Impact of Multiple En Face Image Averaging on Quantitative Assessment from Optical Coherence Tomography Angiography Images

Recent advances and applications of optical coherence tomography angiography in diabetic retinopathy

Introduction

Optical coherence tomography angiography (OCTA), a noninvasive imaging technique, is increasingly used in managing ophthalmic diseases like diabetic retinopathy (DR). This review examines OCTA's imaging principles, its utility in detecting DR lesions, and its diagnostic advantages over fundus fluorescein angiography (FFA).

Methods

We systematically analyzed 75 articles (2015-2024) from the Web of Science Core Collection, focusing on OCTA's technical principles, clinical applications in DR diagnosis, and its use in diabetes mellitus (DM) without DR and prediabetes. The use of artificial intelligence (AI) in OCTA image analysis for DR severity evaluation was investigated.

Results

OCTA effectively identifies DR lesions and detects early vascular abnormalities in DM and prediabetes, surpassing FFA in noninvasiveness and resolution. AI integration enhances OCTA's capability to diagnose, evaluate, and predict DR progression.

Discussion

OCTA offers significant clinical value in early DR detection and monitoring. Its synergy with AI holds promise for refining diagnostic precision and expanding predictive applications, positioning OCTA as a transformative tool in future ophthalmic practice.

Nonperfused Retinal Capillaries-A New Method Developed on OCT and OCTA

Purpose

This study aims to develop a new method to quantify nonperfused retinal capillaries (NPCs) and evaluate NPCs in eyes with AMD and diabetic retinopathy (DR).

Methods

We averaged multiple registered optical coherence tomography (OCT)/OCT angiography (OCTA) scans to create high-definition volumes. The deep capillary plexus slab was defined and segmented. A developed deep learning denoising algorithm removed tissue background noise from capillaries in en face OCT/OCTA. The algorithm segmented NPCs by identifying capillaries from OCT without corresponding flow signals in OCTA. We then investigated the relationships between NPCs and known features in AMD and DR.

Results

The segmented NPC achieved an accuracy of 88.2% compared to manual grading of NPCs in DR. Compared to healthy controls, both the mean number and total length (mm) of NPCs was significantly increased in AMD and DR eyes (P < 0.001, P < 0.001). Compared to early and intermediate AMD, the number and total length of NPCs were significantly higher in advanced AMD (number: P < 0.001, P < 0.001; total length: P = 0.002, P = 0.003). Geography atrophy, macular neovascularization, drusen volume, and extrafoveal avascular area (EAA) significantly correlated with increased NPCs (P < 0.05). In DR eyes, NPCs correlated with the number of microaneurysms and EAA (P < 0.05). The presence of fluid did not significantly correlate with NPCs in AMD and DR.

Conclusions

A deep learning-based algorithm can segment and quantify retinal capillaries that lack flow using colocalized OCT/OCTA. This new biomarker may be useful in AMD and DR in predicting progression of these diseases.

Vascular Perfusion Variability in Diabetic Retinopathy: A Sequential Interscan Optical Coherence Tomography Angiography Assessment

Background/Objectives: The aim of this study was to quantify the interscan variability of vascular perfusion in patients with diabetic retinopathy (DR) using sequential optical coherence tomography angiography (OCT-A) scans. Methods: Patients with low-grade DR (DRSS score 20) underwent five sequential OCT-A imaging sessions. Vessel perfusion density (VPD) values of the superficial capillary plexus (SCP), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and choriocapillaris (CC) were computed using ImageJ Version 1.54 software via a binarization process. The binarized images were analyzed to compute VPD using vessel density plugins. Inter-session variability was assessed using the coefficient of variation (CV) and intraclass correlation coefficient (ICC). The results were compared with an age-matched group of healthy controls. Results: A total of 16 eyes from 16 patients with DR (6 females, 37.5%) and 16 eyes from healthy controls (6 females, 37.5%) were included. Mean VPD values for SCP, ICP, DCP, and CC in patients with DR were 23.64, 13.64, 15.31, and 36.57, respectively. Corresponding values for the healthy subjects were 37.65, 23.32, 22.05, and 49.00, respectively. No significant differences were found in VPD across consecutive scanning sessions (p > 0.05) in either group. However, significant differences in VPD were observed between patients who were healthy and patients with diabetes. Conclusions: Sequential OCT-A imaging demonstrated no significant inter-session variability in both healthy subjects and subjects with diabetes. The Spectralis OCT-A system showed high reliability for imaging both healthy and diseased conditions.

"Setting the standard": an analysis of different acquisition patterns for macular OCT-angiography

PURPOSE

This study aimed to determine the optimal OCT angiography (OCT-A) scanning pattern using the SPECTRALIS HRA-OCT2 device to evaluate macular microvasculature perfusion in healthy subjects.

METHODS

Healthy subjects were imaged using the SPECTRALIS OCT-A Module (Heidelberg Engineering) with the following scanning protocols: 10ºX10º-512 ART 7 [P1], 10ºX10º-256 ART 5 [P2], 10ºX10º-512 ART 5 [P3], and 15ºX10º-256 ART 5 [P4], all centered on the macula. Vessel perfusion density (VPD) and vessel length density (VLD) of the superficial vascular complex (SVC) were calculated using ImageJ software to evaluate the differences between scanning patterns. Three additional 10ºx1º, ART 7 high-density images were also obtained using the in-built software (SP-X1701 Update 3, based on Heyex Software Version 1.9.215.0 H) in the macular area and the VPD and VLD for all the three10ºx1º pattern size images with the corresponding area of pattern 1 image[P1]. Two retinal specialists conducted a blind qualitative assessment of the foveal avascular zone and image quality.

RESULTS

Twenty eyes from 20 consecutive healthy patients were included in the study. The mean VPD for P1, P2, P3, and P4 were 35.60, 31.67, 31.18, and 31.16, respectively. Mean VLD for P1, P2, P3, and P4 were 7.54, 5.86, 6.74, and 4.40, respectively. Significant differences were found between P1 and the other patterns for both the VPD and VLD, but not between P2, P3, and P4. VPD and VLD for 10ºx1º high-density images were 33.20 and 4.61, respectively, with significant VLD differences compared to P1, but not for VPD. P1 scored the highest and P4 the lowest in the qualitative assessments.

CONCLUSIONS

The 10ºX10º-512 ART 7 pattern showed statistically significant qualitative superiority and appeared optimal for blood flow detection with reduced noise in quantitative assessments.

ASSESSING THE REPEATABILITY OF INNER CHOROID FLOW DEFICIT PERCENTAGE IN INTERMEDIATE AGE-RELATED MACULAR DEGENERATION AND CONTROLS: A Comparative Study Between Different Post-Processing Approaches

PURPOSE

To assess repeatability of macular inner choroid flow deficit percentage in intermediate age-related macular degeneration and controls using various postprocessing approaches.

METHODS

Cross-sectional, observational study. The authors included 1) 22 intermediate age-related macular degeneration and 24 control eyes, with 2) age >50 years, 3) visual acuity >20/32, and 4) no additional ocular and systemic confounders. Participants underwent four consecutive 6 × 6-mm optical coherence tomography angiography scans (2 acquired at 100-kHz and 2 at 200-kHz speed; PLEX Elite 9000) for intrasession analysis. Same protocol was repeated after 30 minutes for intersession analysis. Three slabs of different thicknesses were generated underneath Bruch membrane (4-14, 4-19, 4-24 µ m). All slabs were processed with: 1) binarization-only using Phansalkar method (r = 4-15 pixels); 2) compensation + binarization; 3) averaging + binarization; 4) averaging + compensation + binarization. Inner choroid flow deficit percentage was measured within 3-mm and 5-mm circles, and measurements were repeated after excluding drusen areas. Repeatability was analyzed with generalized linear mixed-effects models, intraclass correlation coefficients, and Levene variance test.

RESULTS

Most postprocessing approaches demonstrated high repeatability (intraclass correlation coefficient >0.75) with no significant test-retest differences ( P > 0.05). Compensation + binarization of 15- µ m slabs at 200 kHz showed the highest repeatability (intraclass correlation coefficient: 0.96-0.98). Excluding drusen did not significantly affect inner choroid flow deficit percentage measurements ( P > 0.05), showing increased intraclass correlation coefficients for 10-µm-thick and binarized-only slabs.

CONCLUSION

Strong repeatability can be achieved with various postprocessing methods for assessing inner choroid flow deficit percentage, especially with compensation + binarization of 15- µ m slabs acquired at 200 kHz. Drusen removal does not seem to affect repeatability in intermediate age-related macular degeneration when using a swept-source device, except for specific settings. These results contribute to refining choriocapillaris assessment, paving the way for future applications.

