Between-Eye Asymmetry in Keratoconus

PURPOSE.To report baseline differences between eyes on key variables in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study cohort compared with a retrospectively assembled group of myopic contact lens wearers without ocular disease. METHODS.A total of 1,079 keratoconus patients who had not undergone a penetrating keratoplasty in either eye before their baseline visit were enrolled and examined at baseline. Records from 330 contact lens-wearing myopes were reviewed. Corneal curvature (keratometry), visual acuity, refractive error (manifest refraction), and corneal scarring were measured. RESULTS.The mean differences between keratoconic eyes are as follows (better eye–worse eye for each variable, separately). Flat keratometry−3.59 ±4.46 D and steep keratometry−4.35 ±4.41 D; high-contrast best-corrected visual acuity7.30 ±6.83 letters; low-contrast best-corrected visual acuity8.53 ±7.51 letters; high-contrast entrance visual acuity9.03 ±8.40 letters; low-contrast entrance visual acuity9.43 ±7.88 letters; spherical equivalent refractive error3.15 ±3.84 D; and refractive cylinder power 1.55 ±1.42 D. Twenty-one percent of the keratoconus patients had corneal scarring in only one eye. There is an association between patient-reported unilateral eye rubbing and greater asymmetry in corneal curvature, and between a history of unilateral eye trauma and greater asymmetry in corneal curvature and refractive error, with the rubbed/traumatized eye being the steeper eye most of the time. CONCLUSIONS.Keratoconus is asymmetric in the CLEK Study sample.