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Supervisor: Dr. Larichev A.V.


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It is well known that the human eye is not a perfect optical system. The imperfection of the eye optics is caused by aberrations induced by the cornea, lens, and ocular media. Generally, the human eye without pathologies in refraction (like myopia and astigmatism), can be considered as almost diffraction limited at the eye pupil diameter of about 2mm. When the iris is opened wider, the optical aberrations significantly reduce the vision quality.

There are two major tasks where precise measurements and correction of eye aberrations is vital: excimer laser vision correction and clinical diagnostics of the retina.

Laser vision correction, like LASIK with novel "flying spot" lasers, requires precise knowledge about the overall aberrations of the eye. In such a case, it's possible to perform "customized ablation" and to significantly improve the operation success rate, especially in complex cases.

Among several possible techniques for aberration measurements, the Shack-Hartman wavefront analyzer gathered worldwide attention. The majority of custom cornea ablation systems (like VISX, Carl Zeiss Meditec, Baush&Lomb, etc) utilize Shack-Hartman aberrometers.

The basic principle of human eye aberration measurement with a conventional Shack-Hartman wavefront sensor is illustrated in Figure 1. The eye focuses a low-power laser beam on the retina, producing a virtual point source. The scattered laser radiation is reflected back and acquires the aberrations induced by the ocular media, lens, and cornea. A lenslet array (Fig. 2) samples the distorted wavefront, forming a regular spot pattern called a Hartmanogram (Fig. 3). The deviations of the spot centers from the reference grid are proportional to the local slopes of the wavefront. Thus, by reconstructing the wavefront slope map with subsequent Zernike wavefront approximation [ see Zernike polynomials ] it’s possible to obtain the complete aberration map of the eye.

However, in reality the aberrations of the living eye are not stationary due to many factors, including tear film variations, fluctuations of accommodation, etc. Thus, the “single snapshot” type of measurement does not provide any reliable data for the diagnosis and treatment. Our group was one of the first who suggested and implemented the principle of dynamic aberrometry.

In dynamic aberrometry, the aberrations of the eye are measured with a temporal resolution exceeding the shortest period of aberration fluctuations. Since the spectrum of the aberration fluctuations (Fig.4) is located within the 10-12 Hz bandwidth, the sampling rate should exceed 20-25Hz. Having a series of dynamic data, one can (automatically or manually) figure out the most significant and stationary aberrations, which need to be corrected by refractive corrections techniques. The poster [ Utility of dynamic aberrometry for acuity measurements and testing ] (in PDF, 1.55 Mb) contains more detailed information on dynamic aberrometry.

During last few years we have been developed several aberration diagnostic instruments capable of measuring human eye aberrations in real time (up to 80 measurements per second). The unique feature of the instruments is a scanning reference spot, which greatly improves the measuring accuracy and speed (US patent #US 6331059 B1, Russian Patent #2268637). The instrument has powerful analytical software with open data exchange capability. A more detailed specification of the instrument can be found [ here ].

Another aspect of the visual optics research carried out by our group concerns studying the influence of different aberrations on the visual acuity. For this purpose, in 2002 we (together with Dr.M.Mrochen* from Swiss National Institute of Technology) developed a dynamic aberrometer with adaptive optics. This instrument (Fig. 5) includes a deformable mirror capable of compensating aberrations up to the 4th order (such as coma, trefoil, spherical aberration, etc.) [ see Zernike polynomials ]. The aberrations of the human eye can be automatically compensated (or introduced) while the patient looks at a specific target. Thus, one can study the influence of aberrations on the subjective visual acuity and simulate the results of customized refraction correction procedures.

The main field of application of the instruments is the research in the field of visual optics, such as aberration dynamics, accommodation, etc. The technology is currently commercialized by Visionica Ltd.

A special version of the aberrometer has been developed for the Russian excimer laser complex MicroScan 2000. [ Physics Instrumentation Center ]



Larichev A.V., Ivanov P.V., Iroshnikov N.G., Shmalhauzen V.I., Otten L.J., Adaptive system for eye-fundus imaging, Quantum Electronics, 32, N10, 2002, p.902.

A. Larichev, P. Ivanov, I. Irochnikov, S.C. Nemeth, A. Edwards, P. Soliz, High Speed Measurement of Human Eye Aberrations with Shack-Hartman Sensor. [ARVO Abstract] Invest Ophthalmol Vis Sci., 42 (2001) 897

A.V.Larichev, P.V.Ivanov, I.G.Irochnikov, V.I.Shmal'gauzen, Measurement of eye aberrations in a speckle field, Quantum Electronics, 31 (2001) 1108

Jos j. Roesema, Dirk E.M. Van Dyck, M.-J. Tassignon, Clinical comparison of 6 aberrometers. Part 1: Technical specifications, J Cataract Refract Surg 2005; 31:1114–1127

Jos j. Roesema, Dirk E.M. Van Dyck, Micha Pauw, Bas van Der Spek, M.-J. Tassignon, Clinical comparison of 5 commercially available aberrometers II: statistical comparison on a test group

N. G. Iroshnikov, A. V. Larichev, Adaptive optics in ophthalmology, Proc. SPIE Vol. 6284, 62840B. Sep 2006

Goncharov A.S., Larichev A.V., Iroshnikov N.G., Ivanov V.Yu., Gorbunov S.A., Modal tomography of human eye aberrations, Laser Physics, 2006, V.16, N12, p.1689.

Goncharov A.S., Larichev A.V., Speckle Structure of a Light Field Scattered by Human Eye Retina, Laser Physics, 2007, V.17, N9, p.1157-1165