Name: optic nerve sheath point of care ultrasound: image acquisition
Uploaded: 2023-08-18T13:50:00.000+00:00
Duration: 6 min 9 s
Description: Watch this Scientific Journal Video about Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition at JoVE.com

This effort was partially sponsored by the US Government under Other Transactions (W81XWH-15-9-0001/W81XWH-19-9-0015) and the Medical Technology Enterprise Consortium (MTEC) under 19-08-MuLTI-0079.

This procedure is in accordance with the ethical standards of the institutional committee on human experimentation and with the Helsinki Declaration of 1975. Ultrasound is considered minimal risk procedure, so written consent from the patient is not required.
1. Probe selection
NOTE: ONSD POCUS can be performed with a multitude of different transducers. To evaluate abnormalities in suspected cases of increased ICP, choose a linear high-frequency (5-14 MHz) probe to evaluate ONSD. The probe nomenclature varies by manufacturer; however, the linear probe will be flat and usually have an L in the probe name. Choose a probe 37 mm long or smaller. Almost any probe size can be used to obtain transverse images of the optic nerve. However, sagittal views are difficult to obtain with larger probe sizes. Using a probe 37 mm long consistently allows both transverse and sagittal images in adults, while a 55 mm probe can be used in some adults but not all. Some representative probe heads are shown in Figure 1.
<ol>
	<li>Press the Select Scanner tab</li>
	<li>Choose a linear high-frequency probe. On this machine, choose L7HD.</li>
	<li>Allow the probe to connect wirelessly</li>
</ol>
2. Ultrasound setup
<ol>
	<li>Go to presets, and choose Ocular if available. If not, choose Small Parts.</li>
	<li>Check the frequency. With the scanner used in this demonstration, the frequency is visible on the lower-left side of the screen next to the frame rate. A frequency of 10 MHz can be found with most bedside linear scanners in an intensive care unit, but frequencies from 5-14 MHz can be used.</li>
	<li>Set the depth to 4 cm for most adult patients. The depth is seen on the right side of the image and can be adjusted on this model by scrolling up or down with a finger on the touchscreen.</li>
	<li>Set the focal zone to 2.5 cm. This is noted by the arrow on the depth ruler.</li>
	<li>Check the Mechanical Index (MI) and Thermal Index (TI). If using an ophthalmic setting, these will display on the image. Ensure to keep the MI &#60; 0.23 and the TI &#60; 1.0. Further, ensure that the acoustic output (AO) is in the range of 20%-25% power. 
	NOTE: One key difference from cardiac or abdominal scanning is the lower power that should be used in ophthalmic scanning. While little attention is paid to MI and TI in most point-of-care ultrasound applications, it is important in ophthalmic imaging. To avoid damage to the delicate ocular structures, the MI and TI must be kept below the levels described above. If an ophthalmic preset is available, this will be the default. If it is not available on the scanner, the small parts setting can be used.</li>
	<li>Set the length of the video capture to at least 4 s.</li>
	<li>Set the mode to B-mode, 2-dimensional greyscale ultrasound. 
	&#8203;NOTE: Although A-mode (1-dimensional) scans are traditionally used for ocular scans involving melanoma and retinal detachments, the measurement of the ONSD is best done in B-mode. Additionally, the motion (M) mode is not valuable for measuring the ONSD.</li>
</ol>
3. Patient selection
<ol>
	<li>Inclusion criteria: Include patients with a concern for intracranial hypertension, such as severe traumatic brain injury with a Glasgow Coma Score of less than 8 or other signs of traumatic brain injury.</li>
	<li>Exclusion criteria: The only real exclusion criterion is ocular trauma. Exclude patients with ocular trauma.</li>
</ol>
4. Patient positioning
<ol>
	<li>Position the patient in the default position with the head of the bed at 30&#176;, since most patients are in the ICU. However, the exam can be performed with the patient sitting up or supine. 
	&#8203;NOTE: In the ophthalmology office, when patients are being scanned for other indications, the patient is asked to move their eye to straighten out the optic nerve so that it heads directly posterior from the eye. However, for the indication of severe traumatic brain injury, the patient will not be able to cooperate.</li>
</ol>
5. Scanning technique
<ol>
	<li>Apply the ultrasound gel to cover the length of the transducer, which is usually several milliliters.</li>
	<li>Close the eyelid of the patient, and use a transparent film dressing to hold the eyelid closed to prevent corneal abrasion or other damage to the eye during the exam. See Figure 2. 
	NOTE: In an emergency, gel can be applied directly to the eyelid while it is held closed, but this should be avoided when possible.</li>
	<li>Position the probe for the transverse view. See Figure 3. Center the probe over the pupil, and sweep or fan the probe over the eye to bring the nerve into view. The globe is very hypoechoic with a distinct transition visible at the back of the eye. The optic nerve will be visible as a linear hypoechoic structure posterior to the globe. The sheath will be visible as a hyperechoic boundary of the nerve. 
	NOTE: Commonly, the probe will need to be angled about 10&#176;-15&#176; medially to find where the optic nerve contacts the back of the globe.</li>
	<li>Obtain an adequate view.
	<ol>
		<li>Attempt to obtain a view with the nerve headed directly posterior from the back of the eye. This may not be possible in patients unable to cooperate in terms of adjusting the position of their eye.</li>
		<li>Ensure that the nerve is visible 3 mm posterior to the globe.</li>
	</ol>
	</li>
	<li>Once an adequate view is acquired, take a video.</li>
	<li>Scroll back on the video until the maximum diameter of the optic nerve sheath is seen.</li>
	<li>Alternatively, press the Freeze button when at the maximum ONSD, and use the review slider to ensure that the maximum ONSD has been captured. The Freeze button looks like a snowflake.</li>
