Protein Biomarkers in Uveitis

Microglial mediators in autoimmune Uveitis: Bridging neuroprotection and neurotoxicity

Autoimmune uveitis, a severe inflammatory condition of the eye, poses significant challenges due to its complex pathophysiology and the critical balance between protective and detrimental immune responses. Central to this balance are microglia, the resident immune cells of the central nervous system, whose roles in autoimmune uveitis are multifaceted and dynamic. This review article delves into the dual nature of microglial functions, oscillating between neuroprotective and neurotoxic outcomes in the context of autoimmune uveitis. Initially, we explore the fundamental aspects of microglia, including their activation states and basic functions, setting the stage for a deeper understanding of their involvement in autoimmune uveitis. The review then navigates through the intricate mechanisms by which microglia contribute to disease onset and progression, highlighting both their protective actions in immune regulation and tissue repair, and their shift towards a pro-inflammatory, neurotoxic profile. Special emphasis is placed on the detailed pathways and cellular interactions underpinning these dual roles. Additionally, the review examines the potential of microglial markers as diagnostic and prognostic indicators, offering insights into their clinical relevance. The article culminates in discussing future research directions, and the ongoing challenges in translating these findings into effective clinical applications. By providing a comprehensive overview of microglial mechanisms in autoimmune uveitis, this review underscores the critical balance of microglial activities and its implications for disease management and therapy development.

Evolution of research in diagnosis and management of uveitis over four decades in India

Uveitis and its complications are more common in the developing world, in which the condition occurs in up to 714 per 100,000 in the population and accounts for up to 25% of all blindness. In India, the ophthalmic sub speciality of uveitis greatly evolved in the last four decades. In the early decades most of the studies were epidemiological studies. In recent years, more research has been published due to tremendous advancements in clinical diagnosis, laboratory investigations and ancillary test and treatment modalities. In this review article, we did a medline search with key words 'uveitis' and 'India', and selectively incorporated articles showing the evolution of this sub-speciality in India.

Bilateral retinal vasculitis due to presumed sarcoidosis with rickettsial retinitis

OBJECTIVE

To describe a case of bilateral retinal vasculitis due to presumed sarcoidosis and rickettsial retinitis complicated with neovascularization with tear biomarker analysis.

METHODS

A retrospective case report.

RESULTS

A 16-year-old male presented with bilateral retinal vasculitis and retinitis in both eyes with inferotemporal quadrant neovascularization in the right eye. Multimodal imaging revealed the presence of active inflammation in both eyes. Weil Felix test was positive with raised ACE levels. This patient was treated with local and systemic steroids, doxycycline, and laser photocoagulation followed by oral methotrexate therapy which resulted in clinical resolution with recovery of visual acuity. Tear biomarker analysis showed raised sICAM-1 and MMP-9 levels in both eyes which significantly reduced following treatment.

CONCLUSION

Ocular sarcoidosis with rickettsial infection is a rare association. Tear biomarkers correlated well with clinical and imaging manifestations. High index of suspicion and aggressive anti-inflammatory therapy can help control inflammation and restore good vision.

Proteomic analysis of human aqueous humor from fuchs uveitis syndrome

Fuchs uveitis syndrome (FUS) is a commonly misdiagnosed uveitis syndrome often presenting as an asymptomatic mild inflammatory condition until complications arise. The diagnosis of this disease remains clinical because of the lack of specific laboratory tests. The aqueous humor (AH) is a complex fluid containing nutrients and metabolic wastes from the eye. Changes in the AH protein provide important information for diagnosing intraocular diseases. This study aimed to analyze the proteomic profile of AH in individuals diagnosed with FUS and to identify potential biomarkers of the disease. We used liquid chromatography-tandem mass spectrometry-based proteomic methods to evaluate the AH protein profiles of all 37 samples, comprising 15 patients with FUS, six patients with Posner-Schlossman syndrome (PSS), and 16 patients with age-related cataract. A total of 538 proteins were identified from a comprehensive spectral library of 634 proteins. Subsequent differential expression analysis, enrichment analysis, and construction of key sub-networks revealed that the inflammatory response, complement activation and hypoxia might be crucial in mediating the process of FUS. The hypoxia inducible factor-1 may serve as a key regulator and therapeutic target. Additionally, the innate and adaptive immune responses are considered dominant in the patients with FUS. A diagnostic model was constructed using machine-learning algorithm to classify FUS, PSS, and normal controls. Two proteins, complement C1q subcomponent subunit B and secretogranin-1, were found to have the highest scores by the Extreme Gradient Boosting, suggesting their potential utility as a biomarker panel. Furthermore, these two proteins as biomarkers were validated in a cohort of 18 patients using high resolution multiple reaction monitoring assays. Therefore, this study contributes to advancing of the current knowledge of FUS pathogenesis and promotes the development of effective diagnostic strategies.

