Retinal Detachment v Hemorrhage

By Dr. Raashee Kedia

Acute vision change

A 51 year old female with a history of diabetes presented to the ED with acute onset of left eye painless blurry vision. Vitals were within normal limits. Fingerstick was 450.

On exam : Visual acuity was 20/30 in the right eye but could only count fingers in left eye at 1 foot. There were no external signs of trauma, conjunctivitis or proptosis. Pupils were equal and reactive to light. Ocular ultrasound of her right and left eyes were performed and shown below:

R eye

Leye

IN the left eye a bright echogenic linear structure can be seen floating in the posterior aspect of the globe.  This was concerning for retinal detachment, which is a clear ocular emergency. Ophthalmology evaluated the patient in the emergency department and diagnosed a vitreous hemorrhage. The patient was discharged home.

How do you tell the difference between a vitreous hemorrhage and a retinal detachment?

First, a little anatomy of the eye:

eyeana
Courtesy: National Eye Institute, National Institutes of Health (NEI/NIH).

The vitreous is a clear, gelatinous, and avascular substance, filling the space bound by the lens, retina, and optic disc. The retina is composed of multiple layers that form the posterior wall of the globe behind the vitreous. A retinal detachment occurs when these layers separate.

There is an internal membrane that separates the retina from the vitreous. This forms a potential space between the membrane and the vitreous called the subhyaloid space.

A vitreous hemorrhage occurs when blood extravasates into the vitreous or in the subhyaloid space. If bleeding has occurred in the subhyaloid space, it can appear boat-shaped on the surface of the retina, forming a superior straight line in an upright patient but changing with the position of the patient.

Ocular ultrasound is a quick and accessible way to assess ocular pathology. In patients with acute visual change, evaluation for retinal detachment is important to prevent complete and possibly permanent visual loss.

Ocular ultrasound is highly sensitive in the detection of retinal detachment in the ED.

With ocular ultrasound it can be difficult to distinguish between vitreous hemorrhage and retinal detachment. However, it is important to distinguish between these pathologies as they carry two different treatments and a different sense of urgency.

In an intact globe, the retina cannot be differentiated from the other choroidal layers on ultrasound.

Ultrasound of retinal detachment will show a thick hyperechoic membrane floating in the posterior globe. It never detaches from the optic nerve posteriorly.

Vitreous hemorrhage may layer and form a hyperdense linear density that can mimic a retinal detachment.

Decrease the gain to help differentiate between the two.

Vitreous hemorrhage is usually less dense and will fade as the gain is decreased. It usually layers inferiorly with gravity. Ocular movements produce a rapid, staccato motion of the hemorrhage, unlike a retinal detachment that is stiffer and slower in movements.

Sources:

Schott, M, Pierog, J.,Williams, S. “Pitfalls in the use of ocular ultrasound for evaluation of acute vision loss.” Journal of Emergency Medicine, Vol 44. Nov 2012.

Yanoff M, Duker JS. Opthalmology. 3rd ed. St Louis, MO: Mosby, An Imprint of Elsevier; 2008.

DiBernardo C, Greenberg E. Opthalmic ultrasound: A diagnostic atlas. 2nd ed. New York: Thieme MEidcal Publisers; 2007.

http://www.nyuemsono.com/wp-content/uploads/2012/10/Pitfalls-in-the-Use-of-Ocular-Ultrasound-for-Evaluation-ofnbspAcutenbspVision-Loss.pdf

Papilledema and the Crescent Sign

 

What’s abnormal in this image?

 

Here’s a hint.  Here is an example of normal.

 

When evaluating for possible elevation in intracranial pressure, it has been shown that optic nerve sheath diameter (ONSD) measurements correlate with elevated intracranial pressures.(1,2)  The optic nerve attaches to the globe posteriorly and is wrapped in a sheath that contains cerebral spinal fluid.  The optic nerve sheath is contiguous with the dura mater and has a trabeculated arachnoid space through which cerebrospinal fluid slowly percolates.

ONSD Normal Ranges

Normal Adults < 5 mm
Children >1 yr < 4.5 mm
Infants < 1 yr <4 mm

 

The ONSD is measured 3 mm posterior to the globe for both eyes.  A position of 3 mm behind the globe is recommended because the ultrasound contrast is greatest.  It is best to average two measurements of each eye.  An average ONSD greater than 5 mm is considered abnormal and elevated intracranial pressure should be suspected.

