October Ultrasound of the Month

Dr. Cornett was able to correctly identify a “Mac off” retinal detachment  in a patient presenting with acute painless vision loss. 
 
Ultrasound Findings
 
A retinal detachment will appear as a hyperechoic membrane  that will appear to float freely in the vitreous with eye movement as demonstrated in the attached video clip. A retinal detachment  will be attached to the back of the globe and not cross the optic nerve and may be tethered at the optic disc posteriorly. This is opposed to a posterior vitreous detachment which will cross the optic nerve.

“Mac on” vs “Mac off”
 
“Mac on” refers to when the retina is still attached to the macula. This  is an ophthalmologic emergency since there are much better visual outcomes if repair can be done prior to progressing to a “Mac off” detachment. The macula is located temporally to the optic nerve, so if you see the retina attached in this region, the patient should get an urgent ophthalmology consult. “Mac off” retinal detachments, as in this case, are less urgent since visual outcomes are similar despite timing of surgery. However the patient should have ophthalmology follow-up as these all typically require repair. 

​Tips for scanning the Eye

• Start with the asymptomatic eye for comparison
• Use high frequency probe 
• Place a generous amount of gel on top of the closed lid 
• Rest the transducer gently on the gel with your hand stabilized on the patient, avoiding pressure on the globe 
• Fan through the entire globe in the transverse and sagittal planes. 
• Use the standard gain setting  to visualize posterior structures including optic nerve sheath 
• You can increase the gain to examine the vitreous. 
• Have the patient look in all directions to evaluate for pathology. 

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Author: Arthur Forbriger 
Editor: Allison Zanaboni ​