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J. B. Ale Magar, A. Ho, F. Manns; Performance of Two-Element Accommodating IOL in the Presence of Tilt and Decentration. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5744.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the theoretical effect of tilt and decentration of two-element translating accommodating IOL (2E-AIOL) on aberrations. Designs for optimal performance in presence of such misalignments are also proposed.
The crystalline lens in a modified finite model eye was replaced with a 2E-AIOL consisting of spherical surfaces. The AIOL system consisted of a +40D front element and a rear element of compensatory negative power to return an emmetropic state at distance setting. Series of analyses were conducted with various degrees of tilt (about x-axis) and decentration (along y-axis) imposed on the individual elements and/or system. Translation of front element to simulate accommodation was effected without changing the imposed misalignment. Ray tracing was performed in optical design software (Zemax) followed by determination of Seidel primary spherical aberration and coma in each analysis. Polynomial up to fourth-order was fitted to the aberration results to identify design curves representing optimum configurations.
Changes in spherical aberration in all analyses was <0.01 µm at maximum decentration (1 mm) and when 10° tilt was introduced. Both tilt and decentration induced significant amount of coma. At distance setting, the rates of change in coma with tilt of front element, rear element and group were 0.024 µm/°, 0.016 µm/° and 0.008 µm/° respectively. The rates for coma with decentration of front element, rear element and group were 0.28 µm/mm, 0.06 µm/mm and 0.22 µm/mm respectively. These increased slightly at near setting.
For a spherical design of 2E-AIOL, spherical aberration is practically insensitive to tilt and decentration whereas coma is affected significantly. Similar effects were observed in earlier studies with standard IOLs. However, misalignment of 2E-AIOL may produce greater clinical impact due to its complex optical and mechanical arrangement.
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