Advances in Optical Coherence Tomography Imaging Technology and Techniques for Choroidal and Retinal Disorders

The morphology of internal elastic lamina corrugations in arteries under physiological conditions

BACKGROUND

In elastic and resistance arteries, an elastin-rich membrane, the Internal Elastic Lamina (IEL), separates the tunica intima from the underlying tunica media. The IEL often appears wrinkled or corrugated in histological images. These corrugations are sometimes ascribed to vessel contraction ex vivo, and to fixation artifacts, and therefore regarded as not physiologically relevant. We examine whether the IEL remains corrugated even under physiological conditions.

METHODS

The diameters of carotid arteries of anesthetized pigs were measured by ultrasound. The arteries were then excised, inflated within a conical sleeve, fixed, and imaged by confocal microscopy. The conical sleeve allows fixing each artery across a wide range of diameters, which bracket its ultrasound diameter. Thus the study was designed to quantify how corrugations change with diameter for a single artery, and test whether corrugations exist when the fixed artery matches the ultrasound diameter.

RESULTS

At diameters below the ultrasound diameter (i.e. when the artery was constricted as compared to ultrasound conditions), the IEL corrugations were found to decrease significantly with increasing diameter, but not fully flatten at the ultrasound diameter. The contour length of the IEL was found to be roughly 10% larger than the circumference of the artery measured by ultrasound. The physiological diameter is likely to be even smaller than the ultrasound diameter since ultrasound was conducted with the animal under general anesthesia, which leads to vasodilation, suggesting a higher level of corrugation under physiological conditions. For arterial cross sections constricted below the ultrasound diameter, the IEL contour length decreased roughly with the square root of the diameter.

CONCLUSION

The primary conclusions of this study are: a) the IEL is corrugated when the artery is constricted and flattens as the artery diameter increases; b) the IEL is corrugated under physiological conditions and has a contour length at least 10% more than the physiological arterial diameter; and c) the IEL despite being relatively stiffer than the surrounding arterial layers, does not behave like an inextensible membrane.

Preoperative OCT Characteristics Contributing to Prediction of Postoperative Visual Acuity in Eyes with Macular Hole

Objectives: To develop a machine learning logistic regression algorithm that can classify patients with an idiopathic macular hole (IMH) into those with good or poor vison at 6 months after a vitrectomy. In addition, to determine its accuracy and the contribution of the preoperative OCT characteristics to the algorithm. Methods: This was a single-center, cohort study. The classifier was developed using preoperative clinical information and the optical coherence tomographic (OCT) findings of 43 eyes of 43 patients who had undergone a vitrectomy. The explanatory variables were selected using a filtering method based on statistical significance and variance inflation factor (VIF) values, and the objective variable was the best-corrected visual acuity (BCVA) at 6 months postoperation. The discrimination threshold of the BCVA was the 0.15 logarithm of the minimum angle of the resolution (logMAR) units. Results: The performance of the classifier was 0.92 for accuracy, 0.73 for recall, 0.60 for precision, 0.74 for F-score, and 0.84 for the area under the curve (AUC). In logistic regression, the standard regression coefficients were 0.28 for preoperative BCVA, 0.13 for outer nuclear layer defect length (ONL_DL), -0.21 for outer plexiform layer defect length (OPL_DL) - (ONL_DL), and -0.17 for (OPL_DL)/(ONL_DL). In the IMH form, a stenosis pattern with a narrowing from the OPL to the ONL of the MH had a significant effect on the postoperative BCVA at 6 months. Conclusions: Our results indicate that (OPL_DL) - (ONL_DL) had a similar contribution to preoperative visual acuity in predicting the postoperative visual acuity. This model had a strong performance, suggesting that the preoperative visual acuity and MH characteristics in the OCT images were crucial in forecasting the postoperative visual acuity in IMH patients. Thus, it can be used to classify MH patients into groups with good or poor postoperative visual acuity, and the classification was comparable to that of previous studies using deep learning.

The Usefulness of 55° Wide-Field Spectral-Domain Optical Coherence Tomography in Monitoring the Features of Peripheral Subretinal Fluid Remnants after Rhegmatogenous Retinal Detachment Surgery

BACKGROUND

This study aimed to assess the effectiveness of 55° wide-field (WF) spectral-domain (SD) optical coherence tomography (OCT) for detecting peripheral subretinal fluid (SRF) after surgery for rhegmatogenous retinal detachment (RRD).