Non-Hospitalized Long COVID Patients Exhibit Reduced Retinal Capillary Perfusion: A Prospective Cohort Study

The mechanism of post-acute sequelae of SARS-CoV-2 (PASC) is unknown. Using optical coherence tomography angiography (OCT-A), we compared retinal foveal avascular zone (FAZ), vessel density (VD), and vessel length density (VLD) in non-hospitalized Neuro-PASC patients with those in healthy controls in an effort to elucidate the mechanism underlying this debilitating condition. Neuro-PASC patients with a positive SARS-CoV-2 test and neurological symptoms lasting ≥6 weeks were included. Those with prior COVID-19 hospitalization were excluded. Subjects underwent OCT-A with segmentation of the full retinal slab into the superficial (SCP) and deep (DCP) capillary plexus. The FAZ was manually delineated on the full slab in ImageJ. An ImageJ macro was used to measure VD and VLD. OCT-A variables were analyzed using linear mixed-effects models with fixed effects for Neuro-PASC, age, and sex, and a random effect for patient to account for measurements from both eyes. The coefficient of Neuro-PASC status was used to determine statistical significance; p-values were adjusted using the Benjamani-Hochberg procedure. Neuro-PASC patients (N = 30; 60 eyes) exhibited a statistically significant (p = 0.005) reduction in DCP VLD compared to healthy controls (N = 44; 80 eyes). The sole reduction in DCP VLD in Neuro-PASC may suggest preferential involvement of the smallest blood vessels.

Changes in Optical Coherence Tomography Angiography Precede Clinical Onset of Placental Insufficiency

Purpose

This prospective cohort study examined the use of optical coherence tomography angiography (OCTA) to detect in vivo retinal and choroidal variations associated with placental insufficiency, manifesting as fetal growth restriction (FGR) and hypertensive disorders of pregnancy (HDP).

Methods

Pregnant women were imaged with OCTA from gestational week 16 and every 4 weeks until week 36. Pregnancy outcomes were categorized into three groups: uncomplicated, complicated by late FGR, or complicated by HDP after 32 weeks. OCTA metrics, including retinal perfusion density (PD), vessel length density (VLD), and choriocapillaris flow deficits (CCFDs), were compared between groups.

Results

In uncomplicated pregnancies, OCTA metrics remained stable throughout gestation. In contrast, the FGR group exhibited significant overall increases in superficial VLD (P = 0.016), decreases in deep VLD (P = 0.029), and increases in CCFDs (P = 0.002) throughout pregnancy when compared to the uncomplicated group. The HDP group showed significant overall decreases in both PD (P < 0.001) and VLD (P = 0.019) in the deep layer when compared to the uncomplicated group. Furthermore, CCFDs demonstrated strong potential for early prediction of FGR as early as week 16 (area under the curve = 0.73; P = 0.012).

Conclusions

Our pilot study highlights the potential of OCTA to identify retinal and choroidal variations as biomarkers for pregnancy complications, particularly increased CCFDs in FGR.

Comparison of one-year real-world outcomes between red (670 nm) subthreshold micropulse laser treatment and intravitreal aflibercept injection for treatment-naïve diabetic macular edema

PURPOSE

To evaluate the treatment outcomes of subthreshold micropulse laser (SMPL) with a wavelength of 670 nm (red) for treatment-naïve diabetic macular edema (DME).

METHODS

A retrospective observational study which included 42 eyes in 34 patients diagnosed with treatment-naïve DME was conducted. Twenty-one eyes underwent red SMPL and the other 21 eyes underwent intravitreal injection of aflibercept (IVA) as initial treatment and were followed up for 12 months. Best-corrected visual acuity (BCVA), central retinal thickness (CRT) on optical coherence tomography (OCT), vessel density (VD), and foveal avascular zone area on OCT angiography (OCTA) were measured and compared between the two groups.

RESULTS

In the red SMPL group, the mean BCVA slightly improved from 0.29 ± 0.28 at baseline to 0.22 ± 0.29 at 12 months (p = 0.18), while the mean CRT significantly decreased from 472 ± 200 µm at baseline to 320 ± 136 µm at 12 months (p = 0.003). At 12 months from baseline, the mean change in BCVA and CRT were similar between the red SMPL and IVA groups (p = 0.79 and p = 0.31, respectively). No significant change was detected in OCTA parameters except for VD at the nasal section in the red SMPL group.

CONCLUSION

Red SMPL for treatment-naïve DME maintained BCVA and significantly reduced CRT at 12 months. These treatment outcomes were equivalent to IVA in real-world settings, which tend to be inferior to clinical trials.

Consensus and guidelines on diagnosis and management of polypoidal choroidal vasculopathy (PCV) from the Asia-Pacific Vitreo-retina Society (APVRS)

A panel of 21 international experts are formed by the Asia-Pacific Vitreo-retina Society to work out the consensus and guidelines on polypoidal choroidal vasculopathy (PCV). PCV is a common subtype of neovascular age-related macular degeneration and is more prevalent in Asian populations. Recent advancement in imaging technology allows greater understanding of the disease process of PCV. Furthermore, non-indocyanine green angiography features in optical coherence tomography angiography have been validated for PCV diagnosis and treatment response monitoring. Clinical trials provide new data on the safety and efficacy of various anti-vascular endothelial growth factor (anti-VEGF) agents as well as protocols that aim to improve the sustainability of treatments. In view of the myriads of emerging information, the panel gathered, reviewed, discussed, formulated and voted on the consensus and guidelines of PCV on four areas: 1) disease entity, 2) investigation and diagnosis, 3) treatment options, and 4) management protocol and future development in a five-point Likert scale (strongly agree, agree, neutral, disagree and strongly disagree). We proposed using a consensus score in which the maximum was 100. The summation of the respective "percentages" of experts voting for "agree" or "strongly agree" would be counted as the actual score. Consensus was achieved when the actual score of 75 or more was reached, which meant at least 75 % of the experts had voted for "strongly agree" or "agree" on the consensus statement concerned.

Early subclinical macular disease in asymptomatic patients with primary antiphospholipid syndrome: A quantitative multimodal retinal evaluation

PURPOSE

To perform a quantitative multimodal evaluation in 25 patients with primary antiphospholipid syndrome (PAPS) without ocular complaints and to compare them with 25 healthy individuals.

METHODS

A structural and functional ophthalmological evaluation using optical coherence tomography angiography (OCTA) and microperimetry (MP) exam in 25 patients with PAPS, followed at a tertiary rheumatology outpatient clinic, was performed. All ophthalmologic manifestations were documented and subsequent statistical analysis was performed for comparative purposes, with significance set at p < 0.05.

RESULTS

We included 100 eyes of 50 subjects (25 patients with PAPS without ocular complaints and 25 healthy individuals). Quantitative OCTA assessment revealed significant differences between PAPS patients and controls in both the superficial vascular complex (SVC) and deep vascular complex (DVC) using high-speed protocol, as well as in the SVC in the high-resolution protocol. Analysis of the foveal avascular zone (FAZ) parameters showed a larger area of FAZ in the DVC in PAPS patients using the high-speed method compared to the control group (p = 0.047). In MP quantitative analysis, the PAPS group exhibited lower central (p = 0.041) and global (p < 0.001) retinal sensitivity compared to the control group, along with sectoral differences, except in the inferior sector.

CONCLUSIONS

PAPS patients present lower vascular density and retinal sensitivity compared to the control group, even in patients without paracentral acute middle maculopathy (PAMM). Our findings underscore the significance of ocular evaluation beyond symptomatic assessment in these patients.

Evaluation of Retinal and Posterior Segment Vascular Changes Due to Systemic Hypoxia Using Optical Coherence Tomography Angiography

Background/Objectives: Retinal vascular occlusions are a significant cause of visual impairment in older adults, resulting in ischemic retinal damage and sudden vision loss. This study evaluates the retinal, optic nerve head (ONH), and choroidal capillary networks in chronic and acute-on-chronic hypoxia compared to normal controls using optical coherence tomography angiography (OCT-A). Methods: We evaluated a prospective study including twenty patients in the hypoxic group (mean age 61.2 ± 10.2) in two phases, chronic hypoxia and acute-on-chronic hypoxia, and 21 control subjects (mean age 59 ± 9.4 years). All patients underwent a comprehensive eye examination, OCT, and OCT-A imaging. The data were analyzed using OCT-A analysis software (Zeiss OCT-A software 2.1.0.55513) and Fiji software (1.51a). Vascular density of the retina and ONH, choriocapillaries, and foveal avascular zone (FAZ) size were measured. Results: The superficial peripapillary vascular density was higher for the control group (0.387 ± 0.03) compared to the hypoxic patients with (0.383 ± 0.03) and without O2 supplementation (0.383 ± 0.03; p = 0.018). No retinal angiographic differences were identified between the two study groups. The ganglion cell layer (GCL) was thinner in the hypoxic group. Both hypoxic subgroups demonstrated denser choriocapillaries (mean 13,073 ± 1812 and 12,689 ± 1815, with and without O2 supplementation, respectively) compared to the control group (mean 9749 ± 2881, p < 0.001 for both groups). Hypoxic patients demonstrated increased area size of choriocapillaries (+O2 supplementation-mean 44,347 ± 10,563; -O2 supplementation-mean 46,984 ± 12,822) compared to the control group (mean 30,979 ± 9635; p < 0.01 and p < 0.001, respectively). Conclusions: Chronic and acute-on-chronic hypoxia did not affect the retinal vascular network, most probably due to the strong autoregulation of vascular function of the retina. However, compared to the control group, GCL, ONH vasculature density, and most choriocapillaries indices were significantly altered among hypoxic patients.

