May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
EVAS II: Advanced Lens Stretcher to Determine Accommodation Forces vs. Power and Geometry
Author Affiliations & Notes
  • K. Ehrmann
    Vision CRC, Sydney, Australia
    IER,
    Sovs, University of New South Wales, Sydney, Australia
  • A. Ho
    Vision CRC, Sydney, Australia
    IER,
    Sovs, University of New South Wales, Sydney, Australia
  • E. Arrieta-Quintero
    OBC, BPEI, University of Miami, Miami, Florida
  • A. Amelickx
    OBC, BPEI, University of Miami, Miami, Florida
  • D. Nankivil
    OBC, BPEI, University of Miami, Miami, Florida
  • D. Borja
    OBC, BPEI, University of Miami, Miami, Florida
  • N. Ziebarth
    OBC, BPEI, University of Miami, Miami, Florida
  • J.-M. Parel
    Vision CRC, Sydney, Australia
    OBC, BPEI, University of Miami, Miami, Florida
  • Footnotes
    Commercial Relationships  K. Ehrmann, None; A. Ho, None; E. Arrieta-Quintero, None; A. Amelickx, None; D. Nankivil, None; D. Borja, None; N. Ziebarth, None; J. Parel, None.
  • Footnotes
    Support  2R01EY14225, The Vision Cooperative Research Centre, Australia, supported by the Australian Federal Government , Florida Lions Eye Bank; P30EY14801 (Center Grant); Henri and Flore Lesieur Foundation
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 3792. doi:https://doi.org/
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      K. Ehrmann, A. Ho, E. Arrieta-Quintero, A. Amelickx, D. Nankivil, D. Borja, N. Ziebarth, J.-M. Parel; EVAS II: Advanced Lens Stretcher to Determine Accommodation Forces vs. Power and Geometry. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3792. doi: https://doi.org/.

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

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Abstract

Purpose: : To develop and validate a method and instrument to simulate and quantify the accommodation mechanism in the primate eye.

Methods: : The newly developed ex-vivo accommodation simulator (EVAS II) stretches the crystalline lens under controlled conditions while obtaining quantitative data on stretching load, optical power and lens diameter changes. It also includes features to determine anterior and posterior lens shape, lens thickness and axial motion and ciliary body motion, using coaxial imaging, OCT (Uhlhorn, ARVO 2007), Scheimpflug (Borja D, UM PhD proposal 2007) and 35-50MHz UBM technologies. A section of the globe containing intact crystalline lens, zonules, ciliary muscle and a segmented sclera is bonded to 8 curved shoes. The shoes are magnetically coupled to computer controlled actuators, pulling the 8 segments radially in 0.5 mm diameter increments to a maximum of 4 mm diameter change. At each step of the stretch and release cycle, measurement data and images are automatically recorded for later analysis. The optomechanical properties of 3 human (48 to 71 years old) and 3 cynomolgus monkey (4 to 8 years old) eyes have been assessed thus far.

Results: : The 3 human eyes were all presbyopic and no change in lens power and diameter was observed. The total zonular stretching force reached 30.4 to 52.0 mN (0.9 to 3.4 mN STDEV). For the 3 pre-presbyopic monkey eyes, a change in lens power of 9.1, 9.4 and 10.1 diopters was measured, which was associated with a lens diameter increase of 0.50, 0.58 and 0.65 mm and a force increase of 29.2, 31.1 and 34.7 mN respectively. There was minimal hysteresis in lens diameter change between the stretch and release cycle (mean: 0.007mm, STDEV: 0.024 mm). Although, both force and diameter increased exponentially with pulling distance, the ratios for diameter per diopter change and the force per diopter change were relatively constant over the stretch distance (0.06 mm/D and 3.33 mN/D respectively). These results compare well with published data (Manns et al, IOVS 2007).

Conclusions: : The new instrument generates reliable optical, geometrical and mechanical measurements for ex-vivo simulated accommodation. The results from human and non-human primate eyes are consistent with the Helmholtz theory of accommodation.

Keywords: accomodation • presbyopia 
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