Differential Gene and Protein Expression of Conjunctival Bleb Hyperfibrosis in Early Failure of Glaucoma Surgery

The early failure of glaucoma surgery is mainly caused by over-fibrosis at the subconjunctival space, causing obliteration of the filtration bleb. Because fibrosis has a suspected basis of genetic predisposition, we have undertaken a prospective study to identify upregulated profibrotic genes in a population of glaucoma patients with signs of conjunctival fibrosis and early postoperative surgical failure. Clinical data of re-operated fibrosis patients, hyperfibrosis patients who re-operated more than once in a short time, and control patients with no fibrosis were recorded and analyzed at each follow-up visit. Conjunctival-Tenon surgical specimens were obtained intraoperatively to evaluate the local expression of a panel of genes potentially associated with fibrosis. In order to correlate gene expression signatures with protein levels, we quantified secreted proteins in primary cultures of fibroblasts from patients. Expression of VEGFA, CXCL8, MYC, and CDKN1A was induced in the conjunctiva of hyperfibrosis patients. VEGFA and IL8 protein levels were also increased in fibroblast supernatants. We propose that an increase in these proteins could be useful in detecting conjunctival fibrosis in glaucoma patients undergoing filtering surgery. Molecular markers could be crucial for early detection of patients at high risk of failure of filtration surgery, leading to more optimal and personalized treatments.

Infrared analysis in the aqueous humor of patients with uveitis: Preliminary results

Inflammatory processes affecting the uvea result in a temporary o permanent blurred vision and represent an important cause of visual impairment worldwide. It is often hard to make a precise diagnosis which is dependent on the clinical expertise, diagnostic tests, laboratory investigations in blood and sometimes in the aqueous humor (AH). With the aim of obtaining proof of principle Fourier Transformed Infrared (FT-IR) absorbance spectroscopy was applied to study the molecular composition of 72 AH samples collected in 26 patients with uveitis and in 44 controls. The unsupervised exploration of the internal structure of the dataset by principal component analysis reduced hundreds IR variables to those most representative allowing to obtain the predictive model that distinguished the AH spectra of patients with uveitis from controls. The same result was obtained by unsupervised agglomerative cluster analysis. After labeling the spectra with some clinical information it was observed that most severe uveitis with active processes were grouped separately from chronic and relapsing uveitis and controls. The consistence of prediction models is discussed in the light of supporting etiological diagnosis by machine learning processes. In conclusion, proof of principle has been obtained that the IR spectral pattern of AH may reflect particular uveal diseases.

Challenges and management of childhood non-infectious chronic uveitis

INTRODUCTION

Childhood uveitis is a sight-threatening condition, because if not properly recognized and treated can lead to several ocular complications and blindness. It represents a real challenge not only from an etiologic/diagnostic point of view, but also for management and therapy.

AREAS COVERED

In this review we will discuss the main etiologies, the diagnostic approach, risk factors associated to childhood non-infectious uveitis (cNIU), and the difficulties in eye examination in childhood. Moreover, we will discuss the treatment of cNIU in term of therapeutic choice, timing of initiation and withdrawal.

EXPERT OPINION

Identification of specific diagnosis is mandatory to prevent severe complications, thus a thorough differential diagnosis is essential. Pediatric eye examination may be extremely challenging due to the scarce collaboration, but novel techniques and biomarkers will help in identify low grade of inflammation, eventually modify long-term outcomes. Once identified the appropriate diagnosis, recognition of children who may benefit of a systemic treatment is crucial. What, When and how long are the key questions to address in this field. Current evidence and future results of ongoing clinical trials will help in driving treatment. A proper ocular screening, not only in the context of systemic disease, should be discussed by experts.

