Pachychoroid Spectrum Disease Research Articles

Prednisolone eye drops as a potential treatment in non-neovascular pachychoroid related diseases.

To investigate the functional and structural outcomes after treatment with prednisolone eye drops in the following pachychoroid related diseases: chronic central serous chorioretinopathy (cCSC), pachychoroid pigment epitheliopathy (PPE) and peripapillary pachychoroid syndrome (PPS). In this retrospective study, 54 eyes of 48 patients with pachychoroid related disease were treated with prednisolone acetate 1% eye drops for 3 times a day. Change in macular volume and retinal central subfield thickness on optical coherence tomography was measured. In addition, foveal or complete resolution of fluid and the change in visual acuity (VA) were studied. The follow-up visit was at a mean of 41.2 ± 14.5 days. In the 44 eyes with cCSC, a significant reduction in retinal central subfield thickness (p < 0.001) and macular volume (p < 0.001) was observed. Foveal intra- or subretinal fluid resolved completely in 22% of the eyes. In the 8 PPS eyes, a reduction in the nasal retinal thickness was observed (p = 0.025). One of the 2 PPE eyes showed structural improvement. No significant change in VA was observed in any of the pachychoroid spectrum diseases. In cCSC, PPS and PPE patients, anatomical improvement was observed after therapy with prednisolone eye drops. VA did not change significantly.

Wide-Field Choroidal Thickness Analysis after Half-Fluence Photodynamic Therapy Combined with Intravitreal Aflibercept Injection in Pachychoroid Neovasculopathy.

Background: Pachychoroid neovasculopathy (PNV) is a pachychoroid-spectrum disease. As blood circulation throughout the choroid may be involved in PNV pathogenesis, analysis using ultra-wide-field (UWF) fundus imaging is crucial. We evaluated choroidal thickness after half-fluence photodynamic therapy (PDT) combined with intravitreal aflibercept injection for PNV using UWF swept-source optical coherence tomography. Methods: Seventeen eyes with PNV that underwent half-fluence PDT with an adjuvant single intravitreal aflibercept injection were analyzed. To compare choroidal thicknesses in the central and peripheral choroids, we set subfields <3, <9, and 9-18 mm from the fovea. The <9 and 9-18 mm subfields were divided into four quadrants. Results: Choroidal thickness in each subfield decreased significantly after half-fluence PDT (p < 0.001); this reduction was more pronounced in the central area. We also investigated the relationship between the dominant side of the deep choroidal veins that harbor choroidal vein efflux from the macula. When choroidal thickness in the supratemporal and infratemporal 9 mm subfields were evaluated, the ratio of choroidal thickness reduction was not significantly different between the dominant and non-dominant sides. The dominant side was not associated with the extent of choroidal thickness reduction in PNV. Conclusions: Half-fluence PDT caused thinning of the entire choroid, especially in the central area, in PNV.

Inversion of Asymmetric Vortex Vein Dilatation in Pachychoroid Spectrum Diseases

PurposeIntervortex venous anastomosis is widely recognized as compensating for vortex vein congestion in pachychoroid spectrum diseases. However, determining the blood flow direction within the compensated drainage route is often challenging. Herein, we investigated the morphological patterns of vortex veins in eyes showing retrograde pulsatile vortex venous flow. DesignRetrospective observational case series. Subjects689 consecutive eyes with treatment-naïve central serous chorioretinopathy, pachychoroid neovasculopathy, or polypoidal choroidal vasculopathy. MethodsWe reviewed the clinical records of patients with these pachychoroid spectrum diseases. Multimodal images including indocyanine green angiography (ICGA) and en face optical coherence tomography were analyzed. Main Outcome MeasuresIntervortex venous anastomosis between superotemporal and inferotemporal vortex veins and the dominant site of dilated temporal vortex veins were determined in the eyes with retrograde pulsatile vortex venous flow in the temporal vortex veins. Results22 eyes with retrograde pulsatile vortex venous flow in the temporal vortex veins were identified utilizing early-phase ICGA videos. In 9 eyes, retrograde pulsatile flow was detected in the superotemporal vortex veins which were connected to the inferotemporal vortex veins via intervortex venous anastomoses. Among these cases, contralateral inferotemporal vortex vein dilatation was dominant in 7 eyes (77.8%), while superotemporal and inferotemporal vortex veins were symmetrically dilated in the other 2 eyes (22.2%). On the other hand, in 13 eyes, the retrograde pulsatile flow was detected in the inferotemporal vortex veins which were linked to the superotemporal vortex veins via intervortex venous anastomoses. In these eyes, contralateral superotemporal vortex vein dilatation was dominant in 10 eyes (76.9%). Superotemporal and inferotemporal vortex veins were symmetrically dilated in 2 eyes (15.4%), while mainly inferotemporal vortex veins were dilated in 1 eye (7.7%). ConclusionsIn pachychoroid spectrum diseases, there are cases wherein congested venous blood might drain into the contralateral vortex veins via intervortex anastomoses. Overloaded contralateral vortex veins may, as a consequence, become more dilated than the primary congested vortex veins. Inversion of asymmetric vortex vein dilatation might thereby develop in pachychoroid spectrum diseases.

