Choriocapillaris Imaging Using Multiple En Face Optical Coherence Tomography Angiography Image Averaging

Progressive Choriocapillaris Changes on Optical Coherence Tomography Angiography Correlate With Stage Progression in AMD

Purpose

We investigated the association between inner choroid flow deficit percentage (IC-FD%) using swept-source optical coherence tomography angiography (SS-OCTA) and progression of AMD.

Methods

Retrospective, observational study including 64 eyes (42 participants) with early or intermediate AMD at baseline. Participants had two or more consecutive swept-source optical coherence tomography angiography covering a period of at least 18 months. Demographics, visual acuity, and AMD staging based on Beckman classification were reviewed. OCT was analyzed for hyperreflective foci, subretinal drusenoid deposits, hyporeflective drusen cores, and subfoveal choroidal thickness. IC-FD% was measured within the central 3- and 6-mm using a 16-µm slab, after compensation and binarization (Phansalkar method). Mixed-effects Cox regression models assessed the association between imaging biomarkers and AMD progression.

Results

During follow-up (37 ± 9 months), 4 eyes with early AMD (31%) progressed to intermediate AMD and 30 (59%) eyes with intermediate AMD developed late AMD (19 geographic atrophy; 11 wet AMD). Baseline hyporeflective drusen core was associated with geographic atrophy development (P < 0.01), whereas greater IC-FD% (3-mm) was associated with wet AMD (P = 0.03). Time-varying analysis showed that faster subfoveal choroidal thickness reduction and IC-FD% (6-mm) increase were associated with geographic atrophy onset (P < 0.05), whereas IC-FD% (3-mm) increase was associated with wet AMD (P = 0.03). Notably, greater IC-FD% increases in the 3 mm (area under the curve = 0.72) and 6 mm (area under the curve = 0.89) were better predictive of wet AMD and geographic atrophy development, respectively.

Conclusions

Our longitudinal IC-FD% assessment emphasizes the role of progressive choriocapillaris changes as a biomarker for AMD progression. Our findings support that widespread choriocapillaris alterations (6 mm) may precede progression to geographic atrophy, whereas more central choriocapillaris loss (3 mm) may provide an ischemic stimulus for wet AMD.

Visualizing features with wide-field volumetric OCT angiography

Optical coherence tomography (OCT) and its extension OCT angiography (OCTA) have become essential clinical imaging modalities due to their ability to provide depth-resolved angiographic and tissue structural information non-invasively and at high resolution. Within a field of view, the anatomic detail available is sufficient to identify several structural and vascular pathologies that are clinically relevant for multiple prevalent blinding diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and vein occlusions. The main limitation in contemporary OCT devices is that this field of view is limited due to a fundamental trade-off between system resolution/sensitivity, sampling density, and imaging window dimensions. Here, we describe a swept-source OCT device that can capture up to a 12 × 23-mm field of view in a single shot and show that it can identify conventional pathologic features such as non-perfusion areas outside of conventional fields of view. We also show that our approach maintains sensitivity sufficient to visualize novel features, including choriocapillaris morphology beneath the macula and macrophage-like cells at the inner limiting membrane, both of which may have implications for disease.

Relationship between visual acuity and OCT angiography parameters in diabetic retinopathy eyes after treatment

PURPOSE

To assess the relationship between visual acuity and OCT angiography parameters in diabetic retinopathy eyes after treatment, and to analyze the relative factors in PDR eyes.

METHODS

A total of 89 eyes, including 42 eyes with non-PDR (NPDR), and 47 eyes after vitrectomy with PDR were included and underwent OCTA. All images were processed by Python or FIJI. Multivariable linear regression models were used to analyze the associations between postoperative BCVA and OCTA parameters in PDR patients.

RESULTS

Postoperative OCTA parameters including deep capillary plexus (DCP) parafoveal and perifoveal vessel density (VD), DCP parafoveal and perifoveal vessel length density (VLD), DCP fractal dimension (FD), choriocapillaris plexus (CCP) VD, CCP VLD, were significantly lower in the PDR group than in the NPDR group. In the superficial capillary plexus (SCP), we found a negative correlation between the postoperative BCVA and VD (parafovea: β coefficient = -0.351, p = 0.023; perifovea: β coefficient = -0.338, p = 0.036). Perifoveal VLD (β coefficient = -0.343, p = 0.031) and FD (β coefficient = -0.375, p = 0.016) of the SCP were also negatively correlated with postoperative BCVA. Regarding the DCP, perifoveal VD (β coefficient = -0.396, p = 0.008), perifoveal VLD (β coefficient = -0.334, p = 0.025), vessel tortuosity (VT) (β coefficient = -0.369, p = 0.015) were negatively correlated with postoperative BCVA. In CCP, VLD (β coefficient = -0.373, p = 0.023) and number of flow voids (β coefficient = -0.334, p = 0.036) exhibited a negative association with postoperative BCVA.

CONCLUSIONS

Postoperative BCVA of PDR patients was related to OCTA parameters of the SCP (parafoveal and perifoveal VD, perifoveal VLD and FD), DCP (perifoveal VD, VLD, and VT) and CCP (VLD and number of flow voids).

MULTIMODAL IMAGING IN NONEXUDATIVE CHOROIDAL NEOVASCULARIZATION: A Pilot Study of Status of Retinal Pigment Epithelium

PURPOSE

To study the status of retinal pigment epithelium in nonexudative and active choroidal neovascularization (CNV) in neovascular age-related macular degeneration.

METHODS

Only treatment-naïve neovascular age-related macular degeneration patients were enrolled in this prospective case-control study, including 17 eyes with nonexudative CNV (6 males and 11 females, 74.9 ± 10.0 years) and 28 eyes with active CNV (8 males and 20 females, 69.3 ± 6.8 years). All patients received a comprehensive ophthalmic examination, optical coherence tomography, dark-field scanning laser ophthalmoscopy, and fundus autofluorescence. The status of the retinal pigment epithelium was assessed with ImageJ software as the brightness of the CNV region on transillumination optical coherence tomography, dark-field scanning laser ophthalmoscopy, and fundus autofluorescence images. Choroidal neovascularization vessel density was measured based on optical coherence tomography angiography.

RESULTS

The brightness of CNV region in nonexudative CNV was statistically significantly lower than in active CNV with both optical coherence tomography transillumination ( P = 0.004) and dark-field scanning laser ophthalmoscopy ( P = 0.0015). No difference in brightness of the CNV region between nonexudative and active CNV was found based on fundus autofluorescence ( P = 0.44). The vessel density of nonexudative CNV was statistically significantly higher than that of active CNV with a median value of 64.5% (95% confidential interval [CI] 53.4-79.0%) and 55.3% (95% CI 52.2-60.0%), respectively ( P = 0.05).

CONCLUSION

Multimodal imaging revealed substantial alteration of the retinal pigment epithelium in active CNV but not in nonexudative CNV which correlates with the higher vessel density of nonexudative CNV.

Pseudoaveraging for denoising of OCT angiography: a deep learning approach for image quality enhancement in healthy and diabetic eyes

BACKGROUND

This study aimed to develop a deep learning (DL) algorithm that enhances the quality of a single-frame enface OCTA scan to make it comparable to 4-frame averaged scan without the need for the repeated acquisitions required for averaging.

METHODS

Each of the healthy eyes and eyes from diabetic subjects that were prospectively enrolled in this cross-sectional study underwent four repeated 6 × 6 mm macular scans (PLEX Elite 9000 SS-OCT), and the repeated scans of each eye were co-registered to produce 4-frame averages. This prospective dataset of original (single-frame) enface scans and their corresponding averaged scans was divided into a training dataset and a validation dataset. In the training dataset, a DL algorithm (named pseudoaveraging) was trained using original scans as input and 4-frame averages as target. In the validation dataset, the pseudoaveraging algorithm was applied to single-frame scans to produce pseudoaveraged scans, and the single-frame and its corresponding averaged and pseudoaveraged scans were all qualitatively compared. In a separate retrospectively collected dataset of single-frame scans from eyes of diabetic subjects, the DL algorithm was applied, and the produced pseudoaveraged scan was qualitatively compared against its corresponding original.

RESULTS

This study included 39 eyes that comprised the prospective dataset (split into 5 eyes for training and 34 eyes for validating the DL algorithm), and 105 eyes that comprised the retrospective test dataset. Of the total 144 study eyes, 58% had any level of diabetic retinopathy (with and without diabetic macular edema), and the rest were from healthy eyes or eyes of diabetic subjects but without diabetic retinopathy and without macular edema. Grading results in the validation dataset showed that the pseudoaveraged enface scan ranked best in overall scan quality, background noise reduction, and visibility of microaneurysms (p < 0.05). Averaged scan ranked best for motion artifact reduction (p < 0.05). Grading results in the test dataset showed that pseudoaveraging resulted in enhanced small vessels, reduction of background noise, and motion artifact in 100%, 82%, and 98% of scans, respectively. Rates of false-positive/-negative perfusion were zero.

CONCLUSION

Pseudoaveraging is a feasible DL approach to more efficiently improve enface OCTA scan quality without introducing notable image artifacts.

Age-Related Alterations of the Macular Choroid in Healthy Eyes Assessed by Swept-Source Optical Coherence Tomography Angiography

OBJECTIVE

To analyze age-related changes in the choroid in healthy eyes using swept-source optical coherence tomography angiography (SS-OCTA).

PATIENTS AND METHODS

This was a cross-sectional, prospective, observational study enrolling 222 eyes of 116 healthy participants. SS-OCTA images were captured using the PLEX Elite 9000 (Carl Zeiss Meditec) with a 6 x 6 mm pattern centered on the fovea. Subfoveal choroidal thickness (CT) and choroidal volume (CV) were generated automatically through manufacturer tools available in the Advanced Retinal Imaging (ARI) hub network. Choroidal vascularity index (CVI) and choriocapillaris flow deficits (CCFD) were computed using ImageJ.

