Cornea - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneafrom pre-EEC rates of 42.0±4.8 blinks/min to average maximum of61.2±4.3 blinks/min. Lens wettability worsened significantly overtime for both CLA and CLB 0.58±0.18 (p=0.01) and 0.65±0.25(p=0.03) respectively. These values are comparable to changes inwettability seen after 8 hrs of wear with both study materials(Luensmann et al; Keir et al.)Conclusions: The LH-EEC exacerbates ocular symptoms and signsafter 180 mins with CL wear. Significant changes in lens wettabilitywere seen during the exposure and yielded values comparable toresults shown in traditional trials with 8 hrs of lens wear. The LH-EEC provides a way to accelerate extended day CL wear andprovides noteworthy research options for a controlled provocationstudy of CL and dry eye signs and symptoms in a shorter time course.Commercial Relationships: Fiona Soong, Inflamax Research (C);Jalaiah P. Varikooty, Alcon (F); Nancy J. Keir, TearScience (F),Alcon (F), Alcon (R), Allergan (F), Johnson & Johnson (F),CooperVision (F), Visioneering, Inc. (F); Lyndon W. Jones, Alcon(F), Alcon (R), Allergan (F), Abbott Medical Optics (R), Bausch &Lomb (R), Ciba Vision (F), Ciba Vision (R), CooperVision (F),Johnson & Johnson (F), Johnson & Johnson (R); Piyush Patel,Inflamax Research (E)Program Number: 500 Poster Board Number: B0137Presentation Time: 10:30 AM - 12:15 PMViscoelasticity and mesh-size at the surface of hydrogelscharacterized with microrheologyThomas E. Angelini, Ryan M. Nixon, Alison C. Dunn, Juan M.Uruena, John Pruitt, W G. Sawyer. MAE, University of Florida,Gainesville, FL.Purpose: Delefilcon A contact lenses contain a water gradientstructure that transitions from a low water content silicone hydrogelcore to a high water content surface gel. This work explores theproperties of the high water content surface gel, designed to mimicthe physical properties of the corneal surface, improving contact lenscomfort. The ~6 µm thick gels have an average water content thatexceeds 80%, yet the properties of the outer layer that makes directcontact with the eye are not known. This study examines the elasticand viscous moduli at the outermost surface of these soft gels tounderstand the physical interactions between contact lenses and theeye.Methods: Microrheological tests were performed on the surfaces of astandard silicone hydrogel (balafilcon A) and on water gradientcontact lenses (delefilcon A). Microspheres (0.5 micron radius) weresandwiched between 3mm sections of lens material and kept indeionized water. Video microscopy was performed at 90xmagnification, and the beads were tracked using digital imageanalysis software.Results: The mean-squared-displacement (MSD) was computed foreach particle, and averaged (N=32 for nelfilcon A; N=80 forbalafilcon A). Beads embedded in the surface gel layer of delefilconA exhibited significant motion, displacing between 50 to 100nm overtimescales below two seconds. By contrast, no detectable beadmotion above the noise threshold was observed in the balafilcon Asystem; beads moved only 10nm to 16nm over the same two secondperiod. We compute the frequency-dependent elastic and viscousmoduli, G’ and G’’ from the MSD measurement. We find moduliwith very weak frequency dependence between 10 and 100 radiansper second, and an elastic modulus that varies between 0.3 and 1 Pa.Thus, from elasticity theory of cross-linked flexible polymers, weestimate that the water content at the outermost region of thedelefilcon A surface gel layer is above 99%.Conclusions: Surface gel layers on contact lenses possess afrequency dependence similar to low concentration polymer gels.Remarkably, the modulus at the outermost surface is over 1000 timeslower than the mean elastic modulus of the entire surface gel layer.This large modulus change, however, only requires roughly 15%reduction in polymer concentration. This suggests that the polymerconcentration marginally drops near the surface as polymer chainsand crosslinks become sparse.Commercial Relationships: Thomas E. Angelini, alcon (F); RyanM. Nixon, Alcon (F); Alison C. Dunn, Alcon (F); Juan M. Uruena,Alcon (F); John Pruitt, Alcon (E); W G. Sawyer, Alcon (F)Program Number: 501 Poster Board Number: B0138Presentation Time: 10:30 AM - 12:15 PMIn vitro Uptake and Release of Natamycin Dex-b-PLANanoparticles from Silicone Hydrogel Contact Lens MaterialsChau-Minh Phan 1 , Lakshman N. Subbaraman 1 , Lyndon W. Jones 1 ,Shengyan Liu 2 , Frank Gu 2 . 1 Centre for Contact Lens Research,School of Optometry and Vision Science, University of Waterloo,Waterloo, ON, Canada; 2 Department of Chemical Engineering,University of Waterloo, Waterloo, ON, Canada.Purpose: To evaluate the uptake and release of the antifungal agentnatamycin encapsulated within poly(D,L-lactide)-dextrannanoparticles (Dex-b-PLA NPs) from model silicone hydrogelcontact lens materials.Methods: Six model contact lens materials (gel A:poly(hydroxyethyl methacrylate, pHEMA); gel B: 85% pHEMA:15% [Tris(trimethylsiloxy)silyl]-propyl methacrylate (TRIS); gel C:75% pHEMA: 25% TRIS; gel D: 85% N,N dimethylacrylamide(DMAA): 15% TRIS; gel E: 75% DMAA: 25% TRIS; gel F:DMAA) were prepared using photoinitiation. The resulting lensmaterials were incubated in two conditions: (1) natamycin dissolