Session Title: FP-16 Vitreoretinal Surgery IV
Session Date/Time: Sunday 14/09/2014 | 11:00-13:00
Paper Time: 11:48
Venue: Boulevard D
First Author: : A.Karamitsos GREECE
Co Author(s): : S. Logothetidis S. Kassavetis L. Lamprogiannis V. Karagkiozaki P. Oikonomidis P. Brazitikos
Mechanical testing and analysis of the vitreo-retinal proliferative membrane (PVR).
1. 1st Ophthalmology Clinic, AHEPA University Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece 2. Laboratory for Thin Films-Nanosystems & Nanometrology, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece
Surgically removed PVR membrane from patient with retinal detachment and proliferative vitreo-retinopathy were analyzed for this study. The sample was obtained during a standard three port pars plana vitrectomy. Dynamic nanoindentation was used to measure the elastic modulus and the hardness, as well as to study the deformation modes of the PVR from the surface to the maximum depth. The tests were performed using a Berkovich type indenter with 50 nm tip nominal radius. The normal applied forces ranged below 100 μΝ. Several nanoindents were made to different surface locations of the PVR. Also the time depended mechanical behavior of the PVR to the nanoindentation creep was studied by applying a 200 second hold period at the ~40 μN maximum load.
Analysis of the load-displacement curves provides information regarding the elastic / plastic properties of the PVR membranes. The Elastic Modulus of the PVR ranged from 0.5 to 2 GPa, depending on the surface location and the depth, while there was a hardness values plateau after ~ 50 nm contact penetration depth at ~ 0.1 GPa. On the other hand the time depended deformation due to the nanoindentation creep showed an exponential increase of the indenter displacement into the PVR with the time.
Quantitative analysis of mechanical properties of human proliferative vitreo-retina membrane could provide essential information toward the improvement of existing surgical instruments for more efficient and safer surgical removal of this pathological membrane.