Midperipheral Microvascular Defects and Their Associations With Vitreoretinal Abnormalities in Early-Stage Familial Exudative Vitreoretinopathy

Purpose

To investigate microvascular growth defects in the temporal midperipheral retina and their correlations with vitreoretinal microstructural abnormalities (VRMAs) in early-stage familial exudative vitreoretinopathy (FEVR).

Methods

We enrolled 127 patients (127 eyes) with early-stage FEVR and 31 healthy subjects (31 eyes). Widefield optical coherence tomography angiography was conducted for all enrolled eyes. Vessel density (VD), vessel diameter index (VDI), and vessel index (VI; VD/VDI) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in temporal midperiphery were further evaluated. The distance from the vessel sprouting point of the optic disc to the avascular area margin (Optic-AVA) was measured to assess retinal vascular dysplasia.

Results

In early-stage FEVR, 61.42% of eyes showed retinal microvascular abnormalities (MVAs) in the temporal midperiphery, all combined with VRMAs. Common MVAs presented disordered vascular anastomoses in the SCP and capillary loss in the DCP, corresponding to deficient neuroretina. The preretinal vasculature (PRV) was detected in 36 eyes. VD and VI were lower in FEVR eyes compared to controls, whereas the VDI in the SCP was larger (all P < 0.001). Optic-AVA was positively correlated with VD and VI in both plexuses and negatively correlated with the VDI in the SCP. PRV existence was independently correlated with decreased VI in the DCP (odds ratio [OR] = 0.322; P < 0.001), and VRMA existence was independently correlated with decreased VI in SCP and DCP (SCP OR = 0.282, P = 0.010; DCP OR = 0.562, P = 0.002).

Conclusions

MVAs in the temporal midperipheral retina were revealed. Microvascular loss may be correlated with Optic-AVA reduction, PRV, and the presence of VRMAs.

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).

Perfusion Deficits in Diabetes Without Retinopathy Localize to the Perivenular Deep Capillaries Near the Fovea on OCT Angiography

Purpose

To localize early capillary perfusion deficits in patients with diabetes mellitus (DM) without clinical diabetic retinopathy (DR) using averaged OCT angiography (OCTA).

Design

Retrospective cross-sectional study.

Participants

Patients with DM without DR and healthy controls.

Methods

We measured perfusion deficits in the full retina, superficial capillary plexus (SCP), and deep capillary plexus (DCP) on averaged 3 × 3-mm OCTA images. Perfusion deficits were defined as the percentage of retinal tissue located >30 μm from blood vessels, excluding the foveal avascular zone (FAZ). One eye from each patient was selected based on image quality. We measured deficits in the parafoveal region, the 300 μm surrounding the FAZ, and 300 to 1000 μm surrounding the FAZ. If a capillary layer within one of these regions was significantly different in DM without DR compared with controls, we further characterized the location of perfusion deficit as periarteriolar, perivenular, or the capillaries between these 2 zones.

Main Outcome Measures

Location of increased perfusion deficits in patients with DM without DR compared with controls.

Results

Sixteen eyes from 16 healthy controls were compared with 16 eyes from 16 patients with DM without DR (age 45.1 ± 10.7 and 47.4 ± 15.2 years respectively, P = 0.64). Foveal avascular zone area and perfusion deficits in the entire parafovea and the 300 to 1000-μm ring around the FAZ were not significantly different between groups (P > 0.05 for all). Perfusion deficits in 300 μm around the FAZ were significantly increased in patients with DM without DR in full retinal thickness, SCP, and DCP (P < 0.05 for all). When analyzing the perivenular, periarteriolar, and capillary zones, only the perivenular DCP perfusion deficits were significantly increased (5.03 ± 2.92% in DM without DR and 2.73 ± 1.97% in controls, P = 0.014).

Conclusions

Macular perfusion deficits in patients with DM without DR were significantly increased in the region nearest the FAZ, mainly at the perivenular deep capillaries. Further research on these early changes may improve our understanding of the capillaries most susceptible to vascular injury and disruption during diabetes.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

ENLARGEMENT OF CHOROIDAL NEOVASCULARIZATION BEFORE RECURRENCE AFTER PHOTODYNAMIC THERAPY FOR PACHYCHOROID NEOVASCULOPATHY

PURPOSE

To investigate predictors of recurrent exudation in choroidal neovascularization (CNV) of pachychoroid neovasculopathy after photodynamic therapy (PDT).

METHODS

Consecutive, treatment-naïve, symptomatic patients with pachychoroid neovasculopathy with subfoveal retinal fluid treated with PDT and followed for 18 months were studied retrospectively. Choroidal neovascularization areas were calculated from optical coherence tomography angiography images obtained at various time points after the initial PDT.

RESULTS

In 52 eyes, the subfoveal retinal fluid resolved completely three months after PDT; in 23 (44%) eyes, exudation recurred during the 18-month follow-up period. In 29 eyes with no recurrence, the mean baseline square root of the CNV area of 1.91 mm (95% CI, 0.27) decreased significantly ( P = 0.006) to 1.47 mm (95% CI, 0.16) at three months after PDT and decreased further until 12 months after PDT (mean, 1.26 mm; 95% CI, P < 0.001) and was maintained thereafter. In 23 eyes with a recurrence, the square root of the CNV area enlarged significantly ( P = 0.028) from 1.43 mm (95% CI, 0.21) at examination three months before the recurrence to 1.73 mm (95% CI, 0.18) at recurrence.

CONCLUSION

Choroidal neovascularization enlargement during the follow-up period after PDT for pachychoroid neovasculopathy may predict recurrence.

Choriocapillaris in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a multifactorial disease characterized by progressive alterations of different retinal structures ultimately leading to vision loss. Among these, the choriocapillaris (CC) has been found to be affected in different stages of AMD. In this review we provide a discussion on the different stages of AMD, focusing particularly on the alterations involving the CC. This has been possible thanks to the introduction of optical coherence tomography-angiography, a recently developed imaging technique which allows the detection of blood flow in choroidal vessels. Therefore, the aim of this review is to provide a description of the various alterations involving the CC in the different stages of AMD.

The Framework of Quantifying Biomarkers of OCT and OCTA Images in Retinal Diseases

Despite the significant advancements facilitated by previous research in introducing a plethora of retinal biomarkers, there is a lack of research addressing the clinical need for quantifying different biomarkers and prioritizing their importance for guiding clinical decision making in the context of retinal diseases. To address this issue, our study introduces a novel framework for quantifying biomarkers derived from optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) images in retinal diseases. We extract 452 feature parameters from five feature types, including local binary patterns (LBP) features of OCT and OCTA, capillary and large vessel features, and the foveal avascular zone (FAZ) feature. Leveraging this extensive feature set, we construct a classification model using a statistically relevant p value for feature selection to predict retinal diseases. We obtain a high accuracy of 0.912 and F1-score of 0.906 in the task of disease classification using this framework. We find that OCT and OCTA's LBP features provide a significant contribution of 77.12% to the significance of biomarkers in predicting retinal diseases, suggesting their potential as latent indicators for clinical diagnosis. This study employs a quantitative analysis framework to identify potential biomarkers for retinal diseases in OCT and OCTA images. Our findings suggest that LBP parameters, skewness and kurtosis values of capillary, the maximum, mean, median, and standard deviation of large vessel, as well as the eccentricity, compactness, flatness, and anisotropy index of FAZ, may serve as significant indicators of retinal conditions.

Underlying Microstructure of the Lamina Cribrosa at the Site of Microvasculature Dropout

Purpose

To determine the microstructure of the lamina cribrosa (LC) associated with microvasculature dropout (MvD) of the deep optic nerve head (ONH) in primary open-angle glaucoma (POAG) and to identify factors related to the presence of MvD.

Methods

POAG eyes that exhibited MvD in the LC (MvD-LC) or MvD in the peripapillary choroid (MvD-PC) underwent optical coherence tomography and optical coherence tomography angiography (OCTA) to evaluate the structure and microvasculature of the deep ONH, respectively. The presence of MvD-LC or MvD-PC was determined using en face OCTA images of the deep ONH. The sectoral LC thickness (LCT) and LC curvature index (LCCI) (at MvD-LC site, when applicable), the mean LCT and LCCI of the global ONH, and other clinical characteristics were measured and compared between eyes with and without MvD-LC.

