The Feasibility of Spectral-Domain Optical Coherence Tomography Grading of Anterior Chamber Inflammation in a Rabbit Model of Anterior Uveitis

Anterior Vitreous Objective Assessment in Uveitis: An Anterior Segment Swept Source Optical Coherence Tomography Study

PURPOSE

To assess inflammatory changes in the anterior vitreous (AV) using a swept source anterior segment optical coherence tomography (SS-ASOCT) and to correlate them with uveitis features and clinical grading of intraocular inflammation.

METHODS

140 eyes from 96 patients were included in this observational, cross-sectional study: 40 ACTIVE uveitis, 40 INACTIVE uveitis and 60 CONTROLS. All eyes underwent intraocular inflammation clinical grading (anterior chamber (AC) cells counting and vitreous haze evaluation) and AV imaging with SS-ASOCT. Cells seen in the AV on OCT were manually counted using imageJ. Vitreous reflectivity variation was indirectly measured by calculating the vitreous/iris pigment epithelium (VIT/IPE) relative intensity. These OCT-based parameters were compared across the groups and correlated with inflammation clinical grading.

RESULTS

The mean [SD] number of AV OCT cells was significantly higher (both p < 0.001) in ACTIVE uveitis (12[9.8]) compared to INACTIVE uveitis (4.5[3.5]) and CONTROLS (4[3.1]). In ACTIVE uveitis the number of AV OCT cells was significantly and positively correlated with the AC cells (p = 0.04), the VIT/IPE relative intensity (p = 0.0002), the uveitis anatomical classification (INTERMEDIATE UVEITIS, p = 0.02) and the vitreous haze clinical grading (p < 0.0001). The mean[SD] VIT/IPE relative intensity of the AV increased from CONTROLS (0.12[0.01]) to INACTIVE uveitis (0.15[0.01]) to ACTIVE uveitis (0.17[0.02]), but with no statistically significant differences.

CONCLUSIONS

We were able to visualize and objectively evaluate changes occurring in the AV in eyes with uveitis by means of a commercially available SS-ASOCT. OCT-cells in the AV could represent an adjunctive tool in the objective evaluation of intraocular inflammation.

Establishing the Normative Data Set Necessary for Imaging-Based Childhood Uveitis Surveillance: A Cross-Sectional Study

Purpose

Anterior segment optical coherence tomography (AS-OCT) is an emerging diagnostic and monitoring tool for anterior uveitis. We investigated AS-OCT findings in the eyes of a large, diverse population of children free of uveitis to establish its potential to "rule out" accurately those without disease.

Methods

In this cross-sectional observational study, image acquisition was performed with swept source AS-OCT (Heidelberg Anterion), using a protocol of 13 B-scans per volume, from 217 children (434 eyes) aged 5 to 15 years, with analysis of acquired images (identification of apparent inflammatory cells, or "cell events") by multiple graders. Outcomes of interest were median and maximum cell event count (MEDCC, MAXCC) per B-scan from each eye and the total cell event count (TCC) per volume scan.

Results

At least one cell event was detected in volume scans of 76% of eyes (329/434) and 87% of children (189/217). The maximum number (MAXCC) per scan ranged from 0 to 6 (median, 2). There was a strong positive association between increasing age (years) and the number of cell events detected within a volume scan following adjustment for gender and iris color (adjusted regression coefficient for TCC 0.5; P < 0.0001; 95% confidence interval, 0.4-0.7).

Conclusions

Our findings demonstrate that apparent inflammatory cells are detectable on AS-OCT in the apparently healthy eyes of children and furthermore suggest early life developmental changes in blood-iris barrier stability that merit further exploration. We provide the foundation for the normative data set necessary for establishing the clinical utility of AS-OCT for surveillance of children with inflammatory eye diseases.

Anterior chamber inflammation grading methods: A critical review

Assessing anterior chamber inflammation is highly subjective and challenging. Although various grading systems attempt to offer objectivity and standardization, the clinical assessment has high interobserver variability. Traditional techniques, such as laser flare meter and fluorophotometry, are not widely used since they are time-consuming. With the development of optical coherence tomography with high sensitivity, direct imaging offers an excellent alternative to assess objectively inflammation with the potential for automated analysis. We describe various anterior chamber inflammation grading methods and discuss their utility, advantages, and disadvantages.

