Optical coherence tomography evaluation of the spatiotemporal effects of 3D bone marrow stromal cell culture using a bioreactor

Performing cell culture in a three-dimensional (3D) environment has various advantages. In cartilage tissue engineering, 3D in vitro cultures utilizing biomaterials and bioreactors can mimic the biological environment. However, the biggest drawback of these 3D culture systems is a limited ability to evaluate 3D cell distribution. Optical coherence tomography (OCT) has recently been used to evaluate 3D cellular morphology and structure in a timely manner. Here, we showed that OCT could be used to visually assess the distribution and the morphology of bone marrow stromal cells under chondrogenic 3D cultivation using alginate gels and rotary culture. In particular, OCT was able to visualize living cells embedded in alginate gels in a non-destructive and 3D manner, as well as quantitatively evaluate cell distribution and spheroid volume. We also found that cells were centralized in rotary culture but peripherally distributed in static culture, while rotary culture enhanced the hypertrophy of marrow stromal cells (MSCs) embedded in alginate gels. Together, our findings demonstrate that OCT can be used to evaluate the spatiotemporal effects of 3D cultivation using alginate gels and rotary culture. Therefore, this method may allow the observation of pre-cultured tissue over time and the optimization of culture conditions for regenerative tissue engineering.

The use of deep learning technology for the detection of optic neuropathy

The emergence of computer graphics processing units (GPUs), improvements in mathematical models, and the availability of big data, has allowed artificial intelligence (AI) to use machine learning and deep learning (DL) technology to achieve robust performance in various fields of medicine. The DL system provides improved capabilities, especially in image recognition and image processing. Recent progress in the sorting of AI data sets has stimulated great interest in the development of DL algorithms. Compared with subjective evaluation and other traditional methods, DL algorithms can identify diseases faster and more accurately in diagnostic tests. Medical imaging is of great significance in the clinical diagnosis and individualized treatment of ophthalmic diseases. Based on the morphological data sets of millions of data points, various image-related diagnostic techniques can now impart high-resolution information on anatomical and functional changes, thereby providing unprecedented insights in ophthalmic clinical practice. As ophthalmology relies heavily on imaging examinations, it is one of the first medical fields to apply DL algorithms in clinical practice. Such algorithms can assist in the analysis of large amounts of data acquired from the examination of auxiliary images. In recent years, rapid advancements in imaging technology have facilitated the application of DL in the automatic identification and classification of pathologies that are characteristic of ophthalmic diseases, thereby providing high quality diagnostic information. This paper reviews the origins, development, and application of DL technology. The technical and clinical problems associated with building DL systems to meet clinical needs and the potential challenges of clinical application are discussed, especially in relation to the field of optic nerve diseases.

Plaque microstructures during metformin therapy in type 2 diabetic subjects with coronary artery disease: optical coherence tomography analysis

BACKGROUND

While metformin is recommended as a first-line cardioprotective therapy for type 2 diabetic patients, whether it exerts direct effects on atherosclerotic plaque remains uncertain. The current study characterized coronary plaque microstructures in type 2 diabetic patients who received metformin.

METHODS

We retrospectively analyzed 409 non-culprit lipid plaques in 313 type 2 diabetic patients with coronary artery disease (CAD) by using frequency-domain optical coherence tomography (FD-OCT) imaging. FD-OCT derived plaque microstructures were compared in patients stratified according to metformin use.

RESULTS

A proportion of 38.6% of study subjects received metformin. Patients receiving metformin more likely exhibited a history of hypertension (79.3% vs. 67.1%, P=0.03) and metabolic syndrome (52.8% vs. 36.4%, P=0.01). On FD-OCT imaging, the prevalence of lipid plaque was lower in the metformin group (66.2% vs. 77.9%, P=0.03). Furthermore, the metformin group demonstrated plaques with a smaller lipid arc (median: 168.7° vs. 208.5°, P=0.008), shorter longitudinal length (media: 5.1 vs. 9.1 mm, P=0.04), and a lower frequency of cholesterol crystal (3.9% vs. 18.2%, P=0.01) and spotty calcification (3.9% vs. 34.8%, P=0.008). These differences remained significant after adjusting for clinical characteristics and glycemic control. However, in patients who received insulin, the favourable effect of metformin on lipid arc was not observed (insulin user: P=0.87; insulin non-user: P=0.009; P value for interaction between two groups, P=0.02).

CONCLUSIONS

Metformin use was associated with a lower prevalence of vulnerable plaque features in type 2 diabetic patients with CAD, especially insulin non-user. These findings suggest the potential of metformin to exert direct plaque stabilization effects in type 2 diabetic subjects.

Quantification of peripapillary vessel density in non-arteritic anterior ischemic optic neuropathy patients with optical coherence tomography angiography

BACKGROUND

Quantitative assessments based on optical coherence tomographic angiography (OCTA) may have potential promising value in the early detection of non-arteritic anterior ischemic optic neuropathy (NA-AION), but there is limited information on the ability of OCTA to distinguish eyes with NA-AION. This study was conducted to evaluate the ability of measurements of peripapillary perfusion using OCTA to distinguish healthy eyes from eyes with NA-AION.

