Super-Resolution Ultrasound Localization Microscopy Using High-Frequency Ultrasound to Measure Ocular Perfusion Velocity in the Rat Eye

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

Diabetic retinopathy screenings in West Virginia: an assessment of teleophthalmology implementation

BACKGROUND

The prevalence of diabetes in the state of West Virginia (WV) is amongst the highest in the United States, making diabetic retinopathy (DR) and diabetic macular edema (DME) a major epidemiological concern within the state. Several challenges exist regarding access to eye care specialists for DR screening in this rural population. A statewide teleophthalmology program has been implemented. We analyzed real-world data acquired via these systems to explore the concordance between image findings and subsequent comprehensive eye exams and explore the impact of age on image gradeability and patient distance from the West Virginia University (WVU) Eye Institute on follow-up.

METHODS

Nonmydriatic fundus images of diabetic eyes acquired at primary care clinics throughout WV were reviewed by retina specialists at the WVU Eye Institute. Analysis included the concordance between image interpretations and dilated examination findings, hemoglobin A1c (HbA1c) levels and DR presence, image gradeability and patient age, and distance from the WVU Eye Institute and follow-up compliance.

RESULTS

From the 5,512 fundus images attempted, we found that 4,267 (77.41%) were deemed gradable.  Out of the 289 patients whose image results suggested DR, 152 patients (52.6%) followed up with comprehensive eye exams-finding 101 of these patients to truly have DR/DME and allowing us to determine a positive predictive value of 66.4%. Patients within the HbA1c range of 9.1-14.0% demonstrated significantly greater prevalence of DR/DME (p < 0.01).  We also found a statistically significant decrease in image gradeability with increased age.  When considering distance from the WVU Eye Institute, it was found that patients who resided within 25 miles demonstrated significantly greater compliance to follow-up (60% versus 43%, p < 0.01).

CONCLUSIONS

The statewide implementation of a telemedicine program intended to tackle the growing burden of DR in WV appears to successfully bring concerning patient cases to the forefront of provider attention.  Teleophthalmology addresses the unique rural challenges of WV, but there is suboptimal compliance to essential follow-up with comprehensive eye exams. Obstacles remain to be addressed if these systems are to effectively improve outcomes in DR/DME patients and diabetic patients at risk of developing these sight-threatening pathologies.

Iris Chafing Syndrome Secondary to Iridociliary Adhesions in a Patient with a Single-Piece Acrylic Intraocular Lens: Case Report

Introduction

We present a unique case of iris chafing syndrome in a patient with a complex ophthalmologic history after successful placement of a single-piece in-the-bag intraocular lens (IOL) in an eye with healthy zonular support.

Case Presentation

A patient with a previous history of multiple retinal surgeries presented with pain and elevated intraocular pressure (IOP) secondary to retained viscoelastic material in the anterior chamber. Following removal of the viscoelastic material in clinic, the patient underwent a combined cataract and glaucoma surgery. Subsequently, the patient developed signs and symptoms of iris chafing syndrome. Anterior segment imaging revealed the cause to be iridociliary adhesion causing an elimination of the sulcus space. Iris chafing syndrome was suspected when the patient presented post-operatively with changes in vision and anterior chamber inflammation. New iris transillumination defects present at the edge of the optic and haptic of the 1-piece lens helped confirm the diagnosis of UGH. Upon further investigation with gonioscopy, ultrasound biomicroscopy and anterior segment optical coherence tomography, it was determined that the patient had iridociliary adhesions. These adhesions eliminated the sulcus space, which resulted in iris chafing. The patient opted for conservative medical management. Best-corrected distance visual acuity remained stable at 20/100 and IOP remained well controlled.

Conclusion

A complex ocular history of multiple retinal surgeries and retained viscoelastic material in the anterior chamber resulted in adhesions of the ciliary processes to the iris, leading to UGH syndrome in a patient with an otherwise unremarkable placement of a single-piece in-the-bag IOL.

Evaluation of machine learning algorithms for trabeculectomy outcome prediction in patients with glaucoma

The purpose of this study was to evaluate the performance of machine learning algorithms to predict trabeculectomy surgical outcomes. Preoperative systemic, demographic and ocular data from consecutive trabeculectomy surgeries from a single academic institution between January 2014 and December 2018 were incorporated into models using random forest, support vector machine, artificial neural networks and multivariable logistic regression. Mean area under the receiver operating characteristic curve (AUC) and accuracy were used to evaluate the discrimination of each model to predict complete success of trabeculectomy surgery at 1 year. The top performing model was optimized using recursive feature selection and hyperparameter tuning. Calibration and net benefit of the final models were assessed. Among the 230 trabeculectomy surgeries performed on 184 patients, 104 (45.2%) were classified as complete success. Random forest was found to be the top performing model with an accuracy of 0.68 and AUC of 0.74 using 5-fold cross-validation to evaluate the final optimized model. These results provide evidence that machine learning models offer value in predicting trabeculectomy outcomes in patients with refractory glaucoma.