Pre-hyperglycemia immune cell trafficking underlies subclinical diabetic cataractogenesis

BACKGROUND

This work elucidates the first cellular and molecular causes of cataractogenesis. Current paradigm presupposes elevated blood glucose as a prerequisite in diabetic cataractogenesis. Novel evidence in our model of diabetic cataract challenges this notion and introduces immune cell migration to the lens and epithelial-mesenchymal transformation (EMT) of lens epithelial cells (LECs) as underlying causes.

METHODS

Paucity of suitable animal models has hampered mechanistic studies of diabetic cataract, as most studies were traditionally carried out in acutely induced hyperglycemic animals. We introduced diabetic cataract in the Nile grass rat (NGR) that spontaneously develops type 2 diabetes (T2D) and showed its closeness to the human condition. Specialized stereo microscopy with dual bright-field illumination revealed novel hyperreflective dot-like microlesions in the inner cortical regions of the lens. To study immune cell migration to the lens, we developed a unique in situ microscopy technique of the inner eye globe in combination with immunohistochemistry.

RESULTS

Contrary to the existing paradigm, in about half of the animals, the newly introduced hyper reflective dot-like microlesions preceded hyperglycemia. Even though the animals were normoglycemic, we found significant changes in their oral glucose tolerance test (OGTT), indicative of the prediabetic stage. The microlesions were accompanied with significant immune cell migration from the ciliary bodies to the lens, as revealed in our novel in situ microscopy technique. Immune cells adhered to the lens surface, some traversed the lens capsule, and colocalized with apoptotic nuclei of the lens epithelial cells (LECs). Extracellular degradations, amorphous material accumulations, and changes in E-cadherin expressions showed epithelial-mesenchymal transformation (EMT) in LECs. Subsequently, lens fiber disintegration and cataract progression extended into cortical, posterior, and anterior subcapsular cataracts.

CONCLUSIONS

Our results establish a novel role for immune cells in LEC transformation and death. The fact that cataract formation precedes hyperglycemia challenges the prevailing paradigm that glucose initiates or is necessary for initiation of the pathogenesis. Novel evidence shows that molecular and cellular complications of diabetes start during the prediabetic state. These results have foreseeable ramifications for early diagnosis, prevention and development of new treatment strategies in patients with diabetes.

Ebola virus disrupts the inner blood-retinal barrier by induction of vascular endothelial growth factor in pericytes

Ebola virus (EBOV) causes severe hemorrhagic fever in humans with high mortality. In Ebola virus disease (EVD) survivors, EBOV persistence in the eyes may break through the inner blood-retinal barrier (iBRB), leading to ocular complications and EVD recurrence. However, the mechanism by which EBOV affects the iBRB remains unclear. Here, we used the in vitro iBRB model to simulate EBOV in retinal tissue and found that Ebola virus-like particles (EBO-VLPs) could disrupt the iBRB. Cytokine screening revealed that EBO-VLPs stimulate pericytes to secrete vascular endothelial growth factor (VEGF) to cause iBRB breakdown. VEGF downregulates claudin-1 to disrupt the iBRB. Ebola glycoprotein is crucial for VEGF stimulation and iBRB breakdown. Furthermore, EBO-VLPs caused iBRB breakdown by stimulating VEGF in rats. This study provides a mechanistic insight into that EBOV disrupts the iBRB, which will assist in developing new strategies to treat EBOV persistence in EVD survivors.

Diagnosis and biomarkers for ocular tuberculosis: From the present into the future

