Mr. S.N is a 21-year-old male with a history of atopy (allergy to dust mites). There is no history of keratoconus in the family.
He complained of a progressive decrease in visual acuity greater in the right than the left eye. He is right-handed and sleeps on the right side.
His refraction at the first visit (02/21th/2017) was : Right Eye (RE) 20/40 with +0,25 (-2,25 x 30 °) and Left Eye (LE) 20/20 with +0,5 (-0,25 x 115 °).
Clinical examination with the slit lamp revealed an irregular inferior corneal bulge more pronounced in the right eye. We also found Fleischer rings (Fleischer rings are pigmented rings in the peripheral cornea, resulting from iron deposition in basal epithelial cells, in the form of hemosiderin), and tarsal papillae (indicating chronic ocular allergy) in both eyes.
Corneal topography revealed the presence of bilateral keratoconus more pronounced in the right eye.
When asked about the possibility of frequent eye rubbing, the patient admitted to rubbing his eyes when working in front of the computer, with the fists and knuckles. His mother, who was present at the consultation, confirmed that she often witnessed her son rubbing his eyes vigorously.
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 treated his allergy by referring him to an allergy specialist to determine the allergens responsible for his ocular pruritus and other symptoms.
Here are pictures of the patient rubbing his eyes and his profiles
This video was taken by his mother during his 10th birthday party. The video reveals eloquently how the patient used to rub his eyes when he was child.
Another video to show how he rubbed his eyes just prior to presentation at our clinic. As he mimics the rubbing movements the patient verbalizes that although he rubs both eyes at the same time, the technique used with the right hand is slightly different from that of the left. There is direct contact between the right eye and the knuckles of the index finger, and the rubbing is particularly vigorous through the upper eyelid. On the left eye, the contact is less direct, as the left hand is a slightly lower than the right one. Part of the rubbing energy delivered by the left hand is directed onto the cheekbone, not the eyeball. This difference in the rubbing technique could account for the increased severity of the corneal deformation in the right eye.
In this case we find many triggers for eye rubbing like allergy, extended work on the computer and a particular sleeping position (on the side, with ocular compression at night). The asymmetry of the keratoconus development may be related to the sleeping position (right side) and the coexistent habit of preferentially rubbing the right eye. We also believe that the dominant hand may have a role in asymmetry because the force applied by the dominant hand is probably higher than that of the non-dominant hand. The rubbing technique was slightly asymmetric, leading to an increased cumulative damage on the right eye. Eye rubbing with the dominant hand may incite more local irritation as it often contains more allergens (since the dominant hand is used more than the non-dominant one). As you can see in the video taken about a decade prior to the first visit, the way he rubs his eyes is different in both eyes…he rubs his right eye more vigorously and for a longer period.
This case is very informative and demonstrative of the direct causal effect of eye rubbing in the pathogenesis of keratoconus. Allergy is a classic risk factor for the disease, but this association exists probably because allergic patients rub their itchy eyes more often and more vigorously than their non-allergic counterparts.
The cessation of eye rubbing and proper allergy therapy are the best tools in the prevention of the onset and/or evolution of keratoconus.