Swept-source optical coherence tomography imaging of the retinochoroid and beyond

Principles of Ophthalmic Ultrasound

Introduction

Ultrasound imaging of the eye was introduced over 50 years ago. While the physical principles of ultrasound imaging have not changed, technology has undergone tremendous and ongoing development.

Areas covered

The fundamentals of ultrasound physics, biometry (A-scan), structural imaging (B-scan) and blood-flow imaging and measurement (Doppler) will be described. Emphasis will be placed on technological development and potential future advances.

Expert opinion

While A- and B-scan ultrasound of the eye has traditionally been performed with focused single-element transducers, the introduction of annular and linear arrays has enhanced clinical utility. Future advances, especially in multielement arrays, and point-of-care systems promise amazing new capabilities for diagnostic imaging of the eye and orbit.

Choroidal thickness in patients with thyroid-associated ophthalmopathy, as determined by swept-source optical coherence tomography

AIM

This study used swept-source optical coherence tomography (SS-OCT) to investigate subfoveal choroidal thickness (SFCT) in patients with thyroid-associated ophthalmopathy (TAO) who displayed different levels of disease activity and severity.

METHODS

Thirty patients with TAO (60 eyes) and 38 healthy controls (67 eyes) in Shanghai, China, were recruited for this study. Disease activity and severity were graded using European Group on Graves' Orbitopathy standardised criteria. SFCT values were determined by SS-OCT.

RESULTS

In total, 129 eyes were included in the final analysis. The mean SFCT was significantly thicker among patients with active disease (276.23±84.01 µm) than among patients with inactive disease (224.68±111.61 µm; p=0.049) or healthy controls (223.56±78.69 µm; p=0.01). There were no differences in SFCT among patients with moderate-to-severe disease, patients with severe disease and healthy controls (p>0.05). Changes in SFCT demonstrated strong predictive ability to distinguish active TAO from inactive TAO (area under the curve=0.659, 95% CI 0.496 to 0.822).

CONCLUSIONS

SFCT was strongly associated with Clinical Activity Score in patients with TAO. Choroidal thickening was observed during active TAO. SS-OCT offers a non-invasive method for follow-up assessment.

Experts Opinion: OCTA vs. FFA/ICG in Uveitis - Which Will Survive?

Will optical coherence tomography angiography (OCTA) replace invasive imaging techniques like fundus fluorescein angiography (FFA) and indocyanine green (ICG) angiography entirely? While OCTA is being increasingly applied in the field of medical retina, will we see this change in the subspeciality of uveitis? In this article, five uveitis specialists with renowned imaging expertise answer to 10 specific questions to address this issue. The final verdict based on the comments of the experts suggests that FFA and ICG cannot be replaced by OCTA in uveitis, at least for now. While OCTA can offer new insights into the pathogenesis of certain inflammatory conditions and help in the diagnosis of complications like inflammatory choroidal neovascularisation, multimodal imaging is still the preferred approach in the assessment of patients with uveitis.

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.

Retinal Microvascular Alterations in Patients with Quiescent Posterior and Panuveitis Using Optical Coherence Tomography Angiography

PURPOSE

To quantify retinochoroidal vascular parameters using swept-source optical coherence tomography (SS-OCTA) in quiescent posterior and panuveitis.

METHODS

In this cross-sectional study, subjects with quiescent posterior and panuveitis underwent fundus imaging using SS-OCTA (DRI Triton®, Topcon, Japan). The metrics calculated were fractal dimension (FD), foveal avascular zone (FAZ) area, retinal vascularity index (capillary density index-CDI), and choroidal vascularity index (CVI).

RESULTS

We included 38 eyes of 20 patients, 9 males aged 34.7 ± 10.5 years, 30 eyes of 30 age- and gender-matched healthy controls, 10 females aged 33.6 ± 8.5 years. Comparing patients with controls, we found a lower FD (p < .001), larger FAZ (p > .001), lower CDI in the superficial plexus (p = .019), and lower CVI (p < .001). We also found lower retinal and choroidal and thicknesses (p < .001 and p = .025, respectively).

CONCLUSIONS

Patients with quiescent posterior and panuveitis have a significantly reduced retinochoroidal vascular density compared to healthy control subjects.

Imaging-based Assessment of Choriocapillaris: A Comprehensive Review

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Retinal and choroidal microvascular alterations in Behcet’s disease without ocular manifestations: A systematic review and meta-analysis

Purpose

We performed a systematic review and meta-analysis to examine the microvascular alterations in non-ocular Behcet’s disease (BD) using optical coherence tomography angiography (OCTA).

