Age-Related Variations in Corneal Asphericity and Long-Term Changes

PURPOSE: Corneal front-surface asphericity is directly related with the optical quality of the eye and with contact lenses fitting. The purpose of this study was to evaluate the corneal asphericity as a function of age, sex, and refractive error measured with autokeratometry and corneal topography and its long-term changes (5- to 10-year period). METHODS: The asphericity and corneal curvature were obtained with the autorefractometer/autokeratometer NIDEK ARK-700A and with the videokeratoscope MODI 2.0 and compared. Corneal asphericity was retrospectively analyzed with NIDEK ARK-700A. The longitudinal study of asphericity was conducted with the same device between 2 appointments within an interval of 5 to 10 years. RESULTS: NIDEK ARK-700A showed agreement of asphericity values with those of MODI 2.0 (P=0.172) for a 7-mm diameter chord. The mean Q value of 1,484 right eyes (58.6% female), with a mean age of 40.2±18.4 years, was -0.24±0.12. No differences were found for Q value between sexes (P=0.424), age groups (P=0.268), and refractive error groups (P=0.107). The longitudinal analysis of corneal asphericity in 190 eyes (62.1% female) over a mean period of 5.9±1.4 years showed no significant differences in the Q value (0.00±0.08, P=0.813) over time. However, 14% showed asphericity changes of ±0.10 or higher while 86% of the subjects showed a change below ±0.10. CONCLUSIONS: The mean Q value observed in this study agrees with the average values of a white population and contributes to slightly reduce the positive spherical aberration of the eye. For the large majority of this population, the asphericity did not show significant changes within a period of 5 to 10 years, but significant changes can be observed in some patients.