Faculty Bibliography

PURPOSE/OBJECTIVE:To report on the presentation, treatment, and visual outcome of stromal keratitis (SK) in the Zoster Eye Disease Study (ZEDS). DESIGN/METHODS:Secondary analysis of SK endpoint of randomized clinical trial. SUBJECTS/METHODS:Herpes Zoster Ophthalmicus (HZO) patients were randomized in a double-masked clinical trial of oral valacyclovir 1g daily or placebo for 1 year. They were followed prospectively every 3 months for 18 months for endpoints of SK, iritis (IR), endothelial keratitis (EK), or dendritiform epithelial keratitis (DEK). METHODS:Presentation of recurrent, new, or worsening SK was evaluated retrospectively by treatment assignment, randomization strata, and use of topical steroids. Investigators had been allowed discretionary treatment of endpoints including open label valacyclovir and topical steroids. Visual outcome and treatment with open label oral valacyclovir and topical steroids were evaluated. MAIN OUTCOME MEASURES/METHODS:Use of open label valacyclovir and topical steroid treatment of recurrent, new, or worsening SK, and visual acuity at 12 months. RESULTS:Recurrent, new, or worsening SK occurred in 105/527(20%) participants. Randomization group was not associated with this complication. Mean best corrected visual acuity at enrollment was logMAR 0.10±0.14 with no difference at 1 year, logMAR 0.13±0.2, and no difference between valacyclovir and placebo groups at enrollment or at 1 year. Among the 105 instances of SK, 79(75%) were recognized at scheduled study visits rather than at episodic visits. In only 11/105(10%) of recurrent, new, or worsening SK, did masked investigators opt to treat with open label oral antiviral. At the time of SK complication, 52/105(50%) were on topical steroid, but 47/52(90%) on topical steroids were using 1x daily or less, 21/47(45%) high potency and 26/47(55%) low potency (p=0.47). Of 48/105(47%) on no topical steroids at recurrent, new, or worsening SK, 18/48(38%) had discontinued steroids in the prior 3 months. 38/48(75%) on no topical steroids at complication SK were subsequently treated with high potency steroids 2x daily or more. Of 26/52(50%) on low potency steroids at complication SK, 23/26(88%) were treated with increase in frequency only. CONCLUSIONS:Individuals with ocular complications of HZO who develop SK generally maintain very good vision without use of oral antiviral therapy when monitored closely and SK is recognized and treated. Low potency topical steroids should be considered for treatment and ongoing suppression of SK in HZO.

Cerebrospinal fluid (CSF), partly driven by sensory stimulation, is crucial for maintaining homeostasis and clearing metabolic waste. Whether such stimulus-driven CSF flow is disrupted in age-related neurodegenerative diseases of the visual system remains unclear. This study examined the CSF flow during visual stimulation in glaucoma patients and healthy older adults using functional magnetic resonance imaging. In glaucoma, CSF inflow becomes progressively decoupled from the visually evoked blood-oxygenation-level-dependent (BOLD) response. Specifically, the characteristic stimulus-locked CSF patterns, which decrease after stimulus onset and increase after offset, diminish with disease severity. Mediation analysis suggests this flattened CSF pattern is driven by a flatter ascending BOLD slope, leading to a shallower CSF trough and a reduced post-stimulus surge. These results indicate that glaucoma-related functional impairments contribute to downstream alterations in CSF dynamics. Overall, this study provides insight into how glaucoma disrupts visually driven CSF inflow and highlights in vivo biomarkers for monitoring CSF dynamics.

Precision-targeted ultrasonic neuromodulation offers immense potential for studying brain function and treating neurological diseases. Yet, its application has been limited by challenges in achieving precise spatio-temporal control and monitoring of ultrasound effects on brain circuits. Here we show that transcranial ultrasound elicits direct and highly focal responses, which can be dynamically steered at spatio-temporal scales relevant for neural function. Furthermore, holographic transcranial ultrasound stimulation allows direct control of the stimulated volume and actively modulates local and mid-range network projections, effectively lowering the activation threshold by an order of magnitude. To better understand this previously unexplored excitability regime not fully explained by the conventional pressure-frequency dyad, we developed a dual modelling framework, where both an empirical and a mechanistic model were constructed to capture the intricacies of holographic transcranial ultrasound stimulation. These models achieve qualitative agreement with our experimental results, suggesting that these findings are predominantly driven by putative network interactions. Our results bring insight on the complex interaction mechanisms of ultrasound with neural tissue and highlight its potential for the noninvasive interfacing of distributed brain networks.

Monitoring intracellular calcium is central to understanding cell signaling across nearly all cell types and organisms. Fluorescent genetically encoded calcium indicators (GECIs) remain the standard tools for in vivo calcium imaging, but require intense excitation light, leading to photobleaching, background autofluorescence and phototoxicity. Bioluminescent GECIs, which generate light enzymatically, eliminate these artifacts but have been constrained by low dynamic range and suboptimal calcium affinities. Here we show that CaBLAM ('calcium bioluminescence activity monitor'), an engineered bioluminescent calcium indicator, achieves an order-of-magnitude improvement in signal contrast and a tunable affinity matched to physiological cytosolic calcium. CaBLAM enables single-cell and subcellular activity imaging at video frame rates in cultured neurons and sustained imaging over hours in awake, behaving animals. These capabilities establish CaBLAM as a robust and general alternative to fluorescent GECIs, extending calcium imaging to regimes where excitation light is undesirable or infeasible.

