Differences in peripheral aberrations in age-balanced hyperopes, emmetropes and myopes

Purpose Aberrations in the peripheral visual field have been implicated in the development of myopia. Investigators have concentrated on myopes and emmetropes. As significantly higher levels of aberrations have been found on-axis in hyperopes than myopes, this study investigated the differences in peripheral aberrations in hyperopic, emmetropic and myopic groups. Methods Cycloplegic peripheral aberration for 5 mm pupils was measured at 39 locations across 42° x 32° of right eye fields with a COAS-HD Hartmann-Shack aberrometer in 9 hyperopes (mean age 29 ± 5 years, spherical equivalent refraction M +1.47 ± 0.58 D), 20 emmetropes (28 ± 7 years, +0.06 ± 0.36 D) and 20 myopes (27 ± 6 years, ‒2.55 ± 1.82 D). Relative peripheral refraction error RPRE and 3rd–4th order Zernike coefficients were determined and compared between the groups using repeated measures ANOVAs. Results Hyperopes and emmetropes had relative peripheral myopia across the visual field, with considerable nasal-temporal asymmetry for both groups and superior-inferior asymmetry for hyperopes. Myopes had minimal RPRE along the horizontal meridian, and less myopic RPRE along the vertical meridian than the other groups. There was little difference between groups in astigmatic components or higher-order Zernike coefficients, except for fourth-order spherical aberration C40 which was more positive in hyperopes than in both emmetropes (mean difference ± 95% CI = +0.048 ± 0.046 µm, p 0.030) and myopes (+0.067 ± 0.042 µm, p 0.003). Coma changed rapidly across the visual field with similar rates for all the groups. The rates for C31 along the horizontal meridian (mean rate ‒0.013 µm/degree), were significantly higher than for C3-1 along the vertical meridian (‒0.009 µm/degree). Conclusions Hyperopes and emmetropes had greater relative peripheral myopia than the myopes. There were asymmetries in RPRE along the vertical meridian for hyperopes which was not present in the emmetropes, suggesting there may be asymmetries in peripheral eye length along the vertical meridian for the former. All higher-order aberrations were affected by field eccentricity, but refractive error affected only the spherical aberration coefficient which was more positive for hyperopes than for other groups. It is unlikely that high levels of aberration contribute to myopia development