Long-term visual outcomes in pachychoroid spectrum diseases and its associating factors of eyes with chronic central serous chorioretinopathy

To analyze the long-term visual outcomes of pachychoroid spectrum diseases (PSD). Retrospective study. We reviewed the medical charts of consecutive patients with PSD, including focal choroidal excavation (FCE), pachychoroid pigment epitheliopathy (PPE), central serous chorioretinopathy (CSC), and pachychoroid neovasculopathy (PNV). The patients initially visited the Tokyo University Hospital from January 2008 to March 2021. Survival analyses were performed, in which loss of vision was defined as visual acuity (VA) of 0.2 logarithm of minimal angle of resolution (logMAR) or worse, 0.5 logMAR or worse, or VA worsening by 0.3 logMAR or greater. Moreover, we further investigated factors associated with visual prognosis, particularly in the CSC group. A total of 741 eyes of 638 patients were included in this analysis. The CSC or PNV group showed significantly worse visual prognosis than the FCE&PPE group for VA to 0.2 logMAR or worse (P = 0.0117 or 0.0001, respectively) and for VA worsening by 0.3 logMAR or greater (P = 0.0283 or 0.0037, respectively). In the CSC group, unlike age, sex, or treatment history, the accumulative duration of subfoveal fluid existence ≥ 12 months (continuous or intermittent) was significantly associated with visual prognosis (P < 0.0001). Among PSD, CSC and PNV were associated with a higher risk of vision loss in the long term than FCE and PPE. The duration of subretinal fluid existence was identified as a significant factor affecting long-term visual outcomes in CSC.

Choroidal features in non-neovascular and neovascular pachychoroid diseases.

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. 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. 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). 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.

Aneurysmal type 2 neovascularization: A new entity

To report three cases of aneurysmal type 2 neovascularization (AT2), a novel entity within the pachychoroid disease (PD) spectrum. We conducted an observational retrospective study of three patients with subretinal polyps treated with intravitreal aflibercept. We reviewed clinical and imaging data of the three patients. Best corrected visual acuity (BCVA), central macular thickness (CMT), choroidal subfoveal thickness, choroidal thickness under the polyps and the presence of a dry macula were assessed at baseline and throughout the follow-up. All of the patients showed granular hypoautofluorescence on fundus autofluorescence. Indocyanine green angiography revealed prominent hyperfluorescent branching vascular networks ending in multiple aneurysmal dilatations. Optical coherence tomography (OCT) demonstrated that the aneurysmal lesions were localized in the subretinal space. Additionally, OCT showed retinal pigment epithelial microtears, the double-layer sign and pachyvessels. En face OCT-A perfectly defined prominent telangiectatic branching vascular networks in all the patients, but only revealed polyps in two out of the three patients. Cross-sectional OCT-A demonstrated polyps as patchy circular hypoflow signals in each case. After the intravitreal treatment, BCVA remained unimproved in all of the patients, despite decreased CMT and achievement of a dry macula, as a result of the development of subretinal fibrosis. In summary, we describe a new entity within the spectrum of PD, which we have termed AT2. This novel disease is characterized by the presence of aneurysmal dilatations in the subretinal space, along with the typical features of PD, such as choroidal vascular hyperpermeability, thickening of the choroid and pachyvessels.

CURRENT VIEW OF THE SPECTRUM OF PACHYCHOROID DISEASES. A REVIEW.

