An overview of optical coherence tomography angiography and the posterior pole

Optical coherence tomography angiography based prognostic factors and visual outcomes in primary rhegmatogenous retinal detachment after pars plana vitrectomy

PURPOSE

To evaluate the visual outcomes and changes in the retinal microcirculation in patients with primary rhegmatogenous retinal detachment (RRD) following successful pars plana vitrectomy (PPV).

METHODS

Nine macula-on RRD and 23 macula-off RRD eyes were retrospectively evaluated. Clinical data was collected at admission and 3 months after PPV. Optical coherence tomography angiography (OCTA) was performed 3 months after PPV. Superficial vascular plexus data obtained with OCTA was compared between affected and fellow eyes and according to macular involvement. Quantitative measurements of the superficial retinal capillary associated with the preoperative and intraoperative factors were analyzed.

RESULTS

Overall RRD inner vessel densities (IVD), full vessel densities (FVD), inner perfusion densities (IPD) and full perfusion densities (FPD) were significantly and positively correlated with best corrected visual acuity (BCVA)(p = 0.002, p = 0.006, p = 0.009, p = 0.023, respectively). In the macula-off RRD, IVD and FVD were significantly decreased compared with macula-on RRD (p = 0.014 and p = 0.034, respectively) and significantly correlated with a longer duration and larger extension of detachment. Higher differences of IVD and FVD between the fellow and affected eyes were significantly correlated with worse BCVA in the macula-off subgroup.

CONCLUSION

Macula-off RRD presented worse OCTA superficial vascular parameters compared with the macula-on group and fellow eyes, which were correlated with a poorer visual outcome and exacerbated by a longer duration and larger extension of the detachment. Macula-off RRD causes not only retinal structural damage but also a reduction in retinal perfusion despite successful anatomical repair.

Correlation between retinal sensitivity and retinal vascular perfusion after idiopathic epiretinal membrane peeling

BACKGROUND

To evaluate the correlations between anatomical and functional changes after idiopathic epiretinal membrane (iERM) surgery.

METHODS

In this prospective, observational, single-center study, consecutive patients who underwent iERM peeling were enrolled. Reported data were pre- and postoperative best-corrected visual acuity (BCVA), retinal sensitivity (RS) and fixation stability values on microperimetry, structural macular features on SD-OCT and OCTA. RS of foveal and parafoveal area was analysed and two sub-groups were identified whether RS improved or remained unchanged/worsened after surgery; consequently, vascular perfusion density (VPD) of the same area was studied.

RESULTS

Twenty-nine eyes of 29 patients were examined. The post-operative improvement in terms of BCVA, RS and fixation within the central 4 degrees was significant (p < 0.001, p < 0.001, p = 0.001), as well as the foveal thickness and macular volume change/reduction (p < 0.001). The pre-operative superficial VPD, choriocapillaris VPD and capillary free zone (CFZ) area were significantly reduced compared to the fellow healthy eye (p = 0.001, p = 0.02, p < 0.001). Choriocapillaris VPD showed a statistically significant increase after surgery (p < 0.02). Superficial, deep and choriocapillaris VPD of the improved RS group showed a significant increase both in foveal (p = 0.03, p = 0.03, p = 0.01) and parafoveal areas (p = 0.01, p = 0.03, p = 0.001).

CONCLUSIONS

We reported a higher VPD in the retinal area that experienced a retinal sensitivity improvement 6 months after ERM surgery. This result objectifies the tight bond between visual function and retinal perfusion in ERM patients.

Insights Into Visual Rehabilitation: Pan-Retinal Photocoagulation for Proliferative Diabetic Retinopathy

This review comprehensively explores pan-retinal photocoagulation (PRP) as a pivotal intervention in visually rehabilitating individuals afflicted with proliferative diabetic retinopathy (PDR). The review begins by elucidating the significance of PDR within the spectrum of diabetic retinopathy (DR), emphasizing the progressive nature of the disease and the consequential impact on visual health. A detailed analysis of PRP follows, encompassing its definition, purpose, and historical development, shedding light on the procedural intricacies and mechanisms of action. The postoperative care and follow-up section underscores the necessity of vigilant monitoring for complications, visual recovery, and the importance of regular ophthalmic check-ups. The subsequent discussion delves into patient education and counseling, stressing the need to manage expectations, encourage lifestyle modifications, and highlight the significance of follow-up appointments. The review concludes with insights into future directions, including advancements in laser technology and emerging therapies, offering a glimpse into the evolving landscape of DR management. By addressing ongoing challenges and embracing innovative approaches, this review provides a comprehensive guide for clinicians, researchers, and healthcare practitioners who visually rehabilitate individuals struggling with PDR.