Recent advances in optical coherence tomography for anterior segment imaging in small animals and their clinical implications

Anterior segment optical coherence tomography (AS-OCT) is a rapidly evolving area of OCT imaging, providing high-resolution and non-invasive volumetric imaging of the anterior segment. This review focuses on recent advances in AS-OCT imaging in small animals, which we categorize into ultrahigh-resolution, spectroscopic, magnetomotive, polarization-sensitive, and angiographic AS-OCTs. We summarize their technical foundations, review their applications to small animal imaging, and briefly discuss their current and future clinical applications.

Artificial Intelligence and Imaging Processing in Optical Coherence Tomography and Digital Images in Uveitis

INTRODUCTION

Computer vision, understood as the area of science that trains computers to interpret digital images through both artificial intelligence (AI) and classical algorithms, has significantly advanced the analysis and interpretation of optical coherence tomography (OCT) in retina research. The aim of this review is to summarise the recent advances of computer vision in imaging processing in uveitis, with a particular focus in optical coherence tomography images.

MATERIAL AND METHODS

Literature review.

RESULTS

The development of computer vision to assist uveitis diagnosis and prognosis is still undergoing, but important efforts have been made in the field.

CONCLUSION

The automatising of image processing in uveitis could be fundamental to establish objective and standardised outcomes for future clinical trials. In addition, it could help to better understand the disease and its progression.

Grading Anterior Chamber Inflammation with Anterior Segment Optical Coherence Tomography: An Overview

The objective grading of anterior chamber inflammation (ACI) has remained a challenge in the field of uveitis. While the grading criteria produced by the Standardization of Uveitis Nomenclature (SUN) International Workshop have been widely adopted, limitations exist including interobserver variability and grading confined to discrete categories rather than a continuous measurement. Since the earliest iterations of optical coherence tomography (OCT), ACI has been assessed using anterior segment OCT and shown to correlate with slit-lamp findings. However, widespread use of this approach has not been adopted. Barriers to standardization include variability in OCT devices across clinical settings, lack of standardization of image acquisition protocols, varying quantification methods, and the difficulty of distinguishing inflammatory cells from other cell types. Modern OCT devices and techniques in artificial intelligence show promise in expanding the clinical applicability of anterior segment OCT for the grading of ACI.

The feasibility of clinical evaluation for anterior uveitis through spectral-domain optical coherence tomography in dogs

OBJECTIVE

To evaluate the clinical application of spectral-domain optical coherence tomography (SD-OCT) for anterior uveitis in dogs.

ANIMALS AND PROCEDURES

Client-owned dogs presenting with anterior uveitis and clinically healthy dogs were enrolled in this study. Included eyes were divided into 5 groups by flare grade and 3 groups by cell grade through slit-lamp biomicroscopy. Each eye was examined using SD-OCT following slit-lamp biomicroscopy. The ratio of aqueous signal intensity to air signal intensity, which is called the aqueous-to-air relative intensity (ARI) index, was used to evaluate the flare grade. Cell number, central corneal thickness (CCT), and the presence of keratic precipitates (KPs) were analyzed on SD-OCT. The OCT parameters, including ARI index, cell number, and CCT, were compared to the slit-lamp clinical flare and cell grade.

RESULTS

Thirty-six eyes with anterior uveitis and 27 healthy eyes were enrolled. The ARI index showed a significant correlation with clinical flare grade (r_s  = 0.811, p < .001). In multiple regression analysis, the ARI index and CCT showed a significant negative correlation (r = -0.258, p = .044). The number of cells on SD-OCT significantly increased with cell grade on slit-lamp biomicroscopy (r_s  = 0.653, p < .001). The clinical flare grade and CCT were significantly correlated in the partial correlation analysis after controlling for age (partial correlation coefficient = 0.471, p = .002). KPs were observed in 61% of the eyes with flare using SD-OCT (22/36 eyes).

CONCLUSIONS

Spectral-domain optical coherence tomography could provide quantitative information, including the ARI index, cell counts, and CCT in dogs. SD-OCT is an auxiliary modality for slit-lamp biomicroscopy when evaluating anterior uveitis in dogs.