Tuberculosis is an airborne disease caused by Mycobacterium tuberculosis (Mtb) and can manifest both pulmonary and extrapulmonary disease, including ocular tuberculosis (OTB). Accurate diagnosis and swift optimal treatment initiation for OTB is faced by many challenges combined with the lack of standardized treatment regimens this results in uncertain OTB outcomes. The purpose of this study is to summarize existing diagnostic approaches and recently discovered biomarkers that may contribute to establishing OTB diagnosis, choice of anti-tubercular therapy (ATT) regimen, and treatment monitoring. The keywords ocular tuberculosis, tuberculosis, Mycobacterium, biomarkers, molecular diagnosis, multi-omics, proteomics, genomics, transcriptomics, metabolomics, T-lymphocytes profiling were searched on PubMed and MEDLINE databases. Articles and books published with at least one of the keywords were included and screened for relevance. There was no time limit for study inclusion. More emphasis was placed on recent publications that contributed new information about the pathogenesis, diagnosis, or treatment of OTB. We excluded abstracts and articles that were not written in the English language. References cited within the identified articles were used to further supplement the search. We found 10 studies evaluating the sensitivity and specificity of interferon-gamma release assay (IGRA), and 6 studies evaluating that of tuberculin skin test (TST) in OTB patients. IGRA (Sp = 71-100%, Se = 36-100%) achieves overall better sensitivity and specificity than TST (Sp = 51.1-85.7%; Se = 70.9-98.5%). For nuclear acid amplification tests (NAAT), we found 7 studies on uniplex polymerase chain reaction (PCR) with different Mtb targets, 7 studies on DNA-based multiplex PCR, 1 study on mRNA-based multiplex PCR, 4 studies on loop-mediated isothermal amplification (LAMP) assay with different Mtb targets, 3 studies on GeneXpert assay, 1 study on GeneXpert Ultra assay and 1 study for MTBDRplus assay for OTB. Specificity is overall improved but sensitivity is highly variable for NAATs (excluding uniplex PCR, Sp = 50-100%; Se = 10.5-98%) as compared to IGRA. We also found 3 transcriptomic studies, 6 proteomic studies, 2 studies on stimulation assays, 1 study on intraocular protein analysis and 1 study on T-lymphocyte profiling in OTB patients. All except 1 study evaluated novel, previously undiscovered biomarkers. Only 1 study has been externally validated by a large independent cohort. Future theranostic marker discovery by a multi-omics approach is essential to deepen pathophysiological understanding of OTB. Combined these might result in swift, optimal and personalized treatment regimens to modulate the heterogeneous mechanisms of OTB. Eventually, these studies could improve the current cumbersome diagnosis and management of OTB.

Differences in biomarker concentrations in serum and urine of patients with Ocular Tuberculosis - A prospective descriptive study

PURPOSE

To describe biomarker concentrations in serum and urine of South African patients with ocular tuberculosis (OTB).

METHODS

A prospective study to compare 29 urine and serum biomarkers in 14 OTB patients at a tertiary eye clinic.

RESULTS

Median age of participants (7 male and 7 female) was 38.5 years (range 25-73) Most biomarker concentrations were significantly higher in serum than in urine (p < 0.01). Only 2 (IL-1RA and IL-2) showed higher concentrations in urine than serum (p < 0.01). Three biomarkers (sIL-2Ra, sTNFRI and IFNγ) showed no difference in concentration between urine and serum (p > 0.05).

CONCLUSIONS

Most biomarkers tested showed significant differences in concentration between serum and urine and therefore these 2 biofluids cannot be used interchangeably when studying biomarker profiles. One notable exception is IFNγ as its concentration did not differ between serum and urine.

Analysis of differentially expressed genes in individuals with noninfectious uveitis based on data in the gene expression omnibus database

Noninfectious uveitis (NIU), an intraocular inflammation caused by immune-mediated reactions to eye antigens, is associated with systemic rheumatism and several autoimmune diseases. However, the mechanisms underlying the pathogenesis of uveitis are poorly understood. Therefore, we aimed to identify differentially expressed genes (DEGs) in individuals with NIU and to explore its etiologies using bioinformatics tools. GSE66936 and GSE18781 datasets from the gene expression omnibus (GEO) database were merged and analyzed. Functional enrichment analysis was performed, and protein-protein interaction (PPI) networks were constructed. A total of 89 DEGs were identified. Gene ontology (GO) enrichment analysis identified 21 enriched gene sets. Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis identified four core enriched pathways: antigen processing and expression signaling, natural killer (NK) cell-mediated cytotoxicity signaling, glutathione metabolic signal transduction, and arachidonic acid metabolism pathways. PPI network analysis revealed an active component-target network with 40 nodes and 132 edges, as well as several hub genes, including CD27, LTF, NCR3, SLC4A1, CD69, KLRB1, KIR2DL3, KIR3DL1, and GZMK. The eight potential hub genes may be associated with the risk of developing NIU. NK cell-mediated cytotoxicity signaling might be the key molecular mechanism in the occurrence and development of NIU. Our study provided new insights on NIU, its genetics, molecular pathogenesis and new therapeutic targets.

