WHAT IS KERATOCONUS?

Keratoconus has long been regarded as a « dystrophy of unknown origin ». The morphological deformation inflicted on the corneal wall in keratoconus is pronounced, but the relative absence of specific genetic and biomolecular abnormalities makes this disease an ophthalmic enigma.
In the following webpages, we will prove to you with the help of scientific and anecdotal evidence what we believe keratoconus to be….A mechanical disease caused by repetitive and vigorous eye rubbing.

Keratoconus is a condition where the cornea becomes thin and assumes a « cone-like » shape. It results in visual blurring or distortion from myopia and irregular astigmatism.

Clinical signs of keratoconus on slit lamp biomicroscopy include a thin cornea (upper left), Fleischer ring (lower left) and Vogt’s striae (upper and lower right). Fleischer rings are pigmented rings in the peripheral cornea from iron deposition in the basal epithelial cells, in the form of hemosiderin. Vogt’s striae are thin vertical streaks located in the posterior corneal stroma, at the level of Descemet membrane. In early cases of keratoconus, examination with the slit lamp may be entirely normal.

Corneal topography enables the morphological characterization of the cornea. It is essential for the diagnosis of keratoconus. This non-invasive exploratory technique has the possibility of achieving a great number of measuring points of both anterior and posterior corneal surfaces, All these data can be processed to extract a series of topographic valuation indices which have be conceived to increase the reliability of the clinical diagnosis.

Corneal topography enables the morphological characterization of the cornea. It is essential for the diagnosis of keratoconus. This non-invasive exploratory technique has the possibility of achieving a great number of measuring points of both anterior and posterior corneal surfaces, All these data can be processed to extract a series of topographic valuation indices which have be conceived to increase the reliability of the clinical diagnosis.

The authors of this website have acquired the certitude that the root cause of keratoconus is eye rubbing (1,2). This assertion, which is difficult to prove, but equally difficult to refute, derives from crossed observations and follow-up of hundreds of keratoconus cases. On this website, we present over fifty cases. These were cases of keratoconus that presented consecutively to our clinics, and were not randomly selected for the sole purpose of supporting our eye rubbing hypothesis. We have yet to find cases where eye rubbing, usually correlated with the sleeping position of the patient, was not in existence before the onset or diagnosis of keratoconus.

Recent biomechanical investigations have shown that corneas with keratoconus are focally but not globally weakened (3). In keratoconus, the central portion of the cornea is thinned and weakened, whereas its periphery shows a normal biomechanical behavior. How could a genetic or biomolecular disease involving corneal collagen and/or fibril structures affect focal areas while sparing other parts of the corneal tissue?

Keratoconus: can it occur spontaneously?

Keratoconus is usually described as an unknown collagen dystrophy associated with environmental, cellular and genetic factors causing a degenerative change in the cornea.  This degenerative change results in a reduction in the corneal stiffness. It is thought that impaired corneal biomechanics makes the corneal dome prone to bulge forward under the action of the intraocular pressure and undergo progressive « ectatic » changes. However, there is at least one perfect counter-example to explain the irrelevance of current theories on the pathogenesis of keratoconus. We will therefore pay attention to this disease named « Marfan syndrome« , and describe what could be labeled « The Marfan paradox« .

Marfan syndrome results from the abnormal synthesis of collagen which alters the biomechanics of the soft tissues of the human body such as skin, ligaments and blood vessel walls.  The  main layer of the cornea (the stroma) is made of collagen fibers. If Marfan syndrome should perfectly support the theories of keratoconus that attempt to explain the ectatic process by the occurrence of an alteration of corneal biomechanics via an unknown molecular abnormality, topographic changes similar to keratoconus should be observed. In Marfan syndrome, the corneal biomechanics are indeed impaired, and the cornea thinner. However, as logical as it may appear at first glance….

