Age-Related Changes in Total Corneal Astigmatism in Eyes With High Myopia

Abstract

Purpose: The purpose of this study was to compare age-related changes in corneal astigmatism in eyes with and without high myopia. Methods: Eight-hundred eyes with high myopia (axial length ≥26.0 mm) and 800 eyes without high myopia (200 eyes each from patients in their 40s, 50s, 60s, and ≥70s) underwent videokeratographic examination. The amounts of vertical/horizontal (Rx) and oblique astigmatism (Ry) components, irregular astigmatism, and corneal shape were compared between eyes with and without high myopia and among age categories. Results: In both groups, the mean Rx significantly changed to more positive with age (P < 0.001), whereas the Ry did not change significantly. The Rx was significantly more negative in the high myopia group than in the control group in all age categories (P ≤ 0.003), whereas the Ry did not differ significantly. The mean changes in the Rx and Ry during each 2 consecutive decades did not differ significantly between groups. The asymmetry and higher-order irregularity components increased with age (P ≤ 0.001) but did not differ significantly between groups, except for the higher-order irregularity in patients in their 60s (P = 0.018). In the averaged map, the corneal shape changed from with-the-rule to against-the-rule astigmatism with age in both groups, but the changes occurred later in the high myopia group. Conclusions: Age-related changes from with-the-rule to against-the-rule astigmatism occurred later in eyes with high myopia compared with eyes without high myopia in middle or older aged patients, but this change in each age decade was comparable between eyes with and without high myopia.