POCUS is a key diagnostic tool that can allow emergency physicians to diagnose a range of injuries. This case highlights the utility of bedside point-of-care ultrasound in differentiating between retinal detachment, vitreous hemorrhage, and posterior retinal detachment.
HISTORY OF PRESENT ILLNESS
A 63-year-old male with a past medical history of type 2 diabetes presents to the emergency department (ED) for a visual disturbance. He woke up 3 weeks ago with floaters in his right eye that are described as "a string going across his vision" with associated flashes of light. He wears reading glasses, does not wear contacts, and denies any trauma to the eye or eye pain.
PHYSICAL EXAMINATION
Vital signs include blood pressure of 152/79, heart rate of 61 beats per minute, temperature 98 °F (36.7 °C), respiratory rate of 18, and an oxygen saturation of 98% on room air. His visual acuity while wearing his reading glasses is 20/30 OD and 20/20 OS. Both eyes have normal appearing conjunctiva, and pupils that are equal, round, and reactive to light. His extraocular movements and visual fields are intact. His intraocular pressures are 16 mmHg OD and 15 mmHg OS. A Woods Lamp assessment using fluorescein stain did not show any focal areas of uptake on his cornea.
POCUS
An ocular point-of-care ultrasound (POCUS) is performed using a high-frequency 7.5 to 10 mHz linear probe. An axial view of the right orbit demonstrates multiple areas of variable hyperechogenicity in the posterior chamber of the eye that are freely mobile with eye movement, consistent with vitreous hemorrhage (VH) (Video/GIF 1). Additionally, a thin and mobile membrane that is not attached to the optic nerve is seen in the posterior chamber, concerning for posterior vitreous detachment (PVD) (Figure 1).
Figure 1. Axial view of the right orbit. Orange arrows indicate hyperechoic areas of vitreous hemorrhage. Red arrows outline the membrane of posterior vitreous detachment.
Discussion
To perform an ocular point-of-care ultrasound (POCUS), use a high-frequency 7.5 to 10 mHz linear probe with an ocular preset so that the transducer will emit lower energy to protect the eyes from potential thermodynamic damage over extended periods of scanning time. Position the patient supine or partially upright with the eyes closed. A protective covering may be placed over the eyelids, and apply generous amounts of ultrasound gel on top. Obtain orthogonal views of both eyes for comparison with the probe marker directed toward the patient's right or cephalad. Instructing the patient to perform extraocular movements and increasing the gain may help with identification of subtle pathology.
Normal anatomy with labeled key structures is shown in Video/GIF 2 and Figure 2. The lens and iris divide the anterior chamber from the posterior chamber. Both the anterior and posterior chambers are filled with anechoic fluid and should be relatively echo free. An intact retina cannot be distinguished from the posterior boundary of the eye. The optic nerve appears as a hypoechoic column that extends from the posterior orbit.
Figure 2. Relevant anatomy of the eye
Video 2. Normal eye in transverse view
Ophthalmologic complaints are a common reason for presentations to the ED, with the Nationwide Emergency Department Sample (NEDS) database estimating nearly 2 million ED visits per year for a primary ophthalmologic concern between 2006 and 2011.1 Three commonly considered diagnoses in the ED ophthalmologic evaluation are retinal detachment (RD), posterior vitreous detachment (PVD), and vitreous hemorrhage (VH).2 Symptoms of all three diagnoses can include painless floaters or clouded vision, making it difficult to distinguish between them based on history alone. Differentiating between them is critically important, as RD requires emergent diagnosis and ophthalmology evaluation. Patients will require a retina specialist to evaluate and treat the patient to preserve their visual acuity. PVD and VH, however, can often be discharged with close outpatient ophthalmology follow-up. POCUS is a safe, readily available tool in the ED that can be used as an adjunct to help differentiate RD from PVD and VH.
