Test Characteristics of Point of Care Ultrasound for the Diagnosis of Retinal Detachment in the Emergency Department

Background

Retinal detachment (RD) is the final diagnosis for 3-4% of patients presenting to the Emergency Department (ED) with ocular complaints. Presenting symptoms most commonly include acute onset flashes and floaters, however, this presentation is not unique. The timely diagnosis and differentiation of RD from more common, benign, and similarly presenting processes, such as posterior vitreous detachment, is important in order to treat RD and prevent the sequela of permanent vision loss.

Point of care ultrasound (POCUS) has been successfully employed in the diagnosis of retinal pathology with high degrees of success according to observed test characteristics (sensitivity 97%-100%; specificity 83-100%) in emergency medicine (EM) literature. The generalizability of this data is limited, however, due to study features, including the use of highly experienced sonographers, inconsistent scanning protocols, and poor reference standards. This investigation seeks to derive the test characteristics for POCUS in the diagnosis of RD when used by a heterogeneous population of emergency physicians (EPs).

Test Characteristics of Point of Care Ultrasound for the Diagnosis of RetinalDetachment in the Emergency Department

Clinical Question

What are the test characteristics (sensitivity and specificity) of POCUS for the diagnosis of RD in patients presenting with chief complaint of flashes or floaters, when performed by a group of emergency physicians with varying degrees of ultrasound experience?

Methods & Study Design

  • Design
    • Prospective study using a convenience sample of patients presenting to the ED with a chief complaint of flashes or floaters in visual fields
  • Population
    • Conducted at Vancouver General Hospital, an urban academic tertiary care center
  • Inclusion Criteria
    • Patients presenting with chief complaint of acute (7 days or less) onset flashes or floaters in one or both eyes between March 2015 and September 2016
  • Exclusion Criteria
    • Age younger than 19 years, known diagnosis of RD, exam compromised due to advanced cataract in the affected eye, ophthalmologic surgery on affected eye within prior two weeks
  • Intervention
    • EP performed ocular POCUS with high-frequency linear transducer
    • Scan performed in both transverse and longitudinal plane with dynamic assessment of posterior chamber (patient looking left/right and up/down)
    • Positive or negative interpretation for RD was recorded
    • Reference Standard
      • Patients were referred to an ophthalmology resident who performed non-blinded assessment including a complete dilated retinal exam
      • Patients were then seen by a retina specialist blinded to the ED POCUS within 1 week, or for patients with a retinal tear or RD diagnosis, within 1 day
    • Standardized training session for emergency providers
      • EM attendings (20), fellows (2), and residents (8) of varying ultrasound experience received a 1 hour lecture on the use of POCUS to detect RD
      • All participating EPs performed one practice scan on a healthy volunteers
  • Outcomes
    • Primary outcome: Accuracy of the EP diagnosis with respect to the reference standard, the retina specialist diagnosis
    • Test characteristics: sensitivity, specificity, diagnostic accuracy, LR+, and LR- 

Results

Flow of Patients Through Study

Primary analysis

    • Sensitivity: 75% (95% CI 48-93%)
    • Specificity: 94% (95% CI 87-98%)
    • Diagnostic accuracy: 91% (95% CI 85-96%)
    • LR-positive: 12.4 (95% CI 5.4-28.3)
    • LR-negative: 0.27 (95% CI 0.11-0.62)

Secondary analyses

    • Test characteristics by level of training
      • Residents and fellows: 100% sensitivity, 95% specificity
      • Attending physicians: 71% sensitivity, 94% specificity
    • Test characteristics by number of patients enrolled by EP
      • 1-2 patients enrolled: 80% sensitivity, 71% specificity
      • 3 or more patients enrolled: 73% sensitivity, 98% specificity

Limitations

    • Insufficiently powered for the secondary analyses
    • Single program study limits generalizability
    • Prior ultrasound experience was not explicitly assessed
    • RD is not always classically presenting, starting with a population defined by classic symptoms may influence observed test characteristics

Authors Conclusion

“In a heterogeneous group of EPs with varying ultrasound experience, POCUS demonstrates high specificity but only intermediate sensitivity for the detection of RD. A negative POCUS scan in the ED performed by a heterogeneous group of providers after a one-hour POCUS didactic is not sufficiently sensitive to rule out RD in a patient with new onset flashes or floaters.”

Our Conclusion

This study demonstrates that emergency physicians of varying training levels and ultrasound experience can successfully employ POCUS in the diagnosis of RD after only a short training session. By incorporating POCUS into the workup of patients presenting with ocular complaints characteristic of RD, true pathology can be identified with high specificity. Appropriate care can then be mobilized expeditiously in these scan-positive patients in order to prevent the permanent vision loss associated with this condition.