Wide Field Optical Coherence Tomography and Optical Coherence Tomography Angiography in Uveitis

BACKGROUND

We review the current literature on the use of wide-field optical coherence tomography (OCT) and wide-field optical coherence tomography angiography (OCTA) in different uveitic phenotypes as well as various sequelae of uveitis and discuss the limitations of this evolving technology.

MAIN BODY

Current consensus guidelines on nomenclature in wide-field OCT and OCTA are described. The specific utility of wide-field OCT and OCTA in assessment of the retina and choroid using different en-face and cross-sectional slabs in various inflammatory diseases is reviewed. Furthermore, we discuss widefield OCT and OCTA in assessment of retinal ischemia and its limitations in assessing retinal vascular leakage.

CONCLUSION

Wide-field OCT and OCTA deliver more sensitive measures of inflammation. With continued advancement in both hardware technology and software processing, these modalities will allow for more accurate assessment of uveitis, better understanding of disease mechanisms, and precise monitoring of treatment response.

Correlation Between Imaging Morphological Findings and Laboratory Biomarkers in Patients with Retinal Vein Occlusion

INTRODUCTION

The aim of this study was to investigate the possible correlation between peripheral blood biomarkers and morphological characteristics of retinal imaging in patients with retinal vein occlusion (RVO).

METHODS

Participants in this cross-sectional observational study were 65 consecutive patients (65 eyes) with treatment-naïve RVO, who underwent spectral-domain optical coherence tomography (SD-OCT) and fundus fluorescein angiography (FFA). In addition, peripheral blood samples were taken to evaluate full blood count and biochemical parameters. The association between imaging characteristics and laboratory parameters was examined.

RESULTS

Eyes with subretinal fluid presented significantly higher neutrophil-to-lymphocyte ratios (p = 0.028). Hyperreflective foci on SD-OCT were found to be associated with higher triglyceride levels (p = 0.024). The presence of cysts on SD-OCT was associated with significantly higher triglycerides (p = 0.010). Central subfield thickness (CST) higher than 464 μm was associated with higher lymphocyte count (p = 0.016) and higher urea (p = 0.015). No significant associations were found between laboratory parameters and intraretinal fluid, ellipsoid zone and external limiting membrane condition, or epiretinal membrane and macular ischemia.

CONCLUSIONS

Specific imaging morphological characteristics were found to be associated with laboratory parameters in patients with RVO. These findings may help reveal the pathophysiology of RVO and its correlation with the development of specific clinical signs, while they could guide individualized treatment.

Correlation of vascular and fluid-related parameters in neovascular age-related macular degeneration using deep learning

PURPOSE

To identify correlations between the vascular characteristics of macular neovascularization (MNV) obtained by optical coherence tomography angiography (OCTA) and distinct retinal fluid volumes in neovascular age-related macular degeneration (nAMD).

METHODS

In this prospective interventional study, 54 patients with treatment-naïve type 1 or 2 nAMD were included and treated with intravitreal aflibercept. At baseline and month 1, each patient underwent a SD-OCT volume scan and volumetric flow scan using a swept-source OCTA. A deep learning algorithm was used to automatically detect and quantify fluid in OCT scans. Angio Tool, a National Cancer Institute algorithm, was used to skeletonize MNV properties and quantify lesion size (LS), vessel area (VA), vessel density (VD), total number of endpoints (TNE), total number of junctions (TNJ), junction density (JD), total vessel length (TVL), average vessel length (AVL) and mean-e-lacunarity (MEL). Subsequently, linear regression models were used to investigate a correlation between OCTA parameters and fluid quantifications.

