Quantitative evaluation of choriocapillaris using optical coherence tomography and optical coherence tomography angiography in patients with central serous chorioretinopathy after half-dose photodynamic therapy

Short term choroidal microvascular changes following photodynamic therapy in chronic central serous chorioretinopathy

BACKGROUND

Central serous chorioretinopathy (CSC) is characterized by focal serous detachment of the retina, primarily affecting the macula. Photodynamic therapy (PDT) is the best choice for treatment of chronic and recurrent patients. In this study we aim to evaluate the early effects of the half dose protocol (3 mg/m2 verteporfine) of PDT laser treatment on the micro vasculature of choroid.

METHODS

Among thirty-one patients (62 eyes), twenty eyes were in the control group and forty-two eyes received PDT laser treatment. Vision log MAR, CMT (central macular thickness), SRF (sub retinal fluid), BCT (baseline choroidal thickness), CVI (choroidal vascular index), and laser treated area were compared between two groups.

RESULTS

Results show that no strong correlation was detected between the impact of laser treatment and resolution of SRF in the first week in the fovea. The mean best corrected visual acuity (BCVA) of the patients significantly increased from 20/63 at the beginning of the study, according to the Snellen chart, to 20/49 in the first week and 20/38 in the sixth week. PDT can significantly reduce SRF and CMT in 6 weeks compared to the control group. Although there was initially a small, non-statistically significant increase in choroidal thickness and CVI after 1 week, a dramatic decrease occurs after 6 weeks. Therefore, after 6 weeks of PDT laser, all the indicators such as SRF, CMT, choroidal thickness, and CVI significantly reduced.

CONCLUSION

PDT laser can significantly reduce SRF and CMT at 1 and 6 weeks and choroidal thickness and CVI at 6 weeks in chronic CSC patients. Also, a larger laser treated area has no impact on the final outcome. Therefore, it seems that the mechanism of PDT in CSC disease is the recovery of choriocapillaris circulation.

Fully automatic segmentation and monitoring of choriocapillaris flow voids in OCTA images

Optical coherence tomography angiography (OCTA) is a non-invasive ophthalmic imaging modality that is widely used in clinical practice. Recent technological advances in OCTA allow imaging of blood flow deeper than the retinal layers, at the level of the choriocapillaris (CC), where a granular image is obtained showing a pattern of bright areas, representing blood flow, and a pattern of small dark regions, called flow voids (FVs). Several clinical studies have reported a close correlation between abnormal FVs distribution and multiple diseases, so quantifying changes in FVs distribution in CC has become an area of interest for many clinicians. However, CC OCTA images present very complex features that make it difficult to correctly compare FVs during the monitoring of a patient. In this work, we propose fully automatic approaches for the segmentation and monitoring of FVs in CC OCTA images. First, a baseline approach, in which a fully automatic segmentation methodology based on local contrast enhancement and global thresholding is proposed to segment FVs and measure changes in their distribution in a straightforward manner. Second, a robust approach in which, prior to the use of our segmentation methodology, an unsupervised trained neural network is used to perform a deformable registration that aligns inconsistencies between images acquired at different time instants. The proposed approaches were tested with CC OCTA images collected during a clinical study on the response to photodynamic therapy in patients affected by chronic central serous chorioretinopathy (CSC), demonstrating their clinical utility. The results showed that both approaches are accurate and robust, surpassing the state of the art, therefore improving the efficacy of FVs as a biomarker to monitor the patient treatments. This gives great potential for the clinical use of our methods, with the possibility of extending their use to other pathologies or treatments associated with this type of imaging.

Artifact-Removed Quantitative Analysis of Choriocapillaris Flow Voids

Objectives

To investigate choriocapillaris flow voids (FV) with a new optical coherence tomography angiography (OCTA) image processing strategy that can eliminate artifacts caused by vitreous opacities, sub-retinal pigment epithelium fluid and deposits, and subretinal fluid (SRF) by thresholding the en-face OCT image of the outer retina.

Materials and Methods

We retrospectively reviewed medical records of patients with drusen and patients with active central serous chorioretinopathy (CSC). FV number (FVn), average area (FVav), and maximum area (FVmax) and the percentage of nonperfused choriocapillaris area (PNPCA) obtained using the proposed strategy were compared with those obtained by removing only artifacts caused by the superficial capillary plexus (SCP).