METHODS

In this retrospective case-control study, newly diagnosed NA-AION patients and healthy controls matched at a ratio of 1:3 by gender and age (±5 years) were enrolled from 1 September 2020 to 30 June 2021. Peripapillary vessel density (pVD) was examined based on the area of vessels by means of a 4.5 mm OCTA scan. In addition, peripapillary retinal nerve fiber layer (pRNFL) thickness was obtained from structural optical coherence tomography (OCT), as was the area under the receiver operating characteristic (ROC) curve (AUC).

RESULTS

A total of 29 eyes from 28 cases with NA-AION and 99 healthy eyes from 68 participants were imaged. All participants were Chinese. The NA-AION group showed a significant reduction of the pVD (P<0.001), while all subregions of pRNFL thickness were prominent in all 8 quadrants (P>0.05). The pVD of the optic disc in the superior temporal (ST) region showed better diagnostic accuracy (AUC =0.86) in discriminating the NA-AION group from healthy controls. After adjusting for confounders, ST was independently associated with the presence of NA-AION [odds ratio (OR) =0.971, 95% confidence interval (CI): 0.943-0.990, P=0.048].

CONCLUSIONS

Decreased pVD was detected by non-invasive measurements of OCTA in the eyes of NA-AION patients. This finding may reveal an association between the ST region and the presence of NA-AION. The pVD may have potential diagnostic ability and may serve as an additional biomarker in the management of the disease.

Emerging Technologies for Dentin Caries Detection-A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed at assessing the diagnostic accuracy of emerging technologies, such as laser fluorescence (LF), transillumination, light-emitting diode devices, optical coherence tomography (OCT), alternating current impedance spectroscopy, fluorescence cameras (FC), photo-thermal radiometry, and modulated luminescence technology. In vivo and in vitro results of such non-ionizing, non-invasive, and non-destructive methods’ effectiveness in non-cavitated dentin caries detection are sometimes ambiguous. Following the PRISMA guidelines, 34 relevant research articles published between 2011–2021 were selected. The risk of bias was assessed with a tool tailored for caries diagnostic studies, and subsequent quantitative uni- and bi-variate meta-analysis was carried out in separate sub-groups according to the investigated surface (occlusal/proximal) and study setting (in vivo/in vitro). In spite of the high heterogeneity across the review groups, in vitro studies on LF and FC proved a good diagnostic ability for the occlusal surface, with area under the curve (AUC) of 0.803 (11 studies) and 0.845 (five studies), respectively. OCT studies reported an outstanding performance with an overall AUC = 0.945 (four studies). Promising technologies, such as OCT or FC VistaProof, still need well-designed and well-powered studies to accrue experimental and clinical data for conclusive medical evidence, especially for the proximal surface. Registration: INPLASY202210097.

Factors Associated With the Presence of Foveal Bulge in Eyes With Resolved Diabetic Macular Edema

Purpose: To evaluate factors associated with the presence of foveal bulge (FB) in resolved diabetic macular edema (DME) eyes.

Methods: A total of 165 eyes with complete integrity of ellipsoid zone (EZ) at the fovea and resolved DME were divided into two groups according to the presence of FB at 6 months after intravitreal injection of ranibizumab treatment. Best-corrected visual acuity (BCVA), central foveal thickness (CFT), outer nuclear layer (ONL) thickness, height of serous retinal detachment (SRD) and non-SRD, and inner segment (IS) and outer segment (OS) lengths of the two groups were measured and compared at baseline and each follow-up. The correlations between the presence of FB and pre- and post-treatment factors were determined by logistic regression analysis.

Results: At baseline, BCVA was significantly better, and CFT and incidence and height of SRD were significantly lower in the FB (+) group (all P < 0.05). At 6 months, FB was present in 65 (39.39%) eyes. Post-treatment BCVA was significantly better and OS length was significantly longer in the FB (+) group at 6 months (all P < 0.05). Multivariate analysis identified younger age, better BCVA, and lower CFT before treatment as significant predictors of the existence of FB at 6 months (all P < 0.05). At 6 months, better BCVA and longer OS length were significantly correlated with the existence of FB (all P < 0.05).

Conclusions: Factors associated with the presence of FB after the resolution of DME include younger age, better baseline BCVA and lower baseline CFT, and better post-treatment BCVA and longer post-treatment OS length.

Associations Between the Choroidal Vascularity Index and Malignant Glaucoma After Trabeculectomy for Primary Angle Closure Glaucoma

Purpose: To compare the choroidal vasculature characteristics by using the choroidal vascularity index (CVI) in eyes with malignant glaucoma (MG), fellow eyes with non-MG, and eyes with uncomplicated primary angle-closure glaucoma (PACG) after trabeculectomy by spectral-domain optical coherence tomography (SD-OCT). Methods: This case-control study included 53 patients diagnosed with MG after trabeculectomy. Eyes with MG (n = 53) and the fellow eyes with non-MG (n = 50) were included. Eyes with PACG without MG after trabeculectomy (n = 60) were also enrolled as controls. The choroidal parameters, including CVI and the subfoveal choroidal thickness (SFCT), were measured by using SD-OCT images. Results: Eyes with MG and the fellow eyes showed a significantly lower CVI than eyes with PACG controls (p < 0.001). After adjusting for age, sex, axial length (AL), and intraocular pressure (IOP), eyes with the greater CVI [odds ratio (OR), 0.44] were significantly related to MG. The area under the receiver operating characteristic curve of the CVI was greater than that of the SFCT in the diagnosis of MG (0.911 vs. 0.840, p = 0.034). Conclusion: Eyes with MG showed a significantly lower macular CVI than eyes with PACG controls. A higher macular CVI was an associated factor of eyes with MG. The CVI serves as a more stable and sensitive indicator for MG than the SFCT in this group of patients with PACG.