Effect of Wetting and Dewetting Dynamics on Atomic Force Microscopy Measurements

Water bridge dynamics between an atomic force microscopy (AFM) tip and a flat substrate is studied by using a multibody dissipative particle dynamics (MDPD) model. First, the numerical model is validated by comparing the present results of droplet contact angles and liquid bridges with those reported in the literature. Then, the ability of MDPD to capture the meniscus shape and behavior for different operating conditions and geometric parameters is examined for both static and dynamic cases. Hence, several parametric studies and analyses of the AFM tip configuration and its operating conditions are reported. It is found that a critical capillary number of about 0.001 is calculated based on 5% change on the force measurements between the static and dynamic results. It is also demonstrated that the hysteresis behavior in the capillary force exerted on the AFM tip can be successfully predicted by using the MDPD model when the tip approaches or retracts from the substrate. Moreover, there is an excellent agreement in the results of breakup distance for different water bridge volumes between the predictions of the MDPD model and the theory. Also, the hysteresis of capillary force exerted on an AFM tip composed of multibody design is studied. The prediction on the transition of the capillary force vs distance between the AFM tip and the substrate is in good agreement with the experimental results. Therefore, we demonstrate a validated MDPD model which can successfully capture liquid bridge dynamics. This model can be used as a powerful design tool for meniscus manipulation technology, such as dip-pen nanolithography, as well as for studying dynamic, e.g., tapping mode AFM tip, interactions with a liquid bridge.

A case of indirect superior rectus pulled-in-two syndrome during superior oblique tenectomy

A 67-year-old white man with a history of right orbital trauma and restrictive strabismus underwent right superior oblique tenectomy for superior oblique restriction. Bleeding was noted from the superior rectus intraoperatively, despite the fact that the muscle was neither exposed nor hooked for the procedure. Subsequent exploration of the muscle revealed a full-width tear across the superior rectus muscle approximately 5 mm posterior to its insertion. The remaining residual distal muscle was removed from the insertion and the proximal end of the torn superior rectus muscle was identified and reattached to the insertion. We postulate that shearing forces exerted by a taut superior oblique tendon were sufficient to tear the overlying superior rectus muscle.

The effects of decorin and HGF-primed vocal fold fibroblasts in vitro and ex vivo in a porcine model of vocal fold scarring

OBJECTIVES

Vocal fold injury can be irreversible, leading to vocal fold scarring, with permanent functional effects and no optimal treatment. A porcine model of vocal fold scarring was used to test effects of decorin and primed vocal fold fibroblasts in vitro using a cell migration assay and immunoblotting, and by using functional measurements of porcine larynges and excised porcine vocal folds.

METHODS

In vitro: primary pig vocal fold fibroblasts (PVFFs) were subjected to cell migration assays (scratch) and treated with decorin 20 μg/mL, hepatocyte growth factor (HGF) 200 ng/mL, epidermal growth factor (EGF) 1 nM, or transforming growth factor-β1 10 ng/mL. Cells also underwent decorin dose response testing. Scratch assays were analyzed in MetaMorph® Imaging; cell lysates were processed for MMP-8 and type I collagen content. Eleven pigs underwent unilateral vocal fold stripping procedures. At day 3 postoperatively, subjects underwent superficial injection into the affected vocal fold either with decorin 20 μg/mL or 1 × 10(6) HGF-primed fibroblasts. Larynges were harvested and either used for ex vivo laryngeal testing or for rheological testing.

RESULTS

Scratch assay indicated significantly reduced cell migration in PVFFs treated with decorin or HGF. MMP-8 production was increased (P <0.01) and collagen was decreased in cells treated with decorin at increasing doses. Viscoelastic measurements suggested somewhat increased stiffness for decorin treated samples. Ex vivo aerodynamic testing suggested improved vocal efficiency scores in decorin-treated larynges.

CONCLUSIONS

Decorin has a noticeable effect on PVFF migration in vitro and appears to increase vocal fold stiffness but either does not change or slightly increases vocal efficiency.

The hematology of bacterial infections in premature infants

A series of premature infants was studied for the presence of bacterial infection. On the basis of clinical evidence and bacteriological studies, they were divided into three groups in which sepsis was considered to be proven, possible, or unlikely. Band neutrophil counts were elevated most frequently in the "sepsis-proven" group and the elevation occurred usually within 24 hours of onset of signs of disease. Qualitative changes in neutrophils (Döhle bodies, toxic granulation, and vacuolization) were more frequent in the sepsis-proven group and, together with the band count, provided valuable techniques for the diagnosis of bacterial infections. Thrombocytopenia occurred frequently in the sepsis-proven group and seemed to result from increased utilization or destruction of platelets rather than failure of production. In such cases, evidence of intravascular coagulation was minimal and it was concluded that thrombocytopenia had resulted from a direct effect of the bacteria or its products on platelets and/or endothelium.