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G. L. Van der Heijde, E. A. Hermans, T. T. Terwee, S. A. Koopmans, M. Dubbelman, R. M. Heethaar; Development of a Ciliary Muscle Driven Accommodative IOL. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5278.
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© ARVO (1962-2015); The Authors (2016-present)
To design a ciliary muscle driven accommodative IOL that has a predictable and large range of variable power. The optical quality at different states of accommodation should be comparable to that achieved with a monofocal IOL.
A concept IOL ("Turtle lens") has been designed with a new focus mechanism that could operate within the dynamics of the ciliary muscle. The new focus mechanism contains two freeform lenses that move perpendicular to the optical axis. The Turtle lens has a base power of 21 D and accommodative amplitude of 8 D. The concept design was optically and mechanically optimized for a typical 60-year-old human eye. Silicon prototypes were made to test mechanical performance in pig and human donor eyes using a laboratory lens stretching device that mimics the ciliary muscle action. Changes in focal length during stretching were measured by laser-based ray tracing and a camera system.
During stretch experiments the focal length of the Turtle lens changed according to the design for 8 D of accommodation. Theoretical ray tracing showed that the modulation transfer function (MTF) of the Turtle lens in different accommodative states did not deviate considerably from the MTF of a monofocal IOL. However, the optical quality of initial prototypes was affected due to deformation of the silicon lenses during the stretch experiments.
In stretch experiments of pig and human cadaver eyes, the results of base power and accommodation were in accordance with the functional design. Therefore, the new focus principle can be used in the development of an IOL that restores accommodation. Both the mechanical and optical design need further optimization to improve optical quality and functionality.
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