Detection of metallic ocular foreign bodies with handheld sonography in a porcine model

Online Learning versus Hands-On Learning of Basic Ocular Ultrasound Skills: A Randomized Controlled Non-Inferiority Trial

Background and objectives: Ocular ultrasound is a core application of point-of-care ultrasound (POCUS) to assist physicians in promptly identifying various ocular diseases at the bedside; however, hands-on POCUS training is challenging during a pandemic. Materials and Methods: A randomized controlled non-inferiority trial was conducted in an academic emergency department from October 2020 to April 2021. Thirty-two participants were randomly assigned to one of two groups. Group H (hands-on learning group) participated individually in a hands-on session with a standardized patient for 30 min, whereas Group O (online learning group) learned training materials and video clips for 20 min. They scanned four eyeballs of two standardized patients sequentially following the ocular POCUS scan protocol. Repeated POCUS scans were performed 2 weeks later to assess skill maintenance. Both groups completed the pre- and post-surveys and knowledge tests. Two emergency medicine faculty members blindly evaluated the data and assigned a score of 0−25. The primary endpoint was the initial total score of scan quality evaluated using non-inferiority analysis (generalized estimating equation). The secondary endpoints were total scores for scan quality after 2 weeks, scan time, and knowledge test scores. Results: The least squares means of the total scores were 21.7 (0.35) for Group O and 21.3 (0.25) for Group H, and the lower bound of the 95% confidence interval (CI) was greater than the non-inferiority margin of minus 2 (95% CI: −0.48−1.17). The second scan scores were not significantly different from those of the first scan. The groups did not differ in scanning time or knowledge test results; however, Group H showed higher subjective satisfaction with the training method (p < 0.001). Conclusion: This study showed that basic online ocular ultrasound education was not inferior to hands-on education, suggesting that it could be a useful educational approach in the pandemic era.

Use of Ophthalmic Sonography to Evaluate for Intraocular Foreign Body in Both Outpatient and Emergency Department/Urgent Care Patients

Intraocular foreign bodies (IOFB) present differently depending on the type of material (wood, glass, metal) for the IOFB, extent of the injury, and location of the injury. IOFB and the injury can cause a perforation or penetration of the globe which can require more extensive treatment including surgery. Proper evaluation of the IOFB and injury can help to determine extent of the injury, the prognosis of the vision, and health of the eye before and after treatment but may be difficult for the physician depending on the view of the posterior chamber being compromised by media or simply by patient sensitivity. The extent of the injury may also prevent proper evaluation due to swelling, lacerations on the lids, or pain. Proper ophthalmic sonography can provide a quick evaluation of the globe for any IOFB in both the outpatient setting as well as emergency department setting. Evaluation via sonography may allow the physician to accurately diagnose and properly treat the patient to help restore and prevent further loss of vision.

Photoacoustic Imaging and Sensing: A New Way to See the Eye

Purpose: Photoacoustics (optoacoustics) is a hybrid technology utilizing light excitation of acoustic responses in targets of interest. It has found numerous applications in biomedicine, including eye research, because of its ability to report both morphological and functional data about the interrogated tissue. This presentation will give an overview of current applications. Methods: Wavelength-dependent absorption of light in a tissue chromophore causes local heating, leading to a thermoelastic expansion-contraction cycle. If nanosecond pulses of light are used to excite this process, the resulting pressure wave is an ultrasound signal propagating through the tissue and detectable at the tissue surface. This is highly advantageous because of the known properties of ultrasound propagation in tissue and the ability to use standard, medical ultrasound equipment for detection. The time of arrival and amplitude of ultrasound signals provide information about the location and nature of the absorber. Results: Due to the wavelength dependence of the photoacoustic response, functional and physiological applications are possible. For example, retinal oximetry can be determined from the different optical absorption properties of oxy- and deoxyhemoglobin. Multispectral imaging of the posterior segment can identify pigments such as melanin or lipofuscin or the nature of foreign bodies. The technique can be combined with other imaging modalities such as ultrasound and optical coherence tomography to produce high-resolution images of retinal structures along with functional information. Conclusion: Photoacoustic technology is a powerful noninvasive tool for ocular research and to study ocular morphology, fundamental physiological parameters, cellular responses, and molecular expression.