Results

The study included 93 eyes with and 51 without MvD-LC. The presence of MvD-LC was associated with lower sectoral LCT (odds ratio [OR] = 0.96, P < 0.001) and mean LCT (OR = 0.97, P = 0.032), larger visual field pattern standard deviation (PSD; OR = 1.20, P = 0.038), and higher pretreatment intraocular pressure (IOP; OR = 1.22, P = 0.012). Fifteen percent of the eyes with MvD-LC (14/93) did not present MvD-PC. Those eyes had younger age (P = 0.043), thicker juxtapapillary choroid (P = 0.018), larger sectoral LCCI (P = 0.040), thicker retinal nerve fiber layer (P = 0.024), smaller PSD (P = 0.008), and higher pretreatment IOP (P = 0.006) than those with both MvD-LC and MvD-PC.

Conclusions

MvD-LC was associated with a localized morphologic alteration of the LC, and eyes with MvD-LC tended to have a higher pretreatment IOP. The clinical implications of MvD-LC should differ from those of MvD-PC in eyes with POAG.

Quantitative Analysis of the Vasculature and Cone Photoreceptors in Subjects With Diabetes Without Diabetic Retinopathy

PURPOSE

To characterize any differences in the vasculature and cone photoreceptor packing geometry (CPG) between subjects with diabetes without/no diabetic retinopathy (NDR) and healthy controls.

METHODS

Eight NDR and five controls were enrolled. Optical coherence tomography angiography (OCTA) taken at the macula was used to measure vessel density, vessel length density, and vessel density index (VDI) in three vascular plexuses, namely, the superficial vascular plexus, intermediate capillary plexus, and deep capillary plexus (DCP). The choriocapillaris (CC) flow deficit (FD) was also measured. OCTA images were binarized and processed to extrapolate the parafovea and parafoveal quadrants and the OCTA indices mentioned above. The CC was processed with six different radii to quantify FD. Adaptive optics - scanning laser ophthalmoscopy images were acquired and processed to extract CPG indices, i.e., cone density (CD), cone-to-cone spacing (CS), linear dispersion index, heterogeneity packing index and percent of cells with six neighbors at 3.6° in the temporal retina.

RESULTS

In all eyes, statistically significant differences were found (i) in parafoveal FD across the six radii (p < 0.001) and (ii) in the correlation between the parafoveal temporal quadrant (PTQ) DCP VDI and CS (r = 0.606, p = 0.048). No other significant correlations were found. For OCTA or CPG indices, no significant differences were found between the cohorts in the parafovea or parafoveal quadrants.

CONCLUSIONS

CS is the most sensitive CPG index for detecting alterations in the cone mosaic. The DCP and the cone photoreceptors are significantly correlated, indicating that alterations in the DCP can affect the cones. Future work elucidating the vascular alterations and neurodegeneration present in diabetic eyes should focus on the DCP and multiple CPG indices, not solely CD. Moreover, such alterations are highly localized, hence using larger regions e.g. parafovea versus smaller areas, such as the PTQ, will potentially mask significant correlations.

OCTA Signal Quality Augmentation Using the Isometric Handgrip Test to Maximize Vascular Flow (SQUEEZE): A Randomized Crossover Trial

Purpose

To determine if performing the isometric handgrip test (IHGT) can augment optical coherence tomography angiography (OCTA) vascular signal quality in eyes with macular abnormalities.

Methods

A randomized, single-blinded crossover trial was conducted including 36 participants with macular abnormalities, randomized to undergo OCTA with or without the IHGT, then crossed over to the alternate "intervention" after 1 minute. The primary outcome was OCTA signal quality after 1 minute of squeezing at 50% maximum grip strength. Secondary outcomes were other measures of vascular flow and systemic blood pressure (BP), also regressed against person- and eye-level covariables.

Results

Primary analysis of OCTA signal quality with versus without the IHGT was nonsignificant (P = 0.73). Nested analyses showed that the IHGT resulted in increased OCTA B-scan retinal vascular flow signal (2.95 [-1.64 to 7.55] Δ%, P < 0.05) and increased systolic BP, diastolic BP, pulse pressure, and mean arterial pressure (4.94 [0.41 to 9.47] to 12.38 [8.01 to 16.75] mm Hg, P < 0.05). OCTA signal quality and en face vessel density and perfusion changes were associated with sex, refraction, race/ethnicity, and right-hand IHGT use (P < 0.05). Greater increases in systolic and diastolic BP and mean arterial pressure were generally associated with right-hand IHGT use and greater maximum grip strength (P < 0.09).

Conclusions

The IHGT can temporarily increase OCTA B-scan retinal vascular flow signal in participants with macular abnormalities. IHGT-induced changes to systemic BP appear to be linked to absolute (rather than relative) grip strength, implying that the IHGT may be ineffective with low grip strength. Further research in larger populations is warranted.

Translational Relevance

This study provides early validation that the IHGT may augment OCTA output, which may lead to improved noninvasive detection of pathologic vascular changes.

Optical Coherence Tomography Angiography: A 2023 Focused Update on Age-Related Macular Degeneration

Optical coherence tomography angiography (OCTA) has extensively enhanced our comprehension of eye microcirculation and of its associated diseases. In this narrative review, we explored the key concepts behind OCTA, as well as the most recent evidence in the pathophysiology of age-related macular degeneration (AMD) made possible by OCTA. These recommendations were updated since the publication in 2020, and are targeted for 2023. Importantly, as a future perspective in OCTA technology, we will discuss how artificial intelligence has been applied to OCTA, with a particular emphasis on its application to AMD study.

Artificial intelligence and hemodynamic studies in optical coherence tomography angiography for diabetic retinopathy evaluation: A review

Diabetic retinopathy (DR) is a rapidly emerging retinal abnormality worldwide, which can cause significant vision loss by disrupting the vascular structure in the retina. Recently, optical coherence tomography angiography (OCTA) has emerged as an effective imaging tool for diagnosing and monitoring DR. OCTA produces high-quality 3-dimensional images and provides deeper visualization of retinal vessel capillaries and plexuses. The clinical relevance of OCTA in detecting, classifying, and planning therapeutic procedures for DR patients has been highlighted in various studies. Quantitative indicators obtained from OCTA, such as blood vessel segmentation of the retina, foveal avascular zone (FAZ) extraction, retinal blood vessel density, blood velocity, flow rate, capillary vessel pressure, and retinal oxygen extraction, have been identified as crucial hemodynamic features for screening DR using computer-aided systems in artificial intelligence (AI). AI has the potential to assist physicians and ophthalmologists in developing new treatment options. In this review, we explore how OCTA has impacted the future of DR screening and early diagnosis. It also focuses on how analysis methods have evolved over time in clinical trials. The future of OCTA imaging and its continued use in AI-assisted analysis is promising and will undoubtedly enhance the clinical management of DR.

Aflibercept Loaded Eye-Drop Hydrogel Mediated with Cell-Penetrating Peptide for Corneal Neovascularization Treatment

Corneal neovascularization (CoNV) is a major cause of visual impairment worldwide. Currently, available treatment options have limited efficacy and are associated with adverse effects due to biological barriers and clearance mechanisms. To address this challenge, a novel topical delivery system is developed-Gel 2_1&Eylea-an aflibercept-loaded eye-drop hydrogel mediated with cell-penetrating peptide 1. Gel 2_1&Eylea demonstrates superior membrane permeability, increased stability, and prolonged drug retention time on the ocular surface, and thus may improve drug efficacy. In a rabbit CoNV model, Gel 2_1&Eylea significantly reduces the density of neovascularization with no adverse effects on normal corneoscleral limbal vessels, demonstrating high efficacy and biocompatibility. This work identifies a promising treatment for CoNV which has the potential to benefit other ocular neovascular diseases.

Application of ImageJ in Optical Coherence Tomography Angiography (OCT-A): A Literature Review

Background

This study aimed to review the literature on the application of ImageJ in optical coherence tomography angiography (OCT-A) images.

Methods

A general search was performed in PubMed, Google Scholar, and Scopus databases. The authors evaluated each of the selected articles in order to assess the implementation of ImageJ in OCT-A images.

Results

ImageJ can aid in reducing artifacts, enhancing image quality to increase the accuracy of the process and analysis, processing and analyzing images, generating comparable parameters such as the parameters that assess perfusion of the layers (vessel density (VD), skeletonized density (SD), and vessel length density (VLD)) and the parameters that evaluate the structure of the layers (fractal dimension (FD), vessel density index (VDI), and lacunarity (LAC)), and the foveal avascular zone (FAZ) that are used widely in the retinal and choroidal studies), and establishing diagnostic criteria. It can help to save time when the dataset is huge with numerous plugins and options for image processing and analysis with reliable results. Diverse studies implemented distinct binarization and thresholding techniques, resulting in disparate outcomes and incomparable parameters. Uniformity in methodology is required to acquire comparable data from studies employing diverse processing and analysis techniques that yield varied outcomes.

