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Central Serous Chorioretinopathy

Eduardo A. Novais, MD; Mark Lane, MBBS Honors; Nadia K. Waheed, MD, MPH; and Jay S. Duker, MD;

Central serous chorioretinopathy (CSCR) is a retinal disorder that is typically unilateral, and predominantly affects young or middle-aged male patients who are otherwise healthy. It is characterized by one or more serous retinal detachments, and is often associated with the concurrent presence of one or more retinal pigment epithelium (RPE) detachments.^1–4 It has been hypothesized that thickened, congested, hyperpermeable choroidal vessels have an increased hydrostatic pressure, which results in leaking fluid through a dysfunctional RPE.^5,6 Risk factors for CSCR include systemic arterial hypertension, pregnancy, emotional stress (type A personality), genotype, corticosteroids, and sympathomimetics use.^3,7–10

There are 2 main forms of CSCR: acute and chronic.^1,3,4,11 Patients with acute CSCR usually present with a sudden loss of central vision, disturbed color vision, central or paracentral scotoma, metamorphopsia, and/or micropsia^11,12 caused by the rapid accumulation of subretinal fluid (SRF) at the macula secondary to a focal leak in the RPE. It is usually self-limiting, with most cases resolving spontaneously within 3 months with little or no residual damage.^13–15 Chronic CSCR is defined as changes in visual acuity that last greater than 3 months with documented clinical features of CSCR on dye-based angiography, or the presence of SRF and RPE changes located at the macula on optical coherence tomography (OCT) scanning. Persistent SRF can result in widespread damage to the RPE layer, which can lead to irreversible photoreceptor damage and permanent visual loss.^14,16

Choroidal neovascularization (CNV) is an important vision-threatening complication of CSCR with an incidence ranging from 2% to 9%.^13,14,17 Patients with long-standing CSCR have a higher risk of developing secondary CNV, with a mean duration of time between diagnosis of CSCR and development of CNV of 139 months (range, 7 to 365 months).^14,18

The development of CNV in this condition warrants prompt treatment, making it important that this complication be diagnosed accurately. Clinical features suggestive of a CNV lesion in a patient with CSCR include subretinal and/or sub-RPE hemorrhage, sub-RPE, subretinal or intraretinal fluid, subretinal hyper-reflective material on OCT, and interruptions or breaks in the RPE on cross-sectional OCT B-scans.^18,19 Features that can be seen in both chronic CSCR with and without CNV include RPE detachments, SRF, intraretinal fluid, cystoid macular degeneration, retinal atrophy, and diffuse irregular hyper-fluorescence on fluorescein angiography (FA) or indocyanine green angiography (ICGA).^{6,13,18,20,21} Therefore there is a need for an imaging modality that provides an unequivocal diagnosis of CNV in patients with CSCR.

FA findings for acute CSCR are characterized by focal fluorescein leaks from the choroid through the RPE, leading to subretinal accumulation of dye. Two patterns of dye leakage can be identified on FA: “inkblot” or “smokestack” leak.22 The “inkblot” leakage has a more uniform dye spread and is present in 93% of cases. The “smokestack” leakage is associated with a pinpoint focal RPE leak that spreads laterally in an umbrella fashion. These are present in only 7% to 20% of patients suffering from CSCR. In both cases the hyper-fluorescence tends to expand over the time course of the FA.²³ Chronic CSCR can result in a multifocal and gravitational hyper-fluorescent “window defect” in areas of RPE atrophy. Capillary dropout and telangiectasias in the chronically detached retina can also be observed.²⁴

Indocyanine Green Angiography

In CSCR, the early phase of ICGA shows a localized hypo-fluorescence with a delay in arterial filling. The mid-phase demonstrates choroidal vascular hyperpermeability manifested by areas of hyper-fluorescence, followed by dispersion of the hyper-fluorescence and a distinctive silhouetting or negative staining of the larger choroidal vessels in the later phase.^6,25 These findings can be contrasted with those found in CNV lesions that are characterized by an early hyper-fluorescent leak that outlines the neovascular membrane, which continues to leak into the late ICGA phase.²⁶ In chronic CSCR, the area of damaged RPE may show persistent hyper-fluorescence.

FA and ICGA are considered the gold standard for imaging the retinal and choroidal vasculature.^27–29 These imaging modalities are dynamic and visualize dye transit over time, allowing direct visualization of large vessel filling and eventual leakage and/or pooling of dye. Small retinal vessels and feeder vessels, however, are often obscured by the subsequent hyper-fluorescence, especially in the late phase of dye transit. This may limit precise assessment of the CNV and its differentiation from chronic CSCR cases. FA and ICGA can help exclude the presence of CNV lesions by establishing the absence of hemorrhages and the CNV vascular network. In some cases, however, the neovascular membrane cannot be identified by dye-based angiography. A significant problem also associated with these modalities is that they are invasive and involve the use of intravenous contrast that can result in systemic side effects and rarely anaphylaxis.^30–32

OPTICAL COHERENCE TOMOGRAPHY

With increasing resolution, OCT has been used in the diagnosis and monitoring of CSCR progression. In active disease, OCT B-scans reveal SRF and an irregular neurosensory retinal detachment that is associated with thickened and elongated photoreceptors. These OCT findings may be correlated with visual acuity prognosis.^33,34 A double-layer sign is characterized by a rippled RPE profile, a hypo-reflective middle layer, and an intact or slightly thickened Bruch’s membrane. Enhanced depth imaging has provided increased insight into choroidal thickness. Several groups have indicated that the choroid is thicker in patients suffering from CSCR, in both the affected and the fellow eye compared with normal controls. This finding correlates well with the hypothesis that choroid vasculature may be hyperpermeable in these patients.^35–38

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FOR CENTRAL SEROUS CHORIORETINOPATHY

Optical coherence tomography angiography (OCTA) is a noninvasive depth-resolved imaging technology that allows for the appreciation of spatial relationship of fundus vessels, and enables detailed en face visualization of the superficial and deep retinal vasculature separately, without the risk of adverse effects associated with the intravenous administration of dyes.^39,40 Using this technology it is possible to view OCT angiograms alongside corresponding structural en face and OCT B-scans. This allows the correlation of clinical features of CSCR including SRF, RPE detachments, intraretinal cysts, and the increased central retinal thickness with microvascular features seen on OCTA (Figure 19-1).

An OCTA image is computed by comparing, on a pixel-by-pixel basis, repeated B-scans acquired at the same retinal location in rapid succession. The underpinning rationale of OCTA is that in static tissue the scatters will be stationary, meaning that the repeated B-scans will be identical. Inside vasculature, however, flowing erythrocytes cause a time-dependency in the backscattered OCT beam, which manifests as differences among the repeated B-scans.^39–41 Leaking fluid in CSCR patients is not visualized by OCTA for at least 2 reasons. First, because CSCR is a consequence of leaking fluid, not erythrocytes, and because this leaking fluid does not strongly backscatter the incident OCT beam, OCTA is not well suited for detecting fluid leakage. Second, the relatively low leakage flux in CSCR means that even if the fluid did appreciably backscatter the OCT beam, the flux would not be detectable with OCTA, which is typically sensitive to backscatters with speeds in the mm/s range (Figures 19-1G and 19-1H).

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