RESULTS

The median amount of fluid within the central 6-mm EDTRS ring was 173.7 nl at baseline, consisting of 156.6 nl of subretinal fluid (SRF) and 2.3 nl of intraretinal fluid (IRF). Fluid decreased significantly in all compartments to 1.76 nl (SRF) and 0.64 nl (IRF). The investigated MNV parameters did not change significantly after the first treatment. There was no significant correlation between MNV parameters and relative fluid decrease after anti-VEGF treatment. Baseline fluid correlated statistically significant but weakly with TNE (p = 0.002, R²  = 0.17), SRF with TVL (p = 0.04, R²  = 0.08), VD (p = 0.046, R²  = 0.08), TNE (p = 0.001, R²  = 0.20) and LS (p = 0.033, R²  = 0.09). IRF correlated with VA (p = 0.042, R²  = 0.08).The amount of IRF at month 1 correlated significantly but weakly with VD (p = 0.036, R²  = 0.08), JD (p = 0.019, R²  = 0.10) and MEL (p = 0.005, R²  = 0.14).

CONCLUSION

Macular neovascularization parameters at baseline and month 1 played only a minor role in the exudation process in nAMD. None of the MNV parameters were correlated with the treatment response.

The impact of laboratory findings and optical coherence tomography biomarkers on response to intravitreal anti-VEGF treatment in patients with retinal vein occlusion

AIMS

To investigate potential laboratory and imaging biomarkers as treatment response predictors to intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents in patients with retinal vein occlusion (RVO).

METHODS

Participants in this prospective study were 53 patients with treatment naïve macular edema secondary to RVO, treated with intravitreal anti-VEGF agents and followed-up for 12 months. At baseline, all participants underwent best-corrected visual acuity measurement, dilated fundoscopy, optical coherence tomography and fluorescein angiography (FFA), while full blood count and biochemical analysis of various parameters was also performed. At month 12, treatment response was examined and classified as "favorable" or "non-response". Potential associations between laboratory/imaging biomarkers and treatment response were assessed.

RESULTS

Univariate analysis showed that "favorable" response at month 12 after initiation of anti-VEGF treatment was correlated with baseline central subfield thickness (CST) < 464 μm (p < 0.001), absence of subretinal fluid (p = 0.004), absence of hyperreflective foci (HF) (p = 0.004), intact ellipsoid zone (EZ) and external limiting membrane (ELM) (p < 0.001 and p = 0.001, respectively), absence of epiretinal membrane (ERM) (p = 0.020) and absence of macular ischemia on FFA (p < 0.001), while increased monocytes-to-lymphocytes ratio was also associated with "favorable" treatment response (p = 0.010). All other laboratory parameters did not reach statistical significance. However, at the multivariate analysis, EZ and ELM status, HF, macular ischemia and monocytes-to-lymphocytes ratio were found to be independent predictors of treatment response.

CONCLUSIONS

Intact EZ and ELM, absence of HF, absence of macular ischemia and increased monocytes-to-lymphocytes ratio at baseline can predict "favorable" treatment response in patients with treatment naïve macular edema secondary to RVO.

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 utility of wide-field optical coherence tomography angiography in diagnosis and monitoring of proliferative diabetic retinopathy in pregnancy

Purpose

Observations

Conclusions and importance

Role of Anterior Segment-Optical Coherence Tomography Angiography in Acute Ocular Burns

Acute ocular burns have varied manifestations which require prompt diagnosis and management to prevent chronic sequelae. Of these, the detection of limbal ischemia poses a challenge because of the subjective nature of its clinical signs. Anterior segment optical coherence tomography angiography (AS-OCTA) offers an objective method of assessing ischemia in these eyes. This review provides an overview of the technology of AS-OCTA and its applications in acute burns. AS-OCTA generates images by isolating the movement of erythrocytes within blood vessels from sequentially obtained b-scans. Limbal ischemia manifests in these scans as absent vasculature and the extent of ischemia can be quantified using different vessel-related parameters. Of these, the density of vessels is most commonly used and correlates with the severity of the injury. Incorporation of the degree of ischemia in the classification of acute burns has been attempted in animal studies and its extension to human trials may provide an added dimension in determining the final prognosis of these eyes. Thus, AS-OCTA is a promising device that can objectively evaluate limbal ischemia. This will facilitate the identification of patients who will benefit from revascularization therapies and stem cell transplants in acute and chronic ocular burns, respectively.