RESULTS

CV was found to be significantly higher in women than men. Overall, there was a significant positive correlation between CVI and CCFD, and a significant negative correlation between CT and CV with age. The relationship, however, was more complex, as a decade-wise analysis showed that CT and CV increased until the second decade, followed by a decrease until the sixth decade, and then an increase again in the seventh and eighth decades. CVI was highest in the seventh decade. In contrast, CCFD increased consistently with age and in all the Early Treatment of Diabetic Retinopathy Study (ETDRS) rings.

CONCLUSION

The choroidal blood flow and its thickness reduces as the age advances. While the choroidal flow deficits show a consistent increase with age and the distance from the foveal center, the relationship of other parameters with age is more complex. Having a normative database from healthy subjects is imperative for understanding the changes taking place in diseased states. Choroidal parameters can show significant variations with age. These differences are not uniform or consistent with age, highlighting the importance of a normative reference database to assess the significance of choroidal alterations associated with disease. [Ophthalmic Surg Lasers Imaging Retina 2023;54:526-534.].

Choriocapillaris Impairment Is Associated With Delayed Rod-Mediated Dark Adaptation in Age-Related Macular Degeneration

Purpose

Progress toward treatment and prevention of age-related macular degeneration (AMD) requires imaging end points that relate to vision. We investigated choriocapillaris flow signal deficits (FD%) and visual function in eyes of individuals aged ≥60 years, with and without AMD.

Methods

One eye of each participant in the baseline visit of the Alabama Study on Early Age-Related Macular Degeneration 2 (ALSTAR2; NCT04112667) was studied. AMD presence and severity was determined using the Age-Related Eye Disease Study (AREDS) grading system. FD% was quantified using macular spectral domain optical coherence tomography angiography (OCTA) scans. Vision tests included rod-mediated dark adaptation (RMDA), best-corrected visual acuity, and contrast sensitivity (photopic and mesopic), and microperimetric light sensitivity (scotopic, mesopic, and photopic). Presence of subretinal drusenoid deposits (SDD) was determined using multimodal imaging.

Results

In 410 study eyes of 410 participants (mean [SD] age = 71.7 years [5.9]), FD% was higher in early AMD (mean [SD] = 54.0% [5.5], N = 122) and intermediate AMD (59.8% [7.4], N = 92), compared to normal (52.1% [5.3], N = 196) eyes. Among visual functions evaluated, RMDA showed the strongest association with FD% (r = 0.35, P < 0.0001), followed by contrast sensitivity (r = -0.22, P < 0.0001). Eyes with SDD had worse FD% (58.3% [7.4], N = 87), compared to eyes without SDD (53.4% [6.0], N = 323, P = < 0.0001).

Conclusions

Choriocapillaris FD% were associated with AMD severity and with impaired vision, especially RMDA. Reduced metabolic transport and exchange across the choriocapillaris-Bruch's membrane retinal pigment epithelium (RPE) complex, a causal factor for high-risk soft drusen formation, also may impair photoreceptor sustenance from the circulation. This includes retinoid resupply, essential to dynamic rod function.

Retinal capillary and choriocapillaris assessment using a beam modifier optical coherence tomography angiography module to increase lateral optical resolution

PURPOSE

To assess a new optical coherence tomography angiography (OCTA) technology and its contribution to retinal vascularization and choriocapillaris (CC) exploration.

METHODS

A new module, named "Beam expander" (BE), which increases the lateral resolution of OCTA, was used in combination with a prototype software in the PLEX® Elite 9000 Swept-Source OCT instrument (ZEISS, Dublin, CA). This prospective study involved 22 healthy subjects imaged with and without BE. Qualitative analysis of superficial capillary plexus (SCP), deep capillary complex (DCC) retinal and CC angiograms were performed. Perfusion density (PD), vessel density (VD), and foveal avascular zone (FAZ) measurements were also compared.

RESULTS

Qualitative analysis of single SCP and DCC retinal angiograms acquired with BE showed significantly better vessel sharpness (respectively, p = 0.0002, and p<0.0001), and greater peripheral image quality (p = 0.028 and p = 0.007) compared to standard OCTA images. Mean VD of whole retina single scans was significantly higher for BE angiograms compared to classic angiograms (28.16 ±1.29 mm-1 and 23.36 ±0.92 mm-1, respectively, p<0.0001). Repeatability of VD, PD and FAZ raw size were found to be similar between the two methods (intraclass correlation coefficient: 0.671, 0.604 and 0.994 with BE versus 0.764, 0.638 and 0.990 without BE). CC image quality was found to be significantly superior with BE, and flow deficits were more visible in all BE scans compared to standard scans.

CONCLUSIONS

An increase in lateral resolution of the OCT beam resulted in higher quality of retinal and choriocapillaris OCTA images in healthy subjects. These results provide significant insights into the future OCTA imaging enhancements.

Comparison of Automated Thresholding Algorithms in Optical Coherence Tomography Angiography Image Analysis

(1) Background: Calculation of vessel density in optical coherence tomography angiography (OCTA) images with thresholding algorithms varies in clinical routine. The ability to discriminate healthy from diseased eyes based on perfusion of the posterior pole is critical and may depend on the algorithm applied. This study assessed comparability, reliability, and ability in the discrimination of commonly used automated thresholding algorithms. (2) Methods: Vessel density in full retina and choriocapillaris slabs were calculated with five previously published automated thresholding algorithms (Default, Huang, ISODATA, Mean, and Otsu) for healthy and diseased eyes. The algorithms were investigated with LD-F2-analysis for intra-algorithm reliability, agreement, and the ability to discriminate between physiological and pathological conditions. (3) Results: LD-F2-analyses revealed significant differences in estimated vessel densities for the algorithms (p < 0.001). For full retina and choriocapillaris slabs, intra-algorithm values range from excellent to poor, depending on the applied algorithm; the inter-algorithm agreement was low. Discrimination was good for the full retina slabs, but poor when applied to the choriocapillaris slabs. The Mean algorithm demonstrated an overall good performance. (4) Conclusions: Automated threshold algorithms are not interchangeable. The ability for discrimination depends on the analyzed layer. Concerning the full retina slab, all of the five evaluated automated algorithms had an overall good ability for discrimination. When analyzing the choriocapillaris, it might be useful to consider another algorithm.

CHORIOCAPILLARIS STRUCTURE IN THE FELLOW EYES OF PATIENTS WITH NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: An OCT Angiography Image Averaging Study

PURPOSE

Histological choriocapillaris abnormalities have been reported in age-related macular degeneration (AMD). Averaging multiple en face optical coherence tomography angiography improves the quality of imaging of the choriocapillaris. This study used multiple en face swept source optical coherence tomography angiography image averaging to examine the structural changes in the choriocapillaris in the fellow eyes of patients with neovascular AMD.

METHODS

All patients underwent macular optical coherence tomography angiography imaging. One eye per subject was repeatedly imaged, and nine raster scan sets were obtained. Registered en face images were averaged, and area of flow voids and number of flow voids were measured using ImageJ software.

RESULTS

Forty-eight patients with neovascular AMD were recruited for analysis. Twenty-seven patients had polypoidal choroidal vasculopathy, and 22 eyes had soft drusen. Twenty-six eyes of 26 healthy individuals were included as age-matched normal controls. The choriocapillaris had a meshwork appearance in all eyes. The mean flow void area of the choriocapillaris was larger in patients with AMD than normal controls (1.14 ± 0.16 mm2 vs. 1.01 ± 0.12 mm2, P = 0.002). The mean size of each flow void was greater in patients with AMD than normal controls (729 ± 210 µm2 vs. 583 ± 120 µm2, P = 0.003). The mean flow void area of the choriocapillaris was larger in eyes with soft drusen than without soft drusen (1.2 ± 0.2 mm2 vs. 1.1 ± 0.1 mm2, P = 0.024).

CONCLUSION

Multiple en face image averaging revealed precise choriocapillaris structures in the fellow eyes of patients with neovascular AMD.

Investigating the macular choriocapillaris in early primary open-angle glaucoma using swept-source optical coherence tomography angiography

Introduction

There has been a growing interest in the role of vascular factors in glaucoma. Studies have looked at the characteristics of macular choriocapillaris in patients with glaucoma but with conflicting results. Our study aims to use swept-source optical coherence tomography angiography (SS-OCTA) to evaluate macular choriocapillaris metrics in normal participants and compare them with patients with early primary open-angle glaucoma (POAG) (mean deviation better than −6dB).

Methods

In this prospective, observational, cross-sectional study, 104 normal controls (157 eyes) and 100 patients with POAG (144 eyes) underwent 3 mm × 3mm imaging of the macula using the Plex Elite 9000 (Zeiss Meditec, Dublin, CA, USA). Choriocapillaris OCTA images were extracted from the device’s built-in review software and were subsequently evaluated for the density and size of choriocapillaris flow deficits.

Results

After adjusting for confounding factors, the density of flow deficits was independently higher in those aged 53 years and above (P ≤ 0.024) whereas the average flow deficit size was significantly larger in those aged 69 years and above (95% CI = 12.39 to 72.91; P = 0.006) in both normal and POAG patients. There were no significant differences in the density of flow deficits (P = 0.453) and average flow deficit size (P = 0.637) between normal and POAG participants.

Conclusion

Our study found that macular choriocapillaris microvasculature on SS-OCTA is unaltered by subjects with POAG. This suggests that OCTA macular choriocapillaris may not be potentially helpful in differentiating early glaucoma from healthy eyes.

Choriocapillaris flow deficit in a pachychoroid spectrum disease using en face optical coherence tomography angiography averaging

Purpose

To investigate the choriocapillaris changes associated with pachychoroid pigment epitheliopathy (PPE) in comparison with healthy eyes.

