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Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editor: Gregory W. Faris
  • Vol. 2, Iss. 7 — Jul. 16, 2007
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Liquid-crystal intraocular adaptive lens with wireless control

Aleksey N. Simonov, Gleb Vdovin, and Mikhail Loktev  »View Author Affiliations


Optics Express, Vol. 15, Issue 12, pp. 7468-7478 (2007)
http://dx.doi.org/10.1364/OE.15.007468


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Abstract

We present a prototype of an adaptive intraocular lens based on a modal liquid-crystal spatial phase modulator with wireless control. The modal corrector consists of a nematic liquid-crystal layer sandwiched between two glass substrates with transparent low- and high-ohmic electrodes, respectively. Adaptive correction of ocular aberrations is achieved by changing the amplitude and the frequency of the applied control voltage. The convex-shaped glass substrates provide the required initial focusing power of the lens. A loop antenna mounded on the rim of the lens delivers an amplitude-modulated radio-frequency control signal to the integrated rectifier circuit that drives the liquid-crystal modal corrector. In vitro measurements of a 5-mm clear aperture prototype with an initial focusing power of +12.5 diopter, remotely driven by a radio-frequency control unit at ~6 MHz, were carried out using a Shack-Hartmann wave-front sensor. The lens based on a 40-μm thick liquid-crystal layer allows for an adjustable defocus of 4 waves, i. e. an accommodation of ~2.51 dioptres at a wavelength of 534 nm, and correction of spherical aberration coefficient ranging from -0.8 to 0.67 waves. Frequency-switching technique was employed to increase the response speed and eliminate transient overshoots in aberration coefficients. The full-scale settling time of the adaptive modal corrector was measured to be ~4 s.

© 2007 Optical Society of America

1. Introduction

Replacing the crystalline lens of the human eye with an artificial intraocular lens (IOL) in cataract surgery or for other medical reasons is a well-established and widely used approach in modern ophthalmic practice. The invasive treatment restores clear vision, but results in a significant loss of accommodation when a fixed monofocal IOL is implanted [1

1. H. Lesiewska-Junk and J. Kaluzny, “Intraocular lens movement and accommodation in eyes of young patients,” J. Cataract. Refract. Surg. 26, 562–565 (2000). [CrossRef] [PubMed]

, 2

2. T. Oshika, T. Mimura, S. Tanaka, Sh. Amano, M. Fukuyama, F. Yoshitomi, N. Maeda, T. Fujikado, Y. Hirohara, and T. Mihashi, “Apperent accommodation and corneal wavefront aberration in pseudophakic eyes,” Invest. Ophthalmol. Vis. Sci. 43, 2882–2886 (2002). [PubMed]

]. Several configurations of accommodating IOLs driven by a natural process of contraction and relaxation of the ciliary body [3–6

3. H. B. Dick, “Accommodative intraocular lenses: current status,” Curr. Opin. Ophthalmol. 16, 8–26, (2005). [CrossRef] [PubMed]

] and pseudoaccommodating IOLs which provide multiple dioptric powers [7–9

7. R. Bellucci and P. Giardini, “Pseudoaccommodation with the 3M diffractive mulifocal intraocular lens: a refraction study of 52 subjects,” J. Cataract. Refract. Surg. 19, 32–35 (1993). [PubMed]

] have been proposed in the past years. Other promising models of accommodative IOLs, for example, recently reported in [10

10. T. Terwee, “Wiederherstellung der Akkomodationsfähigkeit durch Injektion künstlicher Linsenmateralien in den Kapselsack [Restoration of the accommodative function by injection of artificial lens material in the capsular bag],”presented at 20 Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Heidelberg, Germany, 3–4 March 2006.

, 11

11. A. N. Simonov, G. Vdovin, and M. C. Rombach, “Cubic optical elements for an accommodative intraocular lens,” Opt. Express 14, 7757–7775 (2006). [CrossRef] [PubMed]

], are in development. Ideally, an IOL should combine high imaging quality with sufficient accommodation for near work, e.g. reading, and compensate for corneal aberrations of the eye. Correction of aberrations caused by the anterior and posterior surfaces of the cornea may improve significantly the overall performance of the eye since the acuity of vision is limited mainly by the ocular optics [12–14

12. K. N. Ogle, “On the resolving power of the human eye,” J. Opt. Soc. Am. 41, 517–520 (1951). [CrossRef] [PubMed]

].

2. Modal LC phase correctors with wireless control link

Fig. 1. The wirelessly-controlled LC lens: (a) cross section of the LC modal corrector, (b) photograph. 1, glass (BK7) substrates; 2, ITO low-ohmic layer; 3, liquid crystal; 4, contact; 5, high-ohmic layer; R, rectifying diode; A, antenna.

Figure 2 shows the block diagram of the wireless RF control link. The signal of a radio-frequency oscillator (RFO) at ~6 MHz is amplitude modulated by a low-frequency signal at F = 0 - 50 kHz from a function generator (FG). The modulation frequency and depth can be controlled individually by a computer. After a modulator (M), the signal is amplified by an RF amplifier (A) and then is radiated by a loop transmitting antenna (TA). The output RF power does not exceed ~0.5 W, providing the lens operation at distances up to 8 cm from the TA, and can be further reduced for an adaptive LC lens with a resonance receiving antenna. In compliance with the RF exposure safety guidelines [20

20. IEEE standards for safety levels with respect to human exposure to radio frequency electromagnetic fields 3 kHz to 300 GHz, IEEE Standard C95.1-1991.

], the estimated specific absorption rate is well below 0.4 W/kg [20

20. IEEE standards for safety levels with respect to human exposure to radio frequency electromagnetic fields 3 kHz to 300 GHz, IEEE Standard C95.1-1991.

, 21

21. P. Röschmann, “Radiofrequency penetration and absorption in the human body: limitations to high-field whole-body nuclear magnetic resonance imaging,” Med. Phys. 14, 922–931 (1987). [CrossRef] [PubMed]

].

Fig. 2. Wireless RF control link. FG, function generator; RFO, radio-frequency oscillator; M, modulator; A, amplifier; TA, transmitting antenna; RA, receiving antenna, D, demodulator.

Note that the transmitting antenna is supposed to be integrated in a spectacles frame, whereas the driving electronics can be assembled as a small module attached to one arm of the frame.

Fig. 3. Transfer characteristics of the RF link at different driving voltages U LC of the LC lens.

3. Optical setup

Fig. 4. Experimental arrangement for measuring aberrations produced by the LC lens. Inset shows the wireless link. 1, glass walls of the water cell; 2, distilled water; L1, L2, lenses; TA, transmitting antenna; RA, receiving antenna.

In the carried out experiments, the optical aberrations produced by the wirelessly-controlled adaptive LC lens were measured versus the frequency and amplitude of modulation of the RF signal.

4. Experimental results

Defocus (Z 4) and spherical aberration (Z 11) contribute mainly to the LC lens-generated wave-front and their control offers a straightforward way to correct the corresponding aberrations of the human eye. In accordance with [25

25. H. Cheng, J. K. Barnett, A. S. Vilupuru, J. D. Marsack, S. Kasthurirangan, R. A. Applegate, and A. Roorda, “A population study on changes in wave aberrations with accommodation,” J. Vision 4, 272–280 (2004). [CrossRef]

], spherical aberration exhibits the largest change with accommodation among other aberrations (except defocus) of the eye and is mainly associated with the changes in the structure of the crystalline lens.

Fig. 5. Dependence of the LC lens aberrations (defocus a 4, spherical aberration a 11) on the modulation frequency F at fixed voltages U LC across the LC modal corrector: (a) 2.12 V (rms), (b) 2.83 V (rms), (c) 3.53 V (rms), (d) 4.24 V (rms).

As seen from Figs. 5(a)–5(d), the defocus coefficient a 4 (red curve with squares) grows along with ULC and reaches a maximum of ~4 waves at ULC =4.24 V (rms) and F = 27 kHz. The value of the induced defocus a 4 ≅ 4 waves determined at λ = 543.5 nm for a 4.9-mm aperture of the LC lens is equivalent to the change of the focusing power (Φ) by ~2.51 D. Depending on the applied voltage ULC, the maximum of a 4 is attained in the frequency range 22–27 kHz.

