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Hooman Mohammad Pour, Siddharth Devineni, Sangarapillai Kanapathipillai, Fabrice Manns, Arthur Ho; The Effect of Peripherally Positioned Capsulorhexis in Phaco Ersatz studied using 3D Finite Element Model. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3130.
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© ARVO (1962-2015); The Authors (2016-present)
Phaco ersatz is a developing surgical technique for restoring accommodation in presbyopes by replacing the hardened lens with a soft gel refillant. One surgical component of this technique is the creation of a peripherally-positioned mini-capsulorhexis to facilitate lens core removal and refilling. However, the effect of an off-centre capsulorhexis on optical and especially accommodative outcome is unknown. We constructed a 3D FE model of the accommodative system to investigate the effect of peripheral capsulorhexes in phaco-ersatz on lens geometry during accommodation.
A 3D axisymmetric, non-homogeneous (based on AFM results of Weeber et al 2007), non-linear FEM of a lens zonules were constructed to model the effect of lens stretching. In order to be able to compare with results of an ex vivo accommodation simulator (EVAS) (Denham et al 2008) the lens was modelled as mounted in an EVAS. Stretching was effected by displacing the zonules attachment point radially up to 0.24 mm (half-diameter). A capsulorhexis was modelled by removing a circular patch from the anterior capsule. We varied the position (2, 2.4, 2.8., 4 mm) and diameter (0.5 mm to 1.2 mm in 0.1 mm steps) of the capsulorhexes. The lens shape after stretching was extracted for analysis (see figures below).
Lens thickness and diameter change slightly with the size and position of the capsulorhexis. These two parameters also change the stress distribution throughout the lens. Results suggest that incisions closer to the lens edge incur more stresses and are more prone to change in shape. Results are summarised in the table below.
This early investigation of peripherally-located mini-capsulorhexes predicts some small but observable opto-mechanical effect on lens accommodation. These will need to be validated against empirical measurements in future studies.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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