Methods

Nine 3 × 3 mm macular optical coherence tomography angiography images were acquired in patients with PPE and age-matched healthy participants. Multiple en face image averaging of the choriocapillaris was binarized for quantitative image analysis of the flow voids. In PPE eyes, we evaluated the presence of pachyvessels and the association between the location of the choriocapillaris flow deficit and pachyvessels.

Results

Thirty-two eyes with PPE and 30 eyes of healthy participants were included. In PPE eyes, the mean total area (1.16 ± 0.18 vs. 0.91 ± 0.16, p < 0.001) and average size of the flow voids (790 ± 144 vs. 520 ± 138; p < 0.001) were significantly larger than those in control eyes. Composite images of the choriocapillaris and choroid showed choriocapillaris flow deficits just above and outside the pachyvessels. The mean proportion of the flow void area overlying the pachyvessels against the whole flow void area of the choriocapillaris was 21.3% ± 10.2% (9.38%-44.42%) in PPE eyes.

Conclusions

In PPE eyes, the blood flow area of the choriocapillaris decreased diffusely within the macular area compared to control eyes, and the choriocapillaris flow deficit was not necessarily related to pachyvessel location.

Imaging-based Assessment of Choriocapillaris: A Comprehensive Review

PURPOSE

Over the past two decades, advancements in imaging modalities have significantly evolved the diagnosis and management of retinal diseases. Through these novel platforms, we have developed a deeper understanding of the anatomy of the choroidal vasculature and the choriocapillaris. The recently developed tools such as optical coherence tomography (OCT) and OCT angiography (OCTA) have helped elucidate the pathological mechanisms of several posterior segment diseases. In this review, we have explained the anatomy of the choriocapillaris and its close relationship to the outer retina and retinal pigment epithelium.

METHODS

A comprehensive search of medical literature was performed through the Medline/PubMed database using search terms: choriocapillaris, choroid, quantification, biomarkers, diabetic retinopathy, age-related macular degeneration, choroidal blood flow, mean blur rate, flow deficit, optical coherence tomography, optical coherence tomography angiography, fluorescein angiography, indocyanine green angiography, OCTA, Doppler imaging, uveitis, choroiditis, white dot syndrome, tubercular serpiginous-like choroiditis, choroidal granuloma, pachychoroid, toxoplasmosis, central serous chorioretinopathy, multifocal choroiditis, choroidal neovascularization, choroidal thickness, choroidal vascularity index, choroidal vascular density, and choroidal blood supply. The search terms were used either independently or combined with choriocapillaris/choroid.

RESULTS

The imaging techniques which are used to qualitatively and quantitatively analyze choriocapillaris are described. The pathological alterations in the choriocapillaris in an array of conditions such as diabetes mellitus, age-related macular degeneration, pachychoroid spectrum of diseases, and inflammatory disorders have been comprehensively reviewed. The future directions in the study of choriocapillaris have also been discussed.

CONCLUSION

The development of imaging tools such as OCT and OCTA has dramatically improved the assessment of choriocapillaris in health and disease. The choriocapillaris can be delineated from the stromal choroid using the OCT and quantified by manual or automated methods. However, these techniques have inherent limitations due to the lack of an anatomical distinction between the choriocapillaris and the stromal choroid, which can be overcome with the use of predefined segmentation slabs on OCT and OCTA. These segmentation slabs help in standardizing the choriocapillaris imaging and obtain repeatable measurements in various conditions such as diabetic retinopathy, age-related macular degeneration, pachychoroid spectrum, and ocular inflammations. Additionally, Doppler imaging has also been effectively used to evaluate the choroidal blood flow and quantifying the choriocapillaris and establishing its role in the pathogenesis of various retinochoroidal diseases. As tremendous technological advancements such as wide-field and ultra-wide field imaging take place, there will be a significant improvement in the ease and accuracy of quantifying the choriocapillaris.

Computerized Texture Analysis of Optical Coherence Tomography Angiography of Choriocapillaris in Normal Eyes of Young and Healthy Subjects

Computerized texture analysis uses higher-order mathematics to identify patterns beyond what the naked eye can recognize. We tested its feasibility in optical coherence tomography angiography imaging of choriocapillaris. Our objective was to determine sets of parameters that provide coherent and consistent output when applied to a homogeneous, healthy group of patients. This observational cross-sectional study involved 19 eyes of 10 young and healthy Caucasian subjects. En-face macular optical coherence tomography angiography of superficial choriocapillaris was obtained by the RTVue-XR Avanti system. Various algorithms were used to extract texture features. The mean and standard deviation were used to assess the distribution and dispersion of data points in each metric among eyes, which included: average gray level, gray level yielding 70% threshold and 30% threshold, balance, skewness, energy, entropy, contrast, edge mean gradient, root-mean-square variation, and first moment of power spectrum, which was compared between images, showing a highly concordant homology between all eyes of participants. We conclude that computerized texture analysis for en-face optical coherence tomography angiography images of choriocapillaris is feasible and provides values that are coherent and tightly distributed around the mean in a homogenous, healthy group of patients. Homology of blob size among subjects may represent a “repeat pattern” in signal density and thus a perfusion in the superficial choriocapillaris of healthy young individuals of the same ethnic background.

Comparison of Indocyanine Green Angiography and Swept-Source Wide-Field Optical Coherence Tomography Angiography in Posterior Uveitis

Purpose

To compare indocyanine green angiography (ICGA) and swept-source wide-field optical coherence tomography angiography (SS-OCTA) for the assessment of patients with posterior uveitis.

Method

SS-OCTA montage images of 5 x 12 x 12 mm or 2 x 15 x 9 mm, covering ~70-90 degree of the retina of consecutive patients with posterior uveitis were acquired. The choriocapillaries and choroidal slabs were compared to findings on ICGA.

Results

Sixty-eight eyes of 41 patients were included (mean age 47.2 ± 20.4 years; 58.5% female). In 23 (34%) lesions were visible on OCTA, but not discernable on ICGA. In turn, out of the 45 eyes with clearly discernable lesions on ICGA, 22 (49%) and 21 (47%) eyes showed no corresponding areas of flow deficit on OCTA in the CC and choroidal slab, respectively. Lesion size strongly correlated among ICGA and OCTA choriocapillaries- (CC) (r = 0.99, p ≤ 0.0001) and choroidal slabs (r = 0.99, p ≤ 0.0001), respectively. The mean lesion size on the late frames of ICGA (8.45 ± 5.47 mm2) was larger compared to the lesion size on OCTA CC scan (7.98 ± 5.47 mm2, p ≤ 0.0001) and choroidal scan (7.69 ± 5.10 mm2, p = 0.002), respectively. The lesion size on OCTA CC scan was significantly larger than on the OCTA choroidal scan (p ≤ 0.0001).

Conclusion

SS-wide field OCTA may be a promising tool to assess posterior uveitis patients and may replace ICGA to a certain extent in the future.

DENOISING SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY VOLUMETRIC SCANS USING A DEEP LEARNING MODEL

PURPOSE

To evaluate the use of a deep learning noise reduction model on swept source optical coherence tomography volumetric scans.

METHODS

Three groups of images including single-line highly averaged foveal scans (averaged images), foveal B-scans from volumetric scans using no averaging (unaveraged images), and deep learning denoised versions of the latter (denoised images) were obtained. We evaluated the potential increase in the signal-to-noise ratio by evaluating the contrast-to-noise ratio of the resultant images and measured the multiscale structural similarity index to determine whether the unaveraged and denoised images held true in structure to the averaged images. We evaluated the practical effects of denoising on a popular metric of choroidal vascularity known as the choroidal vascularity index.

RESULTS

Ten eyes of 10 subjects with a mean age of 31 years (range 24-64 years) were evaluated. The deep choroidal contrast-to-noise ratio mean values of the averaged and denoised image groups were similar (7.06 vs. 6.81, P = 0.75), and both groups had better maximum contrast-to-noise ratio mean values (27.65 and 46.34) than the unaveraged group (14.75; P = 0.001 and P < 0.001, respectively). The mean multiscale structural similarity index of the average-denoised images was significantly higher than the one from the averaged--unaveraged images (0.85 vs. 0.61, P < 0.001). Choroidal vascularity index values from averaged and denoised images were similar (71.81 vs. 71.16, P = 0.554).

CONCLUSION

Using three different metrics, we demonstrated that the deep learning denoising model can produce high-quality images that emulate, and may exceed, the quality of highly averaged scans.

Choriocapillaris Flow Deficits in Normal Chinese Imaged by Swept-Source Optical Coherence Tomographic Angiography

PURPOSE

To evaluate the ocular and systemic determinants of the choriocapillaris flow deficits percentage (CC FD%) in normal eyes.

DESIGN

Observational cross-sectional study.

METHODS

Healthy Chinese participants without ocular or systemic diseases underwent detailed ophthalmic evaluations, including swept-source optical coherence tomography angiography (SS-OCTA) with 6- × 6-mm macular choriocapillaris images. The CC FD% was assessed in circular regions with diameters of 1.0 and 5.0 mm, rings with 1.0- to 2.5-mm diameters, and rings with 2.5- to 5.0-mm diameters.

RESULTS

The study included 830 individuals (mean ± SD age 58.66 ± 8.75 years). CC FD% (mean ± SD 22.05% ± 1.13%) was the lowest in the 2.5- to 5.0-mm ring, followed by the 1.0- to 2.5-mm ring, and highest in the 1.0-mm circle. In multivariable analysis, a higher CC FD% was associated with older age (β = 0.16 [95% confidence interval {CI}] 0.08-0.24, P < .001), higher intraocular pressure (β = 0.34 [95% CI 0.25-0.42], P < .001), higher serum concentrations of high-density lipoprotein cholesterol (β = 0.24 [95% CI 0.17-0.32], P < .001), and lower image quality score (β = -0.22 [95% CI -0.30 to -0.14], P < .001). CC FD% was also independent of axial length.

