Article, Ophthalmology

Can emergency physicians accurately distinguish retinal detachment from posterior vitreous detachment with point-of-care ocular ultrasound?

a b s t r a c t

Study objective: There is significant overlap between the symptoms of patients presenting with retinal detach- ment (RD) and posterior vitreous detachment (PVD). Urgency to obtain consultation and treatment are depen- dent on the ability to accurately distinguish these two conditions. The objective of this study was to determine the ability of emergency physicians to differentiate RDs from PVDs using point-of-care ocular ultrasound. Methods: Single blinded cross-sectional study at an academic medical center. Emergency physicians with varying ultrasound experience completed a brief tutorial on the Sonographic findings of RD and PVD. Thirty POC ocular ultrasound clips obtained from ED patients with ocular symptoms were presented to emergency physicians. The sonographic findings in these clips were in agreement with the final diagnosis made by consultant ophthal- mologists. There were 14 ultrasound videos showing PVD, 13 videos showing RD, and 3 normal ocular ultrasound videos. The subjects independently reviewed POC ocular ultrasound video clips and submitted their final inter- pretations.

Results: A total of 390 ocular video clips were reviewed by 13 emergency physicians. Overall, physicians were able to accurately diagnose the presence of a RD 74.6% (95%CI, 69.8-79.4) of the time, PVD 85.7% (95%CI, 77.6-93.8) of the time, and normal ultrasounds 94.9% (95%CI 87.3-100.0) of the time. There was no statistically significant re- lationship between correct diagnoses for Ocular abnormalities or normal ultrasound images and number of pre- vious ocular ultrasounds performed by emergency physicians.

Conclusion: Emergency physicians were modestly accurate in distinguishing RD from PVD on POC ultrasound.

(C) 2017

Introduction

The use of point-of-care (POC) ultrasound has greatly expanded within the emergency department (ED), and for many emergency phy- sicians, it is an integral part of their clinical practice. Visual complaints are a significant burden in the ED, as patients often present with com- plaints such as blurry vision, visual disturbance, and Vision loss [1]. Cli- nicians are often tasked with the difficult job of differentiating between various ocular pathologies to determine which patients are safe for dis- charge and which will require emergent consultation or intervention. The accessibility, portability, and noninvasive characteristics of POC

? Abstract was presented at the Society for Academic Emergency Medicine Physicians Research Forum San Diego, CA; May 2015.

* Corresponding author at: Department of Emergency Medicine, The University of Arizona Medical Center, PO Box 245057, Tucson, AZ 85724-5057, United States.

E-mail address: [email protected] (R. Amini).

ultrasound make it an excellent adjunct in the evaluation of patients with ocular complaints. The great value of POC ultrasound lies in its abil- ity to help clinicians accurately distinguish different ocular pathologies, thus directing appropriate treatment in the ED [2].

Prior studies have demonstrated the ability of emergency physicians to accurately perform focused point-of-care ocular ultrasound to diag- nose retinal detachment [2,3]. Retinal detachments (RD) often require ophthalmologic consultation and may require immediate intervention to prevent irreversible vision loss. Unfortunately, posterior vitreous de- tachments (PVD) often present with symptoms similar to those of reti- nal detachments [4,5]. Unlike a RD, an isolated PVD does not necessitate an emergent consultation by ophthalmology. For decades, physicians have relied on consultants to perform indirect ophthalmoscopy to accu- rately distinguish between RD and PVD; however, it is possible that oc- ular ultrasound can help clinicians distinguish between these two clinical entities. Unfortunately, the sonographic findings of these two conditions are not always clear-cut. Furthermore, PVD can coexist

https://doi.org/10.1016/j.ajem.2017.10.010

0735-6757/(C) 2017

N. Baker et al. / American Journal of Emergency Medicine 36 (2018) 774776 775

with RD, making a definitive diagnosis more challenging. The objective of this study was to determine the ability of emergency physicians to differentiate RD from PVD on POC ocular ultrasound.

Methods

Study design and setting

This was a single-blinded, nonrandomized, cross-sectional study at an academic medical center with two emergency medicine residency training programs and one emergency medicine and pediatrics training program. The Department of Emergency Medicine has an active emer- gency ultrasound education program. Each year residents and faculty receive a didactic session on ocular emergencies, which reviews diag- nostic nuances between retinal detachments and posterior vitreous de- tachments. In addition, hands on training is administered by the ultrasound division. Hospital credentialing in POC ultrasound is avail- able for emergency physicians and is based on American College of Emergency Physicians ultrasound guidelines [6]. The study was reviewed and approved by the institutional review board.

