A comparison of choroidal thicknesses between pachychoroid and normochoroid eyes acquired from wide-field swept-source OCT

Choroidal features in non-neovascular and neovascular pachychoroid diseases

PURPOSE

To evaluate choroidal findings on multimodal imaging in eyes within pachychoroid spectrum diseases and to compare quantitative and qualitative choroidal features between non-neovascular (NNV-PDS) and neovascular (NV-PDS) pachychoroid diseases.

METHODS

Retrospective cross-sectional study comparing between NV-PDS and NNV-PDS. All patients underwent multimodal imaging including infracyanine green angiography (IFCGA) and swept source optical coherence tomography (OCT) and angiography (OCT-A). The following parameters were analyzed: subfoveal choroidal thickness (SFCT), choroidal vascular index (CVI), presence of pachyvessels and choroidal vascular interconnections (CVIC), presence of choroidal neovascularization and choriocapillaris density.

RESULTS

Of the 87 eyes included in the study, 63 eyes (73%) had NNV-PDS and 24 eyes (27%) had NV-PDS. Mean SFCT and CVI were significantly higher in NNV-PDS group (p = 0.01; p = 0.022). Pachyvessels were more diffusely distributed in NNV-PD group and more focally distributed in NV-PDS group (p = 0.029). CVIC were more frequently noted in NV-PDS group (p = 0.024). A higher CVI was associated to a thicker choroid (p < 0.001), with significant negative correlations between the presence of CVIC and both SFCT (p = 0.015) and CVI (p = 0.002). We also observed a lower choriocapillaris vascular density and higher number of choriocapillaris flow voids in eyes with NNV-PDS (p = 0.24; p = 0.61).

CONCLUSION

NNV-PDS eyes had a significantly thicker SFCT, higher CVI and a lower rate of detected CVIC than eyes with NV-PDS. These highlighted choroidal vascular changes might lead to a better understanding of pachychoroid disease pathophysiology. More frequently observed in NV-PDS group, CVIC are believed to assess the development of vortex vein anastomoses as a remodelling process for vascular decongestion.

NORMAL PERIPHERAL CHOROIDAL THICKNESS MEASURED BY WIDEFIELD OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

Choroidal stasis plays an important role in the pathogenesis of many conditions and leads to choroidal thickening. However, the normal peripheral choroidal thickness (PCT) pattern remains unknown. This study investigated PCT and associated factors using ultrawidefield optical coherence tomography in healthy eyes.

METHODS

This cross-sectional study included 120 healthy eyes (57 males; age, 52.0 ± 20.5 years). We used choroidal thickness maps created by ultrawidefield optical coherence tomography (viewing angle, 200°) with real-shape correction. The peripheral area was defined from 60° to 100° and further separated vertically and horizontally. The PCT and the correlations between PCT and subjects' characteristics were examined.

RESULTS

The PCT were 227.1 ± 57.0 µ m, 199.6 ± 53.9 µ m, 196.6 ± 57.1 µ m, and 148.0 ± 38.2 µ m in supratemporal, infratemporal, supranasal, and infranasal areas, respectively. The thickest peripheral sector was most frequently observed in supratemporal (69.2%). The PCT negatively correlated with age in all regions ( P -values < 0.001) and axial length in supratemporal, supranasal, and infranasal areas ( P -values ≤ 0.003). The temporal PCT was thicker on the side contiguous with the posterior pole Haller's vessels ( P -values ≤ 0.020).

CONCLUSION

The PCT is associated with age, axial length, and the running pattern of Haller's vessels.

Imaging Characteristics of Neovascular and Atrophic Pachychoroidal Spectrum Diseases

Background

This study qualitatively and quantitatively compared imaging characteristics between neovascular and atrophic pachychoroid spectrum disease (PSD) by optical coherence tomography (OCT), and OCT angiography (OCTA).

Methods

The subtypes of PSD were identified by multi-modality imaging approaches. Subfoveal choroidal thickness (SFCT), choroidal vascular index (CVI), and vascular density of choroidal neovascularization (CNV) were measured.