Conclusion

Researchers and professionals might benefit from using ImageJ because of how quickly and correctly it processes and analyzes images. It is highly adaptable and potent software, allowing users to evaluate images in a variety of ways. There exists a diverse range of methodologies for analyzing OCTA images through the utilization of ImageJ. However, it is imperative to establish a standardized strategy to ensure the reliability and consistency of the method for research purposes.

Optical coherence tomography angiography in diabetic retinopathy

There remain many unanswered questions on how to assess and treat the pathology and complications that arise from diabetic retinopathy (DR). Optical coherence tomography angiography (OCTA) is a novel and non-invasive three-dimensional imaging method that can visualize capillaries in all retinal layers. Numerous studies have confirmed that OCTA can identify early evidence of microvascular changes and provide quantitative assessment of the extent of diseases such as DR and its complications. A number of informative OCTA metrics could be used to assess DR in clinical trials, including measurements of the foveal avascular zone (FAZ; area, acircularity, 3D para-FAZ vessel density), vessel density, extrafoveal avascular zones, and neovascularization. Assessing patients with DR using a full-retinal slab OCTA image can limit segmentation errors and confounding factors such as those related to center-involved diabetic macular edema. Given emerging data suggesting the importance of the peripheral retinal vasculature in assessing and predicting DR progression, wide-field OCTA imaging should also be used. Finally, the use of automated methods and algorithms for OCTA image analysis, such as those that can distinguish between areas of true and false signals, reconstruct images, and produce quantitative metrics, such as FAZ area, will greatly improve the efficiency and standardization of results between studies. Most importantly, clinical trial protocols should account for the relatively high frequency of poor-quality data related to sub-optimal imaging conditions in DR and should incorporate time for assessing OCTA image quality and re-imaging patients where necessary.

In vivo assessment of associations between photoreceptors structure and macular perfusion in type 1 diabetes

PURPOSE

To explore the potential relationships between macular vascular network and different adaptive optics (AO) metrics in patients with type 1 diabetes mellitus (DM1) with no signs (NoDR) or mild non-proliferative diabetic retinopathy (NPDR).

DESIGN

Observational cross-sectional study.

METHODS

Forty eyes of consecutive patients with DM1 (12 NoDR and 28 NPDR) and 10 healthy age-matched control subjects were included. All patients and controls were imaged using AO retinal camera and PLEX Elite 9000 optical coherence tomography (OCT) angiography (OCTA). The AO outcome measures to evaluate the cone photoreceptor mosaic characteristics were as follows: (1) Cone density (CD); (2) Linear Dispersion Index (LDi) and (3) Heterogeneity Packing Index (HPi). The OCTA outcome measures included: (1) superficial capillary plexus (SCP) perfusion density (PD); (2) deep capillary plexus (DCP) PD and (3) the choriocapillaris (CC) flow deficit percentage (FD%).

RESULTS

NPDR group exhibited a close relationship between cone metrics and CC FD. Notably, CC FD% increase along with LDi (p=0.035), while the increasing CC FD% were associated with reducing CD (p=0.042) and the HPi (p=0.017). Furthermore, the OCTA parameters, including PD SCP and DCP, showed a significant negative correlation with CD.

CONCLUSIONS

Our results demonstrated the relationship between macular perfusion at both retinal and choroidal levels and the cone mosaic in patients with DM1 interpolating swept-source-OCTA and AO metrics. In NPDR eyes, the photoreceptor damage was accompanied by CC insufficiency since the early stages of the disease.

ABNORMALITIES IN THE RETINAL CAPILLARY PLEXUSES IN COATS DISEASE IN ADULTHOOD ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To describe and quantify the abnormalities of the retinal capillary plexuses using optical coherence tomography angiography in Coats disease.

METHODS

Retrospective study. Eleven eyes of 11 patients with Coats disease (9 men and two women aged 32-80 years) compared with nine fellow eyes and 11 healthy control eyes. Horizontal bands of contiguous 3 × 3 mm optical coherence tomography angiograms of the superficial vascular plexus and deep capillary complex were acquired from the optic disk to 6 mm temporal to the fovea, through areas with telangiectasia visible on fluorescein angiography in 9 cases.

RESULTS

The vascular density was significantly decreased in both plexuses in eyes with Coats disease compared with normal and fellow eyes within the 6 mm temporal to the fovea (superficial vascular plexus: 21.5 vs. 29.4%, P = 0.00004 and vs. 30.3%, P = 0.00008; deep capillary complex, 16.5 vs. 23.9%, P = 0.00004 and vs. 24.7%, P = 0.00008, respectively). The fractal dimension was also significantly decreased in eyes with Coats disease (superficial vascular plexus: 1.796 vs. 1.848 P = 0.001 and vs. 1.833, P = 0.003; deep capillary complex: 1.762 vs. 1.853, P = 0.003 and vs. 1.838, P = 0.004, respectively).

CONCLUSION

Retinal plexuses' vascular density was decreased in Coats disease, including in areas with no visible telangiectasia.

Macular Perfusion Deficits on OCT Angiography Correlate with Nonperfusion on Ultrawide-field Fluorescein Angiography in Diabetic Retinopathy

OBJECTIVE

To evaluate the correlation between nonperfusion parameters on OCT angiography (OCTA) and ultrawide-field fluorescein angiography (UWF-FA) in subjects with diabetes mellitus (DM).

DESIGN

Prospective, cross-sectional study.

SUBJECTS

Subjects with DM and a wide range of diabetic retinopathy (DR) severity seen at a tertiary referral center.

METHODS

We used averaged 3 × 3 mm OCTA scans to measure geometric perfusion deficit (GPD), vessel density, and vessel length density in the full retina, superficial capillary plexuses (SCPs), and deep capillary plexuses (DCPs). Nonperfusion was manually delineated on UWF-FA to quantify central, peripheral, and total retinal nonperfusion (mm2 and % area).

MAIN OUTCOME MEASURES

Correlation between OCTA parameters and UWF-FA nonperfusion, and accuracy of these OCTA and UWF-FA parameters in detecting clinically referable eyes, using receiver operating characteristic (ROC) curve analysis, sensitivity, specificity, and area under the ROC curve (AUC).

RESULTS

The study included 67 eyes (12 eyes with no signs of DR, 8 mild, 22 moderate, 14 severe nonproliferative DR, and 11 treatment-naive proliferative DR). There was a fair-to-moderate correlation between either central or total retinal nonperfusion on UWF-FA (mm2) and GPD in the SCP (r = 0.482 and r = 0.464, respectively) and DCP (r = 0.470 and r = 0.456, respectively). Receiver operating characteristic analysis showed the DCP GPD significantly superior to other OCTA parameters at the DCP with the largest overall AUC on OCTA for distinguishing referable DR (0.905). Furthermore, the GPD parameter had the largest AUC in each respective capillary layer compared with other parameters. Overall, the total UWF-FA nonperfusion area showed a comparable AUC (0.907) and performed significantly better than peripheral nonperfusion (P = 0.041). Comparing the AUC values between GPD and UWF-FA nonperfusion parameters showed no significant difference in discerning referable DR.

CONCLUSIONS

Nonperfusion as quantified on OCTA (3 × 3 mm) correlated with UWF-FA parameters and both were comparable in detecting referable DR. These macular OCTA metrics, particularly DCP GPD, have the potential for gauging the overall ischemic status of the retina, with an important clinical role in identifying eyes with clinically referable DR.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Widefield choroidal vasculature associated with future condition of subretinal fluid in central serous chorioretinopathy

Purpose

To examine choroidal angiographic features in the posterior pole associated with resolution or persistency of subretinal fluid (SRF) in eyes with central serous chorioretinopathy (CSC).

Design

Observational case series.

Methods

Twenty-nine patients with treatment-naïve CSC were divided into two groups based on the presence or absence of SRF 3 months after the initial visit (month 3) without any treatment. Using enhanced depth imaging of widefield swept-source optical coherence tomography, the choroidal thickness (CT), vessel density (VD), and vessel diameter index (VDI) in the superotemporal and inferotemporal subfields on the temporal side of the 18-mm circle from the disc were measured at the initial visit. We calculated the vertical difference in CT and other choroidal angiographic parameters and evaluated their association with the SRF condition at 3 months.

Results

The SRF-resolved and SRF-persistent groups included 10 and 19 patients, respectively. At the initial visit, sex, age, axial length, symptom duration, the logarithm of the minimum angle of resolution visual acuity, and foveal thickness were not significantly different between the two groups. The SRF status at month 3 was not associated with the vertical difference in CT and choroidal VD (P = .614, .065, respectively). However, the vertical difference in choroidal VDI was positively associated with the future presence of SRF (P = .017).

Conclusions

Vertically asymmetric dilation of choroidal vessels in the posterior pole may be a vasculature feature associated with SRF from CSC and may be a good predictor of future SRF status.