Comprehensive Proteomic Profiling of Vitreous Humor in Ocular Sarcoidosis Compared with Other Vitreoretinal Diseases

Ocular sarcoidosis is an inflammatory disease that manifests as uveitis, and is often difficult to distinguish from other forms of uveitis based on nonspecific findings alone. Comprehensive proteomic analyses of vitreous humor using LC-MS/MS were performed in each patient with ocular sarcoidosis, vitreoretinal lymphoma (VRL), and controls with epiretinal membrane or macular hole. Differential expression proteins (DEPs) were identified by comparing with VRL and controls, and functional pathway analysis was performed. The candidate biomarker proteins for ocular sarcoidosis were validated using enzyme-linked immunosorbent assay. A total of 1590 proteins were identified in all samples. Of these, 290 and 174 DEPs were detected in vitreous of ocular sarcoidosis compared with controls and VRL, respectively. Enrichment pathway analysis revealed that pathways related to the immune system were most upregulated. Validation of two candidate biomarkers for ocular sarcoidosis, neutrophil gelatinase-associated lipocalin (NGAL) and junctional adhesion molecules B (JAMB), confirmed upregulated NGAL and JAMB protein expressions in ocular sarcoidosis compared to controls and VRL. The results of this study revealed that altered vitreous protein expression levels may discriminate ocular sarcoidosis from other uveitis diseases. Vitreous NGAL and JAMB are potential biomarkers and may serve as an auxiliary tool for the diagnosis of ocular sarcoidosis.

Retinal Proteomic Analysis in a Mouse Model of Endotoxin-Induced Uveitis Using Data-Independent Acquisition-Based Mass Spectrometry

Uveitis is a group of sight-threatening ocular inflammatory diseases, potentially leading to permanent vision loss in patients. However, it remains largely unknown how uveitis causes retinal malfunction and vision loss. Endotoxin-induced uveitis (EIU) in rodents is a good animal model to study uveitis and associated acute retinal inflammation. To understand the pathogenic mechanism of uveitis and screen potential targets for treatment, we analyzed the retinal proteomic profile of the EIU mouse model using a data-independent acquisition-based mass spectrometry (SWATH-MS). After systemic LPS administration, we observed activation of microglial cells accompanied with the elevation of pro-inflammatory mediators and visual function declines. In total, we observed 79 upregulated and 90 downregulated differentially expressed proteins (DEPs). Among the DEPs, we found that histone family members (histone H1, H2A, H2B) and blood proteins including haptoglobin (HP), hemopexin (HPX), and fibrinogen gamma chain (FGG) were dramatically increased in EIU groups relative to those in control groups. We identified phototransduction and synaptic vesicle cycle as the top two significant KEGG pathways. Moreover, canonical pathway analysis on DEPs using Ingenuity Pathway Analysis revealed top three most significant enriched pathways related to acute phase response signaling, synaptogenesis signaling, and eif2 signaling. We further confirmed upregulation of several DEPs associated with the acute phase response signaling including HP, HPX, and FGG in LPS-treated retinas by qPCR and Western blot. In summary, this study serves as the first report to detect retinal proteome changes in the EIU model. The study provides several potential candidates for exploring the mechanism and novel therapeutic targets for uveitis and other retinal inflammatory diseases.

Graphene-Based Biosensors for Molecular Chronic Inflammatory Disease Biomarker Detection

Chronic inflammatory diseases, such as cancer, diabetes mellitus, stroke, ischemic heart diseases, neurodegenerative conditions, and COVID-19 have had a high number of deaths worldwide in recent years. The accurate detection of the biomarkers for chronic inflammatory diseases can significantly improve diagnosis, as well as therapy and clinical care in patients. Graphene derivative materials (GDMs), such as pristine graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO), have shown tremendous benefits for biosensing and in the development of novel biosensor devices. GDMs exhibit excellent chemical, electrical and mechanical properties, good biocompatibility, and the facility of surface modification for biomolecular recognition, opening new opportunities for simple, accurate, and sensitive detection of biomarkers. This review shows the recent advances, properties, and potentialities of GDMs for developing robust biosensors. We show the main electrochemical and optical-sensing methods based on GDMs, as well as their design and manufacture in order to integrate them into robust, wearable, remote, and smart biosensors devices. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers with improved sensitivity, reaching limits of detection from the nano to atto range concentration.