Emergency Ocular Ultrasound - Common Traumatic and Non-Traumatic Emergencies Diagnosed with Bedside Ultrasound

Point-of-care ocular ultrasound (POCOUS) in the ambulatory and critical care setting has become an invaluable diagnostic tool for patients presenting with traumatic or atraumatic vision and ocular complaints. Sonographic bedside evaluation is intuitive and easy to perform and can accurately diagnose a variety of pathologies. These include detachment or hemorrhage of the retina or vitreous, lens dislocation, retrobulbar hematoma or air, as well as ocular foreign bodies, infections, tumors, and increased optic nerve sheath diameter that can be assessed in the setting of suspected increased intracranial pressure. The ocular anatomy is easy to visualize with sonography, as the eye is a superficial structure filled with fluid. Over the last two decades, a large number of scientific publications have documented that POCOUS in emergent or critical care settings is an accurate diagnostic tool and expands and improves emergency diagnosis and management. This article will review POCOUS exam techniques as well as normal sonographic findings and common pathologies.

Ultrasound in Austere Environments

Ultrasonography is a noninvasive, reliable, repeatable, and inexpensive technology that has dramatically changed the practice of medicine. The clinical use of portable ultrasound devices has grown tremendously over the last 10 years in the fields of intensive care, emergency medicine, and anesthesiology. In this review we present the various ways that handheld portable ultrasound devices can be used in austere environments. The purpose of this review is to consider the wide-ranging applications for providers going into the austere environment, which include pulmonary, ocular, vascular, and trauma evaluations, the postdisaster setting, and the role of ultrasonography in tropical diseases. This review is not meant to be a comprehensive how-to guide for each study type, but an overview of some of the more common wilderness applications. This review also focuses on the limitation of each study type. The goal is to help wilderness medicine providers feel more comfortable incorporating ultrasonography as part of their tool kit when heading into austere environments.

Detection of Intraocular Foreign Body with Ultrasound

Objective

To evaluate the accuracy of emergency ultrasound in the diagnosis of varying location, size, and composition (metal, plastic, wooden) of intraocular foreign body in a sheep model.

Methods

This was an experimental study using freshly harvested adult articulated sheep eyes. A total of 8 fresh sheep heads were used. Two of the eyes were randomised to include more than one foreign body, the first one with three different sizes of metallic fragments of 0.46×0.81×0.46 mm, 0.46×0.93×0.46 mm, 0.46×0.82×0.46 mm and the second eye containing plastic fragments with a size of 0.97×0.67×0.67 mm and 1.00×0.67×0.67 mm. The wooden fragment was 0.52×0.76 mm and the metallic fragment was 0.45×0.46×0.46 mm. Half of the eyes were chosen as the control group and the sclera of the control group was also punctured. A total of 5 residents, from different postgraduate years, and 2 attending physicians participated in the study.

Results

Regardless of the nature and number of foreign bodies, correct identification of the intraocular foreign body was achieved in 44 of the 56 assessments. The overall sensitivity was 78% (95% confidence interval [CI], 65%-87%), and the overall specificity was 30% (95% CI, 19%-44%). Positive and negative predictive values were 53% and 58% respectively.

Conclusion

The dynamic nature of the ultrasound examination may be helpful in localising and determining the size and composition of the foreign body, but if the intraocular foreign body is a concern and the ultrasound and physical examination are negative, another imaging modality, such as a computed tomography scan of the globe, should be obtained. (Hong Kong j.emerg.med. 2014;21:88-91)

Sonography for determining the optic nerve sheath diameter with increasing intracranial pressure in a porcine model

OBJECTIVES

This study investigated whether it is feasible to use sonography to monitor changes in the optic nerve sheath diameter in a porcine model.

