Ocular Ultrasound: From Floaters to Fogginess

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Written by: Steve Chukwulebe, MD (NUEM PGY-3) Edited by: Michael Macias, MD, (NUEM Graduate 2017, US Fellow UC San Diego) Expert review by:  John Bailitz, MD 


The Case

A 60 year old male with a history of hypertension presents to the emergency department with three days of intermittent floaters in his right eye.  Concurrently, he also notes that vision in the right eye has become progressively blurred, first starting at the base of his visual field and now advancing up towards the center of his vision. He denies any trauma to the area as well as any other neurological complaints.

 

Ocular Exam

Motor: PERRL, EOMI,

Superficial Exam: Clear conjuctiva, left eye cataract

Visual Acuity: OD 20/25, OS 20/40 values corrected for a distance of 10 feet from the chart

Visual Fields: Decreased in the lower quadrants of the R eye to confrontation

 

The Differential Diagnosis for Floaters

  • Retinal detachment (RD)
  • Posterior vitreous detachment (PVD)
  • Vitreous hemorrhage
  • Intraocular foreign body
  • Posterior uveitis/vitreous inflammation
  • Migraine w/ aura

A bedside ultrasound obtained the following image:

 
eye.gif
 

 

The patient was found to have a retinal detachment and was admitted for definitive management under ophthalmology.


 Acute Vision Loss and Floaters

Floaters, often described by patients as lines, circles, dots, cobwebs, and other shapes, are common as part of the degenerative process of the vitreous body.  While in the chronic setting they are thought to be related to condensation of the vitreous collagen fibers, new onset floaters in patients 50 years or older have been related to PVD in 95% of cases. Of patients with vitreous floaters and/or flashes as a consequence of PVD, the incidence of RD is 14% [1]. If the PVD is complicated by vitreous hemorrhage, the incidence of RD rises to 70%.

From a population perspective, the incidence of RD ranges between 6.2-17.9 per 100,000 people with the highest rates occurring in the age group 60-69 [2].  Additionally, patients with history of myopia or uncomplicated cataract surgery have a significantly increased risk of developing RD compared to the general population.  It is also important to note that there is a 3-33% chance of bilateral involvement [3].


Using the Ultrasound for Detection of Retinal Detachment

On ultrasound, RD appears as a hyperechoic rippled (or undulating) line/membrane in the posterior to lateral globe.  A recent paper in Annals of Emergency Medicine reviewed 78 articles and ultimately included three studies (or 201 eyes) in a meta-analysis to evaluate the performance of emergency physicians at identifying RD through ultrasound [4].  Though the 95% confidence intervals for sensitivity and specificity range from 60%-100% in the three studies, each study boasted high accuracy to diagnosing RD.  Furthermore the receiver operating characteristic curve for the three studies had an excellent summary area of 0.97, suggesting that bedside ocular ultrasonography is an accurate tool in an emergency physician’s arsenal when a fundoscopic exam is technically challenging.

 

Keys to Successful Evaluation for Retinal Detachment with Ultrasound
 

Differentiating between RD and PVD - Keep the gain down:

Since the eye is usually a homogeneous fluid filled structure, it provides a great acoustic window for ultrasonography.  Too much posterior retrobulbar acoustic enhancement decreases the observer’s ability to visualize pathology in the vitreous body.  It can be difficult to see a difference between RD and PVD on ultrasound since both may present as a wavy membrane in the posterior orbit.  In this case, it is important to remember that the retina is a highly reflective surface and should still be seen as a thick or stiff undulating membrane with reduced ultrasonographic gain [5]. Another trick is when asking the patient to move their eye, the PVD membrane appears to be more mobile and dynamic, as if it is moving with the motions of the vitreous, while a RD membrane tends to retain its slow oscillation.

 

Ultrasound both eyes not just the affected one:

Though RD commonly occurs with the classic story of painless monocular vision loss, described as if a “curtain” or a “shade” is being pulled over their eye, in this case the patient actually presented with better visual acuity in his affected eye.  Remember that there is a 3-33% likelihood that a RD can be developing in the other eye.

 

Artifacts in the vitreous:

Artifact appears as bright echogenic material in the vitreous body that disappear when the patient is asked to move their eye.  However, if a persistent hyperechoic object is seen in the body, or there is shadowing or reverberations associated with the object, this is concerning for a foreign body or vitreous hemorrhage.

 

Using Tegaderm bandage over the eye:

This technique provides a few advantages.  One, it allows the ultrasonographer to apply as much gel as needed over the eye without the worry of getting it into the patient’s eye.  It is important to note that any pressure on the eye should be avoided if there is any suspicion for globe rupture or foreign body.  By applying a generous amount of gel over the eye and stabilizing the hand by placing a finger on the forehead or bridge of the nose, it is possible to stabilize the probe without having it make any contact with the eyelid.  This technique also allows for easier clean up after the exam, again focusing on preventing any pressure to the eye.


Conclusion

Bedside ultrasound is a useful tool for rapidly diagnosing RD and getting the patient seen by an ophthalmologist emergently.  However, if there is a high enough clinical suspicion for RD and ultrasound is negative, it is still important for the patient to receive a dilated fundoscopic exam by an ophthalmologist in a timely manner.