Symptoms of RD may include decreased visual acuity, flashes of light, floaters, or classically "a dark veil or curtain" in the field of vision.3 Its sonographic appearance is a linear, echogenic membrane in the posterior chamber that is tethered at the optic nerve and moves with eye movements. The sensitivity and specificity for POCUS to diagnose RD is 96.9% and 88.1% respectively when compared to the diagnostic standard of an ophthalmologist evaluation.2
PVD occurs most commonly as a normal consequence of aging with symptoms of acute onset painless floaters or flashes of light. It appears as a linear, echogenic membrane in the posterior chamber that does not attach at the optic nerve posteriorly, which is critical in distinguishing PVD from RD. The echogenic membrane of PVD may undulate with movement of the eye and is also thinner in appearance than in RD although it may be a subtle difference.4 The sensitivity and specificity for POCUS to diagnose PVD is 42.5% and 96% respectively.2
Symptoms of vitreous hemorrhage (VH) typically include painless floaters or clouded vision. The incidence of spontaneous VH is about 7 cases per 100,000 people and is associated with conditions such as diabetes mellitus or coagulopathy.5 VH has a more distinct sonographic appearance compared to PVD or RD but can be seen in conjunction with either pathology. It commonly appears as echogenic debris in the posterior chamber that may layer in the most gravity-dependent area of the eye depending on the volume and age of hemorrhage.3 Increasing the gain settings can help better appreciate subtle areas of hemorrhage. Extraocular movements may result in a “washing machine sign” from swirling of VH which can be appreciated in Video/GIF 1. The sensitivity and specificity for POCUS to diagnose VH is 81.9% and 82.3% respectively.2
Emergency physicians can detect RD, a true ophthalmologic emergency, with high sensitivity and specificity. Other vision-threatening diagnoses such as PVD or VH can also be detected with high specificity, and the emergency physician can communicate their concerns in consultation with ophthalmology. While PVD or VH do not often require emergent ophthalmologic intervention, patients with these conditions should have urgent follow-up with an ophthalmologist due risk of progressive vision loss or RD as a complication.4,6 Ocular POCUS is not intended to replace ophthalmology evaluation but can be a useful adjunct in resource-limited areas or EDs without immediately available ophthalmology services.
Hospital Course/Resolution
During his ED visit, the patient was evaluated by an ophthalmologist and diagnosed with PVD and mild VH OD on dilated funduscopic exam. He was discharged from the ED with instruction to follow up with ophthalmology in 1 week.
References
- Vaziri K, Schwartz SG, Flynn HW Jr, Kishor KS, Moshfeghi AA. Eye-related Emergency Department Visits in the United States, 2010. Ophthalmology. 2016;123(4):917-919.
- Lahham S, Shniter I, Thompson M, et al. Point-of-Care Ultrasonography in the Diagnosis of Retinal Detachment, Vitreous Hemorrhage, and Vitreous Detachment in the Emergency Department. JAMA Netw Open. 2019;2(4):e192162. Published 2019 Apr 5.
- Walker RA, Adhikari S. Eye Emergencies. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill Education; 2020. Accessed July 01, 2024.
- Lyon M, Riester M. Ocular. In: Ma O, Mateer JR, Reardon RF, Byars DV, Knapp BJ, Laudenbach AP. eds. Ma and Mateer's Emergency Ultrasound, 4e. McGraw-Hill Education; 2021. Accessed July 01, 2024.
- Rabinowitz R, Yagev R, Shoham A, Lifshitz T. Comparison between clinical and ultrasound findings in patients with vitreous hemorrhage. Eye (Lond). 2004;18(3):253-256.
- De La Hoz Polo, M., Torramilans Lluís, A., Pozuelo Segura, O., Anguera Bosque, A., Esmerado Appiani, C., & Caminal Mitjana, J. M. (2016). Ocular ultrasonography focused on the posterior eye segment: what radiologists should know. Insights into imaging, 7(3), 351–364.