Results

The SRF group included 21 eyes with active CSC and the drusen group included 29 eyes with nonexudative age-related macular degeneration. FVav, FVmax, FVn, and PNPCA obtained using the algorithm were significantly lower than those obtained by removing only SCP-related artefacts in both groups (all p<0.05). The algorithm was also able to remove 96.9% of artifacts secondary to vitreous opacities and all artifacts secondary to serous pigment epithelial detachments.

Conclusion

Choriocapillaris nonperfusion areas on OCTA images may be overestimated in eyes with RPE abnormalities and SRF due to artifacts. These artifact areas on choriocapillaris OCTA images can be removed using thresholded images of the outer retina en-face OCT scans. Our new artifact-removal strategy is useful in the assessment of choriocapillaris FV in eyes with SRF, drusen, drusen-like deposits, and pigment epithelial detachment.

Repeatability of choriocapillaris flow voids by optical coherence tomography angiography in central serous chorioretinopathy

PURPOSE

To assess the repeatability of flow signal voids (FSV) measurements of the choriocapillaris (CC) and choroid (CH) in central serous chorioretinopathy (CSCR) by Swept-Source optical coherence tomography angiography (SS-OCTA).

METHODS

Cross-sectional study including 104 eyes of 52 patients with unilateral CSCR. Two consecutive macular 6x6 mm SS-OCTA scans (Plex Elite 9000; Zeiss, Dublin, CA) were obtained from the affected eyes with persistent subretinal fluid (SRF) (CSCR group) and the fellow unaffected eyes (control group). FSV area and the number of contours measurements were analyzed using three slabs: inner CC, outer CC and CH. The repeatability of the measurements was assessed with intraclass correlation coefficients (ICC) and coefficients of variation (CV).

RESULTS

In the CSCR group, ICCs for the FSV area in the three slabs were all ≥0.859, observing higher values for the outer CC and the CH (0.959 and 0.964) than for the inner CC (0.859). Similar ICC values were obtained for the FSV area in control eyes, observing the highest values for the outer CC (0.949), followed by the CH (0.932) and inner CC (0.844). Regarding the FSV number of contours measurements, ICCs were higher for the outer CC and CH (0.949 and 0.932) than for inner CC (0.844). CV for the FSV area was 4.7%, 3.8% and 8.6% in the CSCR eyes and 4.8%, 3.9% and 9.3% in the control group for the inner CC, outer CC and CH respectively.

CONCLUSION

SS-OCTA offers good repeatability to quantify macular FSV in CSCR eyes and fellow eyes.

Central serous chorioretinopathy: Treatment

Central serous chorioretinopathy (CSC) is a pachychoroid spectrum disease characterized by serous detachment of the neurosensory retina with subretinal fluid in young and middle-aged adults. The pathogenesis of CSC is not yet fully understood. However, it is considered a multifactorial disease that is strongly associated with choroidal dysfunction or vascular engorgement. Although there is no consensus on the treatment of CSC, photodynamic therapy has been effectively used to manage serous retinal detachment (SRD) in CSC. Moreover, micropulse diode laser photocoagulation and focal laser treatment have also been used. Recently, oral medications, including mineralocorticoid receptor antagonists, have been proposed for the management of CSC. Multimodal imaging plays a significant role in the diagnosis and treatment of CSC. Optical coherence tomography angiography (OCTA) has the advantage of detecting vascular flow in the retina and choroid layer, allowing for a better understanding of the pathology, severity, prognosis, and chronicity of CSC. In addition, early detection of choroidal neovascularization in CSC is possible using OCTA. This review article aims to provide a comprehensive and updated understanding of CSC, focusing on treatment.

Pathophysiology of central serous chorioretinopathy: a literature review with quality assessment

The pathogenesis of central serous chorioretinopathy (CSCR), a pachychoroid disease, is poorly understood. While choroid hyperpermeability and retinal pigment epithelium dysfunction are cornerstones for developing CSCR, the mechanisms at the retinal, vascular, retinal pigment epithelium, and cellular level continue to be an enigma. A few preclinical studies and the development of small-sized, poorly controlled clinical trials have resulted in limited insight into the disease mechanism. Effective treatments for CSCR are still lacking as current trials have produced inconsistent results for functional and structural gains. Thus, critically evaluating the literature to explore disease mechanisms and provide an up-to-date understanding of pathophysiology can provide valuable information and avenues to new treatments. In this study, a comprehensive summary of the mechanistic insight into CSCR is presented while highlighting the shortcomings of current literature. The mechanism was divided into seven sub-categories including mechanical obstruction, inflammation, oxidative stress, paracrine factors, autonomic dysfunction, mineralocorticoid receptors activation, and medications. We implemented validated tools like the JBI and CAMARADES to objectively analyze the quality of both clinical and preclinical studies, respectively. Overall, our analysis of the literature showed that no single mechanism was populated with a large number of sufficiently sized and good-quality studies. However, compiling these studies gave hints not only to CSCR pathogenesis but also pachychoroid disease in general while providing suggestions for future exploration.

