Abstract
Purpose :
This study aims to investigate whether the eye’s optical properties offer the peripheral retina the necessary information to distinguish positive from negative defocus. Specifically, we examined the wavelength-dependent optical anisotropy arising from the interaction of peripheral monochromatic and chromatic aberrations. Exploring the nuances of peripheral polychromatic image quality may contribute to further understanding mechanisms of accommodation, emmetropization and improving therapeutic interventions for myopia control.
Methods :
For wavelengths across the visible spectrum (405 to 695 nm, 7 steps), retinal image quality was computed across the horizontal nasal visual field (0, 10, 20 and 30 degrees) using previously reported lower and higher order monochromatic aberrations for a 4 mm pupil for three refractive error groups: emmetropes, myopes and hyperopes. The two-dimensional through-focus modulation transfer function (MTF) was computed from -3 to +3 D in 0.1 D steps at each eccentricity. Two image quality metrics were used: (1) overall image quality (vMTF, defined as the volume under the MTF) and (2) optical anisotropy (OA, defined as the ratio of horizontal and vertical meridians of the MTF). Monochromatic point spread functions were superimposed using previously published longitudinal and transverse chromatic aberration data to evaluate peripheral chromatic optical cues.
Results :
In the nasal visual field at 20 and 30 deg, both emmetropes and hyperopes exhibited horizontally elongated blur (OA < 1) for all wavelengths. Alternatively, for myopes, blur was vertically elongated (OA > 1) at 10, 20 and 30 deg for wavelengths longer than 655, 605 and 505 nm, respectively. Furthermore, myopes demonstrated optimal optical quality (highest vMTF) for short wavelengths in the periphery, whereas hyperopes exhibited optimal optical quality for long wavelengths. Emmetropes showed relatively little shift in optimal wavelength in the periphery.
Conclusions :
Chromatic and peripheral monochromatic aberrations interact to affect optical quality differently in myopes, emmetropes and hyperopes. The eye's peripheral chromatic properties (contrast and anisotropy) may allow the discernment of positive from negative defocus. Whether the eye utilizes the optical information predicted by this model remains to be seen.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.