The term "pachychoroid" (greek pachy- [παχύ] - thick) was first used by Warrow et al. in 2013. It is defined as an abnormal and permanent increase in choroidal thickness ≥ 300 μm, which is caused by dilatation of the choroidal vessels of the Haller's layer, thinning of the Sattler's layer and the choriocapillaris layer. Literary research focused on the current view of pachychoroid spectrum diseases, including clarification of the pathophysiological theories of the formation of "pachychoroid". It is assumed that "pachychoroid" disease has an autosomal dominant type of heredity. Depending on the further activity of various exogenous and/or endogenous factors, pachychoroid diseases may appear. According to the current knowledge, the spectrum of pachychoroid disease covers six clinical entities: pachychoroid pigment epitheliopathy, central serous chorioretinopathy, pachychoroid neovasculopathy, polypoid choroidal vasculopathy, focal choroidal excavation and peripapillary pachychoroid syndrome. In this study, we describe the clinical symptoms and objective findings of focal choroidal excavation and peripapillary pachychoroid syndrome. The current pathophysiological theory of pachychoroid diseases is based on impaired venous outflow from the choroid ("venous overload choroidopathy") and thickening of the sclera in the eyes of affected patients. Pachychoroid diseases should be included in the differential diagnosis of characteristic features observed during multimodal imaging analysis of choroidal changes.

Hyperreflective material in patients with non-neovascular pachychoroid disease

BackgroundThis study aimed to report eleven cases of non-neovascular pachychoroid disease with hyperreflective material (HRM) that occurred in Japanese patients.MethodsA retrospective review of data from eleven patients who had non-neovascular retinal pigment epithelium (RPE) protrusion with HRM in the neurosensory retina between March 2017 and June 2022 was conducted. Clinical examination, color fundus photography, fluorescein angiography, spectral-domain optical coherence tomography (SD-OCT), and OCT angiography data were analyzed. Main outcome measures were patient characteristics, changes in SD-OCT findings, and symptom outcomes.ResultsAll cases had RPE protrusion and HRM with dilated choroidal veins, which were characteristic of pachychoroid disease. However, none of the cases had macular neovascularization (MNV). In 9 eyes (81.8%), HRM improved spontaneously without intervention and resulted in alterations in RPE, referred to as pachychoroid pigment epitheliopathy (PPE) or focal choroidal excavation (FCE). In these cases, symptoms such as metamorphopsia and distortion improved without treatment. In the remaining two cases (18.2%), HRM still persisted during the follow-up period.ConclusionThere are some cases of non-neovascular pachychoroid disorder with HRM, which might be a new entity of pachychoroid spectrum disease or an early stage of PPE or FCE. These cases should not be misdiagnosed as MNV, and careful observation is necessary.

Pachychoroid Spectrum Disorders: An Updated Review.

Pachychoroid disease spectrum is a recent term that has been associated with an increasing number of phenotypes. This review discusses updated findings for each of the typical pachychoroid entities (central serous chorioretinopathy, pachychoroid pigment epitheliopathy, pachychoroid neovasculopathy, polypoidal choroidal vasculopathy, peripapillary pachychoroid syndrome, and focal choroidal excavation), as well as two relatively new additions (peripapillary pachychoroid neovasculopathy and peripheral exudative hemorrhagic chorioretinopathy). Here, we discuss the potential pathogenic mechanisms for these diseases and relevant imaging updates. Finally, we argue for a consistent classification scheme for these entities.

Focal Choroidal Excavation: Epidemiology, Clinical Characteristics and Multimodal Imaging Findings

Focal choroidal excavation (FCE) is one of the pachychoroid spectrum diseases. It may be an isolated lesion or associated with other ophthalmological disorders. The aim of the study was to present the epidemiology, clinical features and multimodal imaging findings in FCE. This is a case series of 14 consecutive patients with a diagnosis of FCE, confirmed by multimodal imaging, from a review of the 5076 optical coherence tomography (OCT) scans in 2538 patients. Choroidal thickness (CT) was measured under the fovea and in the area of maximum choroidal thickening in the affected eye and under the fovea in the fellow eye. The mean age of the subjects was 40 ± 13.58 years. FCE occurred unilaterally and was an isolated lesion in all cases. The fellow eye did not show any macular pathology in all patients. Twelve eyes presented conforming FCEs and two non-conforming FCEs. In 79% of cases, FCE was subfoveal. The mean maximum CT was 390 μm in the affected eye with the presence of pachyvessels. A total of 13 patients were asymptomatic, while one patient reported a visual disturbance due to neovascularization secondary to FCE. Of all the multimodal imaging techniques, optical coherence tomography (OCT) provided the most important data in the diagnosis of FCE. Our study confirmed that FCE is a rare ocular condition, but it may be more common in Caucasian population than previously known. Multimodal imaging methods, mainly OCT, are crucial in FCE diagnostics. Further studies are needed to expand the available knowledge about its etiology and clinical course.