Indeed, a 74% sensitivity is too low for POCUS to reliably be utilized by a heterogeneous population of EPs as a tool to rule-out RD, especially given the consequences of a missed diagnosis. It would be reasonable practice, therefore, as the authors suggest, for all patients with new onset flashes and/or floaters to continue be referred for further ophthalmologic evaluation to definitively rule-out RD and other conditions at-risk for progression to RD. It should also be noted, however, that a trend towards increased specificity was observed amongst physicians who enrolled more patients in this study. Taken in context with test characteristics reported in prior literature, these findings may suggest that specificity can be improved upon with experience, and in the hands of a trained sonographer, POCUS may also be used as a tool to reliably rule-out RD.

The Bottom Line

Emergency providers can reliably use point-of-care ultrasound to diagnose retinal detachment with high specificity after a short, one-time training course, but must recognize the limitations of POCUS as a tool to rule-out RD in this setting, given a relatively low sensitivity when used for this purpose.

Authors

This post was written by Oretunlewa Soyinka, MS4 at UCSD. Review and further commentary was provided by Cameron Smyres, MD, Ultrasound Fellow at UCSD.

References

1 .  Hikichi T, Hirokawa H, Kado M, et al. Comparison of the prevalence of posterior vitreous
detachment in whites and Japanese. Ophthalmic Surg 1995; 26:39-43.

2.  Hollands H, Johnson D, Brox AC, et al. Acute-onset floaters and flashes: is this patient at
risk for retinal detachment? JAMA 2009; 302:2243-9

3.  Alotaibi AG, Osman EA, Allam KH, et al. One month outcome of ocular related
emergencies in a tertiary hospital in Central Saudi Arabia. Saudi Med J 2011; 32:1256-60.

4.  Mitry D, Charteris DG, Fleck BW, et al. The epidemiology of rhegmatogenous retinal
detachment: geographical variation and clinical associations. Br J Ophthalmol 2010;
94:678-84.

Case # 13: What Lies Beneath

A 30 year old male presents to the emergency department after blunt trauma to the face from an altercation. He notes he was punched several times in the face but did not pass out. His exam is notable for significant right periorbital ecchymosis and edema with inability to open his eye. You are unable to perform a direct eye exam given the significant periorbital swelling.  A CT maxillofacial is performed which shows an isolated right inferior orbital wall fracture.

Vitals: T 98.6 HR 85 BP 142/81  RR 14 O2 98% on RA

Prior to ENT consultation, a bedside ultrasound of the orbits is performed.  In spite of being unable to open the eye, what can you tell your consultant regarding your exam?

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Answer and Learning Points

Answer

Using ultrasound as an adjunct to your exam, you are able to tell the consultant that there is a normal appearing, reactive pupil and that the extra-ocular movements of the eye are intact. The consultant is appreciative over the phone and is happy to come in and see the patient whom after evaluation is discharged home with close outpatient follow up.

Learning Points

It is often the case where a patient suffers such significant facial trauma that a complete physical exam of the orbit due to periorbital swelling is not possible. Ultrasound can be a critical tool in these cases to provide useful information to assess for multiple potential pathologies. Previous studies have shown the ability of ocular ultrasound in trauma to detect elevated intracranial pressure (via optic nerve sheath diameter), retinal detachment, vitreous hemorrhage, and retrobulbar hematoma. It can also be used for early detection of muscular entrapment in the case of an orbital wall fracture, as well as performed serially for pupillary response in patients with significant neurological injury at risk for deterioration and potential herniation.

  • To evaluate extraocular movements:
    • Prepare the patient by laying the bed backwards and having their face parallel to the ceiling,  supporting the patient's head and neck with a pillow or blanket.
    • (Optional) Place a tegaderm over the eye. If you do, ensure there is no air between the tegaderm and the eyelid.
    • Place a small amount of ultrasound gel on the closed eyelid  and prepare the linear probe with the gain turned almost all the way up.
    • Stabilize your hand on the patient's nasal bridge or zygoma, with the probe marker to your left, and place the probe transverse on the orbit with minimal pressure being applied directly to the eye. This is very important in trauma as the area is likely painful and theoretically the patient could have a ruptured globe.
    • Adjust the depth to ensure the optic nerve is just visualized at the bottom of the screen. The anterior chamber and lens should be used as visual landmarks to ensure you are in proper location.
    • Next, have the patient look left and right, then turn the probe to a sagittal orientation and have the patient look up and down. During these maneuvers you should be evaluating for symmetric movements of the orbit in each direction.
    • If you do not appreciate symmetric movements of the orbit in all directions then you may have entrapment of an extraocular muscle.
  • To evaluate for pupillary response and shape:
    • Be sure to dim the lights in the room prior to performing this exam to allow for an adequate pupillary response.
    • Gently apply the linear probe with gel in a transverse plane just inferior to the eye, angling superiorly towards the patient's head (Depending on the location of the swelling around the eye, you can also place the probe superior to the eye, angling inferiorly towards the patient's feet).
    • Keep flattening out your probe angle relative to the skin until you have a cross section of the pupil and iris in view.
    • The pupil should be evaluated for symmetry as an asymmetric or oblong pupil could suggest globe rupture. You can then shine a light in the affected or non-affected eye (consensual light reflex) and observe the pupil for constriction.