Role of Optical Coherence Tomography Imaging in Predicting Progression of Age-Related Macular Disease: A Survey

In developed countries, age-related macular degeneration (AMD), a retinal disease, is the main cause of vision loss in the elderly. Optical Coherence Tomography (OCT) is currently the gold standard for assessing individuals for initial AMD diagnosis. In this paper, we look at how OCT imaging can be used to diagnose AMD. Our main aim is to examine and compare automated computer-aided diagnostic (CAD) systems for diagnosing and grading of AMD. We provide a brief summary, outlining the main aspects of performance assessment and providing a basis for current research in AMD diagnosis. As a result, the only viable alternative is to prevent AMD and stop both this devastating eye condition and unwanted visual impairment. On the other hand, the grading of AMD is very important in order to detect early AMD and prevent patients from reaching advanced AMD disease. In light of this, we explore the remaining issues with automated systems for AMD detection based on OCT imaging, as well as potential directions for diagnosis and monitoring systems based on OCT imaging and telemedicine applications.

The association of leukocyte telomere length and intermediate coronary lesions - a retrospective study

BACKGROUND

Intermediate coronary lesions (40-70% stenosis) present a higher risk for future cardiovascular events for instability of plaques. Shortened telomere is an indicator of cellular senescence, which is associated with age-related diseases. However, the relationship between telomere length and severity of intermediate coronary lesions remains largely unknown.

METHODS

A total of 121 lesions of 121 patients with intermediate coronary disease that underwent intravascular optical coherence tomography were enrolled. These patients were retrospectively divided into two groups according to whether accept percutaneous coronary intervention (PCI) treatment: non-PCI group and PCI group.

RESULTS

Leukocyte telomere length (LTL) in patients of PCI group were significantly shorter (12.54±2.70 vs. 15.32±3.72 kb, P<0.001) than non-PCI group. The PCI group had longer lipid length (17.17±9.94 vs. 12.21±10.15 mm, P=0.01) and greater lipid index (4,286.82±3,012.54 vs. 2,444.87±2,677.59 °*mm, P<0.001). There was a significant difference in the prevalence of thin-cap fibroatheroma (36.6% vs. 16.0%, P=0.013), macrophages (56.3% vs. 38.0%, P=0.047), plaque rupture (23.9% vs. 6.0%, P=0.009), cholesterol crystal (49.3% vs. 30.0%, P=0.034), dissection (23.9% vs. 4.0%, P=0.003) between PCI and non-PCI group. Logistic regression revealed that LTL was independently associated with PCI after adjusting for confounding factors (OR 0.952, CI: 0.930-0.974, per 1unit increase, P<0.001). Receiver operating characteristic (ROC) analysis revealed a LTL area under the ROC curve (AUC) of 0.714 (95% CI: 0.619-0.808, P<0.001) in the study population. Furthermore, LTL was inversely correlated with lipid length (r =-0.190, P=0.037), lipid arc (r =-0.301, P=0.001), lipid index (r =-0.182, P=0.046), and positive correlation with FCT (r =0.213, P=0.034).

CONCLUSIONS

LTL was independently associated with possibility of receiving PCI in intermediate coronary lesion patients and LTL is also significantly related to plaque instability features that evaluated by optical coherence tomography. LTL may be as an indicator to assess the necessity of PCI in intermediate coronary lesion patients.

Ellipsoid Zone and External Limiting Membrane-Related Parameters on Spectral Domain-Optical Coherence Tomography and Their Relationships With Visual Prognosis After Successful Macular Hole Surgery

Purpose: To compare structural diameters of the ellipsoid zone (EZ) and external limiting membrane (ELM) bands on spectral domain-optical coherence tomography (SD-OCT) images between vision-improved (group A) and vision-unimproved (group B) patients, and investigate the connection between these parameters and visual prognosis.

Materials and Methods: Forty-five eyes of 43 patients with idiopathic full-thickness macular hole closed after vitrectomy were retrospectively reviewed. Best-corrected visual acuity (BCVA) and SD-OCT were conducted preoperatively and at 1 week, 1 month and 6 months postoperatively. Structural and functional parameters were then measured using ImageJ software.

