Abstract
Abstract: :
Purpose: To investigate whether severity of eye rubbing is correlated with the degree of keratoconus. Methods: Patients responded to a questionnaire at an initial interview and again at a second interview approximately 1 week later. The questionnaire assessed more than 30 parameters including past and current eye rubbing habits, such as severity of rubbing and the portion of the hand used for rubbing (N=204 eyes). A criterion for inclusion in this study was that the data obtained from the questionnaire be verified in all instances via communication with a patient's family member. The degree of keratoconus was graded as incipient, mild, moderate or severe based upon predetermined ranges of keratometric measurements and other clinical signs. The degree of keratoconus was then correlated with severity of eye rubbing, classified as either light, medium or severe. The severity depended upon the amount of pressure, measured in kg/cm, exerted on the eye. Results: Eye rubbing was highly prevalent among patients with keratoconus, 93.3% of whom rubbed their eyes as compared to 81.6% of a control group of patients without keratoconus (N=196 eyes) (Pearson's chi: value 6.300, P=0.012). Patients with keratoconus rubbed more forcefully than patients without keratoconus (Pearson's chi: value 27.366, P=0.000; Pearson's R: value 0.368, P=0.000; Spearman correlation: value 0.356, P=0.000); however, there was no correlation between the degree of keratoconus and severity of rubbing (Pearson's chi: value 8.607, P=0.377; Pearson's R: value 0.101, P=0.149; Spearman correlation: value 0.092, P=0.193). Interestingly, 75.3% of patients with keratoconus rubbed their eyes using a rotary motion as opposed to 31.3% of patients without keratoconus (Pearson's chi: value 34.359, P=0.000). Patients with keratoconus also tended to rub their eyes with a specific subset of knuckles, particularly the proximal interphalangeal joint of the index finger, which was used by 47.4% of keratoconic patients vs. 22.5% of non-keratoconic patients (Pearson's chi: value 11.797, P=0.001). Conclusions: We conclude that eye rubbing severity correlates with keratoconus, but not with the degree of keratoconus. This study suggests that the degree of keratoconus may be related to the manner and motion in which force is applied to the cornea rather than solely by the magnitude of the force.