CONCLUSIONS

In healthy adult Chinese individuals, a higher CC FD% was associated with older age, higher intraocular pressure, and higher high-density lipoprotein cholesterol serum concentration. These factors may influence clinical assessments of the choriocapillaris. The lack of an association between CC FD% and axial length is consistent with similar findings for Bruch membrane thickness, macular retinal thickness, and macular retinal pigment epithelium cell density.

Correlations among age, sex, axial length, and subfoveal choroidal thickness in the choriocapillaris structure analyzed using multiple en face image averaging optical coherence tomography angiography

Purpose

To analyze the structure of the choriocapillaris in healthy eyes by using averaged en face images acquired using swept source optical coherence tomography angiography and to examine the changes in the macular profile in relation to age, sex, axial length, and choroidal thickness.

Methods

This prospective, cross-sectional study included 81 eyes of 81 subjects without ophthalmologic or systemic diseases who underwent a full ophthalmologic examination, including 3 × 3-mm macular optical coherence tomography angiography. Four to nine choriocapillaris en face images were registered and averaged. The averaged images were then binarized and analyzed.

Results

The averaged choriocapillaris images showed a continuous capillary meshwork, whereas the unaveraged images had a granular appearance. The mean total area and size of flow voids were 0.99 ± 0.20 mm² and 567.8 ± 201.5 μm², respectively, and these values correlated positively with age (p = 0.002, R = 0.336 and p = 0.026, R = 0.247, respectively). Age-related gains in the mean total area and flow void size were 4.20 × 10⁻³ mm² and 3.07 μm² per year, respectively. However, the mean total area and flow void size had no significant correlation with axial length, subfoveal choroidal thickness, or sex.

Conclusions

Multiple averaged en face swept source optical coherence tomography angiography is more effective than a single optical coherence tomography angiography scan for better visualizing the choriocapillaris. The total area and size of flow voids within a 3 × 3-mm macular area positively correlated with age. This technique can be useful for investigating the changes arising in macular diseases.

Optical coherence tomography (OCT) angiolytics: a review of OCT angiography quantitative biomarkers

Optical coherence tomography angiography (OCTA) provides a non-invasive method to obtain angiography of the chorioretinal vasculature leading to its recent widespread adoption. With a growing number of studies exploring the use of OCTA, various biomarkers quantifying the vascular characteristics have come to light. In the current report, we summarize the biomarkers currently described for retinal and choroidal vasculature using OCTA systems and the methods used to obtain them. Further, we present a critical review of these methods and key findings in common retinal diseases and appraise future directions, including applications of artificial intelligence in OCTA .

Prevention of Image Quality Degradation in Wider Field Optical Coherence Tomography Angiography Images Via Image Averaging

Purpose

To evaluate the mutual effect of widening the field of view and multiple en face image averaging on the quality of optical coherence tomography angiography (OCTA) images.

Methods

This prospective, observational, cross-sectional case series included 20 eyes of 20 healthy volunteers with no history of ocular or systemic disease. OCTA imaging of a 3 × 3-mm, 6 × 6-mm, and 12 × 12-mm area centered on the fovea was performed nine times using the PLEX Elite 9000. We acquired averaged OCTA images generated from nine en face OCTA images. The corresponding areas in the three scan sizes were evaluated for the original single-scanned OCTA images and averaged OCTA images both qualitatively and quantitatively. Quantitative measurements included vessel density (VD), vessel length density (VLD), fractal dimension (FD), and contrast-to-noise ratio (CNR).

Results

Significant differences in VD, VLD, FD, and CNR (P < 0.001) were observed due to the mutual effect of averaging and differences in scan size. Both qualitative and quantitative evaluations indicated that the quality of 6 × 6-mm averaged images was equal to or better than that of 3 × 3-mm single-scanned images. However, the quality of 12 × 12-mm averaged images did not reach that of 3 × 3-mm single-scanned images.

Conclusions

To some extent, multiple en face OCTA image averaging can compensate for the deterioration in image quality caused by widening the field of view.

Translational Relevance

Multiple en face OCTA image averaging can be a technique for acquiring wider field OCTA images with good quality.

Impact of image averaging on vessel detection using optical coherence tomography angiography in eyes with macular oedema and in healthy eyes

Purpose

To assess the repeatability of multiple automatic vessel density (VD) measurements and the effect of image averaging on vessel detection by optical coherence tomography angiography (OCTA).

Methods

An observational study was conducted in a series of healthy volunteers and patients with macular oedema. Five sequential OCTA images were acquired for each eye using the OptoVue HD device. The effect of the averaging of the 5 acquisitions on vessel detection was analysed quantitatively using a pixel-by-pixel automated analysis. In addition, two independent retina experts qualitatively assessed the change in vessel detection in averaged images segmented in 9 boxes and compared to the first non-averaged image.

Results

The automatic VD measurement in OCTA images showed a good repeatability with an overall mean intra-class correlation coefficient (ICC) of 0.924. The mean ICC was higher in healthy eyes compared to eyes with macular oedema (0.877 versus 0.960; p < 0.001) and in the superficial vascular plexus versus the deep vascular complex (0.967 versus 0.888; p = 0.001). The quantitative analysis of the effect of the averaging showed that averaged images had a mean gain of 790.4 pixels/box, located around or completing interruptions in the vessel walls, and a mean loss of 727.2 pixels/box. The qualitative analysis of the averaged images showed that 99.6% of boxes in the averaged images had a gain in vessel detection (i.e., vessels detected in the averaged image but not in the non-averaged image). The loss of pixels was due to a reduction in background noise and motion artifacts in all cases and no case of loss of vessel detection was observed.

Conclusion

The automatic VD measurement using the OptoVue HD device showed a good repeatability in 5 acquisitions in a row setting. Averaging images increased vessel detection, and in about a third of boxes, decreased the background noise, both in healthy eyes and, in a greater proportion, in eyes with macular oedema.

Topographic Variation of Retinal Vascular Density in Normal Eyes Using Optical Coherence Tomography Angiography

Purpose

To establish a continuous topography of retinal vessel density in normal eyes using optical coherence tomography angiography (OCTA).

Methods

A retrospective chart review was performed, and 8-mm × 8-mm OCTA images from 22 normal eyes were analyzed. Vessel density was plotted as a continuous function of distance from the foveal center (radial vessel density) and directional meridians (directional vessel density) for the superficial capillary plexus and deep capillary plexus.

Results

Continuous radial and directional vessel density plots for the superficial and deep capillary plexus were generated. Radial vessel density analysis revealed transition points at 657 microns (95% confidence interval [CI], 619-696) and 950 microns (95% CI, 903-997) from the foveal center for the superficial plexus and deep plexus, respectively. Directional vessel density analysis demonstrated significant vessel density variations in these vascular layers and provided greater detail compared to traditional quadrant analysis.

Conclusions

There are significant topographic variations of retinal vessel density in normal eyes. Continuous vessel density analysis offers greater sensitivity in detecting topographic vessel density changes compared to traditional methods of analysis.

Translational Relevance

This study establishes a normative continuous vessel density topography that may help elucidate the role of the vascular bed in different chorioretinal diseases.

Enhanced medical diagnosis for dOCTors: a perspective of optical coherence tomography

SIGNIFICANCE

After three decades, more than 75,000 publications, tens of companies being involved in its commercialization, and a global market perspective of about USD 1.5 billion in 2023, optical coherence tomography (OCT) has become one of the fastest successfully translated imaging techniques with substantial clinical and economic impacts and acceptance.

AIM

Our perspective focuses on disruptive forward-looking innovations and key technologies to further boost OCT performance and therefore enable significantly enhanced medical diagnosis.

APPROACH

A comprehensive review of state-of-the-art accomplishments in OCT has been performed.

RESULTS

The most disruptive future OCT innovations include imaging resolution and speed (single-beam raster scanning versus parallelization) improvement, new implementations for dual modality or even multimodality systems, and using endogenous or exogenous contrast in these hybrid OCT systems targeting molecular and metabolic imaging. Aside from OCT angiography, no other functional or contrast enhancing OCT extension has accomplished comparable clinical and commercial impacts. Some more recently developed extensions, e.g., optical coherence elastography, dynamic contrast OCT, optoretinography, and artificial intelligence enhanced OCT are also considered with high potential for the future. In addition, OCT miniaturization for portable, compact, handheld, and/or cost-effective capsule-based OCT applications, home-OCT, and self-OCT systems based on micro-optic assemblies or photonic integrated circuits will revolutionize new applications and availability in the near future. Finally, clinical translation of OCT including medical device regulatory challenges will continue to be absolutely essential.

CONCLUSIONS

With its exquisite non-invasive, micrometer resolution depth sectioning capability, OCT has especially revolutionized ophthalmic diagnosis and hence is the fastest adopted imaging technology in the history of ophthalmology. Nonetheless, OCT has not been completely exploited and has substantial growth potential-in academics as well as in industry. This applies not only to the ophthalmic application field, but also especially to the original motivation of OCT to enable optical biopsy, i.e., the in situ imaging of tissue microstructure with a resolution approaching that of histology but without the need for tissue excision.