	<li>Measure the nerve.
	<ol>
		<li>Press the Annotation button. Choose the Distance caliper. Using the caliper function, measure 3 mm posterior from where the optic nerve attaches to the retina (Figure 4).</li>
		<li>Press the Distance caliper again. Measure the outermost lateral borders of the optic nerve sheath. The sheath is what tends to increase in size with increasing intracranial pressure, so measuring the outer diameter of the sheath is important.</li>
		<li>Save the annotated image by pressing the Save button on the bottom right of the screen. This button looks like a camera for this brand.</li>
	</ol>
	</li>
	<li>Obtain a sagittal view.
	<ol>
		<li>Center the probe on the eye, as seen in Figure 3B. 
		NOTE: The added benefits of measuring in the sagittal plane are unclear, but it is easy to do and has a negligible risk to the patient, so it is recommended to obtain the maximum information to guide clinical decision-making if possible. Some authors9 average the transverse and sagittal measurements to minimize the impact of technique variability.</li>
		<li>Use the same steps as for the transverse view, specifically steps 5.3-5.8, to obtain an adequate image and measure the ONSD. It may not be possible to obtain a sagittal view if the probe is greater than 37 mm in length.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Hansen, H. C., Helmke, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validation+of+the+optic+nerve+sheath+response+to+changing+cerebrospinal+fluid+pressure:+ultrasound+findings+during+intrathecal+infusion+tests.">Validation of the optic nerve sheath response to changing cerebrospinal fluid pressure: ultrasound findings during intrathecal infusion tests.</a> Journal of Neurosurgery. 87 (1), 34-40 (1997).</li><li>Bauerle, J., Lochner, P., Kaps, M., Nedelmann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-+and+interobsever+reliability+of+sonographic+assessment+of+the+optic+nerve+sheath+diameter+in+healthy+adults.">Intra- and interobsever reliability of sonographic assessment of the optic nerve sheath diameter in healthy adults.</a> Journal of Neuroimaging. 22 (1), 42-45 (2012).</li><li>Lochner, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-+and+interobserver+reliability+of+transorbital+sonographic+assessment+of+the+optic+nerve+sheath+diameter+and+optic+nerve+diameter+in+healthy+adults.">Intra- and interobserver reliability of transorbital sonographic assessment of the optic nerve sheath diameter and optic nerve diameter in healthy adults.</a> Journal of Ultrasound. 19 (1), 41-45 (2016).</li><li>Shokoohi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+nerve+sheath+diameter+measured+by+point-of-care+ultrasound+and+MRI.">Optic nerve sheath diameter measured by point-of-care ultrasound and MRI.</a> Journal of Neuroimaging. 30 (6), 793-799 (2020).</li><li>Montorfano, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mean+value+of+B-mode+optic+nerve+sheath+diameter+as+an+indicator+of+increased+intracranial+pressure:+A+systematic+review+and+meta-analysis.">Mean value of B-mode optic nerve sheath diameter as an indicator of increased intracranial pressure: A systematic review and meta-analysis.</a> The Ultrasound Journal. 13 (1), 35 (2021).</li><li>Jeon, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+optic+nerve+sheath+diameter+with+directly+measured+intracranial+pressure+in+Korean+adults+using+bedside+ultrasonography.">Correlation of optic nerve sheath diameter with directly measured intracranial pressure in Korean adults using bedside ultrasonography.</a> PLoS One. 12 (9), e0183170 (2017).</li><li>Maissan, I. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonographic+measured+optic+nerve+sheath+diameter+as+an+accurate+and+quick+monitor+for+changes+in+intracranial+pressure.">Ultrasonographic measured optic nerve sheath diameter as an accurate and quick monitor for changes in intracranial pressure.</a> Journal of Neurosurgery. 123 (3), 743-747 (2015).</li><li>Sedwick, L. A., Burde, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unilateral+and+asymmetric+optic+disk+swelling+with+intracranial+abnormalities.">Unilateral and asymmetric optic disk swelling with intracranial abnormalities.</a> American Journal of Ophthalmology. 96 (4), 484-487 (1983).</li><li>Chen, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonic+measurement+of+optic+nerve+sheath+diameter:+a+non-invasive+surrogate+approach+for+dynamic,+real-time+evaluation+of+intracranial+pressure.">Ultrasonic measurement of optic nerve sheath diameter: a non-invasive surrogate approach for dynamic, real-time evaluation of intracranial pressure.</a> British Journal of Ophthalmology. 103 (4), 437-441 (2019).</li><li>Copetti, R., Cattarossi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+nerve+ultrasound:+artifacts+and+real+images.">Optic nerve ultrasound: artifacts and real images.</a> Intensive Care Medicine. 35 (8), 1488-1489 (2009).</li><li>Aspide, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+proposal+for+a+new+protocol+for+sonographic+assessment+of+the+optic+nerve+sheath+diameter:+The+CLOSED+protocol.">A proposal for a new protocol for sonographic assessment of the optic nerve sheath diameter: The CLOSED protocol.</a> Neurocrit Care. 32 (1), 327-332 (2020).</li><li>Robba, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+non-invasive+measurement+of+intracranial+pressure+in+neurointensive+care:+A+prospective+observational+study.">Ultrasound non-invasive measurement of intracranial pressure in neurointensive care: A prospective observational study.</a> PLoS Medicine. 14 (7), e1002356 (2017).</li><li>Anas, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transorbital+sonographic+measurement+of+normal+optic+sheath+nerve+diameter+in+Nigerian+adult+population.">Transorbital sonographic measurement of normal optic sheath nerve diameter in Nigerian adult population.</a> The Malaysian Journal of Medical Sciences. 21 (5), 24-29 (2014).</li></ol>

