Keratoconus: definition, causes and risk factors
Keratoconus is an eye disease whose symptoms stem from a deformation of the cornea.
This deformation is responsible for astigmatism, an appearance (increase) in myopia, and various symptômes visuels some of which are not corrected by wearing glasses: splitting of bright images on a dark background (such as the outline that appears splitted or tripled from the moon in the sky), persistent visual blur, etc.
The primitive cause of keratoconus is mechanicsAll patients who develop keratoconus have rubbed their eyes excessively in duration, intensity and frequency: these patients are often allergic, and more generally have risk factors for eye rubbingchronic diseases: atopy, dry eyes, night work, prolonged screen work, etc.
Irreversible biomechanical lesions caused by friction appear all the faster as the cornea is initially thinner and less resistant.
The diagnosis of keratoconus is confirmed by an examination of corneal topography (study of the shape and variations in corneal curvature and thickness).
Contrary to what is taught in classical treatises and many specialities:
Keratoconus is a condition originally mechanicalnot primitively genetic: corneal deformation is induced by eye rubbingexcessive corneal deformation. At the beginning, the deformation inflicted by friction is of an elastic nature (reversible when friction stops). Above a certain threshold (which depends on the intensity of friction and the native characteristics of the cornea) the deformation becomes "deformed". plastic« i.e. permanent.
Indeed, friction acts both on the plane mechanics (disorganization of the weft of the collagen fibers of the cornea) and biomolecular (mechanical cytotoxicity, cellular reaction with cytokine secretion and pro-inflammatory enzymes). These mechanisms combine to cause progressive thinning and a reduction in corneal stiffness, which are at the origin of the plastic deformation of the cornea.
This deformation explains the development or evolution of astigmatism, which is usually myopic in nature.
The perception with an eye of a doubling, or multiple images, ghosts, around the light sources, can make search for the presence of a Keratoconus: these symptoms reflect the presence of an astigmatism said irregular. The duplication and ghosting can be mitigated with a correction of glasses but they do not disappear completely (contrary to the symptoms caused by a simple astigmatism regular, correcgible in glasses). Beware, these symptoms are not specific to Keratoconus. A beginner cataract can also cause a slight duplication of perceived images.
When it is of corneal origin, any sensation of duplication or multiple images is not necessarily a sign of a keratoconus, but reflects a certain degree of reduction in the optical quality of the cornea. For example, superficial keratitis can cause the same type of symptoms.
The more the keratoconus is evolved, the more pronounced the intensity of these visual abnormalities is. In the casemajority of keratoconus, images "drool" mainly downwards or obliquely downwards. More about the vision of an eye reached by Keratoconus here
There is an urgent need to redefine the keratoconus
The classic but partially erroneous definition of the keratoconus diverts us from the real challenge of stabilizing and preventing the progression of the disease; the eviction of the eye rubbingexcessive.
The keratoconus, from the Greek Kératos for cornea and conus for cone shape, is defined classically as a bilateral, asymmetric, non-inflammatory corneal dystrophy (unknown cause). The keratoconus is characterized by a thinning and progressive deformation of the cornea. In optical terms, this deformation induced in theregular and irregular astigmatism (optical aberrations of high degree) caused by a marked alteration of the geometry of the cornea. Relegating them eye rubbingto a subordinate role (that of a "risk factor") is a serious error with serious public health consequences. This confuses correlation and causality, as if UV rays were considered a risk factor for sunburn, whereas they are the main cause.
An alternative and modern redefinition of the keratoconus is required.
For the classic, descriptive and functional definition of the keratoconus, the author of this site proposes to substitute a more causal definition. The keratoconus is characterized by the appearance of a corneal deformation responsible for visual symptoms and evocative topographical signs.
This deformation is directly related to the action of Repeated eye rubbing, responsible for a Mechanical stress of the cornea.
Keratoconus is not a primary dystrophy, nor a genetic disease, but a Mechanical condition of origin: Without friction, without repeated mechanical stress, there is no occurrence of deformation of the corneal dome, and therefore of keratoconus (See page dedicated the role of eye rubbing repeated with respect to the incidence of Keratoconus, see article « Eye rubbing. a sine qua non for keratoconus?« , see article"No Rub, no Cone, the Keraotconus Conjecture".
A site is totally dedicated to understanding the origin, as well as the modern management of the keratoconus: https://defeatkeratoconus.com/.
De nombreux case of Keratoconus are presented and illustrate the fact that eye rubbingare an essential and necessary element for the genesis of the keratoconus.
In particular, the study of the strictly unilateral forms of the disease, which do exist, simply allows us to deduce the essential element that is necessary to trigger the keratoconus. Patients who rub one eye and spare the other (or only slightly rub it) have a unilateral keratoconus.
These observations are instructive. Here is an example of this:
However, the majority of patients tend to rub both eyes, but often asymmetrically: invariably, the most rubbed eye is the most affected (the cornea is thinner and deformed). The most rubbed eye is often the one that undergoes the most compression at night in casea sleeping position on the belly or side.
The stop of friction guarantees the absence of progression of corneal deformation, which confirms the direct responsibility and indispensability of friction in the induction of the keratoconus.
The keratoconus is not an idiopathic dystrophy but a syndrome whose topographic expression reflects plastic deformation of the cornea, caused by mechanical stress represented by eye rubbingrepeated.
This explanation has the merit of simplicity and is compatible with all the data published in the medical literature. It is crucial to explain to patients who are affected and at risk (allergic, night workers, on screen, etc.) not to rub their eyes. This simple prescription has the potential to eradicate this disease, and to stop its progression.
This explanation of keratoconus is not popular with some practitioners who recommend that certain surgical procedures be performed, sometimes at the first consultation, during diagnosis, because it calls into question the validity of their interventionist attitude. It is never urgent to perform cross linking, ring placement or laser photoablation.
To consider keratoconus as a pathology whose main origin is mechanical is a paradigmatic disruption in the ophthalmological world that is not yet fully accepted, far from it. In addition to the aspects related to the loss of certain indications such as cross-linking, the weight of teaching or certain specious reasoning hinders the adoption of a theory that could nevertheless save from the progression and appearance of the keratoconus many eyes. Some practitioners argue, for example, that friction could be the consequence of keratoconus! This position is difficult to defend since a simple interrogation of patients with keratoconus invariably reveals that friction always precedes, by several months or years, the appearance of the first symptoms of keratoconus.
There is only one emergency in Keratoconus: stop any unwanted eye friction
The disease (caused by friction) no longer progresses as soon as they stop, and with the correction of the sleeping position (stop sleeping on the stomach or side, with the head stuck in the pillow, the arm or the hand in contact with the orbits etc.).
Cross linking, which is supposed to harden corneal tissue (in clinical practice this effect is not demonstrated), is not a logical response to keratoconus. The continuation of forttements after cross linking leads to the aggravation of the keratoconus.