We first investigated the similarity in optical quality of a batch of diffractive intraocular lenses (DIOLs), providing experimental evidence for one DIOL as representative of a batch. Using adaptive optics, we then evaluated one DIOL under different levels of Zernike spherical aberration (SA) by applying both a point spread function test and a psychophysical visual acuity test. We found that for small aperture size SA has the effect of shifting the through-focus curve of DIOL. Also, for a relatively large aperture size, it has different effects on the distant and near foci.
Wavefront aberrations of human eye are expected to change when the eye accommodates to targets from infinite distance to clear visual threshold distance (25 centimeters distance from target to eye). It is significant to measure and analyze the wavefront aberrations in the accommodated human eye, which helps to evaluate visual performance and has clinical value.
The previous research on the effect of accommodation on the wavefront aberration all adopted subjective measurement technique. In this paper, we firstly adopt Hartmann-Shack wavefront sensor technique, which possesses advantages in comparison with the psychophysical subjective technique such as larger sampling points. Data from 20 eyes are reported in this study. Ages of all subjects range from 19 to 38 and defocus of them range from -6D to +3D. Every pupil size is greater than 5mm for whole eye measurements. No one in this experiment has a record of ocular disease.
Root-mean-square (RMS) and peak-to-valley (PV) values of wavefront aberration have been evaluated. In a comparison between the clear visual threshold condition and the infinite distance condition, the subject DQ has the larger change in RMS wavefront error, from 0.85 μm at infinite distance to 0.43 μm at clear visual threshold distance. The RMS difference is about 0.42 μm which is 50% in proportion to the RMS value at infinite distance. While the subject JL has the smaller change of 23% in RMS wavefront error, just from 0.66 μm to 0.51 μm between two different accommodative conditions. Defocus and astigmatism have been excluded in this paper. It is found that accommodation influences wavefront aberrations of whole eye and the situation varies substantially from individual to individual. We have to consider not only the wavefront aberration at the infinite distance but also that at the clear visual threshold distance during clinical ocular therapy.
Based on the widely used Gullstrand-Le Grand eye model, the individual human eye model has been established here, which has individual corneal data, anterior chamber depth and the eyeball depth. Furthermore the foremost thing is that the wavefront aberration calculated from the individual eye model is equal to the eye's wavefront aberration measured with the Hartmann-shack wavefront sensor. There were four main steps to build the model. Firstly, the corneal topography instrument was used to measure the corneal surfaces and depth. And in order to input cornea into the optical model, high order aspheric surface-Zernike Fringe Sag surface was chosen to fit the corneal surfaces. Secondly, the Hartmann-shack wavefront sensor, which can offer the Zernike polynomials to describe the wavefront aberration, was built to measure the wavefront aberration of the eye. Thirdly, the eye's axial lengths among every part were measured with A-ultrasonic technology. Then the data were input into the optical design software -ZEMAX and the crystalline lens's shapes were optimized with the aberration as the merit function. The individual eye model, which has the same wavefront aberrations with the real eye, is established.
A novel wavefront reconstruction algorithm used in the visual science for the wavefront aberration of the human eye with use of the Hartmann-Shack (H-S) sensor is proposed in this paper. We model the gradients of H-S sensor with the Fried geometry. Iterative discrete Fourier transform and the correspondent inverse filter in spatial frequency domain are introduced. The processing of the boundary condition in our algorithm becomes easy and natural, and it is with no necessary to derive the boundary gradients from the measured data. The simulations and experimental results show that the new iterative algorithm can accurately offer the estimated wavefront and gradient data, especially in high precision measurement where the signal-to-noise ratio is high.
This paper presents a novel synthetic generated hologram (SGH) system, in which a digital micromirror device (DMD) is used as space light modulator (SLM). In the system, the object light beam is directed through a sequence of digital images on a space light modulator, digital micromirror device (DMD), rather than the transparent films used in the conventional SGH. A computer controlled distributing device replace manual operation. With this system, threedimensional full color hologram can be generated by synthesizing a series of two-dimension digital images, obtained by digital camera or generated by computer software. The preliminary experimental results have been obtained with this system. The possible future development has also been discussed.