Results

The CVI and SFCT of 174 PSD eyes were 67.6% ± 5.48% and 362.2 ± 131.88 μm, respectively. After adjustment for age, linear regression indicated that SFCT was positively associated with CVI (p &lt; 0.001), and patched hyper-reflective lesions in choriocapillaris layers (p = 0.009). Compared with neovascular PSD eyes, atrophic PSD eyes had similar patient age (57.1 ± 16.72 years, p = 0.639), SFCT (332.0 ± 111.00 μm, p = 0.51), and CVI (67.6% ± 3.94%, p = 0.527). There were no differences between polypoidal choroidal vasculopathy (PCV) eyes with aneurysmal polypoidal lesions and PCV eyes with tangled polypoidal lesions in terms of age, CVI, SFCT, vascular density, or the occurrence of double layer signs (DLSs, all p &gt; 0.05). Logistic regression indicated that age (p = 0.003), SFCT (p = 0.003), patched hyper-reflective lesions in choriocapillaris layers (p = 0.009), and DLSs (p &lt; 0.001) were predictive factors for CNV progression in PSD eyes (all p &lt; 0.05).

Conclusions

Our study highlighted the similarities in SFCT and CVI between neovascular and atrophic PSD, both of which were late stage lesions. Besides, age, SFCT, patched hyper-reflective lesions in choriocapillaris layers, and DLSs were risk factors for CNV in PSD. Our results showed that atrophic PSD is an important change in the late stage of PSD disease, which is helpful for in-depth understanding of the pathological mechanism of PSD and corresponding intervention.

Choroidal Thickness Profile in Chorioretinal Diseases: Beyond the Macula

Enhanced depth imaging optical coherence tomography (EDI-OCT) and swept-source OCT (SS-OCT) have emerged as essential diagnostic tools in the study and management of various chorioretinal diseases. Evidence from early clinical studies using EDI-OCT and SS-OCT indicates that choroidal dysfunction plays a major role in the pathogenesis of chorioretinal diseases. Measurement of choroidal thickness (CT) has already become a major research and clinical method, and CT is considered as an indicator of choroidal status in a variety of ophthalmic diseases. Recently, CT measurement has also been proposed as a non-invasive marker for the early detection and monitoring of various systemic diseases. Among the several possible CT measurement locations, subfoveal CT has rapidly become a reliable parameter for measuring CT in healthy and diseased eyes. Moreover, recent advancements in OCT technology have enabled faster and wider imaging of the posterior part of the eye, allowing the various changes in CT as measured outside the macula to be shown accordingly. In this review, we first provide an overview of the results of clinical studies that have analyzed the healthy macular choroid and that in various chorioretinal diseases, and then summarize the current understanding of the choroid outside the macula. We also examine the CT profile as an index that encompasses both within and outside of the macula. Furthermore, we describe the clinical applications of ultrawide OCT, which enables visualization of the far periphery, and discuss the prospects for the development of more reliable choroidal parameters that can better reflect the choroid's characteristics.

Evaluation of Choroidal Thickness Using Optical Coherent Tomography: A Review

The choroid is the main source of blood and nourishment supply to the eye. The dysfunction of the choroid has been implicated in various retinal and choroidal diseases. The identification and in-depth understanding of pachychoroid spectrum disorders are based on the tremendous progress of optical coherence tomography (OCT) technology in recent years, although visibility of choroid is challenging in the era of the time or spectral domain OCT. The recent rapid revolution of OCTs, such as the enhanced depth imaging OCT and the swept-source OCT, has greatly contributed to the significant improvement in the analysis of the morphology and physiology of the choroid precisely, especially to the choroid-scleral boundary and vasculature. The present review highlights the recently available evidence on the measurement methodology and the clinical significance of choroidal thickness in retinal or choroidal disorders.

Wide-Field Swept-Source OCT Analysis of Interocular Symmetry of Choroidal Thickness in Subjects with Uncomplicated Pachychoroid

BACKGROUND

We aimed to study the bilateral choroidal thickness (CT) symmetry and difference in uncomplicated pachychoroid subjects using wide-field swept-source optical coherence tomography (SS-OCT).