Fig. 6. Dependences of the optimal modulation voltage U m (and corresponding voltage U LC applied to the LC lens) and the modulation frequency F versus focusing power variation ΔΦ. Interferograms of the LC lens were simulated using the measured aberrations.

Fig. 7. Transient dynamics of the LC lens aberrations (defocus a 4, spherical aberration a 11) at: (a) periodic turning on (20 s) and off (20 s) of a control voltage U LC=2.83 V (rms), F changes stepwise from 4 kHz to 14 kHz by 2 kHz every 40 s; (b) two-level stepwise frequency and amplitude control. The upper diagrams represent U LC sequences.

Since the Hartmann method can be insensitive to light scatter, additional measurements were carried out using a Mach-Zehnder interferometer aiming at verifying the overall efficiency and optical quality of the LC lens. The wirelessly-controlled LC lens and a 50-mm focal length objective (both in air), in a telescopic arrangement, were placed into the object arm of the interferometer operating at λ = 633 nm. Figure 8 shows the interferograms and the corresponding phase cross sections obtained at (a) a fixed frequency F=10.5 kHz and different U LC and (b) a fixed voltage U LC=2.12 V (rms) and various F.

Fig. 8. LC lens phase cross sections and the corresponding interferograms obtained in a Mach-Zehnder interferometer at: (a) a fixed frequency F=10.5 kHz and different U LC, (b) a fixed voltage U LC=2.12 V (rms) and various F.

As seen, the directly recorded interferograms reveal a high contrast level and very low scattering. In compliance with [18

18. M. Yu. Loktev, V. N. Belopukhov, F. L. Vladimirov, G. V. Vdovin, G. D. Love, and A. F. Naumov, “Wave front control systems based on modal liquid crystal lenses,” Rev. Sci. Instrum. 71, 3290–3297 (2000). [CrossRef]

], the total transmission of polarized light by the LC lens without anti-reflection coatings amounts to ~70%.

5. Discussion and further work

Fig. 9. Monochromatic MTFs of the model eye with the LC modal lens: (a) based on the measured 11 aberration coefficients of the lens prototype accommodated at +2.4 D, (b) optimized shape of the LC lens glass substrates.

z=S(x,y)=r2R{1+1(1+k)×(rR)2},
(1)

where, r=x2+y2; x,y are the transverse coordinates; R is the radius of curvature; k is the conic parameter.

Aside from the dynamic range, imaging quality and response time of the wirelessly-controlled LC-based IOL prototype, there are several aspects that should be taken into account in the final IOL design:

  • Biological compatibility of the LC material and the lens optics with the ocular media. Not all LC materials comply with safety regulations [32

    32. B. Simon-Hettich and W. Becker, “Toxicological investigations of liquid crystals,” presented at 28th Freiburg Workshop on Liquid Crystals; Freiburg, Germany, 1999.

    ]. However, according to Merck [33

    33. W. Becker, B. Simon-Hettich, and P. Hnicke, “Toxicological and ecotoxicological investigations of liquid crystals and disposal of lcds,” Merck brochure, Merck KGaA, Liquid Crystals Division and Institute of Toxicology 64271 Darmstadt, September 25 (2001).

    ], liquid crystals can be characterized as “not acutely toxic” and the tests performed with 224 LC substances indicated that 215 LCs had no toxic effect. In order to satisfy the medical device regulations and to reduce the weight of the implant, the LC lens substrates can be fabricated from approved plastics. The LC lens should remain sealed for many years in a saline environment of the capsular bag at ~37°C. This can be achieved by a proper isolation of the LC layer. In the prototype a two-component epoxy glue was employed.
  • The receiving antenna and the rectifier should be integrated with a LC modal corrector and completely isolated from all outside, i. e. aqueous solution. A “silicon-on-anything” [34

