Differential flow signal strength of choroidal neovascular membrane on optical coherence tomography angiography in central serous chorioretinopathy

Abstract

A 62-year-old woman with no associated risk factors was diagnosed as a case of type 1 choroidal neovascularisation (CNV) associated with central serous chorioretinopathy in both the eyes based on clinical features and multimodal imaging. She was primarily treated with low fluence photodynamic therapy and responded well to the treatment. There was persistence of neovascular network seen on optical coherence tomography angiography (OCTA) without any signs of activity on optical coherence tomography. However, after 5 years she developed recurrent CNV in the left eye with a new type 2 CNV as seen on OCTA which had a higher flow signal strength as compared with the previous type 1 CNV. Following two doses of intravitreal ziv-aflibercept, the new type 2 CNV network regressed as evident on OCTA along with improvement in best corrected visual acuity.

Background

Choroidal neovascularisation (CNV) is one of the major causes of vision loss in cases of long-standing central serous chorioretinopathy (CSCR).¹ Incidence of CNV as a sequelae of CSCR ranges from 2% to 9%.^1–3 Due to the overlap of certain clinical features like pigment epithelium detachment, intraretinal fluid and subretinal fluid (SRF), retinal pigment epithelium (RPE) atrophy, cystoid macular degeneration and diffuse hyperfluorescence on fluorescein, and indocyanine green angiography (ICG), it becomes a challenge to confirm or refute a diagnosis of CNV in CSCR. There has been a upsurge in the sensitivity and specificity in diagnosing CNV in CSCR with the advent of a non-invasive imaging modality like optical coherence tomography angiography (OCTA) with split spectrum amplitude decorrelation algorithm. This case highlights the use of OCTA in not only making the diagnosis of CNV, but also in identifying the different patterns of CNV based on the difference in the flow signal strength of the network on OCTA and their response to treatment.

Case presentation

A 62-year-old woman presented with metamorphopsia and diminished vision in both eyes for 4–5 months. Best corrected visual acuity (BCVA) in the right and left eye was 20/25 and 20/80, respectively. On examination, the anterior segment in both eyes was normal and intraocular pressure was 14 and 16 mm Hg in the right and left eye, respectively.

Fundus examination of both the eyes showed the presence of retinal pigment epithelium alterations at the macula. Spectral domain optical coherence tomography (SD-OCT) (figure 1A,B) showed SRF and pachychoroid suggestive of CSCR in both the eyes. ICG showed the presence of type 1 choroidal neovascular membrane (CNVM) (figure 1C,D) in both the eyes. Reduced fluence photodynamic therapy (PDT) was done in both the eyes and the patient was doing well thereafter, with improvement in BCVA to 20/25 and 20/40 in right and left eye, respectively. A quiescent CNV network on OCTA (figure 2B–D) was present without any signs of activity on swept-source optical coherence tomography (SS-OCT) (figure 2A–C).

Figure 1.

Spectral domain optical coherence tomography (figure 1A,B) showing ellipzoid zone disruption, subretinal fluid, double layer sign and pachychoroid neovasculopathy suggestive of central serous chorioretinopathy in both the eyes. Indocyanine green angiography showed the presence of type 1 choroidal neovascular membrane (figure 1C,D—solid circle) in both the eyes.

Figure 2.

After low fluence photodynamic phototherapy, optical coherence tomography angiography (figure 2B–D—dotted circle) showing quiescent choroidal neovascularisation network without any signs of activity (subretinal fluid/intraretinal fluid) on swept-source optical coherence tomography (figure 2A–C) in both the eyes.

However, at 5-year follow-up, her BCVA in the left eye reduced to 20/125 and clinically she had subretinal and intraretinal haemorrhages at the macula (figure 3A). SS-OCT at this visit showed recurrence with SRF and subretinal hypereflective material (SHRM) (figure 3C). OCTA showed persistence of old type 1 CNV along with a new type 2 CNV component (figure 3F) at the level of outer retinal layers. She thereafter received two doses (1.25 mg/0.05 mL) of intravitreal ziv-aflibercept (IVZ) in view of the recurrence of CNV in the left eye.

Figure 3.

At 5-year follow-up, left eye fundus and near-infrared photograph showing subretinal and intraretinal haemorrhages at the macula (figure 3A—dotted circle and figure 3B). The swept-source optical coherence tomography at this visit showing subretinal hypereflective material, subretinal fluid, double layer sign and pachychoroid neovasculopathy (figure 3C). Fundus fluorescein angiography (figure 3D—solid arrow) showing early hyperfluorescence along with stippled hyperfluorescence in the late phase. Indocyanine green angiography (figure 3E—solid arrow) showing a new neovascular network along with the old choroidal neovascularisation (CNV) network seen earlier in the mid phase. Optical coherence tomography angiography showing persistence of old type 1 CNV (dotted square) along with a new type 2 CNV component (solid arrow) which had a higher flow signal strength (figure 3F) as compared with the type 1 CNV at the level of outer retinal layers.

