Is there any truth to the idea of ‘no rub, no cone?’
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Eye rubbing is the root cause and the necessary ingredient of keratoconus
The “no rub, no cone” theory states that excessive eye rubbing is a necessary ingredient in the genesis of keratoconus, which is considered a traumatic condition. Current dogma states that keratoconus is a multifactorial condition whose mechanisms remain to be elucidated, and eye rubbing is considered as a simple risk factor. This is a major mistake from my point of view and an example of confusion between correlation and cause, although usually confusion occurs in the other direction (correlated factors are confused with causal mechanisms). It is important to reinterpret the medical literature and realize that repeated eye rubbing episodes exerted on the cornea, which precede by months or years the discovery of keratoconus, can inflict tissue trauma that alone can cause the corneal deformation and thinning characteristic of the disease.
Keratoconus is often given an inflammatory dimension. Indeed, inflammation is the possible source of irritation leading to reflex ocular friction but also the consequence of friction itself (simply rubbing the cornea for 30 seconds causes the release of many pro-inflammatory molecules and collagenases).
While a genetic condition is hardly able to explain the local and asymmetrical nature of keratoconus, a well-conducted interview with the patient can often link corneal involvement with the type and practice of eye rubbing. For example, in the case of a unilateral or asymmetrical case, patients almost always state there is rubbing exerted solely or preferably on the most affected side. Incidentally, we realized that there was a striking correlation between the affected side (excessively rubbed) and the sleeping position responsible for prolonged eye compression on the bedding or the forearm.
A prospective study conducted on a cohort of patients with keratoconus is underway at the Rothschild Foundation. In patients who stop rubbing (and incidentally change their sleeping position), we can observe the arrested progression of the disease. Unfortunately, and as expected, those who persevere with this behavior see the corneal deformity progress. These observations, which I will present at the CXL Experts’ Meeting, provide another striking confirmation for the veracity of the “no rub, no cone” theory and open up exciting prospects for noninvasive management of the condition. These results echo the call for a rethinking of the current definition of keratoconus and pave the way for a simple but effective way to stop the progression of or even eradicate the disease by a simple but effective maneuver: the total cessation of eye rubbing.
Damien Gatinel, MD, PhD, is from Rothschild Foundation, Paris. Disclosure: Gatinel reports no relevant financial disclosures.
Peer-reviewed evidence does not support eye rubbing is cause of keratoconus
We all agree that there is a relationship between eye rubbing and keratoconus. This fact is not controversial in the slightest, and this is why we take measures to stop patients from rubbing their eyes. As a clinician, I tell my patients to stop rubbing their eyes, and I send them to an allergist if needed.
However, stating that there is a causal relationship and using a slogan such as “no rub, no cone” is far from ideal: It must be substantiated by evidence. This slogan is an oversimplification and potentially dangerous because it may keep patients with active keratoconus from receiving the only treatment modality we know today — corneal cross-linking.
Eye rubbing is not the cause of keratoconus but rather a trigger. Once the trigger has activated the disease, and the disease is still in its early stages, it might indeed stop. However, there will be a “point of no return,” and once the state of keratoconus reaches this point, progression will continue with or without the stimulating trigger.
As a clinical researcher, I am trying to look at these issues factually, so I ask myself: What is known in the peer-reviewed literature? When searching for “cross-linking and keratoconus,” 1,206 publications emerge. This search includes publications such as Goodefrooij and colleagues’ paper showing that the number of keratoplasties in the Netherlands has decreased to half since the introduction of corneal cross-linking.
For “eye rubbing and keratoconus,” I found 119 publications, mostly case reports, case series and small population studies. When searching for peer-reviewed data showing that eye rubbing is the cause of keratoconus, no publications were found.
So, until there is clear, peer-reviewed evidence that stopping eye rubbing is all we need to stop keratoconus progression, I suggest that we follow what the published evidence tells us. I will change my opinion if proven wrong, but for now, I stand by my statement that stopping eye rubbing alone will not stop keratoconus progression in every case. In other words: “No rub, no cone — no way.”
Farhad Hafezi, MD, PhD, is from ELZA Institute, Zurich, Switzerland. Disclosure: Hafezi reports he is the named co-inventor on PCT applications CH2012/0000090 and PCT2014/CH000075 and is chief scientific officer at EMAGine SA, Switzerland.