Results: Among structural and functional parameters, the relative reflectivity of EZ and the ratio of continuous ELM and EZ in group A were significantly higher than in group B from the 1-month postoperative visit. At the 6-month follow-up, the diameter of EZ disruption in group A was significantly smaller than in group B, and the relative reflectivity of ELM/EZ was significantly higher than group B. At 6-months, BCVA was statistically significantly correlated with baseline BCVA, basal diameter (BD), macular hole index (MHI), and diameter of ELM/EZ disruption. Change in BCVA from baseline was found to be significantly correlated with axial length and diameter hole index (DHI).

Conclusions: Postoperative BCVA outcome was significantly correlated with integrity, thickness and reflectivity of the EZ band. Patients with smaller diameter of EZ disruption and higher reflectivity of EZ band tended to have better visual outcomes. Given that the EZ band reflects the recovery of mitochondria in photoreceptors, it is a promising parameter for their functional evaluation.

An in-vitro study of subretinal perfluorocarbon liquid (PFCL) droplets and the physics of their retention and evacuation

PURPOSE

To investigate the physics associated with the retention and removal of subretinal perfluorocarbon liquid (PFCL), as inspired by a series of anecdotal cases of spontaneous 'disappearance' of subretinal PFCL.

METHODS

The profiles of subretinal PFCL in situ from published OCT images were studied and compared with that of PFCL droplets resting on a hydrophilic surface in vitro. A mathematical model based on Sampson's and Poiseuille's formula was developed to explain how evacuation of subretinal PFCL without aspiration could occur.

RESULTS

The mathematical model suggested that in vivo subretinal PFCL can completely evacuate in less than a second via a 41-guage retinal hole. Perfluorocarbon liquid (PFCL) droplets in situ subretinally substantially varied in their aspect ratios (from 0.28 to 2.71) and their contact angles with the retinal pigment epithelium (from 98° to 155°). Conversely, PFCL in vitro had aspect ratios and contact angles close to 1 and 150° respectively.

CONCLUSION

This study showed evidence that stretching of the retina to accommodate subretinal PFCL occurs, which might be responsible for the varied profile of the droplets and resultant forces that can cause retinal holes, and spontaneous evacuation of large PFCL droplets. By filling the vitreous cavity with PFCL, a small retinotomy alone might allow spontaneous evacuation without the need for aspiration.

Automatic Segmentation of the Retinal Nerve Fiber Layer by Means of Mathematical Morphology and Deformable Models in 2D Optical Coherence Tomography Imaging

Glaucoma is a neurodegenerative disease process that leads to progressive damage of the optic nerve to produce visual impairment and blindness. Spectral-domain OCT technology enables peripapillary circular scans of the retina and the measurement of the thickness of the retinal nerve fiber layer (RNFL) for the assessment of the disease status or progression in glaucoma patients. This paper describes a new approach to segment and measure the retinal nerve fiber layer in peripapillary OCT images. The proposed method consists of two stages. In the first one, morphological operators robustly detect the coarse location of the layer boundaries, despite the speckle noise and diverse artifacts in the OCT image. In the second stage, deformable models are initialized with the results of the previous stage to perform a fine segmentation of the boundaries, providing an accurate measurement of the entire RNFL. The results of the RNFL segmentation were qualitatively assessed by ophthalmologists, and the measurements of the thickness of the RNFL were quantitatively compared with those provided by the OCT inbuilt software as well as the state-of-the-art methods.

Glaucoma and optical coherence tomography changes in migraine: A comparative cross-sectional study

Purpose

To study the prevalence of glaucoma among adults with migraine and the effect of migraine on peripapillary retinal nerve fiber layer (pRNFL) and central macular thickness (CMT) using optical coherence tomography (OCT) compared to those without migraine headache, i.e. in tension-type headache (TTH) and normal group.

Methods

One hundred and eleven patients (222 eyes) were recruited in three groups. migraine, TTH, and normal subjects visiting hospital outpatient services. After noting demographic details and pertinent history, ophthalmological evaluation including optic disc for glaucomatous changes along with computerized visual field testing and OCT for pRNFL thickness and CMT was performed in all eyes. Continuous variables were compared using ANOVA or Kruskal-Wallis test, while categorical variables including the association of glaucoma with migraine were analyzed using Chi-square or Fisher's exact test.

Results

Prevalence of glaucoma in migraine group (12.2%) was more than in comparison groups (6.8% in TTH, 4.1% in normal) which was however not significant (Fisher's exact P = 0.207). Average pRNFL thickness (103.59 ± 12.82 μm) and thickness in nasal (90.49 ± 19.19 μm) and temporal quadrants (70.58 ± 16.13 μm) and CMT (213.78 ± 19.81 μm) were significantly reduced (ANOVA P < 0.05) in migraine patients when compared to the other groups and this was independent of the presence of glaucoma.

Conclusion

Prevalence of glaucoma is not significantly higher in migraine patients. However, migraine causes thinning of retinal layers on OCT that is statistically significant.