METHODS

All subjects underwent a wide-field 16-mm one-line scan using SS-OCT. Bilateral CT was measured at, and compared among, the following 12 points: three points at 900-µm intervals from the nasal optic disc margin (nasal peripapillary area), one point at the subfovea, six points at 900-µm intervals from the fovea to the nasal and temporal areas (macular area), and two peripheral points 5400 and 8100 µm from the fovea (peripheral area).

RESULTS

There were no statistically significant differences in CT between the right and left eyes in any area (all p > 0.05); they all showed significant positive correlations (all p < 0.01). However, the correlation coefficients (ρ) were smaller for the nasal peripapillary and peripheral areas compared to the macular area.

CONCLUSIONS

The CTs in each region were bilaterally symmetrical in subjects with uncomplicated pachychoroid. However, interocular difference in CT increased from the center to the periphery, indicating that the anatomical variation of the nasal peripapillary and peripheral choroid was greater than that of the macula.

A case of bilateral pachychoroid disease: polypoidal choroidal vasculopathy in one eye and peripheral exudative hemorrhagic chorioretinopathy in contralateral eye

Background

We report a case of bilateral pachychoroid disease manifesting polypoidal choroidal vasculopathy (PCV) with punctate hyperfluorescent spot (PHS) in one eye, and peripheral exudative hemorrhagic choroidal retinopathy (PEHCR) with central serous chorioretinopathy (CSC) and PHS in the contralateral eye.

Case presentation

: A 51-year-old healthy woman presented with complaint of blurred vision in her right eye. Corrected visual acuity was 20/20 in the right and 24/20 in the left eye. Fundus examination was normal in the left eye. In the right eye, fundus finding of an orange-red nodular lesion and optical coherence tomography (OCT) finding of polypoidal lesions led to a diagnosis of PCV. Four aflibercept intravitreal injections were performed in her right eye. After treatment, indocyanine green angiography (ICGA) confirmed residual polypoidal lesions with branching vascular networks and PHS with choroidal vascular hyperpermeability. OCT showed PHS associated with small sharp-peaked retinal pigment epithelium (RPE) elevation in peripheral fundus and small RPE elevation in posterior fundus. Based on the above findings, PCV with PHS was finally diagnosed in the right eye. Posttreatment corrected visual acuity in the right eye was 20/20. She presented again 32 months later, with complaint of vision loss in her left eye. Left corrected visual acuity was 20/20, and fundus examination showed mild vitreous hemorrhage. Vitrectomy was performed. In temporal midperipheral fundus, fluorescein angiography revealed CSC, and OCT showed pachychoroid. ICGA depicted abnormal choroidal networks and PHS in peripheral fundus. Furthermore, polypoidal lesions were confirmed by OCT. Based on the above findings, PEHCR and CSC with PHS was finally diagnosed in the left eye. Postoperative corrected visual acuity in the left eye was 20/20, and aflibercept intravitreal injection was performed for prevention of recurrence of vitreous hemorrhage.

Conclusions

This is the first case report of PCV with PHS in one eye, and PEHCR with CSC and PHS in the contralateral eye. This case suggests that PCV, PEHCR, and CSC may be linked pathologies of pachychoroid spectrum disease.

Pachychoroid Spectrum Disease: Underlying Pathology, Classification, and Phenotypes

PURPOSE

Pachychoroid spectrum disease encompasses a set of macular disorders secondary to an abnormally thick choroid. However, the pathological process underlying pachychoroid spectrum disease and its overlap with age-related macular degeneration (AMD) remain unclear. This review aimed to understand the underlying pathology, classification, and phenotypes of pachychoroid spectrum disease.

METHODS

This comprehensive literature review was performed based on a search of peer-reviewed published papers relevant to the current knowledge of pachychoroid disease spectrum.

RESULTS

Pachychoroid is primarily a bilateral phenomenon; the main pathological lesions include choriocapillaris attenuation and abnormally dilated pachyvessels. Chronic central serous chorioretinopathy (CSC) and pachychoroid neovasculopathy (PNV) show similar morphological changes and angiogenic cytokine levels. The subretinal fluid in PNV may not accurately indicate PNV activity. Besides, types 1 and 2 of choroidal neovascularization (CNV) may be involved in primary pachychoroidal disease. Both choroidal arteriosclerosis and higher hydrostatic pressure contribute to hyalinized choroidal arteries and aneurysmal dilatations, resulting in PNV progression to polypoidal choroidal vasculopathy (PCV). Thus, pachychoroid-related type 2 CNV and chronic CSC could be considered as PNV (IIIc) and as a precursor of PNV (IIIa), respectively. Tangled PCV on optical coherence tomography angiography that fails to develop aneurysms should be classified as a subtype of PNV or a forme fruste of PCV.