The weaker cornea in a Marfan patient, unlike in keratoconus, tends NOT TO BE steeper, irregular and ectatic, but rather globally FLATTER and not much irregular(4,5) !

This may not in fact be that surprising: without any additional external trauma, the biomechanical alteration of the corneal tissue in the eyes of Marfan patients causes the cornea to progressively distend. This mechanism may better describe what a « corneal ectasia » truly is : a progressive distension, globally harmonious, which incurs a progressive thinning and flattening of the corneal surfaces (as the radius of curvature of the cornea increases). It is not the same as what is commonly observed in early and mild keratoconus, in which the term « irregular deformation » or « warpage » may better describe the condition affecting the corneal wall. This deformation is caused by repeated local trauma due to the shearing forces vehicled by the hands, fingers and knuckles during eye rubbing episodes.

marfan vs keratoconus defeatkeratoconus.comSide by side comparison between the main features of Marfan syndrome and keratoconus.
Eye rubbing has been considered a risk factor for keratoconus and its progression (6-9). But could it be in fact the root cause of keratoconus?

The Marfan syndrome comparison highlights some pertinent observations:  that soft corneas from a genetic and/or biomolecular collagen abnormality do not undergo the changes seen in eyes with keratoconus i.e. irregular central steepening and focal thinning. In addition, the many clinical cases shared on this website support the hypothesis of eye rubbing as a first and necessary hit for inducing the progressive ectatic deformation of the corneal wall seen in keratoconus.

Both the increase in the incidence of atopy in the general population and time spent in front of the computer screen could account for an increased tendency for eye rubbing, and lead to the perceived increase of prevalence of keratoconus in both urban and non-urban areas.
The cases presented on this website are intended to provide evidence of the hypothesis that the mechanical stress imposed on the cornea may not be as much as a second hit exacerbating the signs of a predisposed cornea exhibiting progressive collagen alteration, but rather the necessary trigger and root cause for the keratoconus disease itself. Even if this hypothesis remains to be formally proven, the evidence is compelling, and this should increase public awareness on the deleterious effects of eye rubbing, and dramatically reduce the incidence of keratoconus, and stop its progression in eyes already affected.

We strongly believe that the current accepted definition of keratoconus being a « spontaneous ectatic deformation of the cornea » should be revised. The definition should be changed to reflect the true cause of keratoconus and solve this two century-old etiologic mystery.
Bibliography
  • 1 Gatinel D. Eye rubbing, a sine qua non for keratoconus? Int J Kerat Ect Cor Dis 2016;5(1):6-12
  • 2 https://www.gatinel.com/recherche-formation/keratocone-2/no-rub-no-cone-the-keratoconus-conjecture/
  • 3 Roberts CJ, Dupps WJ Jr. Biomechanics of corneal ectasia and biomechanical treatments. J Cataract Refract Surg. 2014 ;40(6):991-8.
  • 4 Sultan G, Baudouin C, Auzerie O, De Saint Jean M, Goldschild M, Pisella PJ; Marfan Study Group. Cornea in Marfan disease: Orbscan and in vivo confocal microscopy analysis. Invest Ophthalmol Vis Sci. 2002;43(6):1757-64.
  • 5 Maumenee IH. The eye in the Marfan syndrome. Trans Am Ophthalmol Soc. 1981;79:684-73(4). Review.
  • 6 McMonnies CW. Mechanisms of rubbing-related corneal trauma in keratoconus. Cornea. 2009;28(6):607-15.
  • 7 McMonnies CW, Boneham GC. Keratoconus, allergy, itch, eye-rubbing and hand-dominance. Clin Exp Optom. 2003;86(6):376-84.
  • 8 Sugar J, Macsai MS. What causes keratoconus? Cornea. 2012;31(6):716-9
  • 9 Carlson AN. Expanding our understanding of eye rubbing and keratoconus. Cornea. 2010;29(2):245.
Discover specific cases of Keratoconus
To find out more about The Keratoconus Diary