    34. J. Bruines, “Process outlook for analog and rf applications,” Microelectr. Engineer. 54, 35–48 (2000). [CrossRef]

    ] technology is one of the most promising approaches to solving this problem. This technology potentially allows making foldable LC-based IOLs and, thus, meeting the requirements of ophthalmic surgery.
  • As soon as LC-based devices are sensitive to the light polarization, linearly-polarized light is required for proper operation of the LC lens [16

    16. A. F. Naumov, M. Yu. Loktev, I. R. Guralnik, and G. Vdovin, “Liquid-crystal adaptive lenses with modal control,” Opt. Lett. 23, 992–994 (1998). [CrossRef]

    ]. An additional linear polarizer – resulting in 50 % loss of light, or a combination of two LC correctors acting on orthogonal polarization states can be used for randomly-polarized light.
  • By increasing the number of control channels, the precision of wave-front correction can be improved. In the current prototype, a single-channel RF AM analog control is implemented which allows correction of defocus and spherical aberration. The configurations of the LC modal phase corrector, analogous to those described in [35

    35. S. P. Kotova, M. Yu. Kvashnin, M. A. Rakhmatulin, O. A. Zayakin, I. G. Guralnik, N. A. Klimov, P. Clark, G. D. Love, A. F. Naumov, C. D. Saunter, M. Yu. Loktev, G. V. Vdovin, and L. V. Toporkova, “Modal liquid crystal wavefront corrector,” Opt. Express 10, 1258–1272 (2002). [PubMed]

    ] and [36

    36. G. V. Vdovin, I. R. Guralnik, M. Y. Loktev, A. F. Naumov, and S. V. Sheenkov, “Dynamic method for control of wavefront shape of a light beam and device for its realization,” Russian patent 2214617, December 1999 (in Russian).

    ], can be used for the multi-channel adaptive lens. Such multi-channel systems can successfully correct asymmetric aberrations.
  • A closed-loop control is needed for an adaptive LC modal lens. We suggest that the feedback signals can be obtained by measuring and subsequent real-time processing the electroencephalographic activity of the visual cortex of the human brain [37, 38

    38. G. Thut, A. Nietzel, S. A. Brandt, and A. Pascual-Leone, “Alpha-band electroencephalographic activity over occipital cortex indexes visuospatial attention bias and predicts visual target detection,” J. Neuroscience 26, 9494–9502 (2006). [CrossRef]

    ].

6. Conclusion

Acknowledgments

The authors thank Svetlana Kotova (Lebedev Institute of Physics, Russia) for her assistance in fabrication of liquid-crystal lenses The work was supported by the “Nederlandse organisatie voor Wetenschappelijk Onderzoek” (NWO), grant DOE 6190.

References and links

1.

H. Lesiewska-Junk and J. Kaluzny, “Intraocular lens movement and accommodation in eyes of young patients,” J. Cataract. Refract. Surg. 26, 562–565 (2000). [CrossRef] [PubMed]

2.

T. Oshika, T. Mimura, S. Tanaka, Sh. Amano, M. Fukuyama, F. Yoshitomi, N. Maeda, T. Fujikado, Y. Hirohara, and T. Mihashi, “Apperent accommodation and corneal wavefront aberration in pseudophakic eyes,” Invest. Ophthalmol. Vis. Sci. 43, 2882–2886 (2002). [PubMed]

3.

H. B. Dick, “Accommodative intraocular lenses: current status,” Curr. Opin. Ophthalmol. 16, 8–26, (2005). [CrossRef] [PubMed]

4.

A. Rana, D. Miller, and P. Magnante, “Understanding the accommodating intraocular lens,” J. Cataract. Refract. Surg. 29, 2284–2287 (2003). [CrossRef]

5.

S. D. McLeod, V. Portney, and A. Ting, “A dual optic accommodating foldable intraocular lens,” Br. J. Ophthalmol. 87, 1083–1085 (2005). [CrossRef]

6.

S. Masket, “Accommodating IOLs: emerging concepts and design,” Cataract and Refract. Surg. Today, 32–36 (July, 2004), http://www.crstoday.com/PDF%20Articles/0704/crst0704 F1 Masket.pdf.

7.