METHODS

In this retrospective observational study, the retinal periphery was examined to evaluate the possible presence of persistent SRF after surgery. OCT scans were acquired in infrared mode to use any peripheral vessel as a landmark for better repeatability in monitoring fluid remnants.

RESULTS

A total of 80 patients (10% with high myopia) were examined using 55° WF SD OCT after successful pars plana vitrectomy (83.8%) or scleral buckling (16.3%) for RRD. A total of 18 patients (22.5%), 16 of whom underwent pars plana vitrectomy and 2 who underwent scleral buckling, showed SRF at the OCT examination during the follow-up. Potential risk factors associated with SRF persistence were analyzed, revealing a significative association with young age (p = 0.009). After a follow-up period of 7.05 ± 2.44 months (ranging from 3 to 12 months), a complete resorption in all patients (100%) within 12 months was observed. Best-corrected visual acuity significantly improved in both groups over time.

CONCLUSION

Using 55° WF SD-OCT successfully assessed the course of SRF reabsorption, offering a viable alternative for all those realities where technologies such as ultra-wide-field (UWF) OCT are not available.

The Complement System as a Therapeutic Target in Retinal Disease

The complement cascade is a vital system in the human body's defense against pathogens. During the natural aging process, it has been observed that this system is imperative for ensuring the integrity and homeostasis of the retina. While this system is critical for proper host defense and retinal integrity, it has also been found that dysregulation of this system may lead to certain retinal pathologies, including geographic atrophy and diabetic retinopathy. Targeting components of the complement system for retinal diseases has been an area of interest, and in vivo, ex vivo, and clinical trials have been conducted in this area. Following clinical trials, medications targeting the complement system for retinal disease have also become available. In this manuscript, we discuss the pathophysiology of complement dysfunction in the retina and specific pathologies. We then describe the results of cellular, animal, and clinical studies targeting the complement system for retinal diseases. We then provide an overview of complement inhibitors that have been approved by the Food and Drug Administration (FDA) for geographic atrophy. The complement system in retinal diseases continues to serve as an emerging therapeutic target, and further research in this field will provide additional insights into the mechanisms and considerations for treatment of retinal pathologies.

Pachychoroid Associated With Acute Retinal Necrosis Secondary to Varicella Zoster Virus

Purpose: To report a case of pachychoroid associated with acute retinal necrosis secondary to the varicella zoster virus (VZV). Methods: A retrospective review of a single case was performed. Results: The VZV-related acute retinal necrosis with pachychoroid resolved with quiescence of the acute infectious process. Conclusions: Acute retinal necrosis can result in choroidal thickening adjacent to retinitis. Previous reports have described choroidal sparing in these cases.

Lithospermum erythrorhizon Siebold & Zucc. extract reduces the severity of endotoxin-induced uveitis

BACKGROUND

Uveitis is an inflammatory eye condition that threatens vision, and effective anti-inflammatory treatments with minimal side effects are necessary to treat uveitis.

PURPOSE

This study aimed to investigate the effects of Lithospermum erythrorhizon Siebold & Zucc. against endotoxin-induced uveitis in rat and mouse models.

METHODS

Endotoxin-induced uveitis models of rats and mice were used to evaluate the effects of l. erythrorhizon treatment. Clinical inflammation scores and retinal thickness were assessed in the extract of l. erythrorhizon-treated rats. Histopathological examination revealed inflammatory cell infiltration into the ciliary body. Protein concentration, cellular infiltration, and prostaglandin-E2 levels were measured in the aqueous humor of the extract of l. erythrorhizon-treated rats. Protective effects of l. erythrorhizon on the anterior segment of the eye were examined in mice with endotoxin-induced uveitis. Additionally, we investigated the effect of l. erythrorhizon on the expression of pro-inflammatory cytokines [tumor necrosis factor alpha, interleukin-6, and interleukin-8] in lipopolysaccharide-stimulated THP1 human macrophages and examined the involvement of nuclear factor kappaB/activator protein 1 and interferon regulatory factor signaling pathways. Furthermore, three components of l. erythrorhizon were identified and assessed for their inhibitory effects on LPS-induced inflammation in RAW264.7 macrophage cells.