Preventive effects of cristacarpin on experimentally induced uveitis by targeting NF-κB

Cristacarpin is a novel prenylated pterocarpan that reportedly exhibits broad anti-cancer activity by enhancing endoplasmic reticulum stress. However, whether and how cristacarpin affects in-flammatory processes remain largely unknown. In the present study, the anti-inflammatory effect of cristacarpin on lipopolysaccharide (LPS)-induced inflammation was investigated using zebrafish embryos, RAW 264.7 macrophages, and mouse uveitis models. In the non-toxic concentration range (from 20 to 100 μM), cristacarpin suppressed pro-inflammatory mediators such as interleukin (IL)-6 and tumor necrosis factor (TNF)-α, while stimulating anti-inflammatory mediators such as IL-4 and IL-10 in LPS-stimulated RAW 264.7 cells and uveitis mouse models. Cristacarpin decreased cell adhesion of macrophages through downregulation of the expression of Ninjurin1 and matrix metalloproteinases. Furthermore, cristacarpin reduced macrophage migration in zebrafish embryos in vivo. Cristacarpin also increased cytosolic levels of inhibitor of nuclear factor-κB and suppressed the nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells. Collectively, our results suggest that cristacarpin is a potential therapeutic candidate for developing ocular anti-inflammatory drugs.

The potential of tear proteomics for diagnosis and management of orbital inflammatory disorders including Graves' ophthalmopathy

BACKGROUND

Orbital compartments harbor a variety of tissues that can be independently targeted in a plethora of disorders resulting in sight-threatening risks. Orbital inflammatory disorders (OID) including Graves' ophthalmopathy, sarcoidosis, IgG4 disease, granulomatosis with polyangiitis, and nonspecific orbital inflammation constitute an important cause of pain, diplopia and vision loss. Physical examination, laboratory tests, imaging, and even biopsy are not always adequate to classify orbital inflammation which is frequently deemed "nonspecific". Tear sampling and testing provide a potential "window" to the orbital disease process through a non-invasive technique that allows longitudinal sampling as the disease evolves. Using PubMed/Medline, we identified potentially relevant articles on tear proteomics published in the English language between 1988 and 2021. Of 303 citations obtained, 225 contained empirical data on tear proteins, including 33 publications on inflammatory conditions, 15 in glaucoma, 15 in thyroid eye disease, 1 in sarcoidosis (75) and 2 in uveitis (77,78). Review articles were used to identify an additional 56 relevant articles through citation search. In this review, we provide a short introduction to the potential use of tears as a diagnostic fluid and tool to investigate the mechanism of ocular diseases. A general review of previous tear proteomics studies is also provided, with a focus on Graves' ophthalmopathy (GO), and a discussion of unmet needs in the diagnosis and treatment of orbital inflammatory disease (OID). The review concludes by pointing out current limitations of mass spectrometric analysis of tear proteins and summarizes future needs in the field.

Reliability of Aqueous Flare Measurements During Uveitis by a Spot Fluorometer

Purpose: To evaluate the reliability of intensity of light scatter (ILS) for diagnosing mild-to-moderate uveitis, which is difficult to score by the subjective standardized uveitis nomenclature (SUN) grading. Methods: ILS (in millivolts) was measured in healthy subjects and uveitis patients by a custom-made Spot fluorometer. The reliability was assessed by noise analysis of the instrument using turbid samples and intra- and interobserver variabilities. Results: ILS increased with the severity of inflammation: healthy (0.1498 ± 0.0564) and SUN0 (0.1590 ± 0.0564) < SUN1+ (0.2050 ± 0.0887) < SUN2+ (0.4283 ± 0.1895). The increase in ILS was more significant between healthy and SUN1+ (P < 0.0001) compared to the difference between SUN0 and SUN1+ (P = 0.0006). The instrument noise was small (σ = 0.002). Intraobserver measurements revealed no variability (P > 0.98) between measurements and predicted repeatability coefficients of 0.0754, 0.0522, and 0.0532 in healthy, SUN0, and SUN1+, respectively. Interobserver measurements also showed no variability (P > 0.88) and predicted intraclass correlation coefficient > 0.63 in healthy and uveitis subjects. Conclusions: The fluorometer enables precise measurement of ILS with negligible instrument noise, and the measurements are unaffected by intra- and interobserver variabilities. However, the difference in mean ILS between SUN0 and SUN1+ is greater than the instrument noise and comparable to intra- and interobserver variabilities. Thus, ILS measurements are likely impacted by blinking, eye movements, and focusing jitter. The impact of these factors must be reduced before using the fluorometer to distinguish mild-to-moderate uveitis.