Choroidal Thickness is Increased following Restraint Stress in Rats

Purpose Central serous chorioretinopathy is a stress-induced disease and often shows pachychoroid; however, the relationship between stress and choroid remains unlear. The purpose of this study was to investigate, using optical coherence tomography, whether the choroid thickens when rats are subjected to restraint stress. Methods Eight-week-old male F334/Jcl rats were subjected to 30 min of restraint stress, and choroidal thickness was measured before and after stress loading using optical coherence tomography. In addition, salivary corticosterone levels were measured before and after stress loading. Results Choroidal thickness was significantly increased from 30.1 ± 6.4 µm to 39.7 ± 9.2 µm just after stress loading (p = 0.001). Significant choroidal thickening was not observed on the next day. The salivary corticosterone concentration increased from 1575.3 ± 1040.6 pg/mL before stress loading to 6022.2 ± 6742.6 pg/mL after stress loading, but the difference was not significant (p = 0.10). Conclusions Choroidal thickness increased when rats were subjected to restraint stress, supporting the hypothesis that stress is one of the causes of pachychoroid spectrum disease, as exemplified by central serous chorioretinopathy.

Surgical Management of Full-Thickness Macular Hole In A Patient with Pachychoroid Spectrum Disease with Atypical Fundus Autofluorescence After Surgery

Surgical Management of Full-Thickness Macular Hole In A Patient with Pachychoroid Spectrum Disease with Atypical Fundus Autofluorescence After Surgery

Current concepts in pachychoroid spectrum diseases: insights into the pathophysiology

Current concepts in pachychoroid spectrum diseases: insights into the pathophysiology

Advancements in ophthalmic imaging for better understanding of pachychoroid spectrum diseases: perspective

Advancements in ophthalmic imaging for better understanding of pachychoroid spectrum diseases: perspective

Choroidal vascularity index: An emerging useful metric for choroidal structure assessment in pachychoroid spectrum disease

AbstractPurpose: To compare choroidal vascularity index (CVI) between eyes with different entities of pachychoroid spectrum diseases (PSD) and a control group.Methods: Eighty‐two eyes of 45 patients with PSD were included in our study. Fifteen eyes had uncomplicated pachychoroid (UCP), 27 eyes had pachychoroid pigment epitheliopathy (PPE), 32 eyes had central serous chorioretinopathy (CSC) and 8 had pachychoroid neovasculopathy (PNV). These eyes were compared to 67 eyes of 34 age‐matched healthy controls. All eyes underwent DRI‐OCT Triton Swept‐Source Optical Coherence Tomography (OCT). B‐scan images were binarized into blood vessels lumen and stroma using ImageJ software. The choroidal vascularity index (CVI) was defined as the ratio of luminal area (LA) to total choroidal area in a subfoveal region of 1500 μm width.Results: Mean CVI in patients with PSD was 64.45 ± 2.74%. A statistically significant difference was found between the PSD patients group and the control group (p &lt; 0.001) with a higher CVI in PSD eyes. Pairwise comparisons revealed statistically significant differences between PPE/PNV groups (p &lt; 0.05), PPE/control groups (p &lt; 0.001), CRSC/control groups (p &lt; 0.05) and CRSC/PPE groups (p = 0.05). The comparison between UCP/control groups, UCP/PPE groups, UCP/CRSC groups, UCP/PNV groups, PNV/control groups and PNV/CRSC groups showed no significant difference.Conclusions: Increased CVI may reflect choroidal vascular structure changes in eyes with PSD. These findings suggest that the CVI could be useful for evaluating choroidal vascular changes in eyes with PSD and predicting a potential progression form PPE to CRSC or PNV.

Are choroidal vascularity parameters influenced by age, hypertension and visual acuity in pachychoroid spectrum diseases?

