BLOG: Can you get eye problems from prone positioning?
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One of the strategies for severely ill patients with COVID-related acute respiratory distress is to place them in prolonged prone positioning.
This face-down position helps improve oxygenation by relieving some lung compression (by the heart and abdominal organs in supine position) and is typically done for at least 16 hours at a time. We’ve known for years that prone positioning — for example, during long surgeries — often causes the eyelids to crack open, which can lead to dramatic exposure keratopathy despite some pre-procedural taping of the lids. Proning has also been known to cause elevated IOP, central retinal vein occlusion, central retinal artery occlusion and ischemic optic neuropathy. Even things like yoga that can involve relatively short amounts of time with head-down positioning have been shown to have substantial IOP increases.
But a complication more serious than all of these is orbital compartment syndrome (OCS). A compartment syndrome happens when the pressure inside a tissue exceeds the perfusion pressure of that tissue. This more easily occurs in a closed “compartment” of the body where there is not much room for the tissue in question to expand. The most common examples of this in the body are in the distal extremities where the muscles of the forearm and lower leg are tightly surrounded by fibrous tissue and the limb is close ended, thus forming a compartment with only one entrance/exit.
For example, if a patient breaks their tibia, blood and edema come into the tissue, increasing the interstitial pressure. If too much fluid enters the tissue, this pressure can overwhelm the perfusion pressure, and new blood flow ceases to the tissue. Now the tissue is in an ischemic state and it’s just a matter of time until the ischemic damage becomes permanent.
The orbit is another perfect example of such a compartment. Surrounded by bone on all sides and the globe anteriorly, if too much fluid would enter the orbit and not recede, ischemic damage could occur in all contents of the orbit. And delicate tissues like the optic nerve do not need much ischemic time before permanent vision loss occurs.
Classically, OCS happens in cases of orbital hemorrhage from trauma or surgery, but it’s now being seen in patients with severe cases of COVID-19. A very interesting article in a recent issue of JAMA Ophthalmology (Sun et al.) focused on four patients with COVID-19 in acute respiratory failure during a single week. Of those four, two developed signs of OCS. All four patients were in prolonged prone position for 18 hours at a time, followed by 6 hours in supine position cycled every 24 hours. Importantly, during proning, “the patient’s head was rotated 45 degrees laterally to accommodate the endotracheal tube. Thus, one eye was always in a more dependent position than the other.”
The two patients who were reported as developing signs of OCS had neither symptoms nor visual acuity assessed, given they were deeply sedated. But the signs in both were documented as: 1) a near-tripling of IOP compared with supine position (measured with Tono-Pen [Reichert]) in the eye that was not compressed into the pillow (the IOP of the more-compressed eye being likely even worse but impossible to measure without moving the patient); 2) externally visualized peri-orbital edema; 3) intra-, sub- and superficial retinal hemorrhages and Roth’s spots; and 4) inferior optic disc swelling.
Of course, no one is arguing to sacrifice lung function in ICU patients with acute respiratory distress simply to reduce the risk for OCS. But there are steps we could take to help these proning patients have the best possible vision once they recover.
The first is simply to raise awareness of this problem. By just monitoring these patients to look for peri-orbital edema and to ensure that the more compressed eye is rotated will help. Second, the article advocates for the “use of protective cushioning of the eyes to avoid mechanical pressure on the globe during prone positioning.” Finally, (depending on the case) it might be appropriate to have an eye care provider examine the patient’s fundi to check for signs of OCS.
Patients who must undergo prolonged prone positioning face a lot of challenges, and OCS is just one. But it’s important for clinicians to know this complication exists. It cannot be addressed if no one is aware of it.
Reference:
- Sun L, et al. JAMA Ophthalmol. 2021;doi:10.1001/jamaophthalmol.2020.4988.