title: Dynamics of epiretinal membrane removal off the retinal surface: a computer simulation project.
abstract: OBJECTIVE
  To use a computer simulation to discern the safest angle at which to peel epiretinal membranes.
  
  
  METHODS
  We used ANSYS V.14.1 software to analyse the dynamics involved in membrane removal off the retinal surface. The geometrical values were taken from optical coherence tomography of 30 eyes with epiretinal membranes. A range of Young's modulus values of 0.03, 0.01 and 0.09 MPa were assigned to the epiretinal membrane and to the retina separately. The ratio of maximum shear stress (MSS) recorded at the attachment pegs over that recorded at the membrane (P/E ratio) was determined at nine displacement angles (DA).
  
  
  RESULTS
  Mean MSS values recorded at the attachment pegs, epiretinal membrane and retina were significantly different at 0.8668, 0.6091 and 0.0017 Pa consecutively (p<0.05). There was a significant negative linear correlation between DA and MSS recorded at the epiretinal membrane when the Young's modulus for the epiretinal membrane was higher than or equal to that for the attachment pegs and the retina. Nevertheless, there was a significant positive linear correlation between DA and P/E ratio when the Young's modulus for the epiretinal membrane was equal to or lower than that for the attachment pegs and the retina.
  
  
  CONCLUSIONS
  Attachment pegs appear to be the most likely part to fail (tear) during removal procedures. Changing the direction at which the edge of the membrane is pulled can relocate the MSS within in the tissue complex. Safer and effective removal could be achieved by pulling epiretinal membranes onto themselves at 165° DA.
authors.affiliation: Department of Ophthalmology, Lister Surgicentre Hospital, Stevenage, Hertfordshire, UK. mahmutdogramaci@hotmail.com
authors.forename: Mahmut
authors.initials: M
authors.lastname: Dogramaci
authors.forename: Tom H
authors.initials: TH
authors.lastname: Williamson
mesh_terms: D003198:Computer Simulation; D019773:Epiretinal Membrane / Q000601:surgery*; D006801:Humans; D008962:Models, Theoretical; D012164:Retinal Diseases / Q000601:surgery*; D012984:Software; D041623:Tomography, Optical Coherence
keywords: Experimental &#8211 laboratory; Macula; Retina; Treatment Surgery; Vitreous