Abstract
The advent of new technologies offering the possibility of analyzing both quantitative and qualitatively choroidal tissue led to new diagnostic approaches to traditional and newly described entities. The purpose of the present chapter is to summarize the key findings on the multimodal imaging approach of pachychoroid pigment epitheliopathy and neovasculopathy.
Keywords
Choroid, Choroidal thickness, Pachychoroid, Haller layer dilation, Pachychoroid pigment epitheliopathy, Pachychoroid neovasculopathy
Pachychoroid
Concept
The term pachychoroid was first introduced by K. Bailey Freund and colleagues when describing a series of eyes showing retinal pigment epithelium (RPE) disturbances associated with an abnormally thick choroid but occurring in the absence of subretinal fluid. They termed these findings “pachychoroid pigment epitheliopathy” and suggested that it might be considered a forme fruste central serous chorioretiopathy. However, defining what should be considered pathologic increases in choroidal thickness is difficult since “normal” may depend on age, spherical equivalent and axial length, and even on the circadian rhythm. In addition, different systemic treatments and disorders, and local diseases can cause fluctuations in choroidal thickness. For these reasons, the term pachychoroid has evolved to encompass not only an abnormally thick choroid, but, more importantly, a focally or diffusely thickened Haller layer inducing secondary and variable compression on the overlying Sattler layer and choriocapillaris. The dilated Haller layer vessels have been termed “pachyvessels.”
Although there is a myriad of ocular diseases that are associated with increased choroidal thickness, the aim of the present chapter is to describe the main features of the newly described pachychoroid pigment epitheliopathy and pachychoroid neovasculopathy.
Pachychoroid Pigment Epitheliopathy
Definition
Pachychoroid pigment epitheliopathy is characterized by the presence of retinal pigment epithelial abnormalities associated with focal or diffuse increase of choroidal thickness and dilated Haller layer vessels (pachyvessels), without any evidence of ongoing or antecedent subretinal fluid.
Fundus Imaging Features
Fundus examination
The dilated fundus examination typically reveals a reddish appearance of the involved macular area with increased pigmentation and decreased tessellation. The overlying RPE changes may resemble the appearance of age-related maculopathy (ARM), inflammatory chorioretinopathies including punctate inner choroidopathy or acute pigment epithelitis, or even those seen in pattern dystrophies of the RPE.
Optical coherence tomography
The hallmark tomographic feature of pachychoroid pigment epitheliopathy is the presence of dilated Haller layer vessels (pachyvessels) that may be focal or diffuse in nature. These pachyvessels compress on the overlying Sattler and choriocapillaris layers. Coincident with these areas, the RPE shows different changes that may include
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Drusen-like hyperreflective deposits under the layer of the RPE, Fig. 10.1
Figure 10.1
Focal retinal pigment epithelium abnormalities (yellow arrows) with associated disruption of the outer retina, overlying areas of pachyvessels at the level of Haller choroidal layer (blue arrows).
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Small RPE protuberances,
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Focal disruption of the ellipsoid layer,
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Shallow irregular pigment epithelial detachments (PEDs), and
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Serous PED without any evidence of subretinal fluid ( Figs. 10.1–10.3 ).
Figure 10.2
Small retinal pigment epithelium protuberances (yellow arrows) with zonal disruption of the ellipsoids and interdigitation outer retinal layers (red lines), associated with underlying significant increase of choroidal thickness with Haller layer dilation (blue arrows).
Figure 10.3
Pigment epithelial detachment (yellow arrow) with no evidence of present or past subretinal fluid overlying an area of increased Haller choroidal layer thickness (blue arrow).
Fundus autofluorescence
Fundus autofluorescence images represent the aforementioned RPE changes as mottling or radiate hyper- and hypoautofluorescent changes. The typical appearance of gravitational serous retinal detachment due to subretinal fluid with mottling hyperautofluorescence should not be present in order to establish the diagnosis of pachychoroid pigment epitheliopathy ( Fig. 10.4 ).
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