Glaucoma is a chronic neurodegenerative disease of the visual system, and treatment is targeted toward lowering intraocular pressure. However, some patients fail to respond to treatment and their intraocular pressure levels remain high, risking continuous vision loss. Explainable machine learning provides a mechanism for both individual prognostication and the identification of factors associated with treatment outcome. Here, we used explainable machine learning to predict intraocular pressure for glaucoma patients receiving medication treatment. We accessed the UK Biobank to obtain information on 290 eyes from 161 participants who reported a diagnosis of glaucoma and were receiving treatment. Features were divided into three distinct datasets containing demographic data only, physiometabolic parameters and medication prescription data, and all data combined. We evaluated five machine learning techniques for each feature set in terms of their ability to predict intraocular pressure at a follow-up visit in a classification task. We then calculated SHapley Additive exPlanation (SHAP) values for the best performing model to determine feature importance, stability, and interactions. We found that eXtreme Gradient Boosting (XGBoost) outperformed all other models when trained and tested on the combined feature set with an area under receiver operating characteristic curve (AUC) of 0.708. Insulin-like growth factor 1 (IGF-1), low-density lipoprotein (LDL), and lymphocyte count ranked as the three most important features for this model. LDL and IGF-1 exhibited a low degree of global variability in contribution to the model output across all cross-validation repeats. SHAP values demonstrated the strongest interactions being between LDL and IGF-1. In summary, our studies indicated the importance of blood LDL and IGF-1 in contributing to the outcomes of intraocular pressure lowering treatment and demonstrated the ability of XGBoost to predict these outcomes.

BACKGROUND:Despite the high potential of transcranial ultrasound stimulation (TUS) for non-invasive brain therapy and interrogation, real-time monitoring of brain responses to TUS remains a challenge. Traditional methods to monitor direct neural responses are invasive and mostly incompatible with precise TUS delivery while other non-invasive approaches to visualize the induced responses suffer from poor penetration depth, lack of sensitivity, or low temporal resolution. OBJECTIVE:We present an integrated approach for high precision delivery of ultrasound into the mouse brain and simultaneous whole-brain oximetry with functional optoacoustic tomography to characterize the hemodynamic response elicited by TUS. METHODS:A spherically focused ultrasound array was employed to non-invasively deliver holographic TUS and simultaneously detect multispectral optoacoustic signals from the brains of anesthetized mice. Ultrasound pressure and pulse duration were varied, while the number of stimuli (5), stimulation duration (15 s), and ultrasound frequency (3 MHz) were kept constant. The acquired optoacoustic data were tomographically reconstructed and spectrally unmixed to render three-dimensional maps of oxygenated and deoxygenated hemoglobin in real time. RESULTS:TUS-evoked brain-wide hemodynamics were efficiently monitored via spectroscopic optoacoustic imaging with high spatial and temporal resolution. Holographic TUS targeted to the somatosensory cortex elicited distinct hemodynamic responses, which extended beyond the stimulated region, involving subcortical arteries and pial veins. CONCLUSIONS:Our method provides new transformative non-invasive capabilities to study the effects of ultrasound on a living brain thus help unleash the strong potential of TUS in neuroscience and medicine.

Focused transcranial ultrasound stimulation (TUS) can affect neural activity with high spatial precision, advancing noninvasive neuromodulation toward targeted treatment of brain disorders. Direct monitoring of TUS responses is crucial for ensuring optimal outcomes. Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging has primarily been used for studying TUS effects in both human and nonhuman primate brains. However, the physiology and mechanisms underlying BOLD remain largely unknown due to its highly convoluted nature. To address these limitations, we developed a hybrid system for concurrent optoacoustic and magnetic resonance imaging of TUS (OMRITUS) to comprehensively characterize the hemodynamic changes in murine brains. Our findings reveal paradoxical negative BOLD signals in the activated cortical regions, coupled with increased total hemoglobin levels simultaneously monitored with optoacoustic tomography. Multispectral optoacoustic readings further demonstrated a stronger increase in deoxygenated versus oxygenated hemoglobin, suggesting a potential molecular basis for the negative BOLD responses. OMRITUS enables the study of complex TUS-hemodynamic interactions, paving the way for precise neuromodulatory interventions.

Inflammation drives various diseases, including cardiovascular, neurodegenerative, and oncological disorders, by altering immune cell dynamics in hematopoietic niches. The bone marrow is the primary site for hematopoietic stem and progenitor cell activity. Here, we present a novel, noninvasive approach using multispectral optoacoustic tomography (MSOT) to track oxygenation dynamics in the murine calvarial bone marrow during acute systemic inflammation induced by lipopolysaccharide (LPS). Our MSOT system provided real-time, label-free imaging of hemoglobin oxygen saturation (sO₂), revealing significant reductions in sO₂ levels in lipopolysaccharide-treated mice, indicative of increased oxygen consumption. Co-registration with microCT enabled precise vascular mapping. Hypoxia was confirmed by ex vivo Pimonidazole staining and optical imaging and was associated with elevated neutrophil counts and enhanced hematopoietic activation. These findings demonstrate MSOT's potential for noninvasive imaging of marrow oxygenation, offering insights into inflammation-driven hematopoietic activation and supporting the development of therapies targeting oxygen-sensitive pathways.