In vivo quantitative analysis of anterior chamber white blood cell mixture composition using spectroscopic optical coherence tomography

Anterior uveitis is the most common form of intraocular inflammation, and one of its main signs is the presence of white blood cells (WBCs) in the anterior chamber (AC). Clinically, the true composition of cells can currently only be obtained using AC paracentesis, an invasive procedure to obtain AC fluid requiring needle insertion into the AC. We previously developed a spectroscopic optical coherence tomography (SOCT) analysis method to differentiate between populations of RBCs and subtypes of WBCs, including granulocytes, lymphocytes and monocytes, both in vitro and in ACs of excised porcine eyes. We have shown that different types of WBCs have distinct characteristic size distributions, extracted from the backscattered reflectance spectrum of individual cells using Mie theory. Here, we further develop our method to estimate the composition of blood cell mixtures, both in vitro and in vivo. To do so, we estimate the size distribution of unknown cell mixtures by fitting the distribution observed using SOCT with a weighted combination of reference size distributions of each WBC type calculated using kernel density estimation. We validate the accuracy of our estimation in an in vitro study, by comparing our results for a given WBC sample mixture with the cellular concentrations measured by a hemocytometer and SOCT images before mixing. We also conducted a small in vivo quantitative cell mixture validation pilot study which demonstrates congruence between our method and AC paracentesis in two patients with uveitis. The SOCT based method appears promising to provide quantitative diagnostic information of cellular responses in the ACs of patients with uveitis.

Implantable anti-angiogenic scaffolds for treatment of neovascular ocular pathologies

The retinal physiology can accrue oxidative damage and inflammatory insults due to age and metabolic irregularities. Two notable diseases that involve retinal and choroidal neovascularization are proliferative diabetic retinopathy and wet age-related macular degeneration. Currently, these diseases are mainly treated with anti-VEGF drugs (VEGF = vascular endothelial growth factor), generally on a monthly dosage scheme. We discuss recent developments for the treatment of these diseases, including bioactive tissue-engineered materials, which may reduce frequency of dosage and propose a path forward for improving patient outcomes. Graphical abstract Development of materials for long-term intravitreal delivery for management of posterior segment diseases.

Testing a Novel Disposable Aqueous Humor Collector: An Approach to Improve Safety, Accuracy, and Efficiency

Aqueous humor (AH) is a useful biofluid for differential diagnosis and disease monitoring in a variety of ophthalmologic conditions. There are no commercially available medical devices specially designed for AH sampling. To improve the safety, accuracy, efficiency, and convenience of anterior chamber (AC) paracentesis, a novel vacuum-based disposable AH collector with a draw volume of 50 μL was designed. The safety and performance of this novel medical device was tested in New Zealand white rabbits. A commonly used 25G 1 mL syringe was used as the control device with target AH collection volume also intentionally set at 50 μL. The 36 eyes included in the study (18 rabbits) were divided into collector (R), collector (L), syringe (R), and syringe (L) subgroups, and each included 9 eyes (R/L indicates the paracentesis was performed by right/left hand). The mean AH volume collected by the collector (R), collector (L), syringe (R), and syringe (L) subgroups were 46.66 ± 3.37 (range: 39.20-50.40), 48.71 ± 2.88 (range: 45.00-53.60), 85.11 ± 18.70 (range: 64.00-123.50), and 80.68 ± 20.87 (range: 36.8-115.8) μL, respectively. The mean absolute deviation from the target volume and mean operation time of the collector subgroups were significantly lower than the syringe subgroups. Seidel tests revealed no AH leakage in any of the tested eyes. This study revealed that this novel AH collector facilitates one-handed AC paracentesis and accurate AH sampling, and appeared to be safer and more efficient than the traditional syringe-based techniques.

Quantitative Analysis of Anterior Chamber Inflammation Using the Novel CASIA2 Optical Coherence Tomography

PURPOSE

We evaluated the clinical utility of a novel anterior segment optical coherence tomography (AS-OCT) device, CASIA2, to evaluate parameters indicative of anterior chamber (AC) inflammation severity in uveitis, including AC cell number, flare, and keratic precipitates (KPs).