RESULTS

Treatment of the extract of l. erythrorhizon significantly reduced clinical inflammation scores and retinal thickening in rats with endotoxin-induced uveitis. Histopathological examination revealed decreased inflammatory cell infiltration into the ciliary body. The extract of l. erythrorhizon effectively reduced the protein concentration, cellular infiltration, and PG-E2 levels in the aqueous humor of rats with endotoxin-induced uveitis. In mice with endotoxin-induced uveitis, the extract of l. erythrorhizon demonstrated a protective effect on the anterior segment of the eye by reducing inflammation and retinal thickening. The extract of l. erythrorhizon suppressed the expression of pro-inflammatory cytokines (tumor necrosis factor alpha, interleukin-6, and interleukin-8) in lipopolysaccharide-induced inflammation in THP1 human macrophages, by modulating nuclear factor kappaB/activator protein 1 and interferon regulatory factor signaling pathways. Moreover, shikonin, acetylshikonin, and β, β-dimethylacryloylshikonin showed dose-dependent inhibition of nitric oxide, tumor necrosis factor alpha and interleukin-6 production in RAW264.7 macrophage cells.

CONCLUSION

The extract of l. erythrorhizon is a potential therapeutic agent for uveitis management. Administration of the extract of l. erythrorhizon led to reduced inflammation, retinal thickening, and inflammatory cell infiltration in rat and mouse models of uveitis. The compounds (shikonin, acetylshikonin, and β, β-dimethylacryloylshikonin) identified in this study played crucial roles in mediating the anti-inflammatory effects of l. erythrorhizon. These findings indicate that the extract of l. erythrorhizon and its constituent compounds are promising candidates for further research and development of novel treatment modalities for uveitis.

From Bedside to Diagnosis: The Role of Ocular Fundus in Systemic Infections

In this comprehensive review, we delve into the significance of the ocular fundus examination in diagnosing and managing systemic infections at the bedside. While the utilization of advanced ophthalmological diagnostic technologies can present challenges in bedside care, especially for hospitalized patients confined to their beds or during infection outbreaks, the ocular fundus examination often emerges as an essential, and sometimes the only practical, diagnostic tool. Recent discussions have highlighted that the role of an ocular fundus examination might not always be advocated as a routine diagnostic procedure. With this context, we introduce a decision tree tailored for assessing the ocular fundus in inpatients with systemic infections. We also present an overview of systemic infections that impact the eye and elucidate key signs detectable through a bedside ocular fundus examination. Targeted primarily at non-ophthalmology clinicians, this review seeks to offer a comprehensive insight into a multifaceted approach and the enhancement of patient clinical outcomes.

Advancing Diabetic Retinopathy Diagnosis: Leveraging Optical Coherence Tomography Imaging with Convolutional Neural Networks

Diabetic retinopathy (DR) is a vision-threatening complication of diabetes, necessitating early and accurate diagnosis. The combination of optical coherence tomography (OCT) imaging with convolutional neural networks (CNNs) has emerged as a promising approach for enhancing DR diagnosis. OCT provides detailed retinal morphology information, while CNNs analyze OCT images for automated detection and classification of DR. This paper reviews the current research on OCT imaging and CNNs for DR diagnosis, discussing their technical aspects and suitability. It explores CNN applications in detecting lesions, segmenting microaneurysms, and assessing disease severity, showing high sensitivity and accuracy. CNN models outperform traditional methods and rival expert ophthalmologists' results. However, challenges such as dataset availability and model interpretability remain. Future directions include multimodal imaging integration and real-time, point-of-care CNN systems for DR screening. The integration of OCT imaging with CNNs has transformative potential in DR diagnosis, facilitating early intervention, personalized treatments, and improved patient outcomes. Abbreviations: DR = Diabetic Retinopathy, OCT = Optical Coherence Tomography, CNN = Convolutional Neural Network, CMV = Cytomegalovirus, PDR = Proliferative Diabetic Retinopathy, AMD = Age-Related Macular Degeneration, VEGF = vascular endothelial growth factor, RAP = Retinal Angiomatous Proliferation, OCTA = OCT Angiography, AI = Artificial Intelligence.

