face OCT using a choroidal slab and closely correspond to those seen on ICGA in (a). d Several areas of choriocapillaris flow impairment can be observed with en face OCTA using the choriocapillaris slab (white arrows). These areas correspond closely to the areas of reduced filling on ICGA in (a). e, f Ultra-widefield (UWF) ICGA can be used to evaluate the arrangement of vortex veins. The example in (e) shows a dilated and congested vortex vein in the inferotemporal quadrant. Anastomosis can be observed between the inferotemporal and superotemporal quadrants (white arrow). The example in (f) shows widespread dilated and congested vortex veins in all four quadrants. Multiple anastomosis can be observed around the optic disc.

Fig. 2

Proposed ‘Multi-hit theory’ in the pathogenesis and evolution of pachychoroid disease.

Fig. 3. Examples of the pachychoroid disease spectrum.

a–e A case of pachychoroid neovasculopathy (PNV) complicating central serous chorioretinopathy (CSC). a OCT at baseline and (b) OCT at follow-up demonstrated worsening of subretinal fluid over a shallow irregular retinal pigment epithelial elevation. Thickened choroid with pachyvessels can be observed at both visits. c OCTA at baseline detected the presence of vascular flow signal due to macular neovascularization. Fluorescein angiography (FA) was performed at baseline (d) and repeated one year later (e). Note the leakage pattern was different at the two visits: an occult leakage pattern in keeping with type 1 MNV was seen at baseline (d). In contrast, smoke-stack pattern was seen arising from a focal point in (e), suggesting CSC-related mechanism was likely the drive for subretinal fluid at this timepoint. f–i Another case of PNV with varying amount of intraretinal fluid (IRF) and subretinal fluid (SRF) at different visits. Severe atrophy of RPE and outer retinal layers including the external limiting membrane are observed. During follow-up, the amount of IRF and SRF fluctuates. It is postulated that the IRF originating from the choroid and/or macular neovascularization enters the neurosensory retina in areas with both RPE and outer retina (external limiting membrane) defects. In addition, choroidal congestion and exudative MNV may contribute to SRF in areas where the outer retina remains intact (g, h). The fluid in both compartments disappeared after a single injection of brolucizumab (i). Note also the reduction of choroidal thickness after treatment in (i) compared with (f, g), which may play a role in fluid resolution.