Enhanced-Depth Imaging Optical Coherence Tomography of the Human Choroid In Vivo Compared With Histology After Enucleation

Impact of Hemodialysis on Subfoveal Choroidal Thickness Measured by Optical Coherence Tomography: A Systematic Review and a Pooled Analysis of Self-Controlled Case Series

INTRODUCTION

Hemodialysis (HD) has various effects on the body, including optimizing body fluid composition and volume, which may have an impact on subfoveal choroidal thickness (SCT) in individuals with end-stage kidney disease (ESKD). However, previous studies have produced conflicting results regarding the effect of HD on SCT in patients with ESKD. Therefore, we conducted a meta-analysis to investigate the influence of HD on SCT.

METHODS

A comprehensive search of relevant studies and bibliographies was conducted using Embase, PubMed, and Web of Science databases up to September 2022. Weighted mean difference (WMD) and 95% confidence interval (CI) were used to summarize the SCT change. Heterogeneity and publication bias were assessed, and a random-effects model was employed for the meta-analysis. Subgroup analyses were also performed to evaluate the influence of factors such as diabetes mellitus (DM), the severity of diabetic retinopathy (DR), diurnal variation adjustment, optical coherence tomography (OCT) types, and OCT scan modes.

RESULTS

A total of 15 studies involving 1010 eyes were eligible for this meta-analysis, including 552 diabetic eyes, 230 non-diabetic eyes, and the remaining 228 eyes were uncategorized. The meta-analysis revealed a significant reduction in SCT after HD (WMD = -13.66 μm; 95% CI -24.29 to -3.03 μm; z = -5.115, P < 0.0001). Subgroup analysis indicated a significant difference between the DM and non-DM groups (WMD = -24.10 μm vs. -15.37 μm, 95% CI -27.39 to -20.80 μm vs. -19.07 to -11.66 μm; P = 0.001). Additionally, the group with proliferative diabetic retinopathy (PDR) exhibited a more pronounced reduction in SCT (WMD =  -28.66 μm; 95% CI -37.10 to -20.23; z = -6.660, P < 0.0001). Adjusting for diurnal variation, different types or scan modes of OCT did not significantly affect the results.

CONCLUSION

HD leads to a significant decrease in SCT among patients with ESKD, especially in patients with DM with PDR.

Choroidal imaging using optical coherence tomography: techniques and interpretations

The choroid is vascularized membranous tissue that supplies oxygen and nutrients to the photoreceptors and outer retina. Choroidal vessels underlying the retinal pigment epithelium are difficult to visualize by ophthalmoscopy and slit-lamp examinations. Optical coherence tomography (OCT) imaging made significant advancements in the last 2 decades; it allows visualization of the choroid and its vasculature. Enhanced-depth imaging techniques and swept-source OCT provide detailed choroidal images. A recent breakthrough, OCT angiography (OCTA), visualizes blood flow in the choriocapillaris. However, despite using OCTA, it is hard to visualize the choroidal vessel blood flow. In conventional structural OCT the choroidal vessel structure appears as a low-intensity objects. Image-processing techniques help obtain structural information about these vessels. Manual or automated segmentation of the choroid and binarization techniques enable evaluation of choroidal vessels. Viewing the three-dimensional choroidal vasculature is also possible using high-scan speed volumetric OCT. Unfortunately, although choroidal image analyses are possible using the images obtained by commercially available OCT, the built-in function that analyzes the choroidal vasculature may be insufficient to perform quantitative imaging analysis. Physicians must do that themselves. This review summarizes recent choroidal imaging processing techniques and explains the interpretation of the results for the benefit of imaging experts and ophthalmologists alike.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

The eye, the kidney, and cardiovascular disease: old concepts, better tools, and new horizons

Chronic kidney disease (CKD) is common, with hypertension and diabetes mellitus acting as major risk factors for its development. Cardiovascular disease is the leading cause of death worldwide and the most frequent end point of CKD. There is an urgent need for more precise methods to identify patients at risk of CKD and cardiovascular disease. Alterations in microvascular structure and function contribute to the development of hypertension, diabetes, CKD, and their associated cardiovascular disease. Homology between the eye and the kidney suggests that noninvasive imaging of the retinal vessels can detect these microvascular alterations to improve targeting of at-risk patients. Retinal vessel-derived metrics predict incident hypertension, diabetes, CKD, and cardiovascular disease and add to the current renal and cardiovascular risk stratification tools. The advent of optical coherence tomography (OCT) has transformed retinal imaging by capturing the chorioretinal microcirculation and its dependent tissue with near-histological resolution. In hypertension, diabetes, and CKD, OCT has revealed vessel remodeling and chorioretinal thinning. Clinical and preclinical OCT has linked retinal microvascular pathology to circulating and histological markers of injury in the kidney. The advent of OCT angiography allows contrast-free visualization of intraretinal capillary networks to potentially detect early incipient microvascular disease. Combining OCT's deep imaging with the analytical power of deep learning represents the next frontier in defining what the eye can reveal about the kidney and broader cardiovascular health.