AbstractPurpose: To identify correlations of subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) with age and best corrected visual acuity in eyes with pachychoroid spectrum diseases (PSD) and their association to systemic hypertension using a retrospective study design.Methods: Our study included 82 eyes of 45 patients with PSD: 15 eyes had uncomplicated pachychoroid (UCP), 27 had pachychoroid pigment epitheliopathy (PPE), 32 had central serous chorioretinopathy (CSC) and 8 had pachychoroid neovasculopathy (PNV). All patients underwent DRI TRITON Swept‐Source Optical Coherence Tomography (SS‐OCT). A 1500 mm width subfoveal choroidal area was defined in SS‐OCT B‐scans and divided into luminal area (LA) and stromal area (SA) by the imageJ binarization technique. CVI was defined as the ratio of LA to the total subfoveal choroidal area (TCA).Results: The mean SFCT was 393, 23 ± 95, 65 μm and it was correlated negatively with age (p = 0.003, R = −0.326). We found a negative correlation of TCA and LA with age (p = 0.043, r = −0.227, p = 0.04, r = −0.230). Mean choroidal vascularity index was 64.45 ± 2, 74% with no correlation with age (p = 0.169, R = −0.155). No parameter among SFCT, CVI, TCA, LA and SA had a significant correlation with BCVA or spherical equivalent. Patients with essential hypertension were found to have significantly thinner SFCT when compared with healthy controls (374, 49 ± 83 141 μm vs. 423, 98 ± 130 466 μm, p = 0.046). CVI was not affected by a history of systemic hypertension (64.05 ± 1.97 vs. 64.83 ± 3.3, p = 0.207). The total choroidal area, luminal area, and stromal area, as well as the CVI correlated with SFCT (p &lt; 0.001, r = 0.817, p &lt; 0.001, r = 0.821, p &lt; 0.001, r = 0.750 and p &lt; 0.001, r = 0.371 respectively).Conclusions: SFCT and CVI are dynamic parameters that are affected in patients with pachychoroid diseases. Unlike CVI, SFCT is also affected by age, ocular and systemic factors like hypertension. CVI may be a more specific biomarker for PSD.

Characteristics and Classification of Choroidal Caverns in Patients with Various Retinal and Chorioretinal Diseases

To investigate the features of choroidal caverns in diverse retinal diseases with swept-source optical coherence tomography (SS-OCT). Subjects with normal eyes, retinitis pigmentosa (RP), wet age-related macular degeneration (wAMD), acute central serous chorioretinopathy (CSC), or chronic CSC were enrolled. The characteristics of choroidal caverns were evaluated with SS-OCT. The prevalence of choroidal caverns in retinal diseases and the correlations between the number, width and depth of choroidal caverns with the thickness of choroid were analyzed. Among 315 eyes of 220 subjects, choroidal caverns were found in 110 eyes (34.9%). Choroidal caverns were divided into two categories based on their location and size. Type I was small and usually lobulated, presented in the choroidal capillary and Sattler's layers. Type II was larger, usually isolated, and presented in the Sattler's and Haller's layers. The prevalence of type I in subjects with normal eyes, RP, wAMD, acute CSC, or chronic CSC was 17.4%, 19.6%, 1.6%, 32.8%, and 85.2%, respectively, while that of type II was 0%, 0%, 21.3%, 13.8%, and 53.7%, respectively. The number, width, and thickness of type II choroidal caverns correlated positively with macular choroidal thickness. Choroidal caverns could be divided into two categories. Type II choroidal caverns appeared associated with the pachychoroid spectrum and RPE atrophic diseases.

Three-dimensional choroidal vascularity index in central serous chorioretinopathy using ultra-widefield swept-source optical coherence tomography angiography.