Methods

A comprehensive search was performed in Pubmed, Embase and Cochrane databases for eligible studies from inception to February 2022. Detailed clinical demographics were extracted from each study by two independent reviewers. The weighted mean difference (WMD) and 95% confidence intervals (CI) were used to compare the OCTA parameters between non-ocular BD and healthy controls. Stata 12.0 was adopted to conduct statistical analyses.

Results

Ten cross-sectional studies involving 386 eyes in non-ocular BD and 418 eyes in healthy volunteers were ultimately included in the present analysis. When considering superficial capillary plexus (SCP) and deep capillary plexus (DCP), no significant differences of vessel densities in the whole enface image, fovea and perifovea were evaluated between two groups. Significantly reduced parafoveal vessel density of SCP was observed in non-ocular BD in comparison with healthy group (WMD = −1.33, 95%CI: −1.78, −0.89; I2 = 0.6%), while slightly decreased parafoveal vessel density was assessed in DCP (WMD = −1.47, 95%CI: −3.30, 0.35; I2 = 89.3%). Significantly increasing foveal avascular zone (FAZ) area was observed in non-ocular BD when compared to healthy controls (WMD = 0.11, 95%CI: 0.03, 0.19; I2 = 95.3%). There was no significant difference in flow area of choriocapillaris between non-ocular BD and control group (WMD = 0.06, 95%CI: −0.19, 0.32; I2 = 0%).

Conclusion

Based on current analysis, our results demonstrated significantly lower parafoveal vessel density of SCP and lager FAZ area in full vasculature in non-ocular BD. The retinal microvascular alterations appear before the emergence of ocular manifestations.

Systematic Trial Registration

[https://www.crd.york.ac.uk/PROSPERO/], identifier [CRD42021244856].

Choroidal and retinal thickness in patients with vitamin C deficiency using swept-source optical coherence tomography

Background

To investigate the effects of vitamin C on central retinal thickness and choroidal thickness.

Methods

A total of 69 patients diagnosed with vitamin C deficiency and 1:1 age- and gender-matched 69 healthy individuals with normal serum vitamin C were included in this study. Demographic characteristics of the individuals were collected. All patients underwent a comprehensive ophthalmic examination. Subfoveal choroidal thickness and retinal thickness were measured using a swept-source optical coherence tomography (SS-OCT).

Results

The average retinal thickness was 269.07 ± 13.51 μm in the vitamin C deficiency group and 276.92 ± 13.51 μm in the control group. The average choroidal thickness was 195.62 ± 66.40 μm in the in the vitamin C deficiency group and 238.86 ± 55.08 μm in the control group. There was a significant decrease in both average choroidal thickness and retinal thickness in vitamin C deficiency group compared with normal individuals (p < 0.001, and = 0.001 respectively).

Conclusion

The central retinal and choroidal thickness were thinner in vitamin C deficiency group compared with normal individuals. These findings suggested that vitamin C deficiency might play an important role in retinal and choroidal diseases.

Macular and Optic Disc Parameters in Children with Amblyopic and Nonamblyopic Eyes under Optical Coherence Tomography Fundus Images

The aim of this study was to investigate the characteristics of macular and optic disc parameters in children with amblyopic and nonamblyopic eyes, using fundus images under optical coherence tomography (OCT). 36 patients with anisometropic amblyopia were selected in the experimental group, and another 36 healthy volunteers were selected in the control group, OCT examinations were performed in all groups, and the mean diopter, mean corrected visual acuity (CVA), mean axial length, mean optic disc retinal nerve fiber layer (RNFL) thickness, and mean macular fovea thickness were recorded in the two groups. The results found that the average diopter of the patients in the control group and the experimental group was +2.30 ± 2.54 D and +5.51 ± 1.76 D, respectively. The average CVA was 0.86 ± 0.07 and 0.22 ± 0.16, respectively; the average eye axial length was 22.41 ± 1.20 mm and 21.11 ± 0.78 mm, respectively. As P < 0.05, the differences were statistically significant in the three indicators between the two groups. There was no significant difference between the two groups in the average thickness of the RNFL of the optic disc and the average thickness of the central fovea of macula (P > 0.05). There was some correlation among CVA, diopter, eye axial length, RNFL thickness, and average thickness of macular fovea, but the correlation was not significant. It was suggested that there were certain differences in the macular and optic disc parameters between amblyopic and nonamblyopic children, but the difference is little. Thereout, a certain objective basis was provided for the early detection and treatment of amblyopia.

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.

The Impact of Laboratory Findings and Optical Coherence Tomography Biomarkers on Response to Intravitreal Anti-VEGF Treatment in Patients with Diabetic Macular Edema

PURPOSE

To investigate potential laboratory and imaging biomarkers as treatment response predictors to intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents in patients with diabetic macular edema (DME).