CONCLUSIONS

Multiple disorders of the pachychoroid spectrum are considered as a continuous disease process, ultimately stimulated by choroidal malfunction. PCV overlaps both AMD and pachychoroid disease, especially for thin-choroid and bilateral types. The terminology and classification of pachychoroid spectrum disease should be used cautiously.

Deep Learning-Based Estimation of Axial Length and Subfoveal Choroidal Thickness From Color Fundus Photographs

This study aimed to develop an automated computer-based algorithm to estimate axial length and subfoveal choroidal thickness (SFCT) based on color fundus photographs. In the population-based Beijing Eye Study 2011, we took fundus photographs and measured SFCT by optical coherence tomography (OCT) and axial length by optical low-coherence reflectometry. Using 6394 color fundus images taken from 3468 participants, we trained and evaluated a deep-learning-based algorithm for estimation of axial length and SFCT. The algorithm had a mean absolute error (MAE) for estimating axial length and SFCT of 0.56 mm [95% confidence interval (CI): 0.53,0.61] and 49.20 μm (95% CI: 45.83,52.54), respectively. Estimated values and measured data showed coefficients of determination of r 2 = 0.59 (95% CI: 0.50,0.65) for axial length and r 2 = 0.62 (95% CI: 0.57,0.67) for SFCT. Bland-Altman plots revealed a mean difference in axial length and SFCT of -0.16 mm (95% CI: -1.60,1.27 mm) and of -4.40 μm (95% CI, -131.8,122.9 μm), respectively. For the estimation of axial length, heat map analysis showed that signals predominantly from overall of the macular region, the foveal region, and the extrafoveal region were used in the eyes with an axial length of < 22 mm, 22-26 mm, and > 26 mm, respectively. For the estimation of SFCT, the convolutional neural network (CNN) used mostly the central part of the macular region, the fovea or perifovea, independently of the SFCT. Our study shows that deep-learning-based algorithms may be helpful in estimating axial length and SFCT based on conventional color fundus images. They may be a further step in the semiautomatic assessment of the eye.

Wide-Field Swept-Source Optical Coherence Tomography Analysis of Interocular Symmetry of Choroidal Thickness in Healthy Young Individuals

Purpose

The purpose of this paper was to study the bilateral choroidal thickness (CT) symmetry and differences in healthy individuals using wide-field swept-source optical coherence tomography (SS-OCT).

Methods

All participants underwent a wide-field 16-mm 1-line scan using SS-OCT. CTs were measured at the following 12 points: 3 points at 900 µm, 1800 µm, and 2700 µm away from the nasal optic disc margin (nasal peripapillary area), 1 point at the subfovea, 6 points at 900 µm, 1800 µm, and 2700 µm away from the subfovea to the nasal and temporal areas (macular area), and 2 peripheral points at 2700 and 5400 µm from temporal point 3 (peripheral area). Bilateral CTs were measured; their correlations and differences in the corresponding regions were analyzed.

Results

There were no statistically significant differences in CTs between the right and left eyes in all corresponding areas (all P > 0.05); they all showed significant positive correlation coefficients (r) (all P < 0.001). However, the nasal peripapillary and peripheral areas had relatively low correlation coefficients, compared to the macular areas. In addition, the bilateral CT differences were 32.60 ± 25.80 µm in the macular area, 40.67 ± 30.58 µm in the nasal peripapillary area, and 56.03 ± 45.73 µm in the peripheral area (all P < 0.001).

Conclusions

Overall, the CTs of each region were bilaterally symmetrical. However, the differences in CTs increased from the center to the periphery, which indicated that the anatomic variation of the nasal peripapillary and peripheral choroid was greater than that of the macula.