R. Bellucci and P. Giardini, “Pseudoaccommodation with the 3M diffractive mulifocal intraocular lens: a refraction study of 52 subjects,” J. Cataract. Refract. Surg. 19, 32–35 (1993). [PubMed]

8.

P. J. Gray and M. G. Lyall, “Diffractive mulifocal intraocular lens implants for unilateral cataracts in presbyopic patents,” Br. J. Ophthalmol. 76, 336–337 (1992). [CrossRef] [PubMed]

9.

T. Walkow, A. Liekfeld, N. Anders, D. T. Pham, C. Hartmann, and J. A. Wollensak “A prospective evaluation of a diffractive versus refractive designed multifocal intraocular lenses. Visual and refractive comparison,” Ophthalm. 104, 1380–1386 (1997).

10.

T. Terwee, “Wiederherstellung der Akkomodationsfähigkeit durch Injektion künstlicher Linsenmateralien in den Kapselsack [Restoration of the accommodative function by injection of artificial lens material in the capsular bag],”presented at 20 Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Heidelberg, Germany, 3–4 March 2006.

11.

A. N. Simonov, G. Vdovin, and M. C. Rombach, “Cubic optical elements for an accommodative intraocular lens,” Opt. Express 14, 7757–7775 (2006). [CrossRef] [PubMed]

12.

K. N. Ogle, “On the resolving power of the human eye,” J. Opt. Soc. Am. 41, 517–520 (1951). [CrossRef] [PubMed]

13.

J. Liang, B. Grimm, S. Goelz, and J. F. Bille, “Objective measurements of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor,” J. Opt. Soc. Am. 11, 1949–1957 (1994). [CrossRef]

14.

G.-Y. Yoon and D. R. Williams, “Visual performance after correcting the monochromatic and chromatic aberrations of the eye,” J. Opt. Soc. Am. A 19, 266–275 (2002). [CrossRef]

15.

G. Vdovin, M. Loktev, and A. Naumov, “On the possibility of intraocular adaptive optics,” Opt. Express 11, 810–817 (2003). [CrossRef] [PubMed]

16.

A. F. Naumov, M. Yu. Loktev, I. R. Guralnik, and G. Vdovin, “Liquid-crystal adaptive lenses with modal control,” Opt. Lett. 23, 992–994 (1998). [CrossRef]

17.

A. F. Naumov, G. D. Love, M. Yu. Loktev, and F. L. Vladimirov, “Control optimization of spherical modal liquid crystal lenses,” Opt. Express 4, 344–352 (1999). [CrossRef] [PubMed]

18.

M. Yu. Loktev, V. N. Belopukhov, F. L. Vladimirov, G. V. Vdovin, G. D. Love, and A. F. Naumov, “Wave front control systems based on modal liquid crystal lenses,” Rev. Sci. Instrum. 71, 3290–3297 (2000). [CrossRef]

19.

T. L. Kelly, A. F. Naumov, M. Yu. Loktev, M. A. Rakhmatulin, and O. A. Zayakin, “Focusing of astigmatic laser diode beam by combination of adaptive liquid crystal lenses,” Opt. Commun. 181, 295–301 (2000). [CrossRef]

20.

IEEE standards for safety levels with respect to human exposure to radio frequency electromagnetic fields 3 kHz to 300 GHz, IEEE Standard C95.1-1991.

21.

P. Röschmann, “Radiofrequency penetration and absorption in the human body: limitations to high-field whole-body nuclear magnetic resonance imaging,” Med. Phys. 14, 922–931 (1987). [CrossRef] [PubMed]

22.

M. J. Stephen and J. P. Straley, “Physics of liquid crystals,” Rev. Mod. Phys. 46, 617–704 (1974). [CrossRef]

23.

http://www.okotech.com/sensors/.

24.

R. Noll, “Zernike polynomials and atmospheric turbulence,” J. Opt. Soc. Am. 66, 207–211 (1976). [CrossRef]

25.

H. Cheng, J. K. Barnett, A. S. Vilupuru, J. D. Marsack, S. Kasthurirangan, R. A. Applegate, and A. Roorda, “A population study on changes in wave aberrations with accommodation,” J. Vision 4, 272–280 (2004). [CrossRef]

26.