METHODS

The study included 36 treatment naïve patients with DME, treated with intravitreal anti-VEGF agents and followed-up for 12 months. At baseline, all participants underwent best-corrected visual acuity (BCVA) measurement, dilated fundoscopy, optical coherence tomography, color fundus photography and fluorescein angiography, 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)≤405 μm (p < .001), absence of subretinal fluid (p = .034), absence of exudates (p = .041), absence of disorganization of the inner retinal layers (p = .037), intact ellipsoid zone (EZ) and external limiting membrane (ELM) (p < .001 and p = .002, respectively), absence of epiretinal membrane (ERM) (p = .040) and absence of macular ischemia (p = .042), while increased lipoprotein(a) was associated with no treatment response (p = .025). At the multivariate analysis, CST was found to be independent predictor of treatment response, while EZ, ELM and ERM were found to predict treatment response perfectly and they could not be entered in the model.

CONCLUSION

Intact EZ and ELM, absence of ERM and CST≤405 μm at baseline can predict favorable treatment response in patients with treatment naïve DME, while no correlation with baseline laboratory parameters was found.

New views on three-dimensional imaging technologies for glaucoma: an overview

PURPOSE OF REVIEW

To summarize the literature on three-dimensional (3D) technological advances in ophthalmology, the quantitative methods associated with this, and their improved ability to help detect glaucoma disease progression.

RECENT FINDINGS

Improvements in measuring glaucomatous structural changes are the result of dual innovations in optical coherence tomography (OCT) imaging technology and in associated quantitative software.

SUMMARY

Compared with two-dimensional (2D) OCT parameters, newer 3D parameters provide more data and fewer artifacts.

Associations Between Diabetic Retinal Microvasculopathy and Neuronal Degeneration Assessed by Swept-Source OCT and OCT Angiography

Purpose: To provide clinical evidence of the associations between retinal neuronal degeneration and microvasculopathy in diabetic retinopathy (DR). Methods: This case-control study included 76 patients (76 eyes) with type 2 diabetes mellitus (DM), and refraction error between -3.0 and +3.0 D. The eyes were assigned into DM (without DR), non-proliferative DR (NPDR), and proliferative DR (PDR) groups. Age-, sex-, and refractive error-matched normal subjects were enrolled as controls. The mean retinal thickness (mRT), the relative mean thickness of the retinal nerve fiber layer (rmtRNFL, mtRNFL/mRT), ganglion cell layer (rmtGCL), ganglion cell complex (rmtGCC) layer, foveal avascular zone area (FAZa), FAZ perimeter (FAZp), FAZ circularity index (FAZ-CI), and vessel density (VD) in superficial capillary plexus (SCP) and deep capillary plexus (DCP) were assessed by swept-source optical coherence tomography (OCT) and OCT angiography (OCTA). Group comparison and Spearman's partial correlation coefficient analysis were applied to evaluate the correlation between these morphological parameters. Results: rmtRNFL, FAZa, and FAZp in SCP and DCP increased with the DR severity (p _rmtRNFL < 0.001; p _{FAZa, SCP} = 0.001; p _FAZa , _DCP = 0.005; p _FAZp , _SCP < 0.001; p _FAZp , _DCP < 0.001). The rmtGCL, FAZ-CI in SCP and DCP, and VD in DCP decreased with the DR severity (p _rmtGCL = 0.002, p _FAZ-CI , _SCP = 0.002; p _{FAZ-CI, DCP} < 0.001, p _VD , _DCP < 0.001). After controlling age, sex, duration of diabetes, and hypertension, the rmtRNFL, FAZa in SCP and DCP, and FAZp in SCP and DCP were correlated with the severity of DR (p < 0.05), while VD in SCP and DCP, FAZ-CI, and rmtGCL were negatively correlated with the severity of DR (p < 0.05). The rmtGCL was negatively correlated with the FAZa in SCP (r = -0.34, p = 0.002) and DCP (r = -0.23, p = 0.033), and FAZp in SCP (r = -0.37, p = 0.001) and DCP (r = -0.32, p = 0.003), but positively correlated with VD in SCP (r = 0.26, p = 0.016), VD in DCP (r = 0.28, p = 0.012), and FAZ-CI in DCP (r = 0.31, p = 0.006). Conclusions: rmtRNFL, FAZ-CI in SCP and DCP, and FAZp in SCP are strong predictors of the severity of DR. The ganglion cell body loss is highly correlated with increased FAZp and FAZa, decreased FAZ-CI, and reduced VD with the severity of DR.