Impact of Epiretinal Membrane on Optical Coherence Tomography Tools Used for Monitoring Glaucoma

Background: Retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) measurements can be influenced by many factors including the presence of concomitant retinal diseases. The aim of this study it to assess the impact of epiretinal membrane (ERM) on RNFL and GCL assessment using optical coherence tomography (OCT). Methods: GCL, peripapillary RNFL (pRNFL), and Bruch’s Membrane Opening Minimum Rim Width (BMO-MRW) thicknesses were analysed using an SD-OCT (Spectralis OCT) in eyes with idiopathic ERM and compared with a control group. Results: 161 eyes were included, 73 eyes in the control group and 88 eyes with idiopathic ERM. The pRNFL analysis revealed a statistically significant difference between the two groups in overall and temporal sector thicknesses. For GCL thickness report, the percentage of scans in which the GCL was erroneously segmented by automatic segmentation was assessed for each eye. A statistically significant difference was found in all sectors (p < 0.001), with the exception of external nasal sector. A statistically significant difference (p < 0.001) in the GCL total volume report was found in ERM group compared to the control group. For MRW at BMO analysis, there was no statistically significant difference in MRW thickness in any sector. Conclusion: In eyes with ERM, the GCL and pRNFL analysis seemed affected by the morphological retinal layers’ modification. MRW-BMO did not appear to be directly affected by the presence of ERM.

Socioeconomic disparity is associated with faster retinal neurodegeneration in multiple sclerosis

Disease course in multiple sclerosis is notably heterogenous, and few prognostic indicators have been consistently associated with multiple sclerosis severity. In the general population, socioeconomic disparity is associated with multimorbidity and may contribute to worse disease outcomes in multiple sclerosis. Herein, we assessed whether indicators of socioeconomic status (SES) are associated with disease progression in people with multiple sclerosis using highly sensitive imaging tools like optical coherence tomography (OCT) and determined if differential multiple sclerosis management or comorbidity mediate any observed SES-associated effects. We included 789 participants with longitudinal OCT and low contrast letter acuity (LCLA; at 1.25% and 2.5%) in whom neighborhood- (derived via 9-digit postal codes) and participant-level SES indicators were available ≤10 years of MS symptom onset. Sensitivity analyses included participants with SES indicators available ≤3years of symptom onset (n = 552). Neighborhood-level indicators included state and national area deprivation indices (ADI), median household income, and the Agency for Healthcare Research and Quality (AHRQ) SES Index. Participant-level indicators included education level. Bi-annual OCT scans were segmented to quantify thickness of the composite macular ganglion cell+inner plexiform layer (GCIPL). We assessed the association between SES indicators and GCIPL atrophy or LCLA loss using mixed models adjusting for demographic (including race and ethnicity) and disease-related characteristics. We also assessed SES indicators in relation to multiple sclerosis therapy changes and comorbidity risk using survival analysis. More disadvantaged neighborhood-level and patient-level SES indicators were associated with faster retinal atrophy. Differences in rate of GCIPL atrophy for individuals in the top quartile (most disadvantaged) relative to the bottom quartile (least) for state ADI were -0.12 µm/year faster (95%CI: -0.19, -0.04; p = 0.003), for national ADI were -0.08 µm/year faster (95%CI: -0.15, -0.005; p = 0.02), for household income were -0.11 µm/year faster (95%CI: -0.19, -0.03; p = 0.008), for AHRQ SES Index were -0.12 µm/year faster (95% CI: -0.19, -0.04) and for education level were -0.17 µm/year faster (95%CI: -0.26, -0.08; p = 0.0002). Similar associations were observed for SES indicators and LCLA loss. Lower SES was associated with higher risk of incident comorbidity during follow-up. Low SES individuals had faster rates of therapy escalation, suggesting the association between SES and GCIPL atrophy may not be explained by differential contemporaneous multiple sclerosis therapy management. In conclusion, socioeconomic disparity is associated with faster retinal neurodegeneration in multiple sclerosis. As low SES was associated with a higher risk of incident comorbidities that may adversely affect multiple sclerosis outcomes, comorbidity prevention may mitigate some of the unfavorable SES-associated consequences.

Comparison of Different Machine Learning Classifiers for Glaucoma Diagnosis Based on Spectralis OCT

Early detection is important in glaucoma management. By using optical coherence tomography (OCT), the subtle structural changes caused by glaucoma can be detected. Though OCT provided abundant parameters for comprehensive information, clinicians may be confused once the results conflict. Machine learning classifiers (MLCs) are good tools for considering numerous parameters and generating reliable diagnoses in glaucoma practice. Here we aim to compare different MLCs based on Spectralis OCT parameters, including circumpapillary retinal nerve fiber layer (cRNFL) thickness, Bruch’s membrane opening-minimum rim width (BMO-MRW), Early Treatment Diabetes Retinopathy Study (ETDRS) macular thickness, and posterior pole asymmetry analysis (PPAA), in discriminating normal from glaucomatous eyes. Five MLCs were proposed, namely conditional inference trees (CIT), logistic model tree (LMT), C5.0 decision tree, random forest (RF), and extreme gradient boosting (XGBoost). Logistic regression (LGR) was used as a benchmark for comparison. RF was shown to be the best model. Ganglion cell layer measurements were the most important predictors in early glaucoma detection and cRNFL measurements were more important as the glaucoma severity increased. The global, temporal, inferior, superotemporal, and inferotemporal sites were relatively influential locations among all parameters. Clinicians should cautiously integrate the Spectralis OCT results into the entire clinical picture when diagnosing glaucoma.

