Dynamics of the eye’s wave aberration

Abstract

It is well known that the eye's optics exhibit temporal instability in the form of microfluctuations in focus; however, almost nothing is known of the temporal properties of the eye's other aberrations. We constructed a real-time Hartmann-Shack (HS) wave-front sensor to measure these dynamics at frequencies as high as 60 Hz. To reduce spatial inhomogeneities in the short-exposure HS images, we used a low-coherence source and a scanning system. HS images were collected on three normal subjects with natural and paralyzed accommodation. Average temporal power spectra were computed for the wave-front rms, the Seidel aberrations, and each of 32 Zernike coefficients. The results indicate the presence of fluctuations in all of the eye's aberration, not just defocus. Fluctuations in higher-order aberrations share similar spectra and bandwidths both within and between subjects, dropping at a rate of approximately 4 dB per octave in temporal frequency. The spectrum shape for higher-order aberrations is generally different from that for microfluctuations of accommodation. The origin of these measured fluctuations is not known, and both corneal/lenticular and retinal causes are considered. Under the assumption that they are purely corneal or lenticular, calculations suggest that a perfect adaptive optics system with a closed-loop bandwidth of 1-2 Hz could correct these aberrations well enough to achieve diffraction-limited imaging over a dilated pupil.

The influence of eye movements on monochromatic wavefront aberrations

“…Aberrationen höherer Ordnung können aufgrund von Akkommodation (Ninomiya et al 2002) und Tränenfilminstabilität (Hofer et al 2001) …”

“…Für diese Studie wurden zur genauen Betrachtung der Aberrationen die ZernikeKoeffizienten bis einschließlich der vierten Ordnung ausgewählt (Liang und Williams 1997, Artal et al 2001, Panagopoulou und Pallikaris 2001, Cheng et al 2003b, Fam und Lim 2004, Yamane et al 2004, Zhu et al 2004). …”

“…Es gibt aber auch Untersucher, welche die Zernike-Koeffizienten bis zur fünften (Porter et al 2001, Hofer et al 2001 Ordnung immer kleiner und haben damit auch einen geringeren Einfluss auf die Bildqualität (Porter et al 2001, Castejón-Mochón et al 2002, Thibos et al 2002b.…”

Evaluating the Clinical Utility of Noninvasive Methods for Measuring Tear Film Surface Quality

“…In the last decade, more attention was given to the developments of non-invasive methods for pre-corneal tear film surface analysis such as repeated measure videokeratography [7], [8], high-speed videokeratoscopy [9]- [11], dynamic wavefront sensing [12], [13] and interferometry [14]- [18]. There are also attempts to combine the techniques as in the case of wavefront sensing and retroillumination [19].…”

Dynamic Image Precompensation for Improving Visual Performance of Computer Users with Ocular Aberrations

“…The OTF of the eye is derived by 25) as the Fourier transform of the PSF, where u and v are the horizontal and vertical spatial frequencies in discrete form. Based on its definition, the MTF is calculated as the modulus of the complex-valued OTF:…”