Visualising the choriocapillaris: Histology, imaging modalities and clinical research - A review

The choriocapillaris plays a considerable role in the normal physiology of the eye as well as in various diseases. Assessing the changes in the choriocapillaris can therefore provide important information about normal ageing and pathogenesis of visual impairment, and even some systemic diseases. In vivo imaging of the choriocapillaris has evolved from non-depth resolved, dye-based angiography to advanced, high-resolution optical coherence tomography angiography (OCTA). However, the intricate microvascular networks within the choriocapillaris are still beyond the resolving limits of most OCTA instruments. Knowledge of histology, meticulous image acquisition methods, recognition of artefact and post-acquisition processing techniques are necessary for optimising OCTA choriocapillaris images. Qualitative and quantitative analyses of the choriocapillaris provide clinical information in age-related macular degeneration (AMD), diabetic retinopathy (DR), pathologic myopia and central serous chorioretinopathy (CSC). Furthermore, studies have revealed choriocapillaris changes in posterior uveitis that are correlated with treatment outcome and have important prognostic significance. In addition to retinal diseases, choriocapillaris changes have been observed in systemic vascular diseases and complications associated with pregnancy.

Impact of large choroidal vessels on choriocapillaris flow deficit analyses in optical coherence tomography angiography

PURPOSE

To investigate the impact of large choroidal vessels (LCV) on Choriocapillaris (CC) flow deficit (FD) analyses with swept-source optical coherence tomography angiography (SS-OCTA).

DESIGN

Prospective, cross-sectional study.

METHODS

Macular 6x6mm SS-OCTA scans were obtained from intermediate age-related macular degeneration (iAMD) and healthy eyes. Images were captured and processed according to most common standards and analyzed for percentage of flow-deficits (FD%) within four 1x1mm squares at the corners of each image. Choroidal thickness (CT), iris color and refraction error were considered as potential influential factors for LCV visibility. A linear mixed model and logistic regression models were calculated for statistical evaluation.

RESULTS

Sixty-nine iAMD and 49 age-matched healthy eyes were enrolled. LCV were visible in at least one sector in 52% of iAMD and 47% of healthy eyes. Within the iAMD group FD% were significantly lower in areas containing LCV (p = 0.0029). Increasing CT resulted in an odds ratio decrease of LCV (OR: 0.94, p<0.0001). Below a CT value of ≤118μm LCV could be expected with a sensitivity of 86% and a specificity of 85%.

CONCLUSIONS

LCV can significantly affect CC FD analyses of SS-OCTA images. Their visibility is negatively associated with CT. The impact of LCV should be taken into account when performing CC FD assessments, especially in patients where reduced CT is to be expected and inclusion of affected areas should be considered carefully.

Correlation of choriocapillaris hemodynamic data from dynamic indocyanine green and optical coherence tomography angiography

To investigate the correlation between posterior pole choroidal blood flow evaluated with digital subtraction indocyanine green angiography and enface optical coherence tomography angiography (OCTA). Imaging in animal study. The anatomy of 2 cynomogulus monkeys was studied. Each monkey was given a 0.75 mg/kg injection of indocyanine green in the saphenous vein. The dynamic angiographic filling sequence was recorded at 15 frames per second using the Heidelberg Spectralis. After image registration, sequential frame subtraction was used to image the dye front moving through the choroid. The OCTA was obtained by frame averaging nine separate choriocapillaris slab flow images obtained from the Zeiss Plex Elite 9000. Posterior pole choriocapillaris filling pattern in relation to the choriocapillaris anatomy as imaged by OCTA. In the posterior pole, the choriocapillaris fills in the pattern of discrete units with variable sizes and shapes. The cycle of dye filling begins in the peripapillary area and progresses toward the periphery in a wavelike manner. This filling pattern repeats in a cyclical manner, consistent with the cardiac cycle. OCTA shows a uniform mesh of vessels. While OCTA shows a uniform meshwork appearance of the choriocapillaris, the dynamic dye angiography suggests an irregular configuration of functional units partitioned by pressure gradients as opposed to structural boundaries. Disturbance of local perfusion pressure within choroidal vasculature may result in abnormal flow patterns, which could be evaluated in the clinic using commercially available equipment.

Investigation of the Peripapillary Choriocapillaris in Normal Tension Glaucoma, Primary Open-angle Glaucoma, and Control Eyes

PRECIS

The peripapillary choriocapillaris (CC) was observed to be significantly impaired in normal tension glaucoma (NTG) subjects compared with normal controls using optical coherence tomography angiography (OCTA).

PURPOSE

The aim was to quantitatively evaluate the peripapillary CC in NTG, primary open-angle glaucoma (POAG), and control eyes using OCTA.

MATERIALS AND METHODS

Ninety eyes (30 controls, 30 NTG, and 30 POAG) from 73 patients were imaged using the Zeiss Plex Elite 9000. Five repeat 3×3 mm OCTA scans were acquired both nasally and temporally to the optic disc and subsequently averaged. Four CC flow deficit (FD) measures were calculated using the fuzzy C-means approach: FD density (FDD), mean FD size (MFDS), FD number (FDN), and FD area (FDA).

RESULTS

Temporal NTG CC parameters were associated with visual field index and mean deviation (P<0.05). The control group showed a significantly lower nasal FDD (nasal: 3.79±1.26%, temporal: 4.48±1.73%, P=0.03), FDN (nasal: 156.43±38.44, temporal: 178.40±45.68, P=0.02), and FDA (nasal: 0.22±0.08, temporal: 0.26±0.10, P=0.03) when compared with temporal optic disc. The NTG group showed a significantly higher FDD (NTG: 5.04±2.38%, control: 3.79±1.26%, P=0.03), FDN (NTG: 185.90±56.66, control: 156.43±38.44, P=0.04), and FDA (NTG: 0.30±0.14 mm2, control: 0.22±0.08 mm2, P=0.03) nasal to the optic disc compared with controls.

CONCLUSIONS

Association between CC parameters and glaucoma severity in NTG, but not POAG subjects, suggests vascular abnormalities may be a potential factor in the multifactorial process of glaucoma damage in NTG patients.

IMAGE EVALUATION OF ARTIFICIAL INTELLIGENCE-SUPPORTED OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IMAGING USING OCT-A1 DEVICE IN DIABETIC RETINOPATHY

PURPOSE

To investigate the effect of denoise processing by artificial intelligence (AI) on the optical coherence tomography angiography (OCTA) images in eyes with retinal lesions.

METHODS

Prospective, observational, cross-sectional study. Optical coherence tomography angiography imaging of a 3 × 3-mm area involving the lesions (neovascularization, intraretinal microvascular abnormality, and nonperfusion area) was performed five times using OCT-HS100 (Canon, Tokyo, Japan). We acquired AI-denoised OCTA images and averaging OCTA images generated from five cube scan data through built-in software. Main outcomes were image acquisition time and the subjective assessment by graders and quantitative measurements of original OCTA images, averaging OCTA images, and AI-denoised OCTA images. The parameters of quantitative measurements were contrast-to-noise ratio, vessel density, vessel length density, and fractal dimension.

RESULTS

We studied 56 eyes from 43 patients. The image acquisition times for the original, averaging, and AI-denoised images were 31.87 ± 12.02, 165.34 ± 41.91, and 34.37 ± 12.02 seconds, respectively. We found significant differences in vessel density, vessel length density, fractal dimension, and contrast-to-noise ratio (P < 0.001) between original, averaging, and AI-denoised images. Both subjective and quantitative evaluations showed that AI-denoised OCTA images had less background noise and depicted vessels clearly. In AI-denoised images, the presence of fictional vessels was suspected in 2 of the 35 cases of nonperfusion area.

CONCLUSION

Denoise processing by AI improved the image quality of OCTA in a shorter time and allowed more accurate quantitative evaluation.

Outer retina dysfunction and choriocapillaris impairment in type 1 diabetes

To study the outer retina morpho-functional characteristics and the choriocapillaris (CC) features in type 1 diabetic (T1D) patients, with and without signs of diabetic retinopathy (NPDR and NoDR). Twenty-five NPDR and 18 NoDR eyes were imaged by Optical Coherence Tomography Angiography. Ellipsoid zone (EZ) “normalized” reflectivity and CC perfusion density parameters, as flow deficits number (FDn), flow deficit average area (FDa) and flow deficit percentage (FD%), were analysed. Multifocal electroretinogram (mfERG) response amplitude densities (RADs) were measured. Mean EZ “normalized” reflectivity, CC FDn and FD% values, were similar (p > 0.05) in both groups, FDa was significant greater (p > 0.05) in NPDR compared with NoDR eyes. MfERG-RADs were similar in both groups. NPDR eyes showed a significant (p < 0.05) linear correlation between RADs and both, CC FDa and FD%. The EZ “normalized” reflectivity was negatively correlated with CC FD% in NoDR eyes. In NPDR T1D eyes a significant relationship between abnormal outer retina functional responses and CC impairment was observed, while in NoDR eyes the photoreceptor reflectivity was correlated to CC abnormalities. The outer retina dysfunction in NPDR correlated to CC drop-out let hypothesize that the outer retinal elements are functionally impaired in proportion to the CC vascular supply deficit.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

The Spectrum of Central Choriocapillaris Abnormalities on Swept-Source Optical Coherence Tomography Angiography in the Fellow Eye of Unilateral Exudative Age-Related Macular Degeneration Patients: From Flow Deficits to Subclinical Non-Exudative Neovascularization

We evaluated the spectrum of choriocapillaris (CC) abnormalities in the fellow eyes of unilateral exudative age-related macular degeneration (AMD) patients using swept-source optical coherence tomography angiography (SS-OCTA). Fellow eyes of unilateral exudative AMD patients were prospectively included between May 2018 and October 2018. Patients underwent a multimodal imaging including a SS-OCTA. Demographics and clinical findings were analyzed. The estimated prevalence of macular neovascularization (MNV) was computed. Number and size of flow deficits (FDs) and percentage of flow deficits (FD%) were computed on the compensated CC flow images with the Fiji software. We included 97 eyes of 97 patients (mean age was 80 ± 7.66 years, 39 males, 58 females). The prevalence of MNV in the studied eyes was 8.25% (8/97 eyes). In the 89 non-neovascular eyes, FD% averaged 45.84% ± 11.63%, with a corresponding total area of FDs of 4.19 ± 1.12 mm². There was a higher prevalence of drusenoid pigment epithelial detachment in eyes with subclinical neovascularization (p = 0.021). Fellow eyes with unilateral exudative AMD encompassed a series of CC abnormalities, from FDs of the aging CC to subclinical non-exudative MNV.