The authors have nothing to disclose.

The most critical steps of this protocol are ensuring the correct settings are used, such as ophthalmic or small parts, to minimize the energy transmitted to the eye. Additionally, ensuring that the optic nerve and not a blooming artifact is being measured is important.
Within diagnostic POCUS, the evaluation of the ONSD is well-suited to investigating patients with traumatic brain injury to evaluate if there is increased ICP. Although invasive intracranial monitoring remains the gold standard for the accurate measurement of ICP, ONSD POCUS serves as an excellent non-invasive alternative for assessing the presence and magnitude of increased ICP. In a previous study, in terms of the diagnostic performance, ONSD demonstrated a superior correlation with invasive measurements in comparison to other ultrasound-based techniques, such as arterial and venous transcranial Doppler12. While most patients with severe TBI will have a monitor placed, POCUS can be especially useful in emergent decision-making when there is not an intracranial monitor in place, such as in the prehospital setting, emergency room, resource-limited institutions, or during an unexpected change in mental status. However, ONSD POCUS has some limitations. First, the inability to follow specific commands (e.g., adjusting their gaze to assist in sheath identification) in patients suffering from a severe TBI may limit the acquisition of an adequate image.
Another limitation of the technique is the variation in ONSD cutoff values, which greatly affects the diagnosis of increased ICP. The cut-off values vary greatly9,10,11,12and can inhibit the diagnostic accuracy of ONSD POCUS measurements. Different cut-off values may exist due to body habitus, age, sex, and, in some instances, ethnicity13. The lack of data for these individual groups hampers the tool&#39;s overall effectiveness but is not enough to totally impair its usability.
Finally, a surmountable limitation of ONSD POCUS is the lack of proficiency and inter-examination variability. Like any ultrasound technique, POCUS is very operator-dependent. One must know how to acquire clinically valuable images to make appropriate decisions. A thorough understanding of the potential artifacts visualized on ocular ultrasound will improve the accuracy. The standardization of ONSD POCUS practice and the establishment of educational curriculums have been highlighted as possible solutions to this limitation. This is a much-needed step to guide academic standards at the national and international levels and to continue to develop this essential diagnostic/procedural tool.