Optical coherence tomography angiography: a review of the current literature

This narrative review presents a comprehensive examination of optical coherence tomography angiography (OCTA), a non-invasive retinal vascular imaging technology, as reported in the existing literature. Building on the coherence tomography principles of standard OCT, OCTA further delineates the retinal vascular system, thus offering an advanced alternative to conventional dye-based imaging. OCTA provides high-resolution visualisation of both the superficial and deep capillary networks, an achievement previously unattainable. However, image quality may be compromised by factors such as motion artefacts or media opacities, potentially limiting the utility of OCTA in certain patient cohorts. Despite these limitations, OCTA has various potential clinical applications in managing retinal and choroidal vascular diseases. Still, given its considerable cost implications relative to current modalities, further research is warranted to justify its broader application in clinical practice.

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.

Perivenular Capillary Rarefaction in Diabetic Retinopathy: Interdevice Characterization and Association to Clinical Staging

Purpose

Geometric perfusion deficit (GPD) is a newly described OCT angiography (OCTA) parameter identifying the total area of presumed retinal ischemia. The aim of our study is to characterize differences in GPD and other common quantitative OCTA parameters between macular full field, perivenular zones, and periarteriolar zones for each clinical stage of nonproliferative diabetic retinopathy (DR) and to assess the influence of ultrahigh-speed acquisition and averaging on the described differences.

Design

Prospective observational study.

Participants

Forty-nine patients, including 11 (22.4%) with no sign of DR, 12 (24.5%) with mild DR, 13 (26.5%) with moderate DR, and 13 (26.5%) with severe DR. Patients with diabetic macular edema, proliferative DR, media opacity, head tremor, and overlapping retinal diseases or systemic diseases influencing OCTA were excluded.

Methods

OCT angiography was performed 3 times for each patient: 1 using Solix Fullrange single volume (V1) mode, 1 using Solix Fullrange 4 volumes mode with automatically averaged scan (V4), and 1 using AngioVue.

Main Outcome Measures

Full macular, periarteriolar, and perivenular perfusion density (PD), vessel length density (VLD), vessel density index, and GPD for both the superficial capillary plexus (SCP) and deep capillary plexus (DCP).

Results

In patients showing no sign of DR, PD and VLD were significantly lower in the perivenular area in both the DCP and SCP using V1 and V4, whereas GPD was significantly higher in the perivenular zone in the DCP and SCP with all 3 devices. In patients with mild DR, all 3 measurements (PD, VLD, and GPD) were significantly different in the perivenular zone with all 3 devices. In patients with moderate DR, PD and VLD were lower in the DCP and SCP when measured with V1 and V4. Moreover, GPD was higher in the perivenular zone in the DCP with all 3 devices, whereas only V4 detected a difference in the SCP. In severe DR, only V4 detected a lower PD and VLD and a higher GPD in the DCP of the perivenular zone. V4 also detected a higher GPD in the SCP.

Conclusions

Geometric perfusion deficit highlights prevalent perivenular location of macular capillary ischemia in all stages of DR. In severe DR patients, only averaging technology allows detection of the same finding.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

VOLUMETRIC THREE-DIMENSIONAL OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF RETINAL NEOVASCULARIZATION IN PROLIFERATIVE DIABETIC RETINOPATHY

PURPOSE

To evaluate structural and angiographic neovascularization in patients with proliferative diabetic retinopathy using volumetric three-dimensional optical coherence tomography angiography (OCTA).

METHODS

This prospective, observational cross-sectional study included 29 eyes of 27 patients with proliferative diabetic retinopathy. The angiogenic structure, feeding vessel (epicenter), flow volume, and flow volume density of the neovasculatures were evaluated using three-dimensional OCTA imaging. The flow area and the flow area density were also measured using en face OCTA imaging.

RESULTS

Sites of neovascularization were imaged successfully in 17 of the 29 eyes (58.6%). Three proposed types of neovascularization were identified on the basis of structural features seen on the three-dimensional OCTA images. Neovascularization of the adhesion type (9 of 17, 52.9%) adhered to the retinal vasculature. Those of the traction type (5 of 17, 29.4%) were partially separated from the retinal vascular plexus. Those of the mushroom type (3 of 17, 17.6%) were connected to the retinal vasculature by several epicenters. There was a significant difference between highly leaky (active) and faintly leaky (inactive) neovascularization for flow volume density, but not for flow area, flow volume, or flow area density ( P = 0.01, 0.9, 0.6, and 0.1, respectively).

CONCLUSION

Volumetric three-dimensional OCTA revealed three types of neovascularization in proliferative diabetic retinopathy and may be useful for assessing neovascular activity and planning vitrectomies.

Baseline retinal vascular bed area on ultra-wide field fluorescein angiography correlates with the anatomical outcome of diabetic macular oedema to ranibizumab therapy: two-year analysis of the DAVE Study

PURPOSE

To determine the relationship between baseline retinal non-perfusion area (NPA) and retinal vascular bed area (RVBA) on ultra-wide field fluorescein angiography (UWF FA) and long-term response to intravitreal ranibizumab therapy in diabetic macular oedema (DMO).

METHODS

A post-hoc, 2-year observational case series. Baseline UWF FA images (Optos 200Tx) of 40 eyes from 29 patients with diabetes mellitus and treatment naïve DMO in the DAVE (NCT01552408) study were montaged and stereographically projected at the Doheny Image Reading Center to adjust for peripheral distortion. The retinal vasculature was automatically extracted to calculate RVBA. NPA was manually delineated by two masked certified graders. RVBA and NPA were computed in mm2 automatically by adjusting for peripheral distortion and then correlated with the severity of DMO.

RESULTS

While global NPA at baseline was not correlated to retinal thickness measurements, baseline NPA in the superior retina was associated with the macular volume (MV) improvement (P = 0.022). Multivariate analysis revealed a smaller RVBA at baseline was correlated with a better MV outcome at two-year follow-up after adjusting for confounding factors (P = 0.049).

CONCLUSION

Eyes with smaller baseline RVBA appear to have a better long-term anatomic outcome of DMO.

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.

Classification of Vogt-Koyanagi-Harada disease using feature selection and classification based on wide-field swept-source optical coherence tomography angiography

Background: Vogt-Koyanagi-Harada (VKH) disease is a common and easily blinded uveitis entity, with choroid being the main involved site. Classification of VKH disease and its different stages is crucial because they differ in clinical manifestations and therapeutic interventions. Wide-field swept-source optical coherence tomography angiography (WSS-OCTA) provides the advantages of non-invasiveness, large-field-of-view, high resolution, and ease of measuring and calculating choroid, offering the potential feasibility of simplified VKH classification assessment based on WSS-OCTA. Methods: 15 healthy controls (HC), 13 acute-phase and 17 convalescent-phase VKH patients were included, undertaken WSS-OCTA examination with a scanning field of 15 × 9 mm². 20 WSS-OCTA parameters were then extracted from WSS-OCTA images. To classify HC and VKH patients in acute and convalescent phases, two 2-class VKH datasets (HC and VKH) and two 3-class VKH datasets (HC, acute-phase VKH, and convalescent-phase VKH) were established by the WSS-OCTA parameters alone or in combination with best-corrected visual acuity (logMAR BCVA) and intraocular pressure (IOP), respectively. A new feature selection and classification method that combines an equilibrium optimizer and a support vector machine (called SVM-EO) was adopted to select classification-sensitive parameters among the massive datasets and to achieve outstanding classification performance. The interpretability of the VKH classification models was demonstrated based on SHapley Additive exPlanations (SHAP). Results: Based on pure WSS-OCTA parameters, we achieved classification accuracies of 91.61% ± 12.17% and 86.69% ± 8.30% for 2- and 3-class VKH classification tasks. By combining the WSS-OCTA parameters and logMAR BCVA, we achieved better classification performance of 98.82% ± 2.63% and 96.16% ± 5.88%, respectively. Through SHAP analysis, we found that logMAR BCVA and vascular perfusion density (VPD) calculated from the whole field of view region in the choriocapillaris (whole FOV CC-VPD) were the most important features for VKH classification in our models. Conclusion: We achieved excellent VKH classification performance based on a non-invasive WSS-OCTA examination, which provides the possibility for future clinical VKH classification with high sensitivity and specificity.

Deep Learning-Based Noise Reduction Improves Optical Coherence Tomography Angiography Imaging of Radial Peripapillary Capillaries in Advanced Glaucoma

PURPOSE

We applied deep learning-based noise reduction (NR) to optical coherence tomography-angiography (OCTA) images of the radial peripapillary capillaries (RPCs) in eyes with glaucoma and investigated the usefulness of this method as an objective analysis of glaucoma.

METHODS

This cross-sectional study included 118 eyes of 94 open-angle glaucoma patients (male/female = 38/56, age: 56.1 ± 10.3 years). We used OCTA (OCT-HS100, Canon) and built-in software (RX software, v. 4.5) to perform NR and calculate RPC vessel area density (VAD) and skeleton vessel length density (VLD). We also examined NR's effect on reproducibility. Finally, we assessed the vascular structure (PRCs)/function relationship at different glaucoma stages with Spearman's correlation.