Structural evaluation in inherited retinal diseases

Ophthalmic genetics is a field that has been rapidly evolving over the last decade, mainly due to the flourishing of translational medicine for inherited retinal diseases (IRD). In this review, we will address the different methods by which retinal structure can be objectively and accurately assessed in IRD. We review standard-of-care imaging for these patients: colour fundus photography, fundus autofluorescence imaging and optical coherence tomography (OCT), as well as higher-resolution and/or newer technologies including OCT angiography, adaptive optics imaging, fundus imaging using a range of wavelengths, magnetic resonance imaging, laser speckle flowgraphy and retinal oximetry, illustrating their utility using paradigm genotypes with on-going therapeutic efforts/trials.

Correlation between Imaging Morphological Findings and Laboratory Biomarkers in Patients with Diabetic Macular Edema

PURPOSE

To investigate the potential association between peripheral blood biomarkers and morphological characteristics of retinal imaging in patients with diabetic macular edema (DME).

METHODS

Participants in this cross-sectional study were 36 consecutive patients (36 eyes) with treatment-naïve DME, who underwent spectral domain-optical coherence tomography (SD-OCT), fundus photography, and fundus fluorescein angiography (FFA). In addition, peripheral blood samples were taken to evaluate full blood count and biochemical parameters. Correlation between imaging characteristics and laboratory parameters was examined.

RESULTS

Eyes with central subfield thickness greater than 405 μm presented significantly higher neutrophils/lymphocytes (p = 0.043) and higher lipoprotein (a) compared to eyes with CST < 405 μm (p = 0.003). Presence of hyperreflective foci on SD-OCT was associated with significantly higher white blood cell count (p = 0.028). Ellipsoid zone disruption was associated with significantly lower hematocrit (p = 0.012), hemoglobin (p = 0.009), and red blood cell count (p = 0.026), as well as with higher lipoprotein (a) (p = 0.015). Macular ischemia on FFA was associated with significantly higher monocytes (p = 0.027) and monocytes/HDL (p = 0.019). No significant associations were found between laboratory parameters and subretinal fluid, intraretinal fluid, exudates, cysts, disorganization of inner retinal layers, epiretinal membrane, and external limiting membrane condition.

CONCLUSION

Specific imaging morphological characteristics were found to be associated with laboratory parameters in patients with DME. These findings may shed light on the pathophysiology of DME and its correlation with the development of specific clinical signs.

Swept-source OCTA quantification of capillary closure predicts ETDRS severity staging of NPDR

Purpose

To test whether a single or composite set of parameters evaluated with optical coherence tomography angiography (OCTA), representing retinal capillary closure, can predict non-proliferative diabetic retinopathy (NPDR) staging according to the gold standard ETDRS grading scheme.

Methods

105 patients with diabetes, either without retinopathy or with different degrees of retinopathy (NPDR up to ETDRS grade 53), were prospectively evaluated using swept-source OCTA (SS-OCTA, PlexElite, Carl Zeiss Meditec) with 15×9 mm and 3×3 mm angiography protocols. Seven-field photographs of the fundus were obtained for ETDRS staging. Eyes from age-matched healthy subjects were also imaged as control.

Results

In eyes of patients with type 2 diabetes without retinopathy or ETDRS levels 20 and 35, retinal capillary closure was in the macular area, with predominant alterations in the parafoveal retinal circulation (inner ring). Retinal capillary closure in ETDRS stages 43–53 becomes predominant in the retinal midperiphery with vessel density average values of 25.2±7.9 (p=0.001) in ETDRS 43 and 23.5±3.4 (p=0.001) in ETDRS 47–53, when evaluating extended areas of 15×9 protocol. Combination of acquisition protocols 3×3 mm and 15×9 mm, using SS-OCTA, allows discrimination between eyes with mild NPDR (ETDRS 10, 20, 35) and eyes with moderate-to-severe NPDR (ETDRS grades 43–53).

Conclusions

Retinal capillary closure, quantified by SS-OCTA, can identify NPDR severity progression. It is located mainly in the perifoveal retinal capillary circulation in the initial stages of NPDR, whereas the retinal midperiphery is predominantly affected in moderate-to-severe NPDR.

Imaging in Tubercular Choroiditis: Current Concepts

PURPOSE

Ocular tuberculosis has protean clinical manifestations. Because of its varied clinical presentation, multimodal imaging is very important to characterize the disease activity, presence of inflammation, determining therapeutic response, and detection of complications.

METHODS

Narrative review.

RESULTS

In this review, various imaging modalities employed in the management of ocular tuberculosis including fluorescein angiography (FA), indocyanine green angiography (ICGA), optical coherence tomography (OCT), and optical coherence tomography angiography (OCTA) have been reviewed. Not only do these imaging tools complement each other in providing a comprehensive assessment of the pathology, they also help in gaining valuable insights regarding the evolution of the disease.

CONCLUSIONS

Fundus imaging plays a vital role in the diagnosis and management of patients with posterior uveitis due to tuberculosis. Fundus imaging may have a useful role in defining clinical endpoints for ocular tuberculosis in the future.