The goal of this protocol is to allow bedside providers to rapidly evaluate patients for intracranial hypertension in a non-invasive fashion using point-of-care ultrasound. In recent years, bedside decision-making and treatment have been augmented by the emergence of point-of-care ultrasound (POCUS). POCUS involves the use of ultrasound for diagnostic or procedural guidance by a patient&#39;s primary treatment provider. This article focuses on the diagnostic POCUS of the optic nerve sheath.
The rationale behind this technique is that the optic nerve and sheath communicate with the central nervous system. Specifically, the subarachnoid space extends from inside the skull around the optic nerve. Thus, when the intracranial pressure increases, the optic nerve sheath increases in size. It has been shown in studies with magnetic resonance imaging (MRI) and computed tomography (CT) that the optic nerve does not change in size with increased ICP, but the optic nerve sheath does. The vitreous of the eye provides excellent transmission of sound waves, resulting in the optic nerve being clearly visible as a hypoechoic structure inserted on the posterior eye, with the sheath visible around it. For these reasons, ultrasound of the optic nerve sheath has been used to detect elevated ICP, thus allowing the diagnosis of potentially life-threatening instances of increased ICP1.
However, despite its clinical significance, the proficiency of physicians in using ONSD POCUS is variable2,3, which limits the appropriate use of this modality4. This study aims to describe a time-efficient yet thorough image acquisition protocol for diagnostic ONSD POCUS and to illustrate the abnormal findings commonly found in clinical practice. Multiple imaging protocols have been described in the literature, and they present variations in the structural interpretation, ultrasound settings, marker placement, and scan technique5. Different marker points have varying sensitivity to changes in ICP, and the placement affects the ability to distinguish between patients with normal and high ICP. For these reasons, in this paper, we outline a standard technique to obtain optic nerve sheath images and measure them consistently.
Differences in the measurement location and technique have resulted in widely different thresholds of what is considered to be an abnormal optic nerve sheath5,6. In a recent meta-analysis, the average ONSD for patients without intracranial hypertension was 4.1 mm, and the average ONSD for those with increased ICP was 5.6 mm. A generally accepted threshold for a dilated ONSD is 5.5 mm, but a change in ONSD from a normal baseline is much more predictive if a baseline is available. In the context of severe TBI, the ONSD of both eyes seems to change together7.&#160;There are some individual cases of increased ONSD on one side, but this is rare8.
There are additional challenges in the measurement of ONSD in the severe traumatic brain injury (TBI) population. Patients with severe TBI (defined as having a Glasgow coma score of &#60;8) are not alert enough to follow commands. This means a different approach is required to measure the nerve in this population compared to in patients being evaluated in an ophthalmology office in an elective fashion for neuritis. An A-scan can be used to measure the optic nerve in a cooperative patient that can hold their eye still for a length of time, but this is not a useful technique in TBI patients, so a B-scan is the standard technique (see step 2.7 below).
The use of this method and protocol should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place. Specific patient populations that may benefit are trauma patients with a clinical concern for traumatic brain injury in the prehospital or emergency room setting. Additionally, patients in the ICU with a sudden change in neurologic status are good candidates for ONSD POCUS.

<table><tbody><tr><td>Butterfly iQ+ with USB-C 2.0</td><td>Butterfly</td><td>n/a</td><td>Used to obtain one of the images</td></tr><tr><td>Clarius L7HD Portable Ultrasound Machine</td><td>Clarius</td><td>n/a</td><td>Used to obtain one of the images</td></tr><tr><td>Ultrasound Gel</td><td>Parker</td><td>n/a</td><td>Used to obtain all images</td></tr><tr><td>Transparent dressing</td><td>3M</td><td>9534HP</td><td>Used to protect eye</td></tr></tbody></table>

optic nerve sheath point of care ultrasound: image acquisition

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter (ONSD). Diagnostic ultrasound of the ONSD to detect intracranial hypertension has traditionally faced many problems because of methodologic discrepancies. Due to inconsistencies in the measuring techniques, the potential for ONSD to become a non-invasive bedside monitoring tool for ICP has been hampered. However, establishing a transparent, consistent methodology for measuring the ONSD would support its use as a valid and reliable method of identifying intracranial hypertension. This is important as it has both high sensitivity and specificity in acute care settings. This narrative review describes ONSD POCUS image acquisition, including patient positioning, transducer selection, probe placement, the acquisition sequence, and image optimization. Further, visual aids are provided to assist in real-time during image acquisition. This method should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place.