RESULTS

Regardless of NR, RPC parameters had excellent coefficients of variation (1.7-4.1%) in glaucoma patients and controls, and mean deviation (MD) was significantly correlated with VAD (NR: r = 0.835, p < 0.001; non-NR: r = 0.871, p < 0.001) and VLD (NR: r = 0.829, p < 0.001; non-NR: r = 0.837, p < 0.001). For mild, moderate, and advanced glaucoma, the correlation coefficients between MD and VLD were 0.366 (p = 0.028) 0.081 (p = 0.689), and 0.427 (p = 0.017) with NR and 0.405 (p = 0.014), 0.184 (p = 0.360), and 0.339 (p = 0.062) without NR, respectively.

CONCLUSION

Denoised RPC images might have the potential for a closer structural/functional relationship, in which the floor effect of retinal nerve fiber layer thickness affects measurements. Deep learning-based NR promises to improve glaucoma assessment.

Studies of the retinal microcirculation using human donor eyes and high-resolution clinical imaging: Insights gained to guide future research in diabetic retinopathy

The microcirculation plays a key role in delivering oxygen to and removing metabolic wastes from energy-intensive retinal neurons. Microvascular changes are a hallmark feature of diabetic retinopathy (DR), a major cause of irreversible vision loss globally. Early investigators have performed landmark studies characterising the pathologic manifestations of DR. Previous works have collectively informed us of the clinical stages of DR and the retinal manifestations associated with devastating vision loss. Since these reports, major advancements in histologic techniques coupled with three-dimensional image processing has facilitated a deeper understanding of the structural characteristics in the healthy and diseased retinal circulation. Furthermore, breakthroughs in high-resolution retinal imaging have facilitated clinical translation of histologic knowledge to detect and monitor progression of microcirculatory disturbances with greater precision. Isolated perfusion techniques have been applied to human donor eyes to further our understanding of the cytoarchitectural characteristics of the normal human retinal circulation as well as provide novel insights into the pathophysiology of DR. Histology has been used to validate emerging in vivo retinal imaging techniques such as optical coherence tomography angiography. This report provides an overview of our research on the human retinal microcirculation in the context of the current ophthalmic literature. We commence by proposing a standardised histologic lexicon for characterising the human retinal microcirculation and subsequently discuss the pathophysiologic mechanisms underlying key manifestations of DR, with a focus on microaneurysms and retinal ischaemia. The advantages and limitations of current retinal imaging modalities as determined using histologic validation are also presented. We conclude with an overview of the implications of our research and provide a perspective on future directions in DR research.

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.

Optical coherence tomography angiography for quantitative microvascular assessment in diabetic retinopathy: inter-device and intra-device agreement and correlation with clinical staging

AIM

To compare acquisitions from single-volume Solix protocol (V1), multi-volume averaged Solix protocol (V4), and AngioVue in patients with diabetic retinopathy (DR) to assess differences in quantitative parameters introduced by high-speed scanning and averaging.

METHODS

Thirty-eight diabetic patients were divided into 4 groups showing either no sign, mild, moderate, or severe DR at fundus examination. For optical coherence tomography angiography (OCTA) acquisitions both AngioVue, Solix V1, and V4 were used on each patient. Outcome measures were macular perfusion density (PD), vessel length density (VLD), and vessel density index (VDI) for both superficial capillary plexus (SCP) and deep capillary plexus (DCP) and flow deficits (FD) in the choriocapillaris (CC).

RESULTS

Our study revealed a good agreement in SCP parameters measured with all 3 devices. DCP measurements with Solix V1 showed moderate agreement with V4 and poor agreement with AngioVue measurements. Inter-device agreement in CC-FD assessment was relatively poor considering all 3 devices. The averaging process led to an underestimation of DCP and SCP parameters in all stages of DR (more evident in mild DR). AngioVue measurements compared to Solix V1 led to overestimation of SCP-PD (more pronounced in severe DR patients) and of DCP parameters (more evidently in moderate DR). The regression model derived from Solix V1 parameters was the best for categorization into the different stages.

CONCLUSIONS

Averaging and high-speed scanning introduce changes in OCTA quantitative parameters in DR. Solix V1 is the most suitable for early diagnosis of DR, while averaged protocol could be the preferred choice in advanced stages of the disease.

Progress of Bulbar Conjunctival Microcirculation Alterations in the Diagnosis of Ocular Diseases

Bulbar conjunctival microcirculation is a microvascular system distributed in the translucent bulbar conjunctiva near the corneal limbus. Multiple ocular diseases lead to bulbar conjunctival microcirculation alterations, which means that bulbar conjunctival microcirculation alterations would be potential screening and diagnostic indicators for these ocular diseases. In recent years, with the emergence and application of a variety of noninvasive observation devices for bulbar conjunctiva microcirculation and new image processing technologies, studies that explored the potential of bulbar conjunctival microcirculation alterations in the diagnosis of ocular diseases have been emerging. However, the potential of bulbar conjunctival microcirculation alterations as indicators for ocular diseases has not been exploited to full advantage. The observation devices, image processing methods, and algorithms are not unified. And large-scale research is needed to concrete bulbar conjunctival microcirculation alterations as indicators for ocular diseases. In this paper, we provide an update on the progress of bulbar conjunctival microcirculation alterations in the diagnosis of ocular diseases in recent five years (from January 2017 to March 2022). Relevant ocular diseases include contact lens wearing, dry eye, conjunctival malignant melanoma, conjunctival nevus, and diabetic retinopathy.

Correlation of Diabetic Disease Severity to Degree of Quadrant Asymmetry in En Face OCTA Metrics

Purpose

To determine if diabetic retinopathy (DR) severity affects quadrant asymmetry (QA) of optical coherence tomography angiography (OCTA) metrics differentially.

Methods

Ninety eyes (60 patients) with no diabetes mellitus (DM) (n = 39) or varying levels of DR (n = 51) had OCTA images (3 × 3 mm, Cirrus5000) acquired five times and averaged. The vessel length density (VLD) and perfusion density (PD) of the superficial retinal layer (SRL) and deep retinal layer (DRL) were measured. QA was defined as the maximum minus minimum value among four parafoveal Early Treatment Diabetic Retinopathy quadrants, and compared with DR severity by linear regression including fixed effects for each individual and eye.

Results

The mean patient age was 55.5 years (range, 24–88 years) and 60% were male. Comparing severe nonproliferative DR or proliferative DR versus no DM/DR eyes, QA was significantly higher for SRL VLD, and PD (+0.67 ± 0.16 and +0.014 ± 0.003; P < 0.001) and DRL VLD, and PD (+1.25 ± 0.16 and +0.032 ± 0.003; P < 0.001). When comparing mild or moderate nonproliferative DR versus no DM/DR, the DRL VLD, and PD were significantly higher (+0.51 ± 0.13 and +0.015 ± 0.003; P < 0.001). For every step increase in DR severity, there was a +0.20 QA for SRL VLD, +0.004 SRL PD, +0.33 DRL VLD and +0.009 DRL PD (P < 0.001). Regression analysis comparing intraquadrant effect on DR severity demonstrated that the superior quadrant was most affected for all OCTA metrics.

Conclusions

DR severity affects VLD and PD more asymmetrically across Early Treatment Diabetic Retinopathy quadrants with a linear increase in QA for each worsening level of DR. Individual intraeye metrics such as QA can accurately quantify DR severity without concerns for intereye variabilities that could affect the reproducibility and reliability of OCTA quantification.

Effect of caffeine on superficial retinal vasculature of the macula in high myopes using optical coherence tomography angiography - A pilot study

PURPOSE

To monitor effect of caffeine on vasculature of the inner retina of high myopes METHODS: This was a crossover, self-control, randomized trial. Healthy young high myopes were recruited to take 200 mg of caffeine capsule and placebo capsule, randomly assigned in two visits separated by at least one week. Superficial retinal vasculature in terms of vessel length density (VD) and perfusion area density (PD) was captured and monitored using a spectral domain optical coherence tomography angiography (OCTA) machine. After baseline measurements, blood pressure (BP), intraocular pressure (IOP), and subfoveal choroidal thickness (ChT) were also monitored at 30-min intervals till 3 h.

RESULTS

Eighteen subjects (6 male, 24.3 ± 3.1 years) completed the study. After taking the caffeine capsule, there was a significant increase in BP (p < 0.01), and reduction in ChT (p < 0.01), with no change in IOP (p = 0.36). VD demonstrated a trend of reduction at the central 1-mm circle, and 1-3 mm annulus (p < 0.01) following the ETDRS grid. Reduction trend of PD appeared at the central 1-mm circle, 1-3 mm annulus, and the entire 3-mm circle (p < 0.01). Compared with baseline, VD and PD reductions were significant 180 min after taking the caffeine capsule at the central 1-mm circle, but the reduction was small (VD: by 1mm^-1; PD: by 1%). Changes in other regions were not significant.

