1689 ISSN 1054-660X, Laser Physics, 2006, Vol. 16, No. 12, pp. 1689–1695. © MAIK “Nauka / Interperiodica” (Russia), 2006. Original Text © Astro, Ltd., 2006. INTRODUCTION The human eye is a complex photooptical physio- logical system. Rays of light from surrounding objects entering the system are refracted and focused on the ret- ina and give the image of these objects. Vision prob- lems are frequently connected with an irregularity of the optical system of the eye, when there is no precise focusing of the image on a retina. Short-sightedness (myopia) and far-sightedness (hyperopia) are wide- spread conditions, but there are also more complex cases when the image is worsened due to aberrations of higher orders. For example, in the case of keratoconus, the distortion of the wavefront is the result of the cor- nea’s irregular shape [1]. Today, the arsenal of methods used by physicians to treat various refractive pathologies is quite diverse, e.g., implantation of intraocular lenses, laser correction of vision, etc. The success of these methods is substan- tially determined by the correct measurement of the optical parameters of an eye [2]. For diagnostics, optometrists usually use autorefractors and corneal topographers [1, 3], but the capabilities of these devices are limited. Thus, autorefractors allow total aberrations of an eye to be determined only up to the second order (astigmatism and defocusing). The corneal topographer determines only the form of the front surface of the cor- nea, while aberrations are also introduced by its back surface and also by other elements of the eye’s optical system, for example, the crystalline lens. There are known cases when the crystalline lens is the primary source of aberrations [4]. Recently, systems have appeared which permit the shape of both surfaces of the cornea, and also the size of the forward chamber of the eye, to be determined. This are the OrbScan corneal topographers (Bausch and Lomb, United States) [5, 6], which analyze light reflected from surfaces of optical elements of the eye with the use of a scanning optical slit. Nevertheless, while completely describing aberrations of the cornea, the device does not allow the aberrations of a crystal- line lens or the total aberrations of the eye to be deter- mined. Other versions of devices include combined topographers, or aberrometers (for example, the OPD- Scan system of Nidek, Japan). This device contains a cornea topography system based on a projection of Placido rings and a unit for measurement of full aberra- tions by a skiascopic method. Note that in such devices it is impossible to completely distinguish the sources of aberrations, because the topographical subsystem of the device does not allow the contribution of the back surface of the cornea to be measured, and measure- ments of the full aberrations are not carried out simul- taneously for various points over the pupil. The limitations of existing devices and techniques make actual the development of a new method allowing the full aberrations and their distribution among the optical elements of the eye to be determined. For measurement of full aberrations of the eye, wave-front sensors (such as Shack-Hartmann [7–9]) are successfully used. A low-power laser beam creates a virtual reference source on the retina. The scattered radiation which has left the eye goes into the wave-front sensor, the information from which is transferred to a computer. The wavefront is then restored from mea- sured local inclinations by means of expansion into Zernike polynomials [10] or by direct integration. Thus, the phase picture of the total aberration of an eye is constructed, including the higher orders. The advan- LASER METHODS IN CHEMISTRY, BIOLOGY, AND MEDICINE Modal Tomography of Aberrations of the Human Eye A. S. Goncharov,* A. V. Larichev,** N. G. Iroshnikov,*** V. Yu. Ivanov,**** and S. A. Gorbunov***** Faculty of Physics, Moscow State University, Vorob’evy gory, Moscow, 119992 Russia *e-mail: goncharov@bk.ru **e-mail: larichev@optics.ru ***e-mail: nikita@optics.ru ****e-mail: ivanoff@genphys.phys.msu.ru *****e-mail: gorbunov@optics.ru Received March 22, 2006; in final form, June 1, 2006 Abstract—The work is devoted to the research and development of a new method of modal phase tomography for diagnostics of aberrations of the human eye. Implementation of the method is based on a series of eye aber- ration measurements taken at different angles to the optical axis by means of a wave-front sensor. The technique of restoration permits the contributions of different elements of the eye to the total aberrations to be separated. The results of numerical research and a model experiment are presented. PACS numbers: 42.15.Fr, 42.62.Be, 42.66.Ct DOI: 10.1134/S1054660X06120152