Optical coherence tomography angiography quantification of choriocapillaris blood-flow after half-fluence photodynamic therapy for chronic central serous chorioretinopathy

PURPOSE

To quantitatively analyze characteristics of choriocapillaris flow using spectral domain optical coherence tomography angiography (SD-OCTA) in eyes with chronic central serous chorioretinopathy (CSC) before and after treatment by photodynamic therapy (PDT).

METHODS

Retrospective interventional study. Macular 3X3 SD-OCT scans were analyzed in eyes diagnosed with chronic CSC before and after treatment with half-fluence PDT. The choriocapillaris en face slabs were extracted from the SD-OCTA device after manual segmentation. En face choriocapillaris flow images were compensated with en face choriocapillaris structure images. Phansalkar local thresholding method was then used with a radius of 4 and 8 pixels. Percentage of flow deficits (FD%), number, size, and total area of FDs were computed for comparison, before and after treatment by half-fluence PDT.

RESULTS

Mean choriocapillaris FD% before PDT was of 58.36 + / - 11.88 and of 60.82 + / - 11.08 after PDT using radius 4 pixels with no significant difference (p = 0.140). Mean choriocapillaris FD% was of 58.63 + / - 11.08 before PDT and of 60.87 + / - 10.36 after PDT using radius 8 pixels with no significant difference (p = 0.200). Similarly, no significative difference was found in number, size, and total area of FDs, before and after half-fluence PDT, using radius 4 and 8 pixels in patients with chronic CSC.

CONCLUSION

Using Phansalkar local thresholding method, quantitative analysis of choriocapillaris with SD-OCTA found no significant change in choriocapillaris flow deficits before and after successful half-fluence PDT in patients with chronic CSC. Therefore, it seems that half-fluence PDT may not alter choriocapillaris perfusion, at least on a relative short-term basis.

Evaluation of the choriocapillaris after photodynamic therapy for chronic central serous chorioretinopathy. A review of optical coherence tomography angiography (OCT-A) studies

PURPOSE

Emerging evidence suggests that choroidal microcirculation and microstructural changes after verteporfin photodynamic therapy (vPDT) for chronic central serous chorioretinopathy (CSC) can be shown in detail using OCT-Angiography (OCT-A). The use of OCT-A for the examination of choriocapillaris (CC) has attracted significant attention as the technique offers potential explanations for the effects of vPDT on choroidal tissue.

METHODS

A meticulous literature search was performed in the PubMed database without restriction on year of publication until June 2021. The reference list of all electronically retrieved articles was carefully reviewed for potentially relevant articles that had not been identified.

RESULTS

We identified and reviewed 11 studies reporting a comprehensive update on microvasculature and morphologic changes of the CC layer as seen on OCT-A in chronic CSC. The reviewed articles extensively analyze both the qualitative and quantitative characteristics of the CC flow pattern after applying vPDT safety-enhanced protocols. The changes in the CC plexus indicate the potential of beneficial or deleterious treatment effect on choroidal tissue remodeling. The reviewed series have revealed variability of flow pattern, vessel density, and perfusion of the CC over time.

CONCLUSION

The CC plexus alterations during the post-vPDT period in chronic CSC may imply the treatment effect on choroidal tissue, indicating the potential of anatomical or functional recovery over time. The reviewed literature may confirm the diagnostic value of OCT-A in the assessment of the pathophysiology of eyes with CSC.

Applications of Multimodal Imaging in Central Serous Chorioretinopathy Evaluation

Central serous chorioretinopathy (CSCR) is a macular disease characterized by serous retinal detachment commonly involving the macular region. CSCR has a wide spectrum of clinical presentations. Although a significant proportion of CSCR cases are self-limiting, patients can suffer from persistent or recurrent disease, sometimes complicated with choroidal neovascularization, resulting in permanent visual loss. Multimodal imaging, including fluorescein angiography, indocyanine green angiography, fundus autofluorescence, and optical coherence tomography, has advanced the diagnosis and classification of CSCR cases. Evolution of new imaging techniques including optical coherence tomography angiography, wide-field imaging, and en face reconstruction imaging has also contributed to better understandings of the pathophysiology of CSCR. This review article summarizes the features of multimodal imaging for CSCR and discusses the application of such features in evaluating the disease.

