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PUBLICATION EXCLUSIVE: Musings on pterodactyl eggs and dry eye
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What if we are wrong about the cause of dry eye disease?
It is not very likely, I know, but what if we are? What if inflammation is not the primary event in the pathophysiology of DED, but is rather no higher than second on the cascade? For some 15 years now we have been discussing whether inflammation or dryness itself is the chicken or the egg. Just for the sake of discussion, what if the root cause of DED is neither?
What if DED is actually a primary neurological disorder?
It is a little wacky, but bear with me here. At the very least, we will get a chance to talk about a couple of new concepts and two new treatments, and remember two really tough clinical problems that definitely involve neuropathology, dry eye and inflammation.
In the rightfully famous Restasis (cyclosporine ophthalmic emulsion 0.05%) slide deck that each of us is so familiar with, Allergan reintroduced the concept of a neural feedback loop that begins on the surface of the eye and circles through the central nervous system by way of the trigeminal nerve. We are shown an example in which this loop is adversely affected by dryness and inflammation on the surface of the eye, and this in turn leads to a diminution of normal tear production. Inflammation is involved in the process on the surface of the eye, and the postulate is that treating the inflammation contributes to the restoration of the normal feedback loop.
There are several examples of neural diseases that produce signs and symptoms that are similar to what we see on the surface of the eye in DED. Let us look at two challenging clinical problems: herpes zoster ophthalmicus and denervation keratitis. Both involve the interruption or disruption of normal trigeminal nerve activity. Surface inflammation is associated with poor tear function, and at various times in the course of both diseases, we see corneas that look for all the world like really bad dry eye. In some way, the affected nerves are unable to participate in the normal feedback arc between the eye and central nervous system. It is almost always necessary to use some sort of anti-inflammatory therapy to successfully treat these problems. Sounds familiar, and all because of a primary neurological problem in both instances.
- Click here to read the full publication exclusive, The Dry Eye, published in Ocular Surgery News U.S. Edition, November 25, 2016.