 

ONSD Measurement

 

Crescent Sign

In severe cases of elevated ICP, one can see an echolucent circle within the optic nerve sheath separating the sheath from the nerve due to increased subarachnoid fluid surrounding the optic nerve.  Ophthalmologists refer to this as the crescent sign.

 

 

 The Case

40 yo female patient presents with several months of frontal headache associated with photophobia and blurry vision.  Symptoms have gotten much worse over the last few days and she has had difficulty reading and watching TV because of her visual symptoms.  She denies fevers, chills, nausea, vomiting, or focal weakness.   Pt is hypertensive 170/100.  Her vital signs are otherwise normal.

  • Visual acuity - 20/30 OD, 20/70 OS
  • CT head is normal
  • Bedside point of care ultrasound

papilledema cropped from Sinai EM Ultrasound on Vimeo.

Papilledema 2 cropped from Sinai EM Ultrasound on Vimeo.

This patient had enlarged ONSD (measurements were 6 mm bilaterally) as well as papilledema(arrow).

 

Arrow notes papilledema

 

Lumbar puncture was performed.  Opening pressure was 44.  30 cc’s of CSF was drained and the closing pressure was 11.  The patient’s headache and visual symptoms improved .  She was started on acetazolamide and admitted to the neurology service.  MRI brain prior to lumbar puncture showed posterior scleral flattening bilaterally with protrusion of the optic nerve in the the globes bilaterally consistent with increased ICP.

This patient’s papilledema and increased ONSD correlated with a markedly increased opening pressure during lumbar puncture and suggests that ocular ultrasound may play a role in the ED management of patients with suspected pseudotumor cerebri.

Pseudotumor cerebri

Elevated intracranial pressure in the abscence of intracranial mass lesion.  Most common in young, over weight women. If the diagnosis is missed, persistently elevated intracranial pressure can lead to optic atrophy and blindness.

Treatment

  • Lumbar puncture to drain CSF to a normal opening pressure.
  • Medical:  Diomox (acetazolamide), high dose steroids
  • Surgical : Optic nerve sheath fenestration, VP shunt

Summary

The ability to diagnose papilledema using bedside sonography is useful to emergency physicians, as many non-ophthalmologist clinicians do not feel confident in their ability to perform an accurate nondilated fundoscopic examination. (3)  Ultrasound provides a useful alternative means of determining the presence or absence of papilledema in a patient in whom fundoscopy cannot be adequately performed.

 

 

[1] Geeraerts T, Launey Y, Martin L, et al. Ultrasonography of the optic nerve sheath may be useful for detecting raised intracranial pressure after severe brain injury. Intensive Care Med 2007;33(10):1704-11 [electronic publication 2007 Aug 1]. PMID: 17668184

 

[2] 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. PMID: 18275454

 

[3] Wu EH, Fagan MJ, Reinert SE, Diaz JA. Self-confidence in and perceived utility of the physical examination: a comparison of medical students, residents, and faculty internists. J Gen Intern Med 2007;22 (12):1725-30 [electronic publication 2007 Oct 6].  PMID: 17922165

 

Pupillary Light Reflex

We’ve all seen ultrasound augment the physical examination and even allow for assessments we could not otherwise accomplish at the bedside. One great example is the use of ultrasound to check the pupillary light reflex. If you are wondering why a pen light would not suffice for this physical examination standby, you have never encountered a patient with facial trauma whose eyes were swollen shut.

We already know what to look for without ultrasound (thanks to Greyson Orlando and Wikipedia for the GIF):

By directing the beam of a high-frequency linear array transducer through the plane of the iris, you can obtain the following image (while shining a light through the closed eyelid of the same or contralateral eye):

It takes a bit of practice to align both planes, and not worth the trouble if the patient can open their eyes.

Placing a Tegaderm over the closed eye prior to applying gel can make cleanup much easier afterwards (a useful tip for any type of ocular ultrasound).

Further reading:

  • Sargsyan AE, Hamilton DR, Melton SL, et al. Ultrasonic evaluation of pupillary light reflex. Critical Ultrasound Journal. 2009 1(2): 53-57.
  • Harries A, Shah S, Teismann N, Price D, Nagdev A. Ultrasound assessment of extraocular movements and pupillary light reflex in ocular trauma. Am J Emerg Med. 2010 Oct; 28(8):956-9.