There are several findings that can be seen on the POCUS of the optic nerve sheath and several pitfalls that can occur in the measurements. As can be seen in Figure 5, the nerve typically heads back from the eye at an angle when the eye is in a neutral position. In patients undergoing elective ultrasound of the eye for optic neuritis, for example, the patient is typically asked to move the eye and straighten the nerve to facilitate the measurement of the diameter along the axis of the nerve. Patients with concern for TBI will rarely be able to follow commands, so the transverse diameter of the nerve sheath will need to be measured at an angle.
Another potential pitfall that can occur is a measurement of the optic nerve instead of the sheath. If appropriate settings are not used, or a low-resolution probe is used, such as those driven on a USB cable, it can be difficult to see the sheath, as is demonstrated in Figure 6. In this figure, two images are shown of the same patient, one demonstrating the nerve sheath and another, which was performed with a low-resolution probe, in which only the nerve is visible. It is important that the nerve sheath can be seen and measured for accuracy. The optic nerve itself does not change substantially in size with elevated ICP, so measuring the nerve instead of its sheath may give a false low measurement.
There are also several artifacts that can interfere with measuring the ONSD. A blooming artifact can confound the measurements. This artifact is hypothesized to be an acoustic shadow caused by the lamina cribrosa, which can be larger than the ONSD10. An example can be seen in Figure 7, where two images from the same patient are seen, one showing the optic nerve sheath and one showing a blooming artifact that is much larger in size. It is important that the head of the nerve be visualized as a rounded-off hypoechoic structure as it inserts into the posterior eye. The blooming artifact will extend from the optic disk and will not have a rounded-off head. Some authors11 recommend the use of color Doppler to clarify the course of the nerve and differentiate it from the blooming artifact. However, we do not think this is necessary for providers experienced in B-mode interpretation.
Normal findings vary, but in normal patients, the mean size of ONSD is 4.1 mm, and the ONSD cut-off value of 5.3 mm strongly predicts increased ICP (sensitivity: 94.7%; specificity: 84.3%)7. The average ONSD in patients with increased ICP is over 6 mm.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64929/64929fig01.jpg" /> 
Figure 1: A series of representative ultrasound probes that can be used for ocular exams. From left to right: a 5-14 MHz probe with a 37 mm footprint (commonly referred to as a hockey stick probe) that can easily obtain transverse and sagittal views; a battery-powered handheld probe; an inexpensive USB probe with a 55 mm footprint that can acquire transverse images consistently and sagittal images on some patients; and a linear probe that cannot obtain sagittal views on most patients. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64929/64929fig02.jpg" /> 
Figure 2: A transparent adhesive dressing is used to keep the eyelid closed during scanning to protect the cornea. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64929/64929fig03.jpg" /> 
Figure 3: Transverse and sagittal views. (A) The transverse view is performed from the anteriormost aspect of the eye. The probe may need to be oriented slightly toward the midline to bring the nerve into the plane. (B) The sagittal view is performed in a similar fashion from the anteriormost aspect of the eye. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/64929/64929fig04.jpg" /> 
Figure 4: Measurement of the ONSD. (A) An unlabeled US image. (B) The same image with the appropriate place to measure the ONSD 3 mm posterior to the optic disk. (C) Transverse measurement of the optic nerve, not the sheath. (D) Measurement of the optic nerve sheath; this is the most relevant measure. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64929/64929fig05.jpg" /> 
Figure 5: Imaging in patients with cooperative eye movements versus those who cannot cooperate. (A) If the patient is cooperative, have them move the eye so that the nerve is headed straight back, as in this example. (B) However, for severe TBI, the patient will not be able to cooperate, and the nerve will head back at an angle. (C) We recommend measuring along the axis of the nerve if it does not head straight back. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/64929/64929fig06.jpg" /> 
Figure 6: Two ultrasounds from the same patient at the same point in time. (A) The optic nerve sheath is visible. (B) US performed with an inexpensive USB-powered ultrasound; the nerve is visible, but not the sheath, even though this is the same patient. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/64929/64929fig07.jpg" /> 
Figure 7: Two ultrasounds from the same patient and the same eye demonstrating a blooming artifact. (A) Demonstration of a blooming artifact from structures on the posterior eye. Note that there is no rounded nerve head, no sheath, and the shadow appears very rectangular. The arrows point to the sides of the blooming artifact. (B) The same patient with the optic nerve and sheath visible. Note that the rounded head of the nerve is demonstrated by the yellow arrow, and the sheath is visible. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64929/64929fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition at JoVE.com

Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

Point-of-care ultrasound (POCUS) of the optic nerve sheath diameter (ONSD) has been shown to be useful in identifying patients with increased intracranial pressure (ICP). However, the non-standardized technique for this POCUS has hampered its use. We present a standardized image acquisition protocol for use in the acute care setting.

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter ...

optic-nerve-sheath-point-of-care-ultrasound-image-acquisition

Nanyang Technological University

Research

JoVE Journal

Medicine

1.3K Views.  Duke University School of Medicine. Point-of-care ultrasound (POCUS) of the optic nerve sheath diameter (ONSD) has been shown to be useful in identifying patients with increased intracranial pressure (ICP). However, the non-standardized technique for this POCUS has hampered its use. We present a standardized image acquisition protocol for use in the acute care setting.