Toward a clinical optoretinogram: a review of noninvasive, optical tests of retinal neural function

The past few years have witnessed rapid development of the optoretinogram—a noninvasive, optical measurement of neural function in the retina, and especially the photoreceptors (Ph). While its recent development has been rapid, it represents the culmination of hundreds of experiments spanning decades. Early work showed measurable and reproducible changes in the optical properties of retinal explants and suspensions of Ph, and uncovered some of the biophysical and biochemical mechanisms underlying them. That work thus provided critical motivation for more recent work based on clinical imaging platforms, whose eventual goal is the improvement of ophthalmic care and streamlining the discovery of novel therapeutics. The first part of this review consists of a selective summary of the early work, and identifies four kinds of stimulus-evoked optical signals that have emerged from it: changes in light scattered from the membranous discs of the Ph’s outer segment (OS), changes in light scattered by the front and back boundaries of the OS, rearrangement of scattering material in and near the OS, and changes in the OS length. In the past decade, all four of these signals have continued to be investigated using imaging systems already used in the clinic or intended for clinical and translational use. The second part of this review discusses these imaging modalities, their potential to detect and quantify the signals of interest, and other factors influencing their translational promise. Particular attention is paid to phase-sensitive optical coherence tomography (OCT) with adaptive optics (AO), a method in which both the amplitude and the phase of light reflected from individual Ph is monitored as visible stimuli are delivered to them. The record of the light’s phase is decoded to reveal a reproducible pattern of deformation in the OS, while the amplitude reveals changes in scattering and structural rearrangements. The method has been demonstrated in a few labs and has been used to measure responses from both rods and cones. With the ability to detect responses to stimuli isomerizing less than 0.01% of photopigment, this technique may prove to be a quick, noninvasive, and objective way to measure subtle disease-related dysfunction at the cellular level, and thus to provide an entirely new and complementary biomarker for retinal disease and recovery.

Counterclockwise Drilling with Different Tapered Drills Condenses the Implant Bed-An Optical Coherence Tomography In Vitro Study

Background and Objectives: To evaluate the condensation and the microarchitecture of implant bed walls of sites prepared with counterclockwise drilling with tapered implant drills using optical coherence tomography. Materials and Methods: Four drill designs with different wall and tip angles were used. Polyurethane laminas resembling type IV bone microarchitecture were superimposed and clamped with a vice to simulate the coronal, middle, and apical aspects of the implant site. Twenty implant beds were prepared at 1200 rpm in clockwise (control) and counterclockwise (test) directions (N = 160). Optical coherence tomography (OCT) was used to evaluate the condensation and microarchitecture characteristics of the implant bed walls. The relative condensation was calculated using the Image J software Bone application. The microarchitecture was evaluated in reconstructed 3D volumes in XY, XZ, and YZ sections. Statistical analysis was performed using one-way ANOVA. Dunnet test was applied to determine differences between groups. Significance was set as p < 0.05. Results: Counterclockwise drilling (Test) condensed and changed the microarchitecture of the apical regions for all the implant beds in all of the groups when compared to clockwise drilling (control). The apical region of test groups showed the highest relative bone condensation (p = 0.026) when compared to controls. Conclusions: The direction of rotation (counterclockwise drilling) and not the design of tapered drills (tip and wall angles) is responsible for the condensation at the apical area observed in polyurethane blocks. The OCT method can be used for the evaluation of changes in density and microstructure of polyurethane blocks.

Post-stenting angiographically silent coronary dissection: OCT comes to the rescue

Stent edge dissection is one of the procedural complications concerning percutaneous coronary intervention (PCI). We present a clinical case of multi-vessel PCI where the patient had to return with recurring symptoms within two weeks of a seemingly successful PCI, only to teach us a valuable lesson in the more frequent and judicious use of intracoronary imaging.

Multi-Compartment Spatially-Derived Radiomics From Optical Coherence Tomography Predict Anti-VEGF Treatment Durability in Macular Edema Secondary to Retinal Vascular Disease: Preliminary Findings

OBJECTIVE

Diabetic macular edema (DME) and retinal vein occlusion (RVO) are the leading causes of visual impairments across the world. Vascular endothelial growth factor (VEGF) stimulates breakdown of blood-retinal barrier that causes accumulation of fluid within macula. Anti-VEGF therapy is the first-line treatment for both the diseases; however, the degree of response varies for individual patients. The main objective of this work was to identify the (i) texture-based radiomics features within individual fluid and retinal tissue compartments of baseline spectral-domain optical coherence tomography (SD-OCT) images and (ii) the specific spatial compartments that contribute most pertinent features for predicting therapeutic response.

METHODS

A total of 962 texture-based radiomics features were extracted from each of the fluid and retinal tissue compartments of OCT images, obtained from the PERMEATE study. Top-performing features selected from the consensus of different feature selection methods were evaluated in conjunction with four different machine learning classifiers: Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA), Random Forest (RF), and Support Vector Machine (SVM) in a cross-validated approach to distinguish eyes tolerating extended interval dosing (non-rebounders) and those requiring more frequent dosing (rebounders).