Clinical features of pachyvessels associated with polypoidal choroidal vasculopathy in chronic central serous chorioretinopathy

To investigate the association between clinical features of chronic central serous chorioretinopathy (CSC) and subsequent development of polypoidal choroidal vasculopathy (PCV). Characteristics and treatment response of PCV secondary to CSC were described. This retrospective observational study included 18 patients with chronic CSC (18 eyes) with subsequent PCV and 36 controls (36 eyes) with chronic CSC without PCV development during follow-up. Clinical features were compared between the two groups. A logistic regression model was used to evaluate the risk factor of PCV formation. Treatments for PCV included anti-vascular endothelial growth factor (VEGF) monotherapy, photodynamic therapy (PDT), or PDT and anti-VEGF combination treatment. Subretinal fluid on optical coherence tomography images were assessed after treatments. Significant between-group differences were observed in best-corrected visual acuity after disease resolution and presence of pachyvessels (P = .001 and P = .003, respectively). The presence of pachyvessels in chronic CSC was associated with subsequent PCV (odds ratio = 6.00; 95% CI, 1.74–20.68; P = .005). CSC recurrence and subfoveal choroidal thickness (SFCT) were not significantly associated with subsequent PCV development (P = .393 and P = .911, respectively). The mean age of PCV diagnosis was 51 years, and the mean time from CSC diagnosis to PCV confirmation was 77.8 months. The mean (range) SFCT of PCV was 327.7 (134–599) μm. Nine patients received anti-VEGF monotherapy and 5 had disease remission. Four patients received PDT and anti-VEGF combination treatment and all of the 4 had disease remission. In chronic CSC, pachyvessel characteristics are associated with subsequent PCV development. This result will assist clinicians to evaluate CSC in clinical practice and provide insights into the pathogenesis of PCV.

Thickness, vessel density of retina and choroid on OCTA in young adults (18-24 years old)

PURPOSE

The purpose of this study was to quantify thickness, vessel density (VD) of retina and choroid in young adults (18-24 years old) using OCTA.

METHODS

This observational, cross-sectional study included 154 eyes from 77 young myopic adults. En-face angiogram OCTA was performed on a 3.00 × 3.00 mm region centered on the macula. Automated thickness calculations and macular maps were measured. Spherical equivalent refraction (SER) and AL were examined to determine associations with thickness, vessel density (VD) of retina and choroid.

RESULTS

A total of 148 healthy eyes from 77 young myopic adults (29 males and 48 females) with a mean age of 21.80 ± 1.32 years (range: 18-24 years) were included. The mean SER and AL were - 4.06 ± 2.26D and 25.25 ± 1.28 mm, respectively. The mean retinal thickness (RT, ILM-RPE layer) was 240.91 ± 13.36 μm, the retinal superficial (SVD) and deep vessel density (DVD) in fovea region were 18.35 ± 4.77% and 32.99 ± 6.01%, respectively. The foveal avascular zone (FAZ) area was 0.31 ± 0.10 mm². The mean subfoveal choroidal thickness (SFCT) and choriocapillaris (CC) perfusion area were 232.16 ± 56.65 μm and 2.17 ± 0.10 mm², respectively. By Pearson's correlation analysis, SER was revealed to be negatively correlated with RT (r = -0.180, p = 0.028) and DVD (r = -0.185, p = 0.025) in fovea region. SER was revealed to be positively correlated with RT in nasal (r = 0.224, p = 0.006) and inferior (r = 0.217, p = 0.008) regions. AL was revealed to be positively correlated with RT (r = 0.250, p = 0.002) and DVD (r = 0.284, p < 0.001) in fovea region. SER was revealed to be positively correlated with SFCT (r = 0.486, p < 0.001). AL was revealed to be negatively correlated with FAZ area (r = -0.232, p = 0.005) and SFCT (r = -0.407). RT was revealed to be negatively correlated with FAZ area (r = -0.645, p < 0.001). SER (r = -0.079), AL (r = 0.071) and SFCT (r = 0.089) did not correlate significantly with the CC perfusion area (all p > 0.05).

CONCLUSION

Myopic eyes present increased RT, DVD and thinned SFCT in fovea, while no significant correlation could be found between SER, AL, SFCT and CC perfusion area. It may indicate that the SFCT thinning may be secondary to ocular elongation, while the CC perfusion area may be a factor independent of AL growth.