M. Loktev, “Modal wavefront correctors based on nematic liquid crystals,” Ph.D. dissertation (Delft University of Technology,Delft, The Netherlands, 2005).

27.

O. Pomerantzeff, H. Fish, J. Govignon, and C. L. Schepens, “Wide angle optical model of the human eye”, Ann Ophthalmol. 3, 815–819 (1971). [PubMed]

28.

O. Pomerantzeff, P. Dufault, and R. Goldstein, “Wide-angle optical model of the eye,” in Advances in Diagnostic Visual Optics, G. M. Breinin and I. M. Siegel, eds., (Springer-Verlag, Berlin, 1983).

29.

D. Malacara and M. Malacara, Handbook of optical design (Marcel Dekker, Inc., New York, 2004).

30.

J. A. Mordi and K. J. Ciuffreda, “Dynamic aspects of accommodation: age and presbyopia,” Vision Res. 44, 591–601 (2004). [CrossRef]

31.

A. K. Kirby and G. D. Love, “Fast, large and controllable phase modulation using dual frequency liquid crystals,” Opt. Express 12, 1470–1475 (2004). [CrossRef] [PubMed]

32.

B. Simon-Hettich and W. Becker, “Toxicological investigations of liquid crystals,” presented at 28th Freiburg Workshop on Liquid Crystals; Freiburg, Germany, 1999.

33.

W. Becker, B. Simon-Hettich, and P. Hnicke, “Toxicological and ecotoxicological investigations of liquid crystals and disposal of lcds,” Merck brochure, Merck KGaA, Liquid Crystals Division and Institute of Toxicology 64271 Darmstadt, September 25 (2001).

34.

J. Bruines, “Process outlook for analog and rf applications,” Microelectr. Engineer. 54, 35–48 (2000). [CrossRef]

35.

S. P. Kotova, M. Yu. Kvashnin, M. A. Rakhmatulin, O. A. Zayakin, I. G. Guralnik, N. A. Klimov, P. Clark, G. D. Love, A. F. Naumov, C. D. Saunter, M. Yu. Loktev, G. V. Vdovin, and L. V. Toporkova, “Modal liquid crystal wavefront corrector,” Opt. Express 10, 1258–1272 (2002). [PubMed]

36.

G. V. Vdovin, I. R. Guralnik, M. Y. Loktev, A. F. Naumov, and S. V. Sheenkov, “Dynamic method for control of wavefront shape of a light beam and device for its realization,” Russian patent 2214617, December 1999 (in Russian).

37.

http://www.biosemi.com/publications.htm.

38.

G. Thut, A. Nietzel, S. A. Brandt, and A. Pascual-Leone, “Alpha-band electroencephalographic activity over occipital cortex indexes visuospatial attention bias and predicts visual target detection,” J. Neuroscience 26, 9494–9502 (2006). [CrossRef]

OCIS Codes
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(010.7350) Atmospheric and oceanic optics : Wave-front sensing
(170.4460) Medical optics and biotechnology : Ophthalmic optics and devices
(230.3720) Optical devices : Liquid-crystal devices
(330.4060) Vision, color, and visual optics : Vision modeling

ToC Category:
Adaptive Optics

History
Original Manuscript: May 1, 2007
Revised Manuscript: May 20, 2007
Manuscript Accepted: May 22, 2007
Published: June 1, 2007

Virtual Issues
Vol. 2, Iss. 7 Virtual Journal for Biomedical Optics

Citation
Aleksey N. Simonov, Gleb Vdovin, and Mikhail Loktev, "Liquid-crystal intraocular adaptive lens with wireless control," Opt. Express 15, 7468-7478 (2007)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-15-12-7468