Macular Ischemia Quantification Using Deep-Learning Denoised Optical Coherence Tomography Angiography in Branch Retinal Vein Occlusion

Purpose

To examine whether deep-learning denoised optical coherence tomography angiography (OCTA) images could enhance automated macular ischemia quantification in branch retinal vein occlusion (BRVO).

Methods

This retrospective, single-center, cross-sectional study enrolled 74 patients with BRVO and 46 age-matched healthy subjects. The severity of macular ischemia was graded as mild, moderate, or severe. Denoised OCTA images were produced using a neural network model. Quantitative parameters derived from denoised images, including vessel density and nonperfusion area, were compared with those derived from the OCTA machine. The main outcome measures were correlations between quantitative parameters, and areas under receiver operating characteristic curves (AUCs) in classifying the severity of the macular ischemia.

Results

The vessel density and nonperfusion area from denoised images were correlated strongly with the corresponding parameters from machine-derived images in control eyes and BRVO eyes with mild or moderate macular ischemia (all P < 0.001). However, no such correlation was found in eyes with severe macular ischemia. The vessel density and nonperfusion area from denoised images had significantly larger area under receiver operating characteristic curve than those derived from the original images in classifying moderate versus severe macular ischemia (0.927 vs 0.802 [P = 0.042] and 0.946 vs 0.797, [P = 0.022], respectively). There were no significant differences in the areas under receiver operating characteristic curve between the denoised images and the machine-derived parameters in classifying control versus BRVO, and mild versus moderate macular ischemia.

Conclusions

A neural network model is useful for removing speckle noise on OCTA images and facilitating the automated grading of macular ischemia in eyes with BRVO.

Translational Relevance

Deep-learning denoised optical coherence tomography angiography images could enhance automated macular ischemia quantification.

CORRELATION OF EN FACE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY AVERAGING VERSUS SINGLE-IMAGE QUANTITATIVE MEASUREMENTS WITH RETINAL VEIN OCCLUSION VISUAL OUTCOMES

PURPOSE

To demonstrate the effect of averaging multiple en face optical coherence tomography angiography images on the correlation between retinal microvasculature quantitative metrics and best-corrected visual acuity (BCVA) in eyes with retinal vein occlusion.

METHODS

A cross-sectional cohort with unilateral retinal vein occlusion was imaged in both eyes. Five 3 mm × 3-mm spectral domain optical coherence tomography angiography images were averaged, and quantitative parameters from averaged versus single images were correlated with logMAR BCVA. Regression analyses were performed to correlate quantitative metrics with BCVA.

RESULTS

Ten patients (5 male, average age 64.3 years) were included. Among retinal vein occlusion eyes, vessel length density was significantly less in averaged versus a single image for both the superficial retinal layer (15.5 ± 2.5 vs. 17.8 ± 2.4/mm, P = 0.05) and deep retinal layer (16.2 ± 1.4 vs. 18.5 ± 1.6/mm, P = 0.003). Multivariate linear regression showed an increased R value with averaging (0.93 to 0.95, for single and averaged groups, respectively). Foveal avascular zone circularity was associated with BCVA on single images (coefficient = -0.96, P = 0.002), but not with averaged images (P = 0.063).

CONCLUSION

Scan averaging of en face optical coherence tomography angiography images improves the clarity of vessels and may allow for more accurate quantification of vessel metrics. Quantitative metrics are significantly associated with BCVA, and averaging does not further improve this association compared with single-scan analysis.

PHOTORECEPTOR DAMAGE IN DIABETIC CHOROIDOPATHY

PURPOSE

To investigate the relationship between choriocapillaris (CC) hypoperfusion and photoreceptor alterations in eyes with nonproliferative diabetic retinopathy (NPDR).

METHODS

In this prospective, observational, case-control study, 30 eyes (30 patients) with NPDR and 30 healthy eyes from 30 controls were enrolled at the University G. d'Annunzio, Chieti-Pescara, Italy. This study cohort underwent an ophthalmologic examination, including optical coherence tomography and optical coherence tomography angiography. The main outcome measures were as follows: 1) "normalized" reflectivity of en face image segmented at the ellipsoid zone level, which was calculated to quantify the photoreceptor damage, and 2) CC perfusion density. Secondary outcome measures were as follows: 1) superficial retinal capillary plexus (SCP), intermediate retinal capillary plexus (ICP), and deep retinal capillary plexus (DCP) perfusion density (based on the area of vessels); 2) SCP, ICP, and DCP vessel length density (based on a map with vessels of 1-pixel width); and 3) SCP, ICP, and DCP vessel diameter.

RESULTS

Mean ± SD age was 58.9 ± 11.1 years (range 38-79 years) in the NPDR group and 61.7 ± 11.3 years (range 39-87 years) in the control group (P > 0.05 for all the comparisons). Compared with controls, NPDR eyes displayed a lower "normalized" reflectivity (0.96 ± 0.25 in controls and 0.73 ± 0.19 in the NPDR group, P < 0.0001). Moreover, the NPDR group was characterized by an impaired perfusion in both the retinal and choroidal vasculature. In multiple regression analysis, ellipsoid zone "normalized" reflectivity displayed a significant direct association with CC perfusion density in patients with NPDR (P = 0.025 and P = 0.476, in NPDR and controls, respectively).

CONCLUSION

Eyes with NPDR are affected by macular hypoperfusion and photoreceptor damage, the latter investigated as ellipsoid zone "normalized" reflectivity. The diabetic choroidopathy seems to be strongly associated with photoreceptor damage.

VARYING OPTICAL COHERENCE TOMOGRAPHY APPEARANCE OF THE INNER CHOROID WITH AGE: Possible Explanation and Histologic Correlate

PURPOSE

To investigate the reflectivity of the structural optical coherence tomography images of the inner choroid as it relates to potential structural composition.

METHODS

The reflectivity of slab images 29 to 49 µm and 45 to 65 µm below the retinal pigment epithelium, obtained with the Zeiss Plex Elite 9000, was evaluated. The mean and SD of a group of subjects with no ocular disorders were determined. Binarization of the images was performed and a threshold level established at the mean plus one SD for each slab depth. The proportion of area binarized was evaluated with generalized estimating equations. Representative histologic images obtained from autopsy donors were stained with Masson's trichrome, a staining method helpful in evaluating collagen and ground substance of tissue.

RESULTS

There were 67 eyes of 38 subjects with a mean age of 44.5 (range 22-82) years. Using generalized estimating equations, age was found to be a significant predictor for the proportion of binarized pixels in both the 29 to 49 µm (P = 0.034) and the 45 to 65 µm (P < 0.001) slabs. The histologic specimens illustrated the loss of ground substance with increasing compaction of collagen fibers in the choroidal stroma with advancing age.

CONCLUSION

The reflectivity from the inner choroid is not uniform and changes with age. As suggested by the histologic specimens, we propose the optical coherence tomography reflectance from the inner choroid is related, in part, to the packing density of collagen fibers present there.

CHORIOCAPILLARIS VASCULAR PARAMETERS IN NORMAL EYES AND THOSE WITH PACHYCHOROID WITH AND WITHOUT DISEASE

PURPOSE

To evaluate the vascular characteristics of the choriocapillaris in eyes with pachychoroid as compared with normal controls.

METHODS

Eyes with pachychoroid disease were defined as those with a history of central serous chorioretinopathy or peripapillary pachychoroid syndrome. Pachychoroid without disease was defined as eyes with no history of disease with a subfoveal choroidal thickness ≥ the age-adjusted 95th percentile thickness. Frame-averaged optical coherence tomography angiography images of the choriocapillaris obtained with a Zeiss Plex Elite were binarized, skeletonized, and evaluated for vascular branching parameters.

RESULTS

There were 7 normal control subjects, 10 subjects with pachychoroid without disease, and 17 pachychoroid disease subjects. Mean choriocapillaris vessel segment length was 12.19 µm in eyes with pachychoroid disease as compared with 11.48 µm in normal controls and 11.62 µm in pachychoroid without disease (P = 0.003 and P = 0.006, respectively). The branches per square millimeter were fewer in pachychoroid disease (1,215), as compared with normal controls (1,471) or pachychoroid without disease (1,384; P < 0.001, and P = 0.002, respectively). The choriocapillaris vessel diameter was larger, but the fractal dimension was smaller in pachychoroid disease eyes as compared with normal eyes or pachychoroid without disease eyes. There was no statistically significant difference between normal controls and pachychoroid without disease for any measured vascular parameter of the choriocapillaris.

CONCLUSION

Choriocapillaris vascular parameters suggest that pachychoroid is not necessarily pathologic. It is possible that choroidal thickening is an epiphenomenon, and there are more significant vascular parameters that are related to disease. These concepts may help guide future prospective studies.

CHORIOCAPILLARIS FLOW DEFICITS AS A RISK FACTOR FOR PROGRESSION OF AGE-RELATED MACULAR DEGENERATION

PURPOSE

To evaluate the association between choriocapillaris (CC) flow deficits and structural optical coherence tomography biomarkers and the progression of intermediate age-related macular degeneration (iAMD) to complete retinal pigment epithelial and outer retinal atrophy.

METHODS

Retrospective analysis of consecutive patients with iAMD with a minimum follow-up of 12 months. Odds ratios of intraretinal hyperreflective foci, hyporeflective drusen cores, subretinal drusenoid deposits, the presence of drusen volume ≥0.03 mm3 within a central 3-mm circle, fellow eye with late stage of AMD, and CC flow deficits at baseline and months of follow-up were estimated from logistic regression.

