Table A1.
Zernike model and simulations of the effects of asymmetries in the shape of the point-spread function (PSF) and magnitude of blur for different low-order aberrations and some high-order aberrations (coma) on the cross-correlation metrics. Z3 = astigmatism (axis 45, 135°); Z4 = defocus; Z5 = astigmatism (axis 90, 180°); Z7 = coma (y-axis or vertical); Z12 = primary spherical aberration.
| Condition (Zernike term manipulated) |
PSF right eye |
PSF left eye |
Signal width |
Signal height |
Noise height |
Signal-to- noise ratio |
Height-to- width ratio |
| 1. No aberrations | 11.4 | 1.0 | 0.13 | 7.8 | 8.8 | ||
| 2. Symmetrical astigmatism, Oblique (+ve Z3, +ve Z4) | 42.2 | 1.0 | 0.18 | 5.5 | 2.4 | ||
| 3. Asymmetrical astigmatism, Oblique (+ve Z3, +ve Z4 OD; −ve Z3, +ve Z4 OS) | 88.5 | 0.6 | 0.21 | 3.1 | 0.7 | ||
| 4. Unequal blur (+ve Z4 OD; Z3, +ve Z4 OS) | 73.1 | 0.8 | 0.21 | 3.7 | 1.1 | ||
| 5. Unequal defocus (Nil OD; +ve Z4 OS) | 64.8 | 0.2 | 0.17 | 1.3 | 0.3 | ||
| 6. Equal defocus (+ve value Z4) | 60.4 | 1.0 | 0.27 | 3.7 | 1.7 | ||
| 7. Symmetrical astigmatism, ATR (+ve Z5, +ve Z4) | 103.8 | 1.0 | 0.22 | 4.6 | 1.0 | ||
| 8. Symmetrical astigmatism, WTR (−ve Z5, +ve Z4) | 37.3 | 1.0 | 0.34 | 2.9 | 2.7 | ||
| 9. Asymmetrical astigmatism, ATR-WTR (+ve Z5, +ve Z4 OD; −ve Z5, +ve Z4OS) | 79.0 | 0.6 | 0.20 | 3.1 | 0.8 | ||
| 10. Asymmetrical coma (−ve Z7 OD; Nil OS) | 13.3 | 0.5 | 0.10 | 4.8 | 3.6 | ||
| 11. Asymmetrical coma (typical values of unequal Z7 combined with equal Z4, Z5, Z12) | 32.3 | 0.9 | 0.25 | 3.7 | 2.9 |