Expert Commentary:

Thank you for sharing this outstanding case describing one of the most straightforward and useful clinical ultrasound (CUS) applications. Few ED shifts go by when I do not need to perform an Ocular US exam. As mentioned, CUS is helpful for the evaluation of patients with suspected PVD, RD, Vitreous Hemorrhage, and Intraocular Foreign Body, but also for the assessment of patients with other ocular injuries or increased intracranial pressure. New clinicians may sometimes not perform an ocular US due to the perceived difficulty of preparing for, and safely performing the exam.

Pro-Tips on Preparing and Performing Ocular CUS Quickly and Safely

A physical examination of any sensitive structure such as the eye begins by first simply explaining the exam thoroughly to the patient. The explanation also provides a nice review for junior trainees in the room and even for the clinician sonographer! So take the time to explain the ocular ultrasound just as you would a Tonopen measurement or Slit Lamp exam.

Tegaderms are important for any patient who may not be entirely reliable or with suspected traumatic injury. However, for the experienced clinician sonographer with a reliable non-trauma patient, covering the orbit with a Tegaderm is not always necessary. Getting every artifact producing air bubble out of the way during the Tegaderm application may prove difficult. And patients may not appreciate the eye lash and brow waxing, as well as sticky residue left behind by the Tegaderm. As long as the patient agrees to keep their eyes completely until all gel is removed, the likelihood of gel getting into the eye is low. If cooperation is at all an issue, then I ask the patient their preference. From having the technique performed without a Tegaderm on myself countless times by students, and performing clinically on hundreds of patients, gel contamination is rare, and minor eye irritation even less so.

Next, recline the patient to a 45 degrees or even completely supine position. Then place a rim of gel on the clean linear probe. Ask the patient to close both eyes completely but not forcefully. Perform the exam from the head of the bed, first stabilizing your hand on the patient’s forehead, then gently placing the probe over the closed lid. With any soft tissue or musculoskeletal exam, always start with the normal side first to relearn your anatomy and optimize your settings. In particular, according to the As Low As Reasonably Achievable (ALARA) Principle, utilize the lowest Mechanical Index (MI) possible when performing ocular ultrasound. This minimizes the theoretical risk of damage to the delicate retinae from excess ultrasound energy. If you do not know how to adjust MI, then just select the Ocular preset on your machine. If you have no ocular preset, but a patient who desperately needs the ultrasound, at the very least be sure to minimize the ultrasound exam duration.

As you finish examining each eye, remind the patient to keep both eyes closed until all gel is removed. Have an assistant gently wipe any gel from the eyelid using gauze to lift the gel completely from the lid and lashes. For most CUS applications, white cotton napkins found in just about every ED work the best for gel removal. Paper towels simply smear gel, chucks are too expensive, and clothe towels hard to locate in a busy ED. For the ocular exam stick with gauze to lift all the gel away and give the patient one after you are finished just in case. With brief but adequate preparation and explanation, ocular CUS is a safe and effective technique to rapidly rule in emergent ocular pathology!

 

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John Bailitz, MD

Associate Professor of Emergency Medicine

Program Director, Northwestern Emergency Medicine

 


FOAMed Resources

1. Just in Time Learning

         a. Jacob Avilla’s 5 Minute Sono; http://5minsono.com/vids/

         b. ACEP Sonoguide https://www.acep.org/sonoguide/smparts_ocular.html

 2. Detailed Learning:

         a. Introduction to Bedside Ultrasound iBook Volume 2 Chapter 16. https://itunes.apple.com/us/book/introduction-to-bedside-ultrasound-volume-2/id647356692?mt=11

          b. Ultrasound of the Week: Ocular Ultrasound https://www.ultrasoundoftheweek.com/tag/ocular/


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 How to cite this post

[Peer-Reviewed, Web Publication]  Chukwulebe S,  Macias M  (2018, March 19). From Floaters to Fogginess.  [NUEM Blog. Expert Review by Bailitz J ]. Retrieved from http://www.nuemblog.com/blog/ultrasound-in-RD. 


References

  1. Lumi X, Hawlina M, Glavač D et al. Ageing of the vitreous: From acute onset floaters and flashes to retinal detachment. Ageing Research Reviews. 21:71-77. 2015.
  2. Mitry D, Charteris DG, Fleck BW, Campbell H, Singh J. The epidemiology of rhegmatogenous retinal detachment: geographical variation and clinical associations. British Journal of Ophthalmology. 94(6):678-684. 2009.
  3.  Gupta OP, Benson WE. The risk of fellow eyes in patients with rhegmatogenous retinal detachment. Current opinion in ophthalmology. 16(3):175-8. 2005.
  4.  Vrablik ME, Snead GR, Minnigan HJ, Kirschner JM, Emmett TW, Seupaul RA. The diagnostic accuracy of bedside ocular ultrasonography for the diagnosis of retinal detachment: a systematic review and meta-analysis. Annals of emergency medicine. 65(2):199-203.e1. 2015.
  5. Schott ML, Pierog JE, Williams SR. Pitfalls in the Use of Ocular Ultrasound for Evaluation of Acute Vision Loss. The Journal of Emergency Medicine. 44(6):1136-1139. 2013.