RESULTS

A total of 112 eyes with iAMD were included. Eyes that progressed were significantly more likely to show intraretinal hyperreflective foci, hyporeflective drusen cores, and drusen volume ≥0.03 mm3. The CC flow deficit was also significantly greater in eyes that developed complete retinal pigment epithelial and outer retinal atrophy. Intraretinal hyperreflective foci, hyporeflective drusen cores, drusen volume ≥0.03 mm3, and higher CC flow deficits were significantly and independently associated with the development of complete retinal pigment epithelial and outer retinal atrophy.

CONCLUSION

The CC flow deficit was significantly greater in iAMD eyes that progressed to complete retinal pigment epithelial and outer retinal atrophy and remained an independent risk factor when structural optical coherence tomography biomarkers were considered. CC flow deficits may be useful for enhancing risk stratification and prognostication of patients with iAMD.

SPATIAL DISTRIBUTION OF CHORIOCAPILLARIS IMPAIRMENT IN EYES WITH CHOROIDAL NEOVASCULARIZATION SECONDARY TO AGE-RELATED MACULAR DEGENERATION: A Quantitative OCT Angiography Study

PURPOSE

To develop an optical coherence tomography angiography (OCTA)-based framework for quantitatively analyzing the spatial distribution of choriocapillaris (CC) impairment around choroidal neovascularization (CNV) secondary to age-related macular degeneration.

METHODS

In a retrospective, cross-sectional study, 400-kHz swept-source OCTA images from 7 eyes of 6 patients with CNV secondary to age-related macular degeneration were quantitatively analyzed using custom software. A lesion-centered zonal OCTA analysis technique-which portioned the field-of-view into zones relative to CNV boundaries-was developed to quantify the spatial dependence of CC flow deficits.

RESULTS

Quantitative, lesion-centered zonal analysis of CC OCTA images revealed highest flow-deficit percentages near CNV boundaries, decreasing in zones farther from the boundaries. Optical coherence tomography angiography using shorter (1.5 ms) interscan times revealed more severe flow deficits than OCTA using longer (3.0 ms) interscan times; however, spatial trends were similar for both interscan times. A detailed description of the OCTA processing steps and parameters was provided so as to elucidate their influence on quantitative measurements.

CONCLUSION

Impairment of the CC, assessed by flow-deficit percentages, was most prominent closest to CNV boundaries. The lesion-centered zonal analysis technique enabled quantitative CC measurements relative to focal lesions. Understanding how processing steps, imaging/processing parameters, and artifacts can affect quantitative CC measurements is important for longitudinal, OCTA-based studies of disease progression, and treatment response.

Prospective deep phenotyping of choroideremia patients using multimodal structure-function approaches

OBJECTIVE

To investigate the retinal changes in choroideremia (CHM) patients to determine correlations between age, structure and function.

SUBJECTS/METHODS

Twenty-six eyes from 13 male CHM patients were included in this prospective longitudinal study. Participants were divided into <50-year (n = 8) and ≥50-year (n = 5) old groups. Patients were seen at baseline, 6-month, and 1-year visits. Optical coherence tomography (OCT), OCT angiography, and fundus autofluorescence were performed to measure central foveal (CFT) and subfoveal choroidal thickness (SCT), as well as areas of preserved choriocapillaris (CC), ellipsoid zone (EZ), and autofluorescence (PAF). Patients also underwent functional investigations including visual acuity (VA), contrast sensitivity (CS), colour testing, microperimetry, dark adaptometry, and handheld electroretinogram (ERG). Vision-related quality-of-life was assessed by using the NEI-VFQ-25 questionnaire.

RESULTS

Over the 1-year follow-up period, progressive loss was detected in SCT, EZ, CC, PAF, and CFT. Those ≥50-years exhibited more structural and functional defects with SCT, EZ, CC, and PAF showing strong correlation with patient age (rho ≤ -0.47, p ≤ 0.02). CS and VA did not change over the year, but CS was significantly correlated with age (rho = -0.63, p = 0.001). Delayed to unmeasurable dark adaptation, decreased colour discrimination and no detectable ERG activity were observed in all patients. Minimal functional deterioration was observed over one year with a general trend of slower progression in the ≥50-years group.

CONCLUSIONS

Quantitative structural parameters including SCT, CC, EZ, and PAF are most useful for disease monitoring in CHM. Extended follow-up studies are required to determine longitudinal functional changes.

Clinical Utility of Artificial Intelligence Algorithms to Enhance Wide-Field Optical Coherence Tomography Angiography Images

The aim of this paper is to investigate the clinical utility of the application of deep learning denoise algorithms on standard wide-field Optical Coherence Tomography Angiography (OCT-A) images. This was a retrospective case-series assessing forty-nine 10 × 10 mm OCT-A1 macula scans of 49 consecutive patients attending a medical retina clinic over a 6-month period. Thirty-seven patients had pathology; 13 had none. Retinal vascular layers were categorised into superficial or deep capillary plexus. For each category, the retinal experts compared the original standard image with the same image that had intelligent denoise applied. When analysing the Superficial Capillary Plexus (SCP), the denoised image was selected as "best for clinical assessment" in 98% of comparisons. No difference was established in the remaining 2%. On evaluating the Deep Capillary Plexus (DCP), the denoised image was preferred in 35% of comparisons. No difference was found in 65%. There was no evidence of new artefactual features nor loss of anatomical detail in denoised compared to the standard images. The wide-field denoise feature of the Canon Xephilio OCT-A1 produced scans that were clinically preferable over their original OCT-A images, especially for SCP assessment, without evidence for causing a new artefactual error.

[Influence of CNV vascular morphology in exudative age-related macular degeneration on development of visual acuity and need for anti-VEGF therapy after 1 year]

BACKGROUND

The aim of this pilot study was to investigate vascular morphological characteristics of choroidal neovascularization (CNV) at the time of the initial diagnosis of exudative age-related macular degeneration (nAMD), which enable a prognosis for the development of visual acuity and the necessity for treatment in the first year.

METHODS

In 57 patients with the initial diagnosis of nAMD, CNV was detected by optical coherence tomography angiography (OCT-A) and an automated quantitative vessel analysis was performed with respect to area, total vessel length, flow value and average vessel caliber of the CNV. After 12 months patients were divided into 2 groups based on visual acuity (visual loss vs. visual gain) and necessity of anti-VEGF therapy (<7 intravitreal injections, IVOM vs. ≥7 IVOM).

RESULTS

The mean CNV area was 0.95 mm² ± 1.07 mm² (group visual loss 1.56 mm² ± 1.54 mm²; group visual gain 0.65 mm² ± 0.53 mm²; p = 0.002/<7 IVOM 1.05 mm² ± 1.40 mm²; ≥7 IVOM 0.98 mm² ± 0.94 mm², p = 0.60). The average total vessel length of the CNV was 9.84 mm ± 11.35 mm (visual loss 16.00 mm ± 16.58 mm; visual gain 6.74 mm ± 5.42 mm; p < 0.003/<7 IVOM 11.21 mm ± 15.10; ≥7 IVOM 9.90 mm ± 9.68 mm; p = 0.68). The mean flow value of the CNV was 0.40 ± 0.06 (visual loss 0.37 ± 0.04; visual gain 0.41 ± 0.07; p = 0.004/<7 IVOM 0.42 ± 0.08; ≥7 IVOM 0.38 ± 0.06; p = 0.02). The average vessel caliber was 28.86 µm ± 2.93 µm (visual loss 28.39 µm ± 2.97 mm; visual gain 29.32 µm ± 3.05 µm; p = 0.24/<7 IVOM 30.26 µm ± 3.49 µm; ≥7 IVOM 28.23 µm ± 2.25 µm; p = 0.02).

CONCLUSION

The results show that a mathematical quantification of the CNV in nAMD is possible using OCT‑A. This analysis confirmed again that the size of the CNV (area and total vessel length) is decisive for the prognosis of visual acuity. It also shows that a larger flow value as a sign of a well-differentiated CNV is associated with a better functional prognosis. The number of IVOMs required, however, depends primarily on the composition of the CNV (flow value and vascular caliber). More precise imaging and larger examination cohorts could possibly reveal further relevant biomarkers.

Guidelines for Imaging the Choriocapillaris Using OCT Angiography

PURPOSE

To provide guidance on how to appropriately quantitate various choriocapillaris (CC) parameters with optical coherence tomography angiography (OCTA).

DESIGN

Evidence-based perspective.

METHODS

Review of literature and experience of authors.

RESULTS

Accurate and reliable quantification of CC using OCTA requires that CC can be visualized and that the measurements of various CC parameters are validated. For accurate visualization, the selected CC slab must be physiologically sound, must produce images consistent with histology, and must yield qualitatively similar images when viewing repeats of the same scan or scans of different sizes. For accurate quantification, the measured intercapillary distances (ICDs) should be consistent with known measurements using histology and adaptive optics and/or OCTA, the selected CC parameters must be physiologically and physically meaningful based on the resolution of the instrument and the density of the scans, the selected algorithm for CC binarization must be appropriate and generate meaningful results, and the CC measurements calculated from multiple scans of the same and different sizes should be quantitatively similar. If the Phansalkar local thresholding method is used, then its parameters must be optimized for CC based on the OCTA instrument and scan patterns used. It is recommended that the window radius used in the Phansalkar method should be related to the expected average ICD in normal eyes.

CONCLUSIONS

Quantitative analysis of CC using commercially available OCTA instruments is complicated, and researchers need to tailor their strategies based on the instrument, scan patterns, anatomy, and thresholding strategies to achieve accurate and reliable measurements.