CONCLUSIONS

The current study found significant reduction in VD and PD after taking 200 mg of caffeine capsule. Such a small amount of alteration may be clinically irrelevant.

Morphology and fluorescein leakage in diabetic retinal microaneurysms: a study using multiple en face OCT angiography image averaging

PURPOSE

To investigate the relevance of microaneurysm morphology in optical coherence tomography angiography (OCTA) image averaging and fluorescein leakage in diabetic retinopathy (DR).

METHODS

In 38 consecutive patients with DR, ten consecutive 3- × 3-mm fovea-centered OCTA (HS100, Canon Inc., Tokyo, Japan) and fluorescein angiography (FA) were performed, and averaged OCTA images were created based on the 10 images. After detecting all microaneurysms in FA images, the morphology was classified into four types (focal bulge, saccular/pedunculated, fusiform, and mixed) using averaged OCTA images. The correlation between microaneurysm leakage in FA, retinopathy stage, and microaneurysm morphology was estimated.

RESULTS

Thirty-eight eyes (50.0%) of the 33 patients were available for analysis, and 370 (63.5%) of the 583 FA-detected microaneurysms were morphologically classifiable (focal bulge, 46; saccular/pedunculated, 143; fusiform, 29; and mixed, 152) in OCTA. There was a significant correlation between stage and percentage of microaneurysm morphology and between morphology and the presence of leakage (P < 0.0001 and P < 0.01, respectively). The proportion of focal bulges decreased with stage progression, while the other three types increased with stage progression. The percentage of FA leakage for focal bulge, saccular/pedunculated, fusiform, and mixed was 41.3%, 66.4%, 82.8%, and 66.4%, respectively, and the fusiform type showed significant FA leakage.

CONCLUSION

Microaneurysm morphology is correlated with the DR stage and FA leakage. Microaneurysm morphology recognition using OCTA image averaging may be useful for the clinical evaluation of DR.

Association Between Retinal Microvascular Metrics Using Optical Coherence Tomography Angiography and Carotid Artery Stenosis in a Chinese Cohort

Objectives: The main aim was to investigate the association between retinal microvascular metrics using optical coherence tomography angiography (OCTA) and carotid artery stenosis (CAS) in an aging Chinese cohort.

Methods: In this cross-sectional and observational study, 138 eyes of 138 participants were examined. Indices of the microcirculation measured by OCTA included mean vessel density (VD), skeleton density (SD), vessel diameter index (VDI), fractal dimension (FD) and foveal avascular zone (FAZ) of the superficial retinal layer (SRL) and deep retinal layer (DRL), and peripapillary vessel caliber. The correlation of these indices with the carotid atherosclerotic lesions including carotid intima media thickness (CIMT) and common carotid artery (CCA) plaque was assessed.

Results: A total of 72 of 138 eyes demonstrated an increased (≥1 mm) CIMT, and 32 of the eyes presented common carotid plaques. Macular VD, SD, and FD were decreased with the increasing CCA caliber diameter (p &lt; 0.05, respectively). Superficial and deep macular FDs were negatively associated with CIMT as well as the existence of CCA plaques (p &lt; 0.05, respectively).

Conclusion: Changes in retinal microvasculature accessed by OCTA may be used as one of the non-invasive early indicators to monitor asymptomatic CAS.

Baseline predictors for good visual gains after anti-vascular endothelial growth factor therapy for myopic choroidal neovascularization

To investigate optical coherence tomography (OCT) and OCT angiography (OCTA) biomarkers for good visual outcomes in eyes with myopic choroidal neovascularization (mCNV) following anti-vascular endothelial growth factor (anti-VEGF) therapy. Patients diagnosed with mCNV via multimodal imaging were retrospectively reviewed. Baseline demographic data and biomarkers were collected. Anti-VEGF treatment based on a pro re nata (PRN) regimen was conducted on all eyes. The visual gains of ≥ 15 ETDRS letters or < 15 letters at 12-month were classified into two groups. Regression analysis was used to identify variables associated with significant best-corrected visual acuity (BCVA) improvement. Among 34 patients, 17 eyes and 17 eyes were classified into the two groups. There were no statistically significant differences in qualitative OCTA biomarkers between the two groups. The ≥ 15 letters group had significantly thicker subfoveal choroid thickness (SFCT) (79.97 ± 33.15 vs. 50.66 ± 18.31, P = 0.003), more ellipsoid zone integrity (58.8% vs. 23.5%, P = 0.037) and lower levels of fractal dimension (1.45 ± 0.101 vs. 1.53 ± 0.082, P = 0.031) than the < 15 letters group. SFCT and the ellipsoid zone integrity were correlated with 15 letters or more VA improvement in both univariable and multivariable analyses (P = 0.023 and P = 0.044, respectively). Thicker SFCT and integrity of the ellipsoid zone at baseline were associated with greater visual gains at 12 months. OCTA biomarkers seem to play a less important role in predicting the visual outcome of mCNV.

Development and quantitative assessment of deep learning-based image enhancement for optical coherence tomography

Purpose

To develop a deep learning-based framework to improve the image quality of optical coherence tomography (OCT) and evaluate its image enhancement effect with the traditional image averaging method from a clinical perspective.

Methods

359 normal eyes and 456 eyes with various retinal conditions were included. A deep learning framework with high-resolution representation was developed to achieve image quality enhancement for OCT images. The quantitative comparisons, including expert subjective scores from ophthalmologists and three objective metrics of image quality (structural similarity index measure (SSIM), peak signal-to-noise ratio (PSNR) and contrast-to-noise ratio (CNR)), were performed between deep learning method and traditional image averaging.

Results

With the increase of frame count from 1 to 20, our deep learning method always obtained higher SSIM and PSNR values than the image averaging method while importing the same number of frames. When we selected 5 frames as inputs, the local objective assessment with CNR illustrated that the deep learning method had more obvious tissue contrast enhancement than averaging method. The subjective scores of image quality were all highest in our deep learning method, both for normal retinal structure and various retinal lesions. All the objective and subjective indicators had significant statistical differences (P < 0.05).

Conclusion

Compared to traditional image averaging methods, our proposed deep learning enhancement framework can achieve a reasonable trade-off between image quality and scanning times, reducing the number of repeated scans.

Towards standardizing retinal optical coherence tomography angiography: a review

The visualization and assessment of retinal microvasculature are important in the study, diagnosis, monitoring, and guidance of treatment of ocular and systemic diseases. With the introduction of optical coherence tomography angiography (OCTA), it has become possible to visualize the retinal microvasculature volumetrically and without a contrast agent. Many lab-based and commercial clinical instruments, imaging protocols and data analysis methods and metrics, have been applied, often inconsistently, resulting in a confusing picture that represents a major barrier to progress in applying OCTA to reduce the burden of disease. Open data and software sharing, and cross-comparison and pooling of data from different studies are rare. These inabilities have impeded building the large databases of annotated OCTA images of healthy and diseased retinas that are necessary to study and define characteristics of specific conditions. This paper addresses the steps needed to standardize OCTA imaging of the human retina to address these limitations. Through review of the OCTA literature, we identify issues and inconsistencies and propose minimum standards for imaging protocols, data analysis methods, metrics, reporting of findings, and clinical practice and, where this is not possible, we identify areas that require further investigation. We hope that this paper will encourage the unification of imaging protocols in OCTA, promote transparency in the process of data collection, analysis, and reporting, and facilitate increasing the impact of OCTA on retinal healthcare delivery and life science investigations.

The intercapillary space spectrum as a marker of diabetic retinopathy severity on optical coherence tomography angiography

Microcirculatory disturbance plays a pivotal role in the pathogenesis in diabetic retinopathy (DR). We retrospectively quantified the total counts and morphological features of intercapillary spaces, i.e., intercapillary areas and nonperfusion areas (NPAs), on swept-source optical coherence tomography angiography (SS-OCTA) images and to evaluate their associations with DR severity grades. We acquired 3 × 3 mm OCTA images in 75 eyes of 62 diabetic patients and 22 eyes of 22 nondiabetic subjects. In the en-face superficial images within the central 2 mm, the areas enclosed by retinal vessels were automatically detected. Their total numbers decreased in some eyes with no apparent retinopathy and most eyes with DR, which allowed us to discriminate diabetic subjects from nondiabetic subjects [area under the receiver operating characteristic curve (AUC) = 0.907]. The areas and area/perimeter ratios continuously increased in DR, indicating a continuum between healthy intercapillary areas and NPAs. The number of intercapillary spaces with a high area/perimeter ratio increased according to DR severity, which showed modest performance in discriminating moderate NPDR or higher grades (AUC = 0.868). These quantified parameters of intercapillary spaces can feasibly be used for the early detection of microcirculatory impairment and the diagnosis of referable DR.