Video: Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging technologies. Existing retinal imaging modalities, such as fundus photography1, confocal scanning laser ophthalmoscopy (cSLO)2, and optical coherence tomography (OCT)3, have significant contributions in monitoring disease onsets and progressions, and developing new therapeutic strategies. However, they predominantly rely on the back-reflected photons from the retina. As a consequence, the optical absorption properties of the retina, which are usually strongly associated with retinal pathophysiology status, are inaccessible by the traditional imaging technologies.
Photoacoustic ophthalmoscopy (PAOM) is an emerging retinal imaging modality that permits the detection of the optical absorption contrasts in the eye with a high sensitivity4-7 . In PAOM nanosecond laser pulses are delivered through the pupil and scanned across the posterior eye to induce photoacoustic (PA) signals, which are detected by an unfocused ultrasonic transducer attached to the eyelid. Because of the strong optical absorption of hemoglobin and melanin, PAOM is capable of non-invasively imaging the retinal and choroidal vasculatures, and the retinal pigment epithelium (RPE) melanin at high contrasts 6,7. More importantly, based on the well-developed spectroscopic photoacoustic imaging5,8 , PAOM has the potential to map the hemoglobin oxygen saturation in retinal vessels, which can be critical in studying the physiology and pathology of several blinding diseases 9 such as diabetic retinopathy and neovascular age-related macular degeneration.
Moreover, being the only existing optical-absorption-based ophthalmic imaging modality, PAOM can be integrated with well-established clinical ophthalmic imaging techniques to achieve more comprehensive anatomic and functional evaluations of the eye based on multiple optical contrasts6,10 . In this work, we integrate PAOM and spectral-domain OCT (SD-OCT) for simultaneously in vivo retinal imaging of rat, where both optical absorption and scattering properties of the retina are revealed. The system configuration, system alignment and imaging acquisition are presented.

Photoacoustic ophthalmology (PAOM), an optical-absorption-based imaging modality, provides the complementary evaluation of the retina to the currently available ophthalmic imaging technologies. We report the using of PAOM integrated with spectral-domain optical coherence tomography (SD-OCT) for simultaneous multimodal retinal imaging in rats.

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging ...

Bioengineering

Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy (oSLO) and Optical Coherence Tomography (OCT)

While fluorescence imaging is widely used in ophthalmology, a large field of view (FOV) three-dimensional (3D) fluorescence retinal image is still a big challenge with the state-of-the-art retinal imaging modalities because they would require z-stacking to compile a volumetric dataset. Newer optical coherence tomography (OCT) and OCT angiography (OCTA) systems overcome these restrictions to provide three-dimensional (3D) anatomical and vascular images, but the dye-free nature of OCT cannot visualize leakage indicative of vascular dysfunction. This protocol describes a novel oblique scanning laser ophthalmoscopy (oSLO) technique that provides 3D volumetric fluorescence retinal imaging. The setup of the imaging system generates the oblique scanning by a dove tail slider and aligns the final imaging system at an angle to detect fluorescent cross-sectional images. The system uses the laser scanning method, and therefore, allows an easy incorporation of OCT as a complementary volumetric structural imaging modality. In vivo imaging on rat retina is demonstrated here. Fluorescein solution is intravenously injected to produce volumetric fluorescein angiography (vFA).

Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy oSLO and Optical Coherence Tomography OCT

Here, we present a protocol to get a large field of view (FOV) three-dimensional (3D) fluorescence and OCT retinal image by using a novel imaging multimodal platform. We will introduce the system setup, the method of alignment, and the operational protocols. In vivo imaging will be demonstrated, and representative results will be provided.

While fluorescence imaging is widely used in ophthalmology, a large field of view (FOV) three-dimensional (3D) fluorescence retinal image is still a big ...

Quantitative Fundus Autofluorescence for the Evaluation of Retinal Diseases

The retinal pigment epithelium (RPE) is juxtaposed to the overlying sensory retina, and supports the function of the visual system. Among the tasks performed by the RPE are phagocytosis and processing of outer photoreceptor segments through lysosome-derived organelles. These degradation products, stored and referred to as lipofuscin granules, are composed partially of bisretinoids, which have broad fluorescence absorption and emission spectra that can be detected clinically as fundus autofluorescence with confocal scanning laser ophthalmoscopy (cSLO). Lipofuscin accumulation is associated with increasing age, but is also found in various patterns in both acquired and inherited degenerative diseases of the retina. Thus, studying its pattern of accumulation and correlating such patterns with changes in the overlying sensory retina are essential to understanding the pathophysiology and progression of retinal disease. Here, we describe a technique employed by our lab and others that uses cSLO in order to quantify the level of RPE lipofuscin in both healthy and diseased eyes.

The retinal pigment epithelium (RPE) supports the sensory retina through recycling visual cycle byproducts, which accumulate as lipofuscin. These products are autofluorescent and can be qualitatively imaged in vivo. Here, we describe a method to quantitatively image RPE lipofuscin using confocal scanning laser ophthalmoscopy.

The retinal pigment epithelium (RPE) is juxtaposed to the overlying sensory retina, and supports the function of the visual system. Among the tasks ...

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in vivo&#8212;rapidly, repetitively, and at a high resolution. This protocol describes OCT imaging in the mouse retina as a powerful tool to study optic neuropathies (OPN). The OCT system is an interferometry-based, non-invasive alternative to common post mortem histological assays. It provides a fast and accurate assessment of retinal thickness, allowing the possibility to track changes, such as retinal thinning or thickening. We present the imaging process and analysis with the example of the Opa1delTTAG mouse line. Three types of scans are proposed, with two quantification methods: standard and homemade calipers. The latter is best for use on the peripapillary retina during radial scans; being more precise, is preferable for analyzing thinner structures. All approaches described here are designed for retinal ganglion cells (RGC) but are easily adaptable to other cell populations. In conclusion, OCT is efficient in mouse model phenotyping and has the potential to be used for the reliable evaluation of therapeutic interventions.

