From non-invasive techniques like multiphoton microscopy to cutting-edge modalities such as fluorescence lifetime imaging ophthalmoscopy (FLIO), experts of the field uncovered the transformative potential of these innovations in improving patient outcomes and enhancing our understanding of ocular diseases on Day Four of the Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO 2024).
Non-invasive corneal examination through multiphoton microscopy
The cornea, being a transparent tissue, rich in collagen and with several cellular layers, is well-suited to be imaged by multiphoton microscopy. First speaker Ana Batista, PhD (University of Coimbra, Portugal), discussed the application of non-invasive corneal examination using multiphoton microscopy, focusing on its potential benefits in various clinical scenarios.
She highlighted the ability of this technique to provide information currently unavailable through conventional methods. Specifically, it can improve the evaluation of corneal viability before transplantation, enhance corneal diagnosis, and facilitate better follow-up after medical procedures. The findings demonstrate changes in corneal characteristics and metabolism under different storage conditions and pathologies. Additionally, the technique shows promise in assessing the effectiveness of medical treatments, such as corneal cross-linking, by detecting changes in collagen fluorescence. She concluded by saying that the development of a medical device based on these imaging modalities has the potential to significantly enhance patient care and follow-up.
Unveiling neuroimmune dynamics through murine corneal intravital imaging
Next, Sejiro Littleton,PhD (Duke University, USA), investigated murine corneal neuroimmune interactions through intravital imaging.
Highlighting the pivotal role of nerve-macrophage interactions in maintaining homeostasis across various bodily systems, from the gut to the brain and retina, he underscored the challenge of capturing these interactions in vivo. However, the cornea emerges as a unique platform for studying such interactions due to its external accessibility and translucency, allowing light to pass through.
Drawing from referenced research, he mentioned the association between resident tissue macrophages and nerves in the peripheral stroma of the murine cornea. Furthermore, he elucidated how macrophage depletion leads to corneal nerve degeneration, mostly affecting nerves responsible for mechanosensation, such as blinking.
Notably, experiments with capsaicin eye drops demonstrate intact nerve function in response to stimuli, indicating that macrophages do not moderate these responses. Concluding with insights from confocal microscopy on diseases characterized by nerve loss in the cornea, Dr. Littleton emphasized the critical role of macrophages in maintaining corneal nerve integrity. Overall, his talk shed light on the intricate interplay between macrophages and nerves in the cornea, offering valuable insights into potential therapeutic strategies for neuroimmune-related conditions.
The role of vitreous macrophages in retinal pathologies
Meanwhile, Dr. Richard B. Rosen (New York City, USA) began his talk by discussing the historical context of intravitreal treatment, which emerged following the development of pars plana vitrectomy in the 1970s and the subsequent introduction of chemical interventions in the 1990s. He highlighted the impact of these treatments on hyalocytes, tissue-resident macrophages within the vitreous, emphasizing their role in maintaining vitreous clarity, ocular immune privilege and the synthesis and degradation of vitreous components. These hyalocytes, though closely related to microglia and macrophages, possess unique characteristics.
Dr. Rosen’s clinical analysis revealed changes in hyalocyte morphology in diabetic retinopathy (DR), where the shape of these cells varies from control to non-proliferative DR (NPDR) to proliferative DR. He noted that while hyalocytes typically remain stationary, posterior vitreous detachment causes them to move off the retina but remain spread out over the hyaloid membrane.
In summary, Dr. Rosen underscored the crucial roles of vitreous macrophages in inter-retinal and preretinal pathologies. He suggested that commercial optical coherence tomography (OCT) can effectively image their distribution and gross morphology, making them potential cellular biomarkers for patient care. For more severe cases, adaptive optics can provide detailed insights into hyalocyte behavior.
Potential of FLIO imaging in uveitis management
Uveitis, a condition that can manifest across all age groups, often presents with ambiguous clinical and phenotypic features. However, the emergence of fluorescence lifetime imaging ophthalmoscopy (FLIO) as a novel and non-invasive imaging technique has demonstrated its utility in categorizing various uveitic diseases solely based on phenotype.
During her talk, Alexandra Vitale, MD Candidate (University of Utah School of Medicine, USA), highlighted the significant potential that FLIO offers in the field of uveitis, particularly due to its ability to detect changes in autofluorescence lifetimes.
In patients with uveitis, there is an overall prolongation of FLIO lifetimes across all areas compared to age-matched healthy controls. However, short FLIO lifetimes are observed in patients with active disease. Despite the rarity of uveitis subtypes and the challenge of obtaining large sample sizes, FLIO has shown promise in providing insights into various diseases. FLIO imaging reveals prolonged lifetimes in regions of atrophy or scarring, while shortened lifetimes are indicative of clinical or symptomatic activity. This suggests that FLIO may be useful in detecting early signs of disease reactivation or quiescence. However, limitations such as the high cost and limited availability of FLIO cameras, with only 12 worldwide, underscore the need for further research and recruitment to fully understand the utility of FLIO in uveitis management, she noted.
Editor’s Note: The Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO 2024) is being held from 5-9 May in Seattle, Washington, USA. Reporting for this story took place during the event.