DESIGN

Prospective evaluation of a diagnostic device.

METHODS

Uveitis eyes were classified into active and inactive groups. The number of hyperreflective dots representing AC cells and optical density ratio (aqueous-to-air relative intensity [ARI] index) for flare qualification were calculated from AS-OCT images. In addition, a program was designed to quantify the posterior corneal surface smoothness (PCSS) of each image for KPs evaluation. The maximum, minimum, and average PCSS values were calculated from 128 images per eye and compared among active uveitis, inactive uveitis, and control eyes. Correlations between Standardization of Uveitis Nomenclature grade and both hyperreflective dot number and ARI index were evaluated. Receiver operating characteristic (ROC) curves were constructed to test the values of these indicators for uveitis diagnosis.

RESULTS

AC hyperreflective dot count, ARI index, and maximum and average PCSS values were all significantly higher in the active uveitis group than in the inactive and control groups. Hyperreflective dot count and ARI index were associated with Standardization of Uveitis Nomenclature cell and flare grade. According to ROC curve analysis, maximum PCSS was the best indicator for the diagnosis of uveitis involving the anterior segment, meanwhile the hyperreflective dot number was the best to identify active AC inflammation from the inactive.

CONCLUSIONS

Quantification of AC cell number, flare, and KPs using the CASIA2 device is a promising strategy for the objective assessment of AC inflammation.

Ocular anterior chamber blood cell population differentiation using spectroscopic optical coherence tomography

There is potential clinical significance in identifying cellular responses in the anterior chamber (AC) of the eye, which can indicate hyphema (an accumulation of red blood cells [RBCs]) or aberrant intraocular inflammation (an accumulation of white blood cells [WBCs]). In this work, we developed a spectroscopic OCT analysis method to differentiate between populations of RBCs and subtypes of WBCs, including granulocytes, lymphocytes and monocytes, both in vitro and in ACs of porcine eyes. We developed an algorithm to track single cells within OCT data sets, and extracted the backscatter reflectance spectrum of each single cell from the detected interferograms using the short-time Fourier transform (STFT). A look-up table of Mie back-scattering spectra was generated and used to correlate the backscatter spectral features of single cells to their characteristic sizes. The extracted size distributions based on the best Mie spectra fit were significantly different between each cell type. We also studied theoretical backscattering models of single RBCs to further validate our experimental results. The described work is a promising step towards clinically differentiating and quantifying AC blood cell types.

Anterior segment optical coherence tomography: its application in clinical practice and experimental models of disease

Optical coherence tomography (OCT) provides non-invasive, high-resolution in vivo imaging of the ocular surface and anterior segment. Over the years, it has become an essential tool for evaluating the anterior segment of the eye to monitor ocular development and ocular pathologies in both the clinical and research fields of ophthalmology and optometry. In this review, the clinical applications relating to the use of anterior segment OCT for imaging and quantifying normal and pathological features of the ocular surface, cornea, anterior chamber, and aqueous outflow system are summarised in a range of human ocular diseases. Applications of anterior segment OCT technology that have improved imaging and quantitation of ocular inflammation in experimental animal models of ocular diseases, such as anterior uveitis, microbial keratitis and glaucoma, are also described. The capacity to longitudinally evaluate anterior segment anatomical changes during development, and inflammation facilitates the understanding of the dynamics of tissue responses, and further enhances the intra-operative in vivo imaging during procedures, such as corneal transplantation and drug delivery. Future developments including in vivo ultrahigh-resolution anterior segment OCT, automated analyses of anterior segment OCT images and functional extensions of the technique, may revolutionise the clinical evaluation of anterior segment, corneal and ocular surface diseases.

Analysis of ocular inflammation in anterior chamber-involving uveitis using swept-source anterior segment OCT

PURPOSE

To evaluate the utility of swept-source (SS) optical coherence tomography (OCT) to objectively analyze the degree of anterior chamber (AC) inflammation.