METHODS

A fiber-optic intracranial pressure transducer was surgically placed through the frontal sinus directly into the brain parenchyma of adult Yorkshire pigs (n = 5). A second bolt was placed on the contralateral side for intraparenchymal fluid infusion. Optic nerve sheath diameter measurements were acquired by each of 2 ultrasound operators around the leading edge of the nerve, 3 to 5 mm distal from the origin of the optic nerve. To induce a change in diameter, intracranial pressure was manipulated by injecting normal saline into the intraparenchymal infusion catheter located in the symmetric contralateral position as the pressure-monitoring probe.

RESULTS

Data from 1 pig were unusable because of a cerebrospinal fluid leak into the sinus and orbital fissure. Saline aliquots of 1 to 10 mL were able to generate intracranial pressures typically starting from 10 to 15 mm Hg and increasing to 75 to 90 mm Hg, which eventually evoked a Cushing response. Fluid injection was controlled to increase pressures by 60 mm Hg over a 15- to 20-minute period. Regression analysis of all animals showed that the optic nerve sheath diameter increased by 0.0034 mm/mm Hg of intracranial pressure; however, this slope ranged from 0.0025 to 0.0046, depending on the animal measured. There was no discernible effect of the ultrasound operator on the slope; however, measurements made by 1 operator were consistently higher than the others by about 8% of the overall diameter range.

CONCLUSIONS

These results suggest that the use of the optic nerve sheath diameter to noninvasively confirm acute changes in intracranial pressure over 1 hour is feasible in a porcine model. We recommend that this method be validated in humans using direct intracranial pressure measurement where possible to confirm it as a screening tool for acute and chronically increased diameters secondary to elevated pressure in clinical settings.

Emergency medicine residents’ ability to identify ocular pathology in a live porcine model

Objective

To evaluate emergency medicine residents’ ability to detect ocular pathology using portable ultrasound (US) in a live porcine model.

Methods

This was a pilot study to evaluate emergency medicine residents’ ability to accurately diagnose ocular pathology in a porcine model using handheld US. Subjects were emergency medicine residents who had all undergone a 2-day US course as part of their emergency medicine orientation month and had reviewed an 1 h self-instruction computer tutorial on ocular US prior to the study. Vitreous hemorrhages, retro-orbital hematomas and intraocular foreign bodies were simulated by placement of porcine blood and metallic objects under ultrasound guidance out of view of the subject population. Residents then performed self-directed US of two eyes each and were asked to comment on any pathology observed. Some residents were also asked to identify central retinal artery flow. Time required for each scan was noted.

Results

A total of 36 residents scanned 6 porcine eyes over 2 lab iterations. EM residents were able to detect a significant abnormality greater than 93% of the time. Vitreous hemorrhages were the most detectable injuries with 95% accuracy. A significant abnormality was detected in the models with intraocular foreign bodies 97% of the time with a clear diagnosis of foreign body noted in 73% of the cases. Retro-orbital hematoma was the most difficult to detect with 62% accuracy. The average time taken for scanning two eyes was 7 min 38 s. Central retinal artery flow was detected in 100% of the 26 cases in which this was documented. Accuracy of diagnoses was similar across levels of EM training.

Conclusion

EM residents can accurately diagnose significant ocular pathology using handheld US in a live porcine model.

Intralenticular intraocular foreign body after stone impact: CT and US findings

INTRODUCTION

Intraocular foreign body (IOFB) is a relatively common entity in emergency departments worldwide. Appropriate ocular assessment is mandatory if an intraocular foreign body is suspected because it is associated with an increased risk of endophtalmitis and a wide range of complications including hyphaema, cataract, vitreous hemorrhage, and retinal tears and detachment.

CASE REPORT

We present a case of intralenticular intraocular foreign body after stone impact.

DISCUSSION

Ultrasonography (US) and computed tomography (CT) show an accurate location of the foreign body inside the lens. This finding enabled the surgeon to perform a phacoemulsification lens extraction with removal of the foreign body, the optimal method of removing intralenticular IOFB. To our knowledge, this is the first US and CT imaging report.