Finite element analysis of ILM pinch peeling technique

Session Details

Session Title: Free Paper Session 15: Mixed Session

Session Date/Time: Friday 08/09/2017 | 16:30-18:00

Paper Time: 17:42

Venue: Room 117

First Author: : M.Dogramaci UK

Co Author(s): :                                 

Abstract Details

Purpose:

Pinch peeling technique of internal limiting membrane (ILM) involves placing partially opened jaws (blades) of the ILM forceps on the surface of the retina pushing enough to indent the surface followed by the closure of the forceps to pinch the ILM. The ILM then is elevated slightly above the surface of the retina and pulled back and forth gently to induce a break in the ILM. Once the break is induced the edge of the split is grasped and a maculorrhexis is created by pulling the ILM in a circumferential manner

Setting:

Princess Alexandra Hospital

Methods:

Finite Element Analysis is used to study the dynamics of pinch peeling, a baseline ILM with Young’s modulus of 0.227 MPa and Poisson's ratio of 0.49 and a thickness of a 3.88µ over a baseline retina with a Young’s modulus of 0.03MPa, Poisson ratio of 0.49 and a thickness of 25µ. The ILM was pinched using two blades of Young’s modulus of 0.227 (range: 0.0088-1.3) MPa and Poisson's ratio: 0.49. Note only 10% of the retinal thickness was considered in the computation to reduce the computational costs of the analysis. The height, stress level and the configuration of the ILM during the pinching simulation was studied in relations to the depth of dent, tilt of blades, the distance between the blades (bite size), the width of the blades, the friction coefficient between the blades and the ILM and the alignment of the blades. The optimum pinch peel was defined as a single fold of ILM that had the max height and the least stress when compressed between the two opposing blades of the forceps.

Results:

The study showed that the optimum depth of dent was 2µ, the optimum tilt angle of the blades was 135º, the optimum bite size (distance between two forceps blades) was 200µ. The optimum width of blade was 200µm, the optimum friction coefficient >1.99 and the optimal blade alignment was a matched and parallel blades of equal sizes. The analysis also showed that more efficient pinch peels could be achieved in more malleable retinal tissues and with stiffer ILM tissues and

Conclusions:

Pinch peeling technique is an effective way of initiation of ILM peel. FEA can help in developing and understanding the most efficient ways to pinch peel and ILM.

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