METHODS

Thirty-eight eyes of 32 patients with uveitis and 20 control eyes were enrolled. SS OCT B-scans were obtained, and the number of cells in the B-scans was counted using two methods: (1) manual grading by Point Picker plug-in of Image J ( http://bigwww.epfl.ch/thevenaz/pointpicker/ ) and (2) automated grading by the Image J Particle Analysis algorithm ( http://imagej.net/Particle_Analysis ). The automated and manual AC cell counts were correlated with the Standardization of Uveitis Nomenclature score.

RESULTS

The average numbers of AC inflammatory cells counted by the automated method were 8 ± 4.0, 18 ± 3.0, 42 ± 14.0, 81 ± 32.0, 117 ± 57.0, and 275 ± 67.0 cells/mm² for grades 0, 0.5 + , 1 + , 2 + , 3 + , and 4 + , respectively. For the same clinical categories, the average manual cell counts were 6 ± 4.0, 18 ± 3.0, 34 ± 14.0, 72 ± 32.0, 92 ± 43.0, and 168 ± 65.0 cells/mm², respectively. Zero cells were detected in the AC of healthy eyes. The automated and manual methods were highly correlated (R = 0.98, p < 0.001) and showed good correlation with the clinical grading (R = 0.88, p < 0.001). A mean AC particle size of 117.4 ± 108.8 μm was obtained by the automated method.

CONCLUSIONS

Quantification of the AC cells imaged by SS AS-OCT shows good correlation with categorical clinical severity assessments in uveitis eyes. This approach may provide a more objective method for monitoring uveitis and response to uveitis therapy.

A cell penetrating peptide from SOCS-1 prevents ocular damage in experimental autoimmune uveitis

We describe an immunosuppressive peptide corresponding to the kinase inhibitory region (KIR) of the intracellular checkpoint protein suppressor of cytokine signaling 1 (SOCS-1) that binds to the phospho-tyrosine containing regions of the tyrosine kinases JAK2 and TYK2 and the adaptor protein MAL, and thereby inhibits signaling downstream from these signaling mediators. The peptide, SOCS1-KIR, is thus capable of downregulating overactive JAK/STAT or NF-kB signaling in somatic cells, including those in many compartments of the eye. Attachment of poly-arginine to this peptide (R9-SOCS1-KIR) allows it to penetrate the plasma membrane in aqueous media. R9-SOCS1-KIR was tested in ARPE-19 cells and was found to attenuate mediators of inflammation by blocking the inflammatory effects of IFNγ, TNFα, or IL-17A. R9-SOCS1-KIR and also protected against TNFα or IL-17A mediated damage to the barrier properties of ARPE-19 cells, as evidenced by immunostaining with the tight junction protein, zona occludin 1 (ZO-1), and measurement of transepithelial electrical resistance (TEER). Experimental autoimmune uveitis (EAU) was generated in B10. RIII mice using a peptide of interphotoreceptor retinal binding protein (IRBP^161-180) as immunogen. Topical administration of R9-SOCS1-KIR, 2 days before (prophylactic), or 7 days after immunization (therapeutic) protected ocular structure and function as seen by fundoscopy, optical coherence tomography (OCT), and electroretinography (ERG). The ability R9-SOCS1-KIR to suppress ocular inflammation and preserve barrier properties of retinal pigment epithelium makes it a potential candidate for treatment of autoimmune uveitis.

Immune Relevant Models for Ocular Inflammatory Diseases

Ocular inflammatory diseases, such as dry eye and uveitis, are common, painful, difficult to treat, and may result in vision loss or blindness. Ocular side effects from the use of antiinflammatory drugs (such as corticosteroids or nonsteroidal antiinflammatories) to treat ocular inflammation have prompted development of more specific and safer medications to treat inflammatory and immune-mediated diseases of the eye. To assess the efficacy and safety of these new therapeutics, appropriate immune-relevant animal models of ocular inflammation are needed. Both induced and naturally-occurring models have been described, but the most valuable for translating treatments to the human eye are the animal models of spontaneous, immunologic ocular disease, such as those with dry eye or uveitis. The purpose of this review is to describe common immune-relevant models of dry eye and uveitis with an overview of the immuno-pathogenesis of each disease and reported evaluation of models from small to large animals. We will also review a selected group of naturally-occurring large animal models, equine uveitis and canine dry eye, that have promise to translate into a better understanding and treatment of clinical immune-relevant ocular disease in man.