Eye rubbing, especially with knuckles, is a significant environmental factor that, researchers are now showing, induces mechanical change in the cornea. Previous research has suggested that keratoconus and atopy are associated because pruritus leads to eye rubbing, which causes mechanical wear of the cornea and progressive ectasia. Not only does eye rubbing induce this mechanical warpage, it also can lead to biochemical changes in the cornea, which can develop into keratoconus.

A newly published study from a French research team looked at 202 keratoconus patients and 355 healthy controls. The researchers collected data regarding the subjects’ eye rubbing habits (pattern of eye rubbing, their dominant hand, sleep health, etc.). Patients who admitted to eye rubbing were asked to demonstrate their technique. They also looked at the patients’ allergies, history of dry eye, sleep habits and make-up application . Other factors not addressed in previous studies—screen time and night-time work—were included as well.

The investigators found that all types of eye rubbing (beneath or inside the eye and with knuckles, base of thumbs or fingertips) put patients at a higher risk, although rubbing with knuckles was significantly more likely to be associated with keratoconus. Additional factors they noted include side and prone sleep positions, suggesting that contact between the eye and the pillow at night could act like rubbing, in that it applies mechanical pressure to the eye. Patients with ocular allergies, dry eyes, blepharitis, eye strain, night-time work and prolonged screen time also experienced elevated rates of keratoconus, the research shows.

Keratoconus has no genetic risk factors and, therefore, a family history of keratoconus isn’t likely to influence a patient’s likelihood of developing it, the study shows. That means that much of the prevention methods are within patients’ control. All they need is the right guidance.

Moran S, Gomez L, Zuber K, Gatinel D. A case-control study of keratoconus risk factors. Cornea. February 12, 2020. [Epub ahead of print].