Purpose

To determine the distribution of Zernike coefficients and higher order aberrations in a normal population and its relationship with age, gender, biometric components, and spherical equivalent.

Methods

During the first phase of the Shahroud cohort study, 6311 people of the 40-64-year-old population of Shahroud city were selected through random cluster sampling. A subsample of participants was examined with Zywave aberrometer (The Bausch & Lomb, Rochester, NY) to measure aberrations. Measurements of aberrations were done before cycloplegic refraction, and values generated from a minimum pupil diameter of 5 mm were reported in this analysis.

Results

After applying exclusion criteria, 904 eyes of 577 people were analyzed in this study and mean age in this study was 49.5 ± 5.7 years and 62.9% were female. Mean root-mean-square (RMS) of the third−, fourth−, and fifth-order aberrations was 0.194 μm (95%CI: 0.183 to 0.204), 0.115 μm (95%CI: 0.109 to 0.121), and 0.041 μm (95%CI: 0.039 to 0.043), respectively. Total RMS coma (Z₃^−1, Z₃¹, Z₅⁻¹, Z₅¹), Total RMS trefoil (Z₃^−3, Z₃³, Z₅⁻³, Z₅³), and spherical aberration (Z₄⁰) in the studied population was 0.137 μm (95% CI:0.129–0.145), 0.132 μm (95% CI: 0.123–0.140), and −0.161 μm (95%CI:−0.174 to −0.147), respectively. Mean higher-order Zernike RMS in this study was 0.306 (95% CI: 0.295–0.318) micrometer, and in the multiple model, it significantly correlated with older age and short axial length. The highest amounts of higher-order RMS were observed in hyperopes, and the smallest in emmetropes. Increased nuclear opacity was associated with a significant increase in HO RMS (p < 0.001). Analysis of Zernike coefficients demonstrated that spherical aberration (Z₄⁰) significantly correlated with nuclear cataract only (age-adjusted Coef = 0.37 and p = 0.012).

Conclusion

This report is the first to describe the distribution of higher-order aberrations in an Iranian population. Higher-order aberrations in this study were on average higher that those reported in previous studies.