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References

  1. H.  Lesiewska-Junk and J.  Kaluzny, "Intraocular lens movement and accommodation in eyes of young patients," J. Cataract. Refract. Surg. 26, 562-565 (2000). [CrossRef] [PubMed]
  2. T.  Oshika, T.  Mimura, S.  Tanaka, Sh.  Amano, M.  Fukuyama, F.  Yoshitomi, N.  Maeda, T.  Fujikado, Y.  Hirohara, and T.  Mihashi, "Apperent accommodation and corneal wavefront aberration in pseudophakic eyes," Invest. Ophthalmol. Vis. Sci. 43, 2882-2886 (2002). [PubMed]
  3. H. B.  Dick, "Accommodative intraocular lenses: current status," Curr. Opin. Ophthalmol. 16, 8-26 (2005). [CrossRef] [PubMed]
  4. A.  Rana, D.  Miller, and P.  Magnante, "Understanding the accommodating intraocular lens," J. Cataract. Refract. Surg. 29, 2284-2287 (2003). [CrossRef]
  5. S. D.  McLeod, V.  Portney, and A.  Ting, "A dual optic accommodating foldable intraocular lens," Br. J. Ophthalmol. 87, 1083-1085 (2005). [CrossRef]
  6. S.  Masket, "Accommodating IOLs: emerging concepts and design," Cataract and Refract. Surg. Today, 32-36 (July, 2004), http://www.crstoday.com/PDF%20Articles/0704/crst0704_F1_Masket.pdf.
  7. R.  Bellucci and P.  Giardini, "Pseudoaccommodation with the 3M diffractive mulifocal intraocular lens: a refraction study of 52 subjects," J. Cataract. Refract. Surg. 19, 32-35 (1993). [PubMed]
  8. P. J.  Gray and M. G.  Lyall, "Diffractive mulifocal intraocular lens implants for unilateral cataracts in presbyopic patents," Br. J. Ophthalmol. 76, 336-337 (1992). [CrossRef] [PubMed]
  9. T.  Walkow, A.  Liekfeld, N.  Anders, D. T.  Pham, C.  Hartmann, and J. A.  Wollensak "A prospective evaluation of a diffractive versus refractive designed multifocal intraocular lenses. Visual and refractive comparison," Ophthalm. 104, 1380-1386 (1997).
  10. T.  Terwee, "Wiederherstellung der Akkomodationsfähigkeit durch Injektion künstlicher Linsenmateralien in den Kapselsack [Restoration of the accommodative function by injection of artificial lens material in the capsular bag],"presented at 20 Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Heidelberg, Germany, 3-4 March 2006.
  11. A. N.  Simonov, G.  Vdovin, and M. C.  Rombach, "Cubic optical elements for an accommodative intraocular lens," Opt. Express 14, 7757-7775 (2006). [CrossRef] [PubMed]
  12. K. N.  Ogle, "On the resolving power of the human eye," J. Opt. Soc. Am. 41, 517-520 (1951). [CrossRef] [PubMed]
  13. J.  Liang, B.  Grimm, S.  Goelz, and J. F.  Bille, "Objective measurements of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor," J. Opt. Soc. Am. 11, 1949-1957 (1994). [CrossRef]
  14. G.-Y.  Yoon and D. R.  Williams, "Visual performance after correcting the monochromatic and chromatic aberrations of the eye," J. Opt. Soc. Am. A 19, 266-275 (2002). [CrossRef]
  15. G.  Vdovin, M.  Loktev and A.  Naumov, "On the possibility of intraocular adaptive optics," Opt. Express 11, 810-817 (2003). [CrossRef] [PubMed]
  16. A. F.  Naumov, M. Yu.  Loktev, I. R.  Guralnik, and G.  Vdovin, "Liquid-crystal adaptive lenses with modal control," Opt. Lett. 23, 992-994 (1998). [CrossRef]
  17. A. F.  Naumov, G. D.  Love, M. Yu.  Loktev, and F. L.  Vladimirov, "Control optimization of spherical modal liquid crystal lenses," Opt. Express 4, 344-352 (1999). [CrossRef] [PubMed]
  18. M. Yu.  Loktev, V. N.  Belopukhov, F. L.  Vladimirov, G. V.  Vdovin, G. D.  Love, and A. F.  Naumov, "Wave front control systems based on modal liquid crystal lenses," Rev. Sci. Instrum. 71, 3290-3297 (2000). [CrossRef]
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