Morphologic and Microvascular Differences Between Macular Neovascularization With and Without Subretinal Fibrosis

Purpose

To evaluate morphologic and microvascular differences between eyes with and without subretinal fibrosis (SF) caused by neovascular age-related macular degeneration (nAMD).

Methods

Patients with nAMD with a minimum history of 12 months of anti-VEGF treatment were prospectively included in this cross-sectional study. Patients were imaged using standard imaging, swept-source optical coherence tomography angiography for quantitative microvascular analysis and polarization-sensitive OCT as an ancillary method for automated SF segmentation. The presence of reticular pseudodrusen, hyperreflective foci (HRF), and outer retinal tubulation (ORT) were also evaluated.

Results

Sixty eyes of 60 participants (37 female) with nAMD and a mean 3.1 (±2.7)-year history of anti-VEGF treatment were included, 20 (33%) of which were diagnosed with SF. Eyes with SF had a higher prevalence of ORT (P < 0.001) and a lower prevalence of HRF (P = 0.004) than eyes without SF. Fifty eyes were analyzed quantitatively for microvascular biomarkers. Eyes with SF had a larger greatest vascular caliber (P = 0.001) and greatest linear diameter (P = 0.042), a larger microvascular neovascularization (MNV) area (P = 0.026), larger vessel area (P = 0.037), higher number of vessel junctions (P = 0.025), longer total vessel length (P = 0.027), higher number of vessel endpoints (P = 0.007), and higher endpoint density (P = 0.047).

Conclusions

This multimodal imaging approach demonstrated in vivo microvascular and morphological differences in eyes with and without SF. Eyes with SF tend to have larger MNV lesions with thicker vessels and are often associated with the presence of ORT.

Translational Relevance

This study points out imaging biomarkers in patients with SF, which may help identifying high-risk patients.

Retinal cross-section motion correction in three-dimensional retinal optical coherence tomography

Motion correction is an important issue in ophthalmic optical coherence tomography (OCT), and can improve the ability of data sets to reflect the physiological structures of tissues and make visualization and subsequent analysis easier. In this study, we present a novel method to correct the cross-sectional motion artifacts in retinal OCT volumes. Motion along the x-direction (fast-scan direction) is corrected through the normalized cross-correlation algorithm, while axial motion compensation is performed using the polynomial fitting method on the inner segment/outer segment (IS/OS) layer segmented by the shortest path faster algorithm (SPFA). The results of volunteers with central serous chorioretinopathy demonstrate that the proposed method effectively corrects motion artifacts in OCT volumes and may have potential application value in the evaluation of ophthalmic diseases such as diabetic retinopathy, glaucoma and age-related macular degeneration.

Superficial and Deep Macula Vessel Density in Healthy, Glaucoma Suspect, and Glaucoma Eyes

PRECIS

Macular superficial capillary plexus (SCP) vessel density is more informative than deep capillary plexus (DCP) vessel density for the detection of glaucoma.

PURPOSE

The purpose of this study was to characterize optical coherence tomography angiography macular SCP and projection-resolved DCP vessel densities and compare their diagnostic accuracies with ganglion cell complex (GCC) thickness in healthy, glaucoma suspect, and glaucoma eyes.

MATERIALS AND METHODS

Sixty-eight eyes of 44 healthy subjects, 26 eyes of 16 preperimetric glaucoma suspects, and 161 eyes of 124 glaucoma patients from the Diagnostics Innovations in Glaucoma Study with good quality high-density 6×6 mm2 macula optical coherence tomography angiography images were included. The diagnostic accuracy of SCP vessel density, projection-resolved DCP vessel density and GCC thickness were compared among groups.