RESULTS

Combination of fluid and retinal tissue features yielded a cross-validated area under receiver operating characteristic curve (AUC) of 0.78±0.08 in distinguishing rebounders from non-rebounders.

CONCLUSIONS

This study revealed that the texture-based radiomics features pertaining to IRF subcompartment were most discriminating between rebounders and non-rebounders to anti-VEGF therapy. Clinical Impact: With further validation, OCT-based imaging biomarkers could be used for treatment management of DME patients.

The Association Between Quantitative Flow Ratio and Intravascular Imaging-defined Vulnerable Plaque Characteristics in Patients With Stable Angina and Non-ST-segment Elevation Acute Coronary Syndrome

Background: This study aimed to examine whether quantitative flow ratio (QFR), an angiography-based computation of fractional flow reserve, was associated with intravascular imaging-defined vulnerable plaque features, such as thin cap fibroatheroma (TCFA) in patients with stable angina, and non-ST-segment elevation acute coronary syndrome. Methods: Patients undergoing optical coherence tomography (OCT) or intravascular ultrasound (IVUS) examinations were identified from two prospective studies and their interrogated vessels were assessed with QFR. Lesions in the OCT cohort were classified into tertiles: QFR-T1 (QFR ≤ 0.85), QFR-T2 (0.85 < QFR ≤ 0.93), and QFR-T3 (QFR > 0.93). Lesions in the IVUS cohort were classified dichotomously as low or high QFR groups. Results: This post-hoc analysis included 132 lesions (83 for OCT and 49 for IVUS) from 126 patients. The prevalence of OCT-TCFA was significantly higher in QFR-T1 (50%) than in QFR-T2 (14%) and QFR-T3 (19%) (p = 0.003 and 0.018, respectively). Overall significant differences were also observed among tertiles in maximum lipid arc, thinnest fibrous cap thickness, and minimal lumen area (p = 0.017, 0.040, and <0.001, respectively). Thrombus was more prevalent in QFR-T1 (39%) than in QFR-T2 (3%), and QFR-T3 (12%) (p = 0.001 and 0.020, respectively). In the multivariable analysis, QFR ≤ 0.80 remained as a significant determinant of OCT-TCFA regardless of the presence of NSTE-ACS and the level of low-density lipoprotein cholesterol (adjusted OR: 4.387, 95% CI 1.297-14.839, p = 0.017). The diagnostic accuracy of QFR was moderate in identifying lesions with OCT-TCFA (area under the curve: 0.72, 95% CI 0.58-0.86, p = 0.003). In the IVUS cohort, significant differences were found between two groups in minimal lumen area and plaque burden but not in the distribution of virtual histology (VH)-TCFA (p = 0.025, 0.036, and 1.000, respectively). Conclusions: Lower QFR was related to OCT-defined plaque vulnerability in angiographically mild-to-intermediate lesions. The QFR might be a useful tool for ruling out high-risk plaques without using any pressure wire or vasodilator.

Interpretation of anatomic correlates of outer retinal bands in optical coherence tomography

By providing the sectioning capability to differentiate individual retinal layers, optical coherence tomography (OCT) is revolutionizing eye disease diagnosis and treatment evaluation. A better understanding of the hyper- and hypo-reflective bands in retinal OCT is essential for accurate interpretation of clinical outcomes. In this article, we summarize the interpretations of clinical OCT and adaptive optics (AO) OCT (AO-OCT) of the outer retina in the human eye, and briefly review OCT investigation of the outer retina in animal models. Quantitative analysis of outer retinal OCT bands is compared to established parameters of retinal histology. The literature review and comparative analysis support that both inner/outer segment (IS/OS) junction and IS ellipsoid zone nonexclusively contribute to the second band; and OS, OS tips, and retinal pigment epithelium apical processes contribute to the third band in conventional OCT. In contrast, AO-OCT might predominantly detect the IS/OS junction and OS tip signals at the second and third bands due to its improved sectioning capability and possible AO effect on the sensitivities for recording ballistic and diffusive photons from different regions of the outer retina.

Protective Effects of Oroxylin A on Retinal Ganglion Cells in Experimental Model of Anterior Ischemic Optic Neuropathy

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of acute vision loss in older people, and there is no effective therapy. The effect of the systemic or local application of steroids for NAION patients remains controversial. Oroxylin A (OA) (5,7-dihydroxy-6-methoxyflavone) is a bioactive flavonoid extracted from Scutellariae baicalensis Georgi. with various beneficial effects, including anti-inflammatory and neuroprotective effects. A previous study showed that OA promotes retinal ganglion cell (RGC) survival after optic nerve (ON) crush injury. The purpose of this research was to further explore the potential actions of OA in ischemic injury in an experimental anterior ischemic optic neuropathy (rAION) rat model induced by photothrombosis. Our results show that OA efficiently attenuated ischemic injury in rats by reducing optic disc edema, the apoptotic death of retinal ganglion cells, and the infiltration of inflammatory cells. Moreover, OA significantly ameliorated the pathologic changes of demyelination, modulated microglial polarization, and preserved visual function after rAION induction. OA activated nuclear factor E2 related factor (Nrf2) signaling and its downstream antioxidant enzymes NAD(P)H:quinone oxidoreductase (NQO-1) and heme oxygenase 1 (HO-1) in the retina. We demonstrated that OA activates Nrf2 signaling, protecting retinal ganglion cells from ischemic injury, in the rAION model and could potentially be used as a therapeutic approach in ischemic optic neuropathy.

