"Genetics of Keratoconus is unclear. The frequency of occurrence within members of the same family are not clearly defined and would be slightly less than 20%. In the hypothesis where the friction are essential to the genesis of the affection, the genetic factors involved are rather related to conditions that predispose to the eye rubbing, or that control the thickness and resistance of the cornea. These conditions include diseases as diverse as Trisomy 21 and atopy. Sleep apnea has been associated with Keratoconus. The lack of quality sleep provides chronic fatigue and fatigue is likely to drive patients to rub their eyes. I met the case of patients who had a Keratoconus of installation late (after 30 years), due to a schedule change (night work) causing chronic fatigue, and the repetitive urge to rub their eyes. A sex ratio slightly biased in favor of men was reported recently for Keratoconus. In my experience, women who wear makeup tend to less rubbing the eyes than men. However, these rub sometimes eye after removal of make-up. Dry eye increases during pregnancy, due to certain hormonal changes: drought-induced irritation can cause the urge to rub their eyes. This could explain the progression of Keratoconus during pregnancy, and the fact that it has been identified as a risk factor for post LASIK ectasia. It is all case easier to explain the significant disparity of age, hit between the eyes, and the wide range of phenotypic expression by eye rubbing repeated by a corneal degeneration genetics and the unidentified molecular mechanisms. For the same intensity and the same amount of friction, the cornea which is less the thickness and resistance may undergo a deformation greater than more strong and thick corneas. Exposure to high degree of pollution and dryness of the air, combined with a bad environmental conditions or work may explain the increased prevalence of Keratoconus in certain ethnic groups. The explosion of work on screen and the generalization of the screens led to the emergence of a disease called ""Computer Vision Syndrome"" (which can be translated as 'Labour on screen Syndrome'). It includes eye fatigue chronic source of irritation and eye pruritus, which can lead to a repeated eye rubbing and play an important role in the increase in the prevalence of Keratoconus."
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