RESULTS

Mean whole image vessel density (wiVD; % of area occupied by vessels containing flowing blood) in the SCP layer was highest in healthy eyes (49.7%), followed by glaucoma suspect eyes (46.0%), and glaucoma eyes (40.9%) (P<0.001). Mean wiVD in the DCP layer was similar in healthy (50.6%), glaucoma suspect (47.3%), and glaucoma eyes (45.7%) (P=0.925). Diagnostic accuracy of both GCC thickness and SCP wiVD was significantly higher than DCP wiVD for classifying healthy and glaucoma eyes [adjusted area under the receiver operating characteristic curve (95% confidence interval): GCC=0.86 (0.72, 0.94), SCP=0.80 (0.66, 0.91) and DCP=0.44 (0.30, 0.57)] (P<0.001).

CONCLUSIONS

SCP vessel densities have better diagnostic accuracy for detecting glaucoma than DCP vessel densities. Although the diagnostic accuracy of the macula SCP is relatively modest, it is more informative than the DCP.

Circumpapillary optical coherence tomography angiography differences in perimetrically affected and unaffected hemispheres in primary open-angle glaucoma and the preperimetric fellow eye

Purpose

Evaluation of circumpapillary vessel density (VD) and perfusion density (PD) on optical coherence tomography angiography (OCTa) in mild-moderate glaucoma patients having unilateral visual field defects, with their fellow eyes and controls.

Methods

Both eyes of 24 patients having a definitive nasal step or arcuate scotoma in one hemisphere of one eye only, and 24 controls, underwent OCTa.

Results

In eyes with a superior field defect, the superior/inferior quadrant ratios, (SQ/IQ) of 3 mm scan of VD and PD were significantly higher in eyes with a superior arcuate scotoma than fellow eyes (P = 0.03,0.02) as also controls, (P = 0.004,0.001). The mean percentage loss of inferior quadrant VD between control to fellow eyes, and superior nasal step eyes were similar, 20.19%/19.57% respectively, P = 0.85, while a loss in arcuate scotoma eyes was 38.81% (P = 0.001). The percentage decrease in inferior quadrant PD in fellow eyes was 14.70%, superior nasal step 23.39%, and an arcuate scotoma 34.74% (P = 0.02). Eyes with a superior nasal step had significantly lower VD and PD absolute values in the inferior quadrant OCTa in 3 mm and 6 mm circle scan only as compared to control eyes, VD, P = 0.03,0.04/PD, P = 0.008,0.02. Fellow eyes of superior field defects had significantly lower VD and PD absolute values in the inferior quadrant in 3 mm and 6 mm circle scan as compared to control eyes, VD, P = 0.006,0.04/PD, P = 0.01,0.03. Eyes with an isolated inferior field defect in only one eye, showed a significant decrease in both VD and PD in all quadrants as compared to fellow eyes and control eyes. A significant positive correlation was found between VD and RNFL thickness in peripapillary superior unaffected quadrants in eyes with superior field defects and inferior unaffected quadrants in inferior defects (P = 0.001 and 0.01).

Conclusion

There was a statistically significant increasing SQ/IQ ratio and percentage loss of vascular parameters from control to fellow eyes, those with a superior nasal step, and those with a superior arcuate scotoma. Inferior VFDs appeared to be associated with a more generalized circulatory loss. The asymmetry between hemispheres and between eyes could be used as a biomarker for early glaucomatous neuropathy.

Looking Ahead: Visual and Anatomical Endpoints in Future Trials of Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy that can lead to progressive and irreversible visual loss. Despite substantial clinical burden, there are no treatments for DMI, no validated clinical trial endpoints, and few clinical trials focusing on DMI. Therefore, generating consensus on validated endpoints that can be used in DMI for the development of effective interventions is vital. In this review, we discuss potential endpoints appropriate for use in clinical trials of DMI, and consider the data required to establish acceptable and meaningful endpoints. A combination of anatomical, functional, and patient-reported outcome measures will provide the most complete picture of changes that occur during the progression of DMI. Potential endpoint measures include change in size of the foveal avascular zone measured by optical coherence tomography angiography and change over time in best-corrected visual acuity. However, these endpoints must be supported by further research. We also recommend studies to investigate the natural history and progression of DMI. In addition to improving understanding of how patient demographics and comorbidities such as diabetic macular edema affect clinical trial endpoints, these studies would help to build the consensus definition of DMI that is currently missing from clinical practice and research.