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in ...

Neuroscience

In vivo Structural Assessments of Ocular Disease in Rodent Models using Optical Coherence Tomography

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable tool to evaluate and characterize changes in a variety of retinal and ocular disease and injury models. In light induced retinal degeneration models, SD-OCT can be used to track thinning of the photoreceptor layer over time. In glaucoma models, SD-OCT can be used to monitor decreased retinal nerve fiber layer and total retinal thickness and to observe optic nerve cupping after inducing ocular hypertension. In diabetic rodents, SD-OCT has helped researchers observe decreased total retinal thickness as well as decreased thickness of specific retinal layers, particularly the retinal nerve fiber layer with disease progression. In mouse models of myopia, SD-OCT can be used to evaluate axial parameters, such as axial length changes. Advantages of SD-OCT include in vivo imaging of ocular structures, the ability to quantitatively track changes in ocular dimensions over time, and its rapid scanning speed and high resolution. Here, we detail the methods of SD-OCT and show examples of its use in our laboratory in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia. Methods include anesthesia, SD-OCT imaging, and processing of the images for thickness measurements.

Here, we describe the use of spectral-domain optical coherence tomography (SD-OCT) to visualize retinal and ocular structures in vivo in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia.

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable ...

Ultrahigh Resolution Mouse Optical Coherence Tomography to Aid Intraocular Injection in Retinal Gene Therapy Research

HR-SD-OCT is utilized to monitor the progression of photoreceptor degeneration in live mouse models, assess the delivery of therapeutic agents into the subretinal space, and to evaluate toxicity and efficacy in vivo. HR-SD-OCT uses near infrared light (800-880 nm) and has optics specifically designed for the unique optics of the mouse eye with sub-2-micron axial resolution. Transgenic mouse models of outer retinal (photoreceptor) degeneration and controls were imaged to assess the disease progression. Pulled glass microneedles were used to deliver sub retinal injections of adeno-associated virus (AAV) or nanoparticles (NP) via a trans-scleral and trans-choroidal approach. Careful positioning of the needle into the subretinal space was required prior to a calibrated pressure injection, which delivers fluid into the sub retinal space. Real time subretinal surgery was conducted on our retinal imaging system (RIS). HR-SD-OCT demonstrated progressive uniform retinal degeneration due to expression of a toxic mutant human mutant rhodopsin (P347S) (RHOP347S) transgene in mice. HR-SD-OCT allows rigorous quantification of all the retinal layers. Outer nuclear layer (ONL) thickness and photoreceptor outer segment length (OSL) measurements correlate with photoreceptor vitality, degeneration, or rescue. The RIS delivery system allows real-time visualization of subretinal injections in neonatal (~P10-14) or adult mice, and HR-SD-OCT immediately determines success of delivery and maps areal extent. HR-SD-OCT is a powerful tool that can evaluate the success of subretinal surgery in mice, in addition to measuring vitality of photoreceptors in vivo. HR-SD-OCT can also be used to identify uniform animal cohorts to evaluate the extent of retinal degeneration, toxicity, and therapeutic rescue in preclinical gene therapy research studies.

Here we demonstrate a novel approach to using high resolution spectral-domain optical coherence tomography (HR-SD-OCT) to assist delivery of gene therapy agents into the subretinal space, assess its areal coverage, and characterize photoreceptor vitality.

HR-SD-OCT is utilized to monitor the progression of photoreceptor degeneration in live mouse models, assess the delivery of therapeutic agents into the ...

Smartphone Fundus Photography

Smartphone fundus photography is a simple technique to obtain ocular fundus pictures using a smartphone camera and a conventional handheld indirect ophthalmoscopy lens. This technique is indispensable when picture documentation of optic nerve, retina, and retinal vessels is necessary but a fundus camera is not available. The main advantage of this technique is the widespread&#160;availability of smartphones that allows documentation of macula and optic nerve changes in many settings that was not previously possible. Following the well-defined steps detailed here, such as proper alignment of the phone camera, handheld lens, and the patient&#39;s pupil, is the key for obtaining a clear retina picture with no interfering light reflections and aberrations. In this paper, the optical principles of indirect ophthalmoscopy and fundus photography will be reviewed first. Then, the step-by-step method to record a good quality retinal image using a smartphone will be explained.

Fundus photography normally requires specialized fundus cameras that are not always available in all clinical settings.&#160;Here, a simple method to record ocular fundus images using a smartphone camera and a conventional high-plus handheld indirect ophthalmoscopy lens is described.

