It was with great interest that we read the article by Cho et al.
1 in which the authors described the spectral-domain optical coherence tomography (SD-OCT) findings of acute retinal pigment epitheliitis as abnormal reflectivity in the RPE layer, with variable abnormalities in the ellipsoid and external limiting membrane (ELM). The authors were keenly astute in concluding that involvement of the ELM was associated with incomplete recovery of visual acuity, as this is consistent with our clinical experience in a variety of macular diseases, including central serous chorioretinopathy (CSC).
We were interested to find out the state of choroidal thickness and choroidal vessel caliber as seen on enhanced depth imaging (EDI-OCT) in these cases of acute retinal epitheliitis. Warrow et al.
2 recently described a clinical entity termed “pachychoroid (pachy-[prefix]:thick) pigment epitheliopathy” in which patients present with a variety of RPE abnormalities directly overlying localized areas of thickened choroid and/or dilated choroidal vessels. The constellation of findings seen in pachychoroid pigment epitheliopathy, including pigmentary changes, small pigment epithelial detachments, choroidal thickening, and choroidal hyperpermeability, likely represents a “forme fruste” of CSC, since none of the patients developed clinically evident subretinal fluid.
2 Pachychoroid pigment epitheliopathy may be found bilaterally or in the fellow eyes of patients with CSC.
2 Interestingly, the fundus findings of pachychoroid pigment epitheliopathy may include RPE stippling with hypopigmented haloes and the SD-OCT findings may include abnormalities in the RPE layer with variable involvement of the ellipsoid and ELM, all of which are similar to those described by the authors
1 in acute retinal pigment epitheliitis.
Cho et al.
1 reported that some of the cases with acute retinal pigment epitheliitis had areas of hyperfluorescence on indocyanine green (ICG) angiography. This could represent choroidal vascular hyperpermeability; hence, knowledge of the choroidal thickness and choroidal vessel caliber would be helpful to establish whether the pathophysiology in these cases involved a pachychoroid-driven process. Pachychoroid pigment epitheliopathy may not always demonstrate hyperpermeability on ICG angiography; however, its presence does support the diagnosis.
We also were interested to find out whether any of the patients with acute retinal pigment epitheliitis had predisposing risk factors for CSC, such as Type A behavior and previous use of corticosteroids. Again, patients with pachychoroid pigment epitheliopathy may not always exhibit these characteristics; however, their presence does support the diagnosis.
Acute retinal pigment epitheliitis was first described
3 before the advent of OCT. With new advances in choroidal imaging, we are able to characterize the choroidal vasculature underlying these RPE abnormalities, in an attempt to understand the true pathophysiology. Disturbances in the choroidal circulation have been postulated to produce RPE dysfunction and abnormalities,
4 although the mechanism of choroidal vessel dilation, which could either precede or follow circulation compromise, is still unknown. It is plausible for dilated choroidal vessels with visually prominent pulsations
5 to deliver mechanical insult to the overlying RPE. In fact, studies have shown that a single dilated choroidal vessel may be visible directly beneath RPE abnormalities,
2,6 and RPE atrophy has been documented to develop directly overlying a dilated choroidal vessel, explained by mechanical stretching of the RPE.
7
Although there are no treatment implications for distinguishing between pachychoroid pigment epitheliopathy and acute retinal pigment epitheliitis, it may be important in recognizing the underlying pathogenic mechanism of the disease. Since pachychoroid pigment epitheliopathy falls within a spectrum of pachychoroid-related diseases, patients may go on to develop CSC, pachychoroid neovasculopathy, and, ultimately, polypoidal choroidal vasculopathy.
2,8