Intra- and Intergrader Agreement for Detection of OCT Angiographic Characteristics Associated With Type 3 Neovascularization

Purpose

To examine the intra- and intergrader agreement on morphologic characteristics of type 3 neovascularization on optical coherence tomography angiography (OCT-A).

Methods

OCT-A images of 22 eyes from 21 patients with a new-onset, treatment-naive type 3 neovascularization were included in this cross-sectional retrospective agreement study. Each image was graded three times by two independent medical retina specialists to assess intra- and intergrader agreement. The graders scored the presence or absence of the following vascular and structural features: intraretinal neovascularization (IRN), subretinal neovascularization, sub-retinal pigment epithelium (RPE) neovascularization (SRPEN), retinal choroidal anastomosis (RCA), intraretinal cysts, subretinal fluid, and pigment epithelial detachment. Agreement was analyzed for each feature using Gwet's AC₁, к statistics, and percentage of agreement.

Results

The best agreement (AC₁) was found for intraretinal neovascularization (within_grader1: 0.94; within_grader2: 0.93 and between: 1.00) and intraretinal cysts (within_grader1, 1.00; within_grader2, 0.97 and between, 1.00). The poorest intragrader agreements were observed for SRPEN (within_grader1, 0.54 and within_grader2, 0.36) and RCA (within_grader1, 0.45 and within_grader2, 0.52), and the poorest intergrader agreement was found for SRPEN, RCA, and pigment epithelial detachment (0.18, 0.37, and 0.15, respectively).

Conclusions

Although the agreement values were high for intraretinal features, considerable grader variability was found for the vascular and structural features in the deeper retina or under the RPE. Clinicians should be careful to base therapeutic decisions on qualitative OCT-A assessment, because even well-trained specialists show a considerable grader variation in their subjective evaluation.

Translational Relevance

The clinical value of OCT-A imaging largely depends on the agreement of subjective evaluations by ophthalmologists.

Vessel Density Changes on Optical Coherence Tomography Angiography after Vascular Endothelial Growth Factor Inhibitor Treatment for Diabetic Macular Edema

Objectives

To evaluate the changes in macular vessel density after treatment with vascular endothelial growth factor (VEGF) inhibitors in center-involving diabetic macular edema (DME) and to compare these changes between anatomical responders and non-responders.

Materials and Methods

This retrospective study included 22 eyes with center-involving DME. All eyes had 3 consecutive administrations of VEGF inhibitors. Optical coherence tomography (OCT) and OCT angiography (OCTA) of the macula with manual adjustment of segmentation lines were performed at baseline and after treatment. Vessel density in the central and parafoveal regions of the superficial and deep capillary plexus (SCP/DCP) were measured at baseline and after treatment. Vessel density and changes therein were compared between anatomical responders and non-responders as defined by changes in central subfield thickness (CST).

Results

Overall, there were no significant differences in vessel density in the central and parafoveal regions of the SCP and DCP after treatment compared to baseline. After categorization by anatomical response, 12 eyes were responders (CST decreased by 173.7±47.7 μm) and 10 eyes were non-responders (CST increased by 20.8±38.9 μm) (p<0.0001). There were no corresponding significant differences between responders and non-responders in SCP and DCP vessel density or changes therein after treatment.

Conclusion

There were no significant changes in macular vessel density after the early stages of VEGF inhibitor treatment for DME, and there was no relationship with the anatomical response. The effect of VEGF inhibitors in DME treatment may not be related to increasing vessel density.

The Effect of Software Versions on the Measurement of Retinal Vascular Densities Using Optical Coherence Tomography Angiography

BACKGROUND

The goal of the study was to determine the effect of different software versions on the measurement of retinal vessel densities using optical coherence tomography angiography (OCTA) in normal subjects.

METHODS

Thirty-two eyes of eighteen healthy subjects were imaged using two OCTA devices: the Optovue RTVue and the Zeiss Cirrus. The macular 3 × 3 mm scan protocol was used. The images acquired using the Optovue OCTA device were exported using two different software versions in the system and compared to the images acquired through the Zeiss OCTA. In addition, the Optovue OCTA images were exported after manual adjustment of the segmentation boundaries according to the intraretinal layer definition. The densities of the superficial vascular plexus (SVP) and deep vascular plexus (DVP) were measured using fractal analysis by box-counting (Dbox).