Progression of Rare Inherited Retinal Dystrophies May Be Monitored by Adaptive Optics Imaging

Inherited retinal dystrophies (IRDs) are bilateral genetic conditions of the retina, leading to irreversible vision loss. This study included 55 eyes afflicted with IRDs affecting the macula. The diseases examined encompassed Stargardt disease (STGD), cone dystrophy (CD), and cone-rod dystrophy (CRD) using adaptive optics (Rtx1™; Imagine Eyes, Orsay, France). Adaptive optics facilitate high-quality visualisation of retinal microstructures, including cones. Cone parameters, such as cone density (DM), cone spacing (SM), and regularity (REG), were analysed. The best corrected visual acuity (BCVA) was assessed as well. Examinations were performed twice over a 6-year observation period. A significant change was observed in DM (1282.73/mm2 vs. 10,073.42/mm2, p< 0.001) and SM (9.83 μm vs. 12.16 μm, p< 0.001) during the follow-up. BCVA deterioration was also significant (0.16 vs. 0.12, p = 0.001), albeit uncorrelated with the change in cone parameters. No significant difference in REG was detected between the initial examination and the follow-up (p = 0.089).

Severe Subconjunctival Hemorrhage After Intravitreal Injection in a Patient With Hemophilia A

Purpose: To report a patient with severe hemophilia A who received intravitreal antivascular endothelial growth factor (anti-VEGF) for exudative age-related macular degeneration (AMD). Methods: A case and its findings were analyzed. A systematic literature was performed. Results: A patient with severe hemophilia A received intravitreal anti-VEGF for exudative AMD, after which he developed a severe subconjunctival hemorrhage requiring hemostatic intervention. The effects of anti-VEGF in patients with preexisting blood-clotting disorders, such as classic hemophilia, have not been widely reported in the current literature. Conclusions: This case illustrates that precautions must be taken when performing ocular procedures on patients with serious hemostasis disorders.

Review of Retinal Imaging Modalities for Hydroxychloroquine Retinopathy

This review provides an overview of conventional and novel retinal imaging modalities for hydroxychloroquine (HCQ) retinopathy. HCQ retinopathy is a form of toxic retinopathy resulting from HCQ use for a variety of autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Each imaging modality detects a different aspect of HCQ retinopathy and shows a unique complement of structural changes. Conventionally, spectral-domain optical coherence tomography (SD-OCT), which shows loss or attenuation of the outer retina and/or retinal pigment epithelium-Bruch's membrane complex, and fundus autofluorescence (FAF), which shows parafoveal or pericentral abnormalities, are used to assess HCQ retinopathy. Additionally, several variations of OCT (retinal and choroidal thickness measurements, choroidal vascularity index, widefield OCT, en face imaging, minimum intensity analysis, and artificial intelligence techniques) and FAF techniques (quantitative FAF, near-infrared FAF, fluorescence lifetime imaging ophthalmoscopy, and widefield FAF) have been applied to assess HCQ retinopathy. Other novel retinal imaging techniques that are being studied for early detection of HCQ retinopathy include OCT angiography, multicolour imaging, adaptive optics, and retromode imaging, although further testing is required for validation.

Optical coherence tomography for dynamic investigation of mammalian reproductive processes

The biological events associated with mammalian reproductive processes are highly dynamic and tightly regulated by molecular, genetic, and biomechanical factors. Implementation of live imaging in reproductive research is vital for the advancement of our understanding of normal reproductive physiology and for improving the management of reproductive disorders. Optical coherence tomography (OCT) is emerging as a promising tool for dynamic volumetric imaging of various reproductive processes in mice and other animal models. In this review, we summarize recent studies employing OCT-based approaches toward the investigation of reproductive processes in both, males and females. We describe how OCT can be applied to study structural features of the male reproductive system and sperm transport through the male reproductive tract. We review OCT applications for in vitro and dynamic in vivo imaging of the female reproductive system, staging and tracking of oocytes and embryos, and investigations of the oocyte/embryo transport through the oviduct. We describe how the functional OCT approach can be applied to the analysis of cilia dynamics within the male and female reproductive systems. We also discuss the areas of research, where OCT could find potential applications to progress our understanding of normal reproductive physiology and reproductive disorders.