Selection of participants

Emergency physicians with varying experience in POC Ocular US were invited to participate in this study. Participation in the study was voluntary. All participants had experience in performing common ED POC ultrasound applications. Participants were emergency medicine residents, fellows, and attending physicians. Emergency physicians with varying POC ultrasound experience completed a brief tutorial re- garding sonographic findings of retinal detachment and posterior vitre- ous detachment. In the tutorial, a Retinal detachment was defined as a hyperechoic line that does not cross the optic nerve, is uniformly thick, more echogenic when compared to a PVD, and less mobile with ocular movements. A peripheral vitreous detachment was defined as a hyperechoic line that can cross the optic nerve, has varying degrees of thickness, is less echogenic when compared to a RD, and is more mobile with ocular movements (Table 1). Detailed information regarding prior scanning experience with POC ocular ultrasound was collected.

Study protocol

Volunteer physicians were presented with thirty clinical scenarios of ocular complaints and concurring POC ocular ultrasound video clips. There were 14 ultrasound videos showing PVD, 13 videos showing RD, and 3 normal ocular ultrasound videos. Images and clinical scenarios were obtained from real ED patients evaluated at our institution. The sonographic findings in these clips were in agreement with the final di- agnosis made by consultant ophthalmologists. All subjects were blinded to the final diagnosis made by ophthalmologists. Participants indepen- dently reviewed POC ocular ultrasound video clips and submitted

Table 1

Comparison of RD and PVD.

Retinal detachments Peripheral vitreous detachments Does not cross the optic nerve Can cross the optic nerve

Uniformly thick Varying degrees of thickness (usually thinner)

More echogenic Less echogenic

their final interpretations. They were asked to interpret the video clips, determine the diagnosis, and express their level of confidence in their diagnosis on a five-point Likert scale. Physicians were also asked to rate the Image quality of the videos on a five-point Likert scale. Each response in a clinical scenario was counted separately during data analysis.

Statistical analysis

All analyses were performed in SAS version 9.3. (Copyright, SAS In- stitute Inc., Cary, NC). Summary statistics along with 95% confidence in- tervals are reported for percent correct answers. The relationship of percent correct responses and ocular ultrasound experience was ana- lyzed using linear regression.

Results

A total of 390 ocular ultrasound video clips were reviewed by 13 emergency physicians with varying POC ocular ultrasound experience. Five physicians had performed 0 to 25 POC ocular ultrasounds, four phy- sicians had performed 26 to 50 POC ocular ultrasounds, and four physi- cians had performed N 50 POC ocular ultrasounds. On a scale of 1 to 5, the average quality score of the images was 3.42 (SD 0.44) and the aver- age physician’s confidence score was 3.75 (SD 0.48).

Overall, physicians were able to accurately diagnose the presence of

a RD 74.6% (95%CI, 69.8-79.4) of the time, PVD 85.7% (95%CI, 77.6-93.8)

of the time, and identify normal ultrasounds 94.9% (95%CI 87.3-100.0) of the time. A breakdown of physician accuracy sub-stratified by POC ocular ultrasound experience is found in Table 2. There was no statisti- cally significant relationship between correct diagnoses for ocular ab- normalities or normal ultrasound images and number of previous ocular ultrasounds performed by emergency physicians.

Discussion

PVD is a common presenting etiology for vision loss and Decreased vision. PVD prevalence increases with age and can occur in 11% to 46% of patients 60-90 years old [7,8]. The set of events that occurs as the eye ages is associated with a series of physiological changes in the vitre- ous gel, with progressive liquefaction and gradual destruction of the collagen-hyaluronic acid network. At age 80, approximately 50% of the vitreous gel has been liquefied. These liquefied vitreous pockets weaken the adhesion between the vitreous and the retina, predisposing the pa- tient to PVD [9]. With our aging population, PVD will be affecting more patients, making it essential to accurately make this diagnosis and dif- ferentiate it from RD.

POC ultrasound is taught and assessed at all academic institutions, and the Emergency Medicine resident physicians are required to meet specific milestones for POCUS before graduation. With an increasing number of emergency physicians trained in bedside ultrasound, POCUS is becoming more commonplace and more frequently used in the evaluation and management of varied chief complaints.

Ocular complaints comprise approximately 3% of all ED visits [10]. In patients with ocular complaints, emergency physicians use various tools such as the visual acuity test, direct ophthalmoscope, tonometer, and slit-lamp with fluorescein stain to evaluate these patients and nav- igate the myriad of differential diagnoses. Over the past decade, emer-

Less mobile with ocular movements

May be tethered directly to the optic nerve

Become thicker and less mobile over time

More mobile with ocular movements Can be focal or extensive

Often present with hemorrhage or inflammatory debris

gency physicians have incorporated ocular ultrasound into their diagnostic toolbox for the evaluation of pathology such as retinal de- tachment, vitreous detachment, lens dislocation, and elevated intracra- nial pressure through optic nerve sheath evaluation [11]. In patients with ocular complaints, the ultimate challenge is to accurately diagnose

A comparison of the features distinguishing RD from PVD [15]. RD – retinal detachment.

PVD – peripheral vitreous detachment.

or differentiate between pathologies in order to prevent morbidity and

allow the emergency physician to determine the urgency for ophthal- mology consultation.