In vivo cellular imaging of the retina: present and future

Összefoglaló. A látószerv különböző betegségei, valamint egyes szisztémás megbetegedések részben vagy kifejezetten az ideghártya károsodásával járnak. A patológia segítségével ma már tudjuk, hogy ezek a betegségek a retina mely rétegének vagy rétegeinek elváltozásait okozzák: míg az időskori maculadegeneratio a külső retinában található fotoreceptorokat érinti kifejezetten a fovea centralis területén, addig a glaucoma a belső retina ganglionsejtjeinek pusztulásával, valamint e sejtek opticusrostjainak károsodásával jár a stratum ganglionaréban és a stratum neurofibrarumban. Az emberi retina sejtjei azonban egyelőre nem maradéktalanul karakterizáltak, az egyes sejttípusok számát csak becsülni tudjuk, így nem írhatók le az egyes sejtszintű elváltozások sem kellő pontossággal. A szövettani feldolgozás és vizsgálat megfelelő részletességgel tájékoztat a diagnózisról és az elváltozás súlyosságáról, értelemszerűen azonban ez a módszer in vivo nem használható a mindennapi klinikai gyakorlatban. A sejtszintű elváltozások ismerete az egyes kórképekben felvetette és szükségessé tette olyan in vivo, a klinikumban is alkalmazható vizsgálómódszerek kifejlesztését, amelyek lehetőséget nyújtanak a retina neurális és egyéb sejtjeinek celluláris és szubcelluláris szintű vizsgálatára, ideértve a vér alakos elemeit is, amelyek egészséges vagy neovascularis eredetű erekben áramlanak. A jelenleg is használt klinikai vizsgálatok mellett ezek a képalkotó módszerek segítségül szolgálhatnak a diagnózis megerősítésében vagy elvetésében, emellett az elváltozás súlyosságának megítélésében, valamint a progresszió vagy remisszió monitorozásában. Orv Hetil. 2021; 162(22): 851-860. Summary. Diseases of the visual system as well as many systemic illnesses are usually associated with retinal damage. With the help of pathology, we can clearly identify the affected layer(s): while age-related macular degeneration mostly damages the photoreceptors in the outer retina at the central fovea, glaucoma promotes ganglion cell death in the ganglion cell layer and damages respective neural fibers. However, the diverse cell types of the human retina have not been fully characterized yet, thus in most cases our knowledge on cellular pathologies is not precise enough. While histopathological preparation and examination of the retinal tissue provide more detailed information about the diagnosis and the severity of the condition, unfortunately, it cannot be used in vivo in everyday clinical practice. Our understanding of the cellular changes in different diseases has revealed a need for new everyday clinical examination methods that can be used in vivo to asses cellular and subcellular changes in neural and other cells of the retina, such as blood cells flowing in healthy vessels or in vessels of neovascular origin. In addition to the currently used clinical examination methods, these imaging methods could help confirm or dismiss diagnoses, assess the severity of a condition, and monitor disease progression or remission. Orv Hetil. 2021; 162(22): 851-860.

Application of OCT-Derived Attenuation Coefficient in Acute Burn-Damaged Skin

BACKGROUND AND OBJECTIVES

There remains a need to objectively monitor burn wound healing within a clinical setting, and optical coherence tomography (OCT) is proving itself one of the ideal modalities for just such a use. The aim of this study is to utilize the noninvasive and multipurpose capabilities of OCT, along with its cellular-level resolution, to demonstrate the application of optical attenuation coefficient (OAC), as derived from OCT data, to facilitate the automatic digital segmentation of the epidermis from scan images and to work as an objective indicator for burn wound healing assessment.

STUDY DESIGN/MATERIALS AND METHODS

A simple, yet efficient, method was used to estimate OAC from OCT images taken over multiple time points following acute burn injury. This method enhanced dermal-epidermal junction (DEJ) contrast, which facilitated the automatic segmentation of the epidermis for subsequent thickness measurements. In addition, we also measured and compared the average OAC of the dermis within said burns for correlative purposes.

RESULTS

Compared with unaltered OCT maps, enhanced DEJ contrast was shown in OAC maps, both from single A-lines and completed B-frames. En face epidermal thickness and dermal OAC maps both demonstrated significant changes between imaging sessions following burn injury, such as a loss of epidermal texture and decreased OAC. Quantitative analysis also showed that OAC of acute burned skin decreased below that of healthy skin following injury.

CONCLUSIONS

Our study has demonstrated that the OAC estimated from OCT data can be used to enhance imaging contrast to facilitate the automatic segmentation of the epidermal layer, as well as help elucidate our understanding of the pathological changes that occur in human skin when exposed to acute burn injury, which could serve as an objective indicator of skin injury and healing.