Abstract
Purpose: :
To compare the impact of individual Zernike coefficients on retinal image quality in normal eyes using a simulation experiment.
Methods: :
Wavefront errors of 500 normal eyes (274 subjects) were reconstructed with Zernike polynomials (2nd-5th order) over a pupil diameter of 6 mm. Distance correction was simulated using a lower-order aberrations (LOA) optimization algorithm based on the VSOTF metric (visual Strehl ratio of the optical transfer function) to minimize the influence of LOA. An ideal, diffraction-limited wavefront served as control. Each coefficient was modified separately from -1 µm to 1 µm in 0.1 µm steps while all other Zernike coefficients were kept constant and the VSOTF metric was calculated from each modified wavefront error. Tolerance to aberration-induced deterioration of retinal image quality was defined as the range over which the VSOTF did not decrease more than 0.2 log units from its maximum value.
Results: :
In the diffraction-limited eye, tolerances ranged from <0.1 µm (C5±1) to 0.4 µm (C2±2). In real eyes, tolerance values varied between 0.24 µm (C5-1) and 1.52 µm (C5-5) with lowest tolerances for the coefficients at the center of the Zernike pyramid. Improvement of retinal image quality with coefficient values different from zero could be observed with C20 (maximum VSOTF at 0.5 µm), C3-1 (-0.1 µm) and C40 (0.1 µm).
Conclusions: :
(1) In eyes with physiological aberrations, the impact of individual Zernike coefficients on retinal image quality was not equal. (2) The presence of physiological higher-order aberrations decreased retinal image quality but mitigated the impact of individual coefficients on image deterioration.
Keywords: aberrations • refractive surgery: optical quality