RESULTS

Both the vessel densities of the SVP and DVP acquired using the Optovue OCTA device were significantly different when compared to those from the Zeiss OCTA device (all, P <.05). No significant difference was found between the vessel densities of the SVP exported using both the new and old versions of Optovue (P >.05). However, the DVP exported using the new Optovue software version was significantly different compared to those exported using the old version (P <.05). The vessel densities of the SVP and DVP were related among the Optovue OCTA software versions and manual adjustment method (r ranged from 0.55 to 0.77; all P <.05).

CONCLUSION

This is the first study to determine that different software versions with various intraretinal layer segmentation methods affect the vessel density measurements of the SVP and DVP.

Evaluation of retinal vascular structure after epiretinal membrane surgery by optical coherence tomography angiography

PURPOSE

To evaluate the retinal vascular structure before and after the epiretinal membrane (ERM) surgery by optical coherence tomography angiography (OCTA).

METHODS

Twenty-two eyes with ERM (study eyes) had been evaluated by OCTA for superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel density (VD) at foveal and parafoveal regions and foveal avascular zone (FAZ) before and after ERM removal surgery. Twenty-two fellow eyes were selected as control group.

RESULTS

Preoperative VD of SCP and DCP were significantly lower in ERM eyes than in controls in both foveal and parafoveal areas (p < 0.05, for all). The difference regressed in SCP (fovea: 18.04 ± 3.1 vs 19.98 ± 18 p = 0.002 and parafovea: 47.33 ± 3.54 vs 49.71 ± 28 p = 0.001), but persisted in DCP (fovea: 17.25 ± 3.52 vs 17.57 ± 4.01 p = 0.856 and parafovea: 50.12 ± 4.35 vs 50.93 ± 3.24 p = 0.791) in study eyes, postoperatively. Superficial and deep FAZ areas were significantly smaller in study eyes than controls. Postoperatively, superficial FAZ area enlarged (0.288 ± 0.10 vs 0.307 ± 0.08 p = 0.012), whereas deep FAZ area did not (0.324 ± 0.09 vs 0.338 ± 0.07 p = 0.435). FAZ area was correlated with the best-corrected visual acuity in ERM eyes.

CONCLUSION

Vascular damage in SCP and DCP was demonstrated by OCTA in eyes with ERM. ERM removal surgery mainly improves superficial changes caused by ERM. Changes in deep retinal flow may be associated with visual outcomes after ERM removal surgery.

Optical Coherence Tomography Angiography Assessed Retinal and Choroidal Microvasculature Features in Patients with Retinitis Pigmentosa: A Meta-Analysis

Background

The aim of this study was to assess the retinal and choroidal microvasculature features using optical coherence tomography angiography (OCTA) in patients with retinitis pigmentosa (RP).

Methods

This study was a meta-analysis of relevant published studies that were included after a comprehensive search of PubMed, Embase, Cochrane Library, and Web of Science databases. Mean difference (MD) with a 95% confidence interval was used to assess continuous variable outcomes. Heterogeneity was evaluated using the chi-squared test based on the values of P and I².

Results

Seven studies were included in this meta-analysis. The vessel density values measured in the superficial and deep foveal zones of RP patients using OCTA were significantly lower than the recorded values in the control groups (MD = −3.58, P=0.04; MD = −4.93, P=0.02, respectively). The superficial and deep parafoveal vessel density values measured with OCTA were also significantly lower in RP patients than in control groups (MD = −9.09, P < 0.00001; MD = −10.74, P < 0.00001, respectively); for choriocapillaris vessel density, there was no statistically significant difference between RP patients and controls (MD = −1.33, P=0.09). The deep foveal avascular zone (FAZ) was significantly larger in RP patients than in controls (MD = 0.15, P=0.01), whereas there was no significant difference in the superficial foveal avascular zones in the two groups (MD = 0.08, P=0.11).

Conclusions

We showed that retinal and choroidal vessels were attenuated in RP patients. Additionally, we revealed that the FAZ was larger in RP patients, especially the deep FAZ. OCTA may become a useful modality in the diagnosis and monitoring of patients with RP.