Smartphone fundus photography is a simple technique to obtain ocular fundus pictures using a smartphone camera and a conventional handheld indirect ...

Quantification of Optic Nerve Cross Sectional Area on MRI: A Novel Protocol using Fiji Software

Optic nerve assessment is an important aspect of glaucoma diagnosis and follow-up. This project describes a protocol for a unified methodology of optic nerve cross-sectional assessment and quantification using 3 T MRI for image acquisition and ImageJ's Fiji software for image processing quantification. Image acquisition was performed using 3 T MRI, with proper instructions for the patient to ensure straight fixation during imaging. A T2-weighted fat suppressed sequence was used. A coronal cut taken 3 mm behind the globe and perpendicular to the optic nerve axis should be uploaded to the software. Using the threshold function, the white matter area of the optic nerve is selected and quantified, thus, eliminating inter-individual measurement bias. We also described the normal limits for the optic nerve cross-sectional area according to age, based on previously published literature. We used the described protocol to assess optic nerve of a suspected glaucoma patient. The optic nerve cross-sectional area was found to be within the normal limits, a finding further confirmed via optical coherence tomography of the optic nerve.

We provided a detailed protocol for a standardized method of optic nerve assessment and quantification using MRI, utilizing a widely available imaging sequence, and open access software for image analysis. Following this standardized protocol would provide meaningful data for comparison between different patients and different studies.

Optic nerve assessment is an important aspect of glaucoma diagnosis and follow-up. This project describes a protocol for a unified methodology of optic ...

Application of Optical Coherence Tomography to a Mouse Model of Retinopathy

Optical coherence tomography (OCT) offers a noninvasive method for the diagnosis of retinopathy. The OCT machine can capture retinal crosssectional images from which the retinal thickness can be calculated. Although OCT is widely used in clinical practice, its application in basic research is not as prevalent, especially in small animals such as mice. Because of the small size of their eyeballs, it is challenging to conduct fundus imaging examinations in mice. Therefore, a specialized retinal imaging system is required to accommodate OCT imaging on small animals. This article demonstrates a small-animal-specific system for OCT examination procedures and a detailed method for image analysis. The results of retinal OCT examination of very-low-density lipoprotein receptor (Vldlr) knockout mice and C57BL/6J mice are presented. The OCT images of C57BL/6J mice showed retinal layers, while those of Vldlr knockout mice showed subretinal neovascularization and retinal thinning. In summary, OCT examination could facilitate the noninvasive detection and measurement of retinopathy in mouse models.

Here, we describe an in vivo imaging technique using optical coherence tomography to facilitate the diagnosis and quantitative measurement of retinopathy in mice.

Optical coherence tomography (OCT) offers a noninvasive method for the diagnosis of retinopathy. The OCT machine can capture retinal crosssectional images ...

Image-Guided Optical Coherence Tomography to Assess Structural Changes in Rodent Retinas

Ocular diseases, such as age-related macular degeneration, glaucoma, retinitis pigmentosa, and uveitis, are always accompanied by retinal structural changes. These diseases affecting the fundus always exhibit typical abnormalities in certain cell types in the retina, including photoreceptor cells, retinal ganglion cells, cells in the retinal blood vessels, and cells in the choroidal vascular cells. Noninvasive, highly efficient, and adaptable imaging techniques are required for both clinical practice and basic research. Image-guided optical coherence tomography (OCT) satisfies these requirements because it combines fundus photography and high-resolution OCT, providing an accurate diagnosis of tiny lesions as well as important changes in the retinal architecture. This study details the procedures of data collection and data analysis for image-guided OCT and demonstrates its application in rodent models of choroidal neovascularization (CNV), optic nerve crush (ONC), light-induced retinal degeneration, and experimental autoimmune uveitis (EAU). This technique helps researchers in the eye field to identify rodent retinal structural changes conveniently, reliably, and tractably.

The protocol presented here details the procedures of data collection and data analysis for image-guided optical coherence tomography (OCT) and demonstrates its application in multiple rodent models of ocular diseases.

Ocular diseases, such as age-related macular degeneration, glaucoma, retinitis pigmentosa, and uveitis, are always accompanied by retinal structural ...

Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

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Chapters in this video

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy (oSLO) and Optical Coherence Tomography (OCT)

Quantitative Fundus Autofluorescence for the Evaluation of Retinal Diseases

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

In vivo Structural Assessments of Ocular Disease in Rodent Models using Optical Coherence Tomography

Ultrahigh Resolution Mouse Optical Coherence Tomography to Aid Intraocular Injection in Retinal Gene Therapy Research

Smartphone Fundus Photography

Quantification of Optic Nerve Cross Sectional Area on MRI: A Novel Protocol using Fiji Software

Application of Optical Coherence Tomography to a Mouse Model of Retinopathy

Image-Guided Optical Coherence Tomography to Assess Structural Changes in Rodent Retinas