Quantitative assessment of choriocapillaris flow deficits in eyes with macular neovascularization

PURPOSE

To investigate choriocapillaris flow deficits (CC FD) in a group of eyes with Type 3 macular neovascularization (MNV) versus a group of eyes with Type 1 and/or 2 MNV versus healthy eyes.

METHODS

In this cross-sectional, retrospective, multicenter, observational study, consecutive patients with Type 3 MNV, Type 1 and/or 2 MNV, and age-matched controls were included. PLEX Elite optical coherence tomography angiography was performed with a 6 × 6 mm scan pattern centered on the fovea. The CC FD was computed in 4 peripheral 1 × 1 mm squares to allow comparison between equidistant regions unaffected by MNV.

RESULTS

Twenty Type 3, 20 Type 1 and/or 2 MNV [13 (65%) Type 1 MNV, 1 (5%) Type 2 MNV, and 6 (30%) mixed Type 1 and 2 MNV], and 20 age-matched controls were included. The mean impairment in the CC in the 4 peripheral squares was 16.07 ± 7.27% in Type 3 MNV eyes, 11.48 ± 5.59% in Type 1/2 MNV eyes, and 9.64 ± 3.59% in controls. Type 3 MNV displayed a statistically significantly higher CC FD compared with both Type 1/2 MNV (P = 0.031) and controls (P < 0.0001). No significant differences were observed between Type 1/2 MNV and controls (P = 0.223).

CONCLUSIONS

CC FD was significantly greater in the peripheral macular regions of eyes with Type 3 MNV compared to eyes with Type 1/2 MNV and normal control eyes. Pathogenic choroidal mechanisms may differ in eyes with different MNV subtypes. Whereas focal CC impairment may drive the development of Type 1/2 MNV, diffuse CC disruption may be more important in eyes with Type 3 MNV.

[Evaluation of choriocapillaris with high-speed spectral-domain optical coherence tomography angiography and image averaging]

PURPOSE

To study the capabilities of high-speed spectral-domain optical coherence tomography angiography (SD-OCTA) with image averaging in the evaluation of choriocapillaries in healthy individuals and patients with central serous chorioretinopathy (CSC).

MATERIAL AND METHODS

All participants underwent OCTA examination on the SOLIX tomograph (Optovue, USA) using quadruplicate 3×3 mm scan with image averaging. Image analysis was performed in 9-µm custom slab with Phansalkar auto local threshold algorithm and calculation of flow voids larger than 5000 µm² and 10 000 µm². The optimal slab depth was determined in healthy eyes by consecutive analysis of the slabs with a 3-µm shift from zero position to 33 µm below Bruch's membrane.

RESULTS

The study included 18 eyes of 18 healthy volunteers (40.4±6.0 years old) and 18 fellow eyes of 18 unilateral CSC patients (37.4±10.7 years old). The slab 12 µm below the Bruch's membrane showed the minimal number of flow voids (23.1±7.0 of >5000 µm² voids per scan) and was chosen for further analysis. The number of flow voids of >5000 µm² in healthy paired eyes of CSC patients was statistically significantly higher than in the eyes of healthy individuals (32.7±10.7 and 25.3±8.1 voids/scan, respectively; p=0.022). The number of flow voids of >10000 µm² was also statistically significantly higher in CSC eyes compared to healthy eyes (5.6±3.3 and 3.5±1.9 voids/scan, respectively; p=0.045). There was no statistically significant difference in total area of the voids between the eyes of healthy individuals and CSC patients (96406.1±3924.5 µm² and 95395.7 ± 3615.1 µm², respectively; p=0.42).

CONCLUSION

The optimal settings for choriocapillaris imaging on the SOLIX tomograph include 9-µm slab 9 to 18 µm below the Bruch's membrane. Using a 9-µm slab 12 µm below the Bruch's membrane, a substantial difference was found in choriocapillaris perfusion between eyes of healthy individuals and CSC patients.

Status of Choriocapillaris in Fellow Eyes of Patients With Unilateral Retinal Vein Occlusions

BACKGROUND AND OBJECTIVE

To study the status of the choriocapillaris in fellow eyes of patients with unilateral retinal vein occlusions (RVOs).

PATIENTS AND METHODS

Thirty-two healthy eyes of patients with unilateral RVO and 16 eyes of healthy age-matched controls were included. Choriocapillaris flow voids and device-specific choriocapillaris total flow areas were quantified based on 3-mm optical coherence tomography angiography (OCTA) scans and their correlation with the number of resolved para-central acute middle maculopathy (PAMM) lesions on 6-mm OCTA scans was calculated.

RESULTS

In fellow eyes of unilateral RVOs and in eyes of healthy individuals, the number of choriocapillaris flow voids was 20.8 ± 5.5 and 13.4 ± 5.4, respectively (P < .001), and choriocapillaris total flow area was 6.0 ± 0.34 mm² and 6.22 ± 0.13 mm², respectively (P = .005). The number of resolved PAMM lesions correlates significantly with the number of choriocapillaris flow voids (r = 0.44; P = .002) and with choriocapillaris total flow area (r = -0.52; P < .001).

CONCLUSION

Fellow eyes of patients with unilateral RVO demonstrate a substantial decrease of perfusion in choriocapillaris, which correlates with the prevalence of small resolved PAMM lesions. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:23-28.].

Association Between Alterations of the Choriocapillaris Microcirculation and Visual Function and Cone Photoreceptors in Patients With Diabetes

Purpose

The purpose of this study was to investigate the association between the choriocapillaris microcirculation and the visual function and cone photoreceptor structure in patients with diabetes.

Methods

Thirteen control subjects and 26 patients with type 2 diabetes were recruited. The patients with diabetes were divided into three groups based on the grade of diabetic retinopathy (DR). The retinal sensitivity (RS) was evaluated using microperimetry. Cone photoreceptor mosaics were imaged using an adaptive optics retinal camera, and the cone heterogeneity packing index (HPi) was calculated. Optical coherence tomography angiography (OCTA) images of the choriocapillaris were obtained using spectral-domain OCTA, and the area of flow deficit (FD) was evaluated. All parameters were evaluated in the foveal and parafoveal areas.

Results

The study included four patients with diabetes without retinopathy, 12 patients with nonproliferative diabetic retinopathy (NPDR), and 10 patients with proliferative diabetic retinopathy (PDR). The foveal and parafoveal FDs were correlated significantly (fovea, r = −0.58; P = 0.046 and r = −0.82; P = 0.003; parafovea, r = −0.59; P = 0.044 and r = −0.72; and P = 0.019, respectively) with the RS in patients with NPDR and PDR, but not in control and no diabetic retinopathy (NDR) groups. There were no differences in the foveal HPi among the groups.

Conclusions

Impaired choriocapillaris microcirculation is associated with impaired visual function but not cone photoreceptor integrity in eyes with DR.

Maternal Optical Coherence Tomography Angiography Changes Related to Small for Gestational Age Pregnancies

Purpose

To study maternal retinal changes in pregnancies that resulted in a small for gestational age (SGA) infant.

Methods

Pregnant women with SGA infants at birth and age-matched pregnant women with appropriate for gestational age (AGA) infants at birth (controls) were enrolled. All subjects underwent spectral domain optical coherent tomography angiography (OCTA) imaging using a 10° × 10° scan pattern centered on the fovea. Vessel density (VD) and vessel length density (VLD) of the superficial capillary plexus (SCP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP) were analyzed and compared between the two groups.

Results

Twelve eyes of eight subjects with SGA infants and 64 eyes of 44 age-matched subjects with AGA infants were included in this study. There was no significant difference in chronic hypertension (P = 1.0), gestational hypertension (P = 1.0), type 1/2 diabetes (P = 1.0), gestational diabetes (P = 0.97), or preeclampsia (P = 0.50) between the SGA group and AGA group. There were significant increases in both VD and VLD in the SCP and ICP layers when comparing the SGA group with the AGA group (P < 0.05).

Conclusions

In this pilot study, subjects with SGA infants had increases in selective retinal vasculature layers that may represent systemic perfusion changes compensating for placental insufficiency.

Translational Relevance

Additional assessment of maternal retinal changes in pregnancy using OCTA could prove the technology useful as a biomarker of fetal morbidity.

Photoreceptor alteration in intermediate age-related macular degeneration

The aim of this study was to analyze photoreceptor alterations occurring in eyes with intermediate age-related macular degeneration (AMD) and to investigate their associations with choriocapillaris (CC) flow. In this retrospective case-control study, we collected data from 35 eyes with intermediate AMD from 35 patients who had swept source optical coherence tomography structural and angiography imaging obtained. A control group of 35 eyes from 35 healthy subjects was included for comparison. Our main outcome measure for comparison between groups was the normalized reflectivity of en face image segmented at the ellipsoid zone (EZ) level, which was calculated to quantify the photoreceptor damage. OCTA metrics to quantify CC flow signal were also computed. These metrics were measured in a circle centered on the fovea and with a diameter of 5 mm. In intermediate AMD eyes, the macular area occupied by drusen was identified. Therefore, the EZ reflectivity and CC flow signal were separately measured in regions without drusen ("drusen-free" region). Measurements were generated using previously published algorithms. Mean ± SD age was 74.1 ± 6.8 years in the intermediate AMD group and 72.1 ± 6.0 years in the control group (p = 0.206). The normalized EZ reflectivity was 0.76 ± 0.10 in the intermediate AMD group and 0.85 ± 0.08 in the control group (p < .0001). In the "drusen-free" region, the normalized EZ reflectivity was 0.77 ± 0.10 (p < .0001  vs. healthy controls) and was positively correlated with the CC flow signal density (ρ = - 0.340 and p = 0.020). In conclusion, eyes with intermediate AMD exhibit a diffuse reduced EZ normalized reflectivity, and this reduction is correlated with CC flow signal in the regions without drusen. This study supports the concept of the damage of the unit comprised of photoreceptor, CC, and intervening tissues as an early event in AMD.