Patient right profile
Mr. M.N is a 20-year-old male. He has asthma and allergy to dust mites and had to undergo desensitization treatment for his allergies in the past. He has a twin brother (monozygotic) who does not have keratoconus and they are currently living together in the same house. Mr M.N presented to us complaining of a progressive decrease in visual acuity greater in the right eye than the left.
His refraction at the first visit at the Rothschild Foundation (on 05/22th/2018) was : Right Eye (RE) 20/80 with -5.75 (-3.5 x 35 °) and Left Eye (LE) 20/32 with -3.5 (-1.5 x 145 °).
Clinical examination with the slit lamp revealed a thin cornea with Vogt’s striae (fine whitish lines in the posterior stroma) and Fleischer rings (Fleischer rings are pigmented rings in the peripheral cornea, resulting from iron deposition in basal epithelial cells, in the form of hemosiderin), in both eyes.
Corneal topography performed at our institution showed the presence of bilateral keratoconus, more pronounced in the right eye.
When first asked about eye rubbing, the patient declared that it did not occur to him that he would particularly rub his eyes, although he would sometimes do it mechanically more as a reflex action because his eyes felt itchy. We asked the patient to pay more attention to possible conscious rubbing episodes, and gave him an appointment for a review visit one month later.
During the second visit, the patient acknowledged that he had come to realize that he was rubbing his eyes way more than he had thought, in particular at the office in front of the computer screen to relieve ocular fatigue and itch or at home after removal of his rigid contact lenses.
He is left handed and he used to rub his both eyes, and preferably his right eye with his right hand. He would use his knuckles to rub both eyes, a gesture that he would perform many times a day.
His twin brother does not rub his eyes.
The patient sleeps on his right side, with the head buried in the pillow (pillow hugging).
We explained to the patient that since vigorous eye rubbing had preceded the drop in visual acuity, this habit may have caused the cornea to deform in his case. We strongly advised him to stop rubbing his eyes, and to change his unhealthy sleeping position. We also treated his ocular allergy with anti-histamine eye drops.
Here are pictures of the patient rubbing his eyes and his profiles
We have here monozygotic twin brothers with an identical genetic makeup, living in the same environment. One rubs his eyes incessantly, the other does not. The former has keratoconus, the other does not.
This case is an important example to support the mechanical (eye rubbing) theory of keratoconus genesis, and effectively debunks the current consensus that keratoconus is an inherited disease primarily caused by a biochemical abnormality, which could be transmitted genetically or occur sporadically. This however, does not imply that genes have no role in the pathogenesis of keratooconus and its progression. Genetics play a role by creating a susceptibility to corneal fragility and in the development of allergies, which cause ocular pruritus (itch), and induces the urge to rub the eyes. .
The key difference between these twin brothers is the eye rubbing habit and the resultant external force exerted on the cornea from the incessant eye rubbing. It is therefore appropriate to consider replacing the current genetic theory with that of a mechanical theory, which advocates that keratoconus is primarily a mechanical disease induced and perpetuated by chronic and vigorous eye rubbing.
The corneal dome can be likened to a shell whose equilibrium geometry depends on the difference between the intraocular pressure (exerted on its posterior surface) and the atmospheric pressure. Beyond a certain threshold, the mechanical stresses (compression and shear) conveyed by eye rubbing results in a biomechanical embrittlement, due to the rupture of the harmonious arrangement of collagen fibers, which causes an irreversible deformation of the cornea (This mechanism is analogous to the « buckling » in resistance of materials).
On this site, we wish to therefore convey the following message: that keratoconus would not appear or evolve without the action of an external mechanical force, which is conveyed by the hands (fingers, knuckles or nails) of patients who rub their eyes. Based on our experience with dozens of documented cases in this website, including this one, it appears that ocular friction (or repeated mechanical stress) is not the consequence of keratoconus or a mere risk factor, but most likely THE CAUSE of keratoconus.
The cessation of eye rubbing and treatment of allergies to curb eye rubbing are the best tools in the prevention of the genesis and/or evolution of keratoconus.
Other cases :
- Date 2 novembre 2018
- Tags Allergy, Asymmetric, Bilateral keratoconus, Childhood rubbing, Eye rubbing, Inferior keratoconus, Knuckles rubbing, Lens removal rubbing, Male, Pillow hugging, Rigid lens, Sleep position, Stabilization