BackgroundTo map and compare the three-dimensional choroidal vascularity index (3D-CVI) in eyes with unilateral central serous chorioretinopathy (CSC), fellow eyes and control eyes using ultra-widefield swept source optical coherence tomography (UWF SS-OCTA).MethodsIn this prospective observational study, the 3D-CVIs were measured in 9 subfields or 1 × 1 mm grids by the UWF SS-OCTA with a viewing angle of horizontal 24 × vertical 20 mm. The proportions of vortex vein anastomoses and their corresponding CVI in the central regions were compared among the CSC, fellow and control eyes. Correlations of CVI and vascular density of the large choroidal vessel layer/choriocapillaris layer/choroidal thickness (CT) were also assessed.ResultsThirty-two eyes in 32 patients with unilateral CSC and 32 normal eyes were included in the study. The mean CVI in the eyes with CSC was significantly greater than that in the fellow eyes of CSC and control eyes (41.99 ± 3.56% vs. 40.38 ± 3.855%, P = 0.003; 41.99 ± 3.56% vs. 38.93 ± 4.067%, P = 0.004, respectively). The CVIs in superotemporal, inferotemporal and inferonasal regions were significantly higher in CSC eyes than control eyes (P = 0.03, P = 0.02, P = 0.008). In CSC eyes, there was a linear positive correlation between 3D-CVI and vascular density of the large choroidal vessel layer and CT in all subfields. The proportion of vortex vein anastomoses in CSC was 25/32 (78.1%), and significantly higher in fellow and control eyes (P < 0.001). The average central CVI was significantly higher in CSC eyes with anastomoses than in CSC eyes without anastomoses (42.8 ± 5.1% vs. 38.4 ± 2.7%, P = 0.039). CVIs in superior, central, inferior, superonasal, nasal and inferonasal regions were significantly correlated with vortex vein anastomoses (P < 0.05), regardless of CSC, fellow or healthy eyes. In addition, whether there were vortex vein anastomoses, CVI in superotemporal region was significantly higher in eyes with CSC (P = 0.002) and fellow eyes (P = 0.014), compared to control eyes. No significant correlation was found between hypertension and CVIs in the three groups.ConclusionRemodeling of choroidal drainage routes by venous anastomosis between superior and inferior vortex veins may be common in CSC. The 3D-CVI could be a comprehensive parameter to evaluate the choroid vasculature and help understand the pathogenesis of pachychoroid spectrum disease.

Hydrodynamic Analysis of the Clinical Findings in Pachychoroid-Spectrum Diseases.

: PurposeWe wish to demonstrate that theorems of fluid dynamics may be employed to hydrodynamically analyze the clinical presentations seen within the pachychoroid-spectrum diseases (PSD). Methods: We employed both the Equation of Continuity Q = A · V in which Q represents blood flow volume, A the sectional area of a vessel, and V blood flow velocity as well as Bernoulli’s Principle 1/2 V2 + P/ρ = constant where V represents blood flow velocity, P static blood pressure and ρ blood density. The Equation of Continuity states that a decrease in flow volume occurs simultaneously with a decrease in the flow velocity and/or sectional area, and vice versa. Bernoulli’s Principle states that a decrease in the velocity of a fluid occurs simultaneously with an increase in static pressure, and vice versa. Results: Hyperpermeability of the choriocapillaris, as visualized on fluorescein angiography and indocyanine green angiography (ICGA), causes a fluid exudation and, therefore, a decrease in the blood flow volume Q which elicits a simultaneous decrease in the blood flow velocity V clinically observable in filling delay into the choriocapillaris on ICGA. An increase in the static blood pressure P will simultaneously occur in venules in accord with Bernoulli’s Principle. Conclusions: A decrease in the blood flow velocity in the choriocapillaris due to its hyperpermeability will hydrodynamically elicit an increase in the blood pressure in venules. This blood pressure rise may expand Sattler and Haller veins, forming pachyveins. The primary lesion of PSD can be in pigment epithelium and choriocapillaris.

A Comparative Study of Short-Term Vascular and Stromal Alterations of the Choroid Following Half-Fluence Photodynamic Therapy in Pachychoroid Neovasculopathy and Chronic Central Serous Chorioretinopathy.

Background: Central serous chorioretinopathy (CSCR) and pachychoroid neovasculopathy (PNV) are among the pachychoroid spectrum diseases (PSDs). Half-fluence photodynamic therapy (hf-PDT) is one of the effective treatment methods for both diseases. The aim of this study was to compare the effect of hf-PDT on the choroidal structure in CSCR and PNV. Methods: This study included 35 patients with chronic CSCR and 18 patients with PNV. The hf-PDT protocol was applied to all eyes. Before and 3 months after hf-PDT, enhanced-depth optical coherence tomography images were analyzed. The total choroidal area (CA), luminal area (LA), and stromal area (SA) were measured using ImageJ software. Results: Compared with baseline values, 3 months after hf-PDT, the mean CA reduced from 1.398 to 1.197 mm2 (p < 0.001) in the CSCR group and the total CA reduced from 1.050 to 1.000 mm2 (p < 0.021) in the PNV group. The mean percentage changes in CA, LA, and SA values were statistically higher in the chronic CSCR group (13.86%, 13.53%, and 14.11%, respectively) than those in the PNV group (4.61%, 4.02%, and 5.74%; p = 0.001, p = 0.002, and p = 0.031, respectively). Conclusion: CSCR and PNV are thought to be PSDs. However, they differ in choroidal morphological response after hf-PDT, which might be a result of the different structural components of the PNV lesions.