 

Author

This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Blaivas M. Bedside emergency department ultrasonography in the evaluation of ocular pathology. Acad Emerg Med 2000;7:947-50.
    2. Blaivas M, Theodoro D, Sierzenski P. A study of bedside ocular ultrasonography in the emergency department. Acad Emerg Med 2002;9(8):791-9.
    3. Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Acad Emerg Med 2008;15(2):201-4.
    4. Tayal VS, Neulander M, Norton HJ, et al. Emergency department sonographic measurement of optic nerve sheath diameter to detect findings of increased intracranial pressure in adult head injury patients. Ann Emerg Med 2007;49(4):508-14.
    5. Harries A, et al. Ultrasound assessment of extraocular movements and pupillary light reflex in ocular trauma. Am J Emerg Med 2010 28(8):956-9.

Case # 12: Bilateral Vision Loss

A 45 year old male with poorly controlled DM presents with bilateral vision loss. His right eye vision acutely worsened 3 days ago with the sensation of a curtain moving back and forth across his visual field. Today his left eye vision acutely worsened with flashes and floaters occurring. He denies any trauma, headache, or new medications.

Vitals: T 98.6 HR 90 BP 149/87  RR 16 O2 98% on RA

A bedside ultrasound of the orbits is performed,  what is the next best step in management?

Left Eye

Left Eye

Right Eye

Right Eye

Answer and Learning Points

Answer

The ultrasound clips demonstrate hypoechoic material in the orbits bilaterally, swirling around with subtle eye movement. This is consistent with bilateral vitreous hemorrhage. The diagnosis was discussed with the patient and he was referred to ophthalmology clinic for dilated eye exam in 24 hours.

Learning Points

Vitreous hemorrhage is a common diagnosis (though usually unilateral) seen in poorly controlled diabetes. The most frequent etiologies include proliferative diabetic retinopathy, posterior vitreous detachment, and ocular trauma, with trauma more common in patients under the age of 40. Since it is difficult to obtain  a good physical exam of the posterior aspects of the eye without a dilated exam, there is high utility in the use of point of care ultrasound in evaluating for acute pathology.  It can be used to distinguish vitreous hemorrhage and retinal detachment, which have significantly different prognoses and treatment pathways. To perform an ocular ultrasound, follow these steps:

    1. Prepare the patient by laying the bed backwards and having their face parallel to the ceiling,  supporting the patient's head and neck with a pillow or blanket.
    2. Place a tegaderm over the eye (optional). If you do, ensure there is no air between the tegaderm and the eyelid.
    3. Place the ultrasound gel on the tegaderm and prepare the linear probe with the gain turned almost all the way up (this will help you visualize both retinal detachment and vitreous hemorrhage.
    4. Stabilize your hand on the patient's nasal bridge or zygoma, with the probe marker to your left, and place the probe transverse on the orbit with minimal pressure being applied directly to the eye.
    5. Adjust the depth to ensure the optic nerve is just visualized at the bottom of the screen. The anterior chamber and lens should be used as visual landmarks to ensure you are in proper location. Next, have the patient look up, down , left and right (oculokinetic echography), to assess for any abnormalities in the posterior aspects of the eye.
    6. Repeat this technique with the probe marker pointed superiorly and have the patient again look in all directions.

Retinal detachment: The common POCUS findings include a thin linear structure tethered to the optic nerve.  It flaps back and forth as the eye is moved giving it the appearance of “swaying seaweed”. This is an ophthalmologic emergency, especially if the macula is still attached,  the ophthalmologist should be immediately consulted.

Vitreous hemorrhage: You will notice a diffuse mobile opacity often described as a “snow globe” that is exacerbated with moving the eye from side to side. If this is seen in a diabetic patient with floaters, there is a high likelihood that the diagnosis is a vitreous hemorrhage. These patients will still need follow up with ophthalmology for further management, but typically there will not be an emergent intervention.

Author

This post was written by Sam Frenkel, MD, PGY-2 UCSD EM. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Yoonessi R, Hussain A, Jang TB. Bedside ocular ultrasound for the detection of retinal detachment in the emergency department. Acad Emerg Med. 2010;17(9):913-7.
    2. Dawson, Mallin. Introduction to Bedside Ultrasound, Volume 2. 2013. Apple iBook.
    3. Kilker B, Holst J, Hoffmann B. Bedside ocular ultrasound in the emergency department. Eur J Emerg Med. 2014;21(4):246-253.
    4. Shinar Z, Chan L, Orlinsky M. Use of ocular ultrasound for the evaluation of retinal detachment. J Emerg Med. 2011;40(1):53-57.