Investigations

At presentation, the horizontal scan on SD-OCT (figure 1A,B) showed ellipzoid zone (EZ) disruption, SRF, double layer sign (DLS), fibrovascular pigment epithelium detachment (FVPED), elongated photoreceptors and PNV suggestive of CSCR in both the eyes. ICG in mid phase showed the presence of hyperfluorescence and a well-defined neovascular network at the macula corresponding to FVPED on SD-OCT, suggestive of type 1 CNVM (figure 1C,D) in both the eyes.

After reduced PDT was done in both the eyes, horizontal and vertical scan on SS-OCT (figure 2A–C) showed resolution of SRF, disrupted EZ and outer retinal layers along with persistence of FVPED in both the eyes. SS-OCT angiography (OCTA) (figure 2B–D) showed persistence of neovascular network in the outer retinal layer slab without any signs of activity on SS-OCT.

At 5-year follow-up, her left eye fundus and near-infrared photos showed subretinal and intraretinal haemorrhages at the macula (figure 3A,B). Horizontal and vertical scans through macula on SS-OCT at this visit showed SHRM, recurrent SRF, DLS and PNV (figure 3C). Fundus fluorescein angiography (figure 3D) showed early hyperfluorescence along with stippled hyperfluorescence in the late phase. ICG (figure 3E) showed a new neovascular network along with the old CNV network seen earlier in the mid phase. OCTA showed persistence of the old regressed CNV network along with a new CNV component (type 2) which had a higher flow signal strength (figure 3F) as compared with the old type 1 CNV at the level of outer retinal layers.

Post antivascular endothelium growth factor (VEGF)injection, retinal haemorrhages (figure 4A,B) and SRF, along with SHRM on SS-OCT, had resolved (figure 4C). However, FVPED along with disruption of EZ and outer retinal layers was still evident on SS-OCT. OCTA showed regression of type 2 CNV (higher flow signal strength) component along with the persistence of old type 1 CNV (figure 4D).

Figure 4.

Post injection, fundus and near-infrared photograph of the left eye showing resolution of retinal haemorrhages (figure 4A,B). Swept-source optical coherence tomography showing resolution of subretinal fluid and subretinal hypereflective material with persistence of fibrovascular pigment epithelium detachment and disruption of ellipzoid zone (figure 4C). Optical coherence tomography angiography showed regression of type 2 choroidal neovascularisation (CNV) component along with the persistence of old type 1 CNV (figure 4D—dotted circle).

Differential diagnosis

In view of the clinical presentation and multimodal imaging findings, differential diagnoses of age-related macular degeneration (ARMD) associated with CNVM, PNV and idiopathic polypoidal choroidal neovasculopathy (IPCV) were considered. Absence of drusens, and corresponding focal or diffuse RPE atrophy, ruled out ARMD. There was no associated tall thumb-like pigment epithelium detachment on optical coherence tomography (OCT) or any associated polypoidal lesion on ICG suggestive of IPCV.

Treatment

The patient was diagnosed as having CNV associated with CSCR in both the eyes at the first visit based on multimodal imaging and was symptomatic with loss of vision and metamorphopsia. Reduced-fluence PDT⁴ was done considering the duration of symptoms and CNV associated with CSR, and also as there was no evident focal leak on fundus fluorescein angiography or indocyanine green angiography (FFA/ICG) amenable to focal laser therapy in both the eyes. Her response to PDT was favourable as was seen with the resolution of SRF on OCT. Thereafter, at 5-year follow-up she developed recurrent CNVM in the left eye which was treated with two doses of IVZ. BCVA, post injection, improved along with resolution of signs of activity on OCT and regressed network on OCTA.

Outcome and follow-up

After PDT, the patient was doing well until 5 years follow-up after which she developed recurrent CNVM in the left eye which resolved following two doses of antiVEGF. She is being followed up at regular intervals since then with a stable BCVA and no signs of activity at 8 months following antiVEGF injection.

Discussion

Association of type 1 CNV and CSCR is well known in the literature.⁵ Also, the sensitivity and specificity of OCTA in dignosing cases of CNV associated with CSCR is well established.^{6 7} In our case, OCTA helped demonstrate type 2 component over a pre-existing type 1 CNV due to the difference in the flow signal strength. In addition, OCTA also demonstrated the regression of type 2 CNV component after antiVEGF therapy and persistence of the type 1 component. Thus, OCTA can help identify different types of CNV and treatment response non-invasively.

Learning points.

• The role of multimodal imaging in eliciting choroidal neovascularisation (CNV) associated with central serous chorioretinopathy (CSCR).

• Use of optical coherence tomography angiography (OCTA) in diagnosing CNV in CSCR.

• Differentiation of the different patterns of CNV based on the flow signal strength on OCTA.