June 2013
Volume 54, Issue 15
ARVO Annual Meeting Abstract  |   June 2013
Prediction of human crystalline lens power and spherical aberration using an anatomically-based discrete shell model
Author Affiliations & Notes
  • Fabrice Manns
    Ophthalmic Biophysics Center, Bascom Palmer Eye Inst, Univ of Miami, Miami, FL
    Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL
  • Arthur Ho
    Brien Holden Vision Institute, Sydney, NSW, Australia
    School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
  • Jean-Marie Parel
    Ophthalmic Biophysics Center, Bascom Palmer Eye Inst, Univ of Miami, Miami, FL
    Vision Cooperative Research Centre, Sydney, NSW, Australia
  • Footnotes
    Commercial Relationships Fabrice Manns, None; Arthur Ho, None; Jean-Marie Parel, CROMA (F), InnFocus (F), Abeamed (F), University of Miami (P)
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 4269. doi:
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      Fabrice Manns, Arthur Ho, Jean-Marie Parel; Prediction of human crystalline lens power and spherical aberration using an anatomically-based discrete shell model. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4269.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: To develop an anatomically-correct aspheric discrete model of the human crystalline lens that predicts power and spherical aberration and the contribution of the refractive index gradient.

Methods: A continuous and a discrete model of a 30 year old relaxed human lens were developed. The shape was modeled using data from Dubbelman et al (Vis Res, 2001): Ant Radius=11.10mm; Ant Asphericity=-3.05; Post Radius = -5.82mm; Post Asphericity=-0.795; Thickness=3.69mm. In the continuous model, the refractive index gradient is represented as a set of aspheric iso-indicial surfaces with radius of curvature R(z) and asphericity Q(z) that vary linearly from the lens equator to the value at the surface. The axial refractive index follows a power-dependence in each half of the lens (Kasthurirangan et al, IOVS 2008): n(z)=1.41-0.032×(z/t)4, where t is the anterior or posterior half-thickness and z is the distance, both measured from the equator. The discrete shell model was created by sampling iso-indicial surfaces of the continuous model at regularly spaced intervals. The ith shell of a model with K shells has thickness tK=tlens/K, is located at position zi = i*tK, radius Ri=R(zi), asphericity Qi=Q(zi), and is surrounded by refractive indices ni-1=n(zi-1) and ni=n(zi). The number of shells ranged from K=6 to K=3000. The contribution of each surface to lens power and Seidel primary spherical aberration was calculated from a paraxial ray trace. The contributions were plotted as a function of axial position and summed to provide the Seidel wavefront aberration coefficient W040, and total power contribution Psum. The power Psum was compared to the effective power Peff.

Results: The spherical aberration coefficient and lens power converge as the number of shell increases. The asymptotic values were W040=0.053mm-3, Psum=22.2D, and Peff=22.3D. For lens power, the number of shells required to reach 90%, 95% and 99% of the asymptote are 20, 40, and 200. For spherical aberration the values are 160, 320, and approx. 1000. The contributions of the anterior and posterior halves of the lens were -0.015mm-3 and 0.068mm-3.

Conclusions: The power and spherical aberration of the crystalline lens can be predicted using a discrete model with tightly packed shells.The discrete model allows calculation of contributions of specific regions of the lens to total spherical aberration from a paraxial ray trace.

Keywords: 626 aberrations • 630 optical properties • 404 accommodation  

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