Simulated Retinal Images of Landolt Rings in Human Eyes Including Asymmetric Aberrations on the Point Spread Function Analysis System

Abstract

Abstract: : Purpose: To simulate retinal images including asymmetric aberrations using a new point spread function analysis system (PSFAS). Methods: The point light source (SLD 840 nm) was projected onto the subject's eye and the reflected image at the retina was captured by the charge coupled device which was in the conjugated point with the retina (double-pass formula). To obtain the modulation transfer function (MTF) of the optical system, equal sized apertures were used as entrance and exit pupils (e.g., 2-2 mm, 4-4 mm, 6-6 mm). To obtain the phase transfer function (PTF), unequal sized apertures were used (e.g., 1-4 mm, 1-6 mm). The MTF was deduced from the square root of the normalized Fourier spectrum with Fourier transform of the modified aerial image, i.e., the double-pass PSF of each equal sized aperture. On the other hand, the PTF was deduced from the phase term with Fourier transform of that of the unequal sized apertures in the same eye. To obtain the simulated retinal images, the Fourier spectrum of the original chart was multiplied by the MTF and the PTF as the phase term of the original chart was added. The inverse Fourier transformation of the Fourier spectrum term and the phase term was the simulated retinal image. The simulated retinal images of the Landolt rings were compared with subjective sensations in the same subject with keratoconus. Results: The simulated retinal images of the Landolt rings in human eyes might sufficiently involve asymmetric aberrations without losing the high-frequency range of spatial frequency. Conclusions: The PSFAS can simulate retinal images, which are based on not only the information from the symmetric aberrations and the scattering and absorption of haze but also on the information from the asymmetric aberrations. The PSFAS can objectively evaluate the characteristics of the human optical system and therefore is useful in an ophthalmology clinic setting.

Keywords: keratoconus • optical properties • quality of life