Prevalence of interocular symmetry in corneal astigmatism and the possible influence of age, sex and refractive error.

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The aim of this study was to investigate, using a power vector approach, whether corneal astigmatism follows a mirror symmetry pattern considering both the magnitude and axis, and whether age, sex and spherical equivalent refractive error can influence the pattern. The IOLMaster 700 optical biometer was used to measure the radii of curvature of the anterior corneal surface. Refractive error was determined by non-cycloplegic subjective refraction. Descriptive statistical analyses and inferential logistic regression were applied over the dichotomous variable of mirror symmetry using J0 and J45 power vector components. An evaluation was carried out based on the subject's age, sex and spherical equivalent refractive error. A total of 2974 Caucasian adults were evaluated. This cross-sectional study revealed that axis orientation follows the isorule symmetry pattern, and in terms of both magnitude and axis orientation, mirror symmetry was present in 70.9% of cases. Age, sex and spherical equivalent refractive error were not significant factors and did not contribute to the clinical improvement of the model despite its statistical significance (refractive error, p = 0.001; age and sex, p = 0.23 and 0.36, respectively). Among an adult Caucasian population, the prevalence of corneal astigmatism mirror symmetry was 70.9% and isorule symmetry was the most common pattern considering axis orientation only. The inclusion of age, sex and spherical equivalent refractive error did not improve the model.