776 N. Baker et al. / American Journal of Emergency Medicine 36 (2018) 774776

Table 2

Physician accuracy sub-stratified by POC ocular ultrasound experience.

Ocular

Experience level

p-Value

Training level

p-Value

0-25

26-50

N 50

Attending

Fellow

Resident

Accuracy for PVD

84.3

89.3

83.9

0.84

86.9

91.1

76.2

0.36

Accuracy for RD

76.9

71.2

75.0

0.59

74.4

71.2

79.5

0.43

Quality

3.16

3.59

3.59

0.24

3.64

3.23

3.24

0.28

Confidence

3.74

3.76

3.76

0.99

3.89

3.46

3.87

0.37

In 2015, Vrablik et al. conducted a systematic review and meta- analysis on the diagnostic accuracy of ocular ultrasound, the studies that were reviewed exhibited high sensitivity and high specificity for bedside ultrasound diagnosis of RD with ROC of 0.957. This means ED ocular ultrasound can differentiate between patients with and without RD with high degree of accuracy [12]. This is congruent with previous literature, which demonstrated 100% sensitivity and 100% specificity for the diagnosis of RD [2]. Our investigation demonstrated diagnostic accuracy for RD to be 74.6%, which is lower than published literature. Al- though our findings demonstrate a reduction in diagnostic accuracy, it should be noted that previous studies were conducted with experts in the field, but our study subjects were emergency physicians with vary- ing levels of ocular ultrasound experience including those with b 25 oc- ular ultrasounds. Furthermore, the number of patients with RD could also have had coexisting PVD, given that PVD can be the initiating cause of RD [13]. In addition, our gold standard for the sonographic di- agnoses of either RD, PVD or normal ocular ultrasound study was the final diagnoses made by consultant ophthalmologists, which is not al- ways perfect.

Based on our literature review, there have been no studies investi- gating the emergency physician’s ability to differentiate between PVD and RD with ultrasound. Our study demonstrates that emergency phy- sicians can effectively differentiate between these two pathologies with ocular ultrasound, despite less education on PVD identification. Al- though PVD is much more common than RD, it still remains an unfamil- iar sonographic entity with focus mainly on identifying and understanding RD on ultrasound.

Both RD and PVD can appear as hyperechoic membranes in the pos- terior ocular chamber and are freely mobile with extraocular move- ments. RD can be slightly more echogenic than PVD. However, the key to differentiating between the two is to identify the optic nerve first. RDs will remain attached to the optic nerve sheath, whereas PVDs will cross over the midline, hence, also crossing over the optic nerve. RD is not so mobile with eye movements, unlike PVD, which is very mobile with eye movements. Generally, RD has same thickness throughout, un- like PVD, which has varying degrees of thickness. As mentioned above, RDs and PVDs can occur together, and the more anterior hyperechoic white membrane is usually the PVD [14].

American College of Emergency Physicians released a policy state- ment in June 2016 regarding ultrasound guidelines. In this document, it states that trainees should perform between 25 and 50 studies of each type of ultrasound, including ocular, to obtain competency [6]. This is based on multiple studies stating that performance of 25 studies is the minimum to achieve basic competency. However, our study sug- gests that there is no difference in diagnostic accuracy between various levels of POC ultrasound training. Perhaps this would change if the study subjects were also evaluated on the acquisition of the images, which is a different skill set than interpreting images that are already ac- quired and optimized.

Our study also demonstrated that regardless of their previous ocular ultrasound training, emergency physicians can differentiate between PVD, RD, and normal ocular ultrasound with modest accuracy. These findings are promising as early recognition or exclusion of this diagnosis can potentially avoid unnecessary consultation. As technology for ocular ultrasound improves (such as three-dimensional imaging), emergency physicians may feel more confident and empowered in integrating

ocular ultrasound into their evaluation of ocular complaints. This can help with decreasing patient morbidity and Health care costs.

Limitations

This study has a number of limitations including a small sample size, limiting the conclusions that could be reached. convenience sampling of emergency physicians may have introduced a selection bias. In addition, conducting this study at an academic institution with an emergency ul- trasound fellowship program and with emergency physicians who are interested in participating in the study could have introduced additional bias. The methods used in this study to determine the ability of emer- gency physicians to identify posterior vitreous detachment were not validated. To our knowledge, no standardized Ultrasound measurement tools are available to assess the accuracy of interpretation, and we be- lieve that the methods adopted in this study are reliable to measure the accuracy. The video clips included in our study did not cover all sonographic abnormalities of ocular disorders seen in ED, and these clips were carefully selected by the investigators as clear examples of both RD and PVD, which may not demonstrate the possible subtleties encountered during real time patient imaging. image acquisition skills of our participants were not assessed. Lastly, we did not administer a hands-on training session prior to evaluation, and thus no determina- tions can be made on the effectiveness of a teaching intervention.

Conclusion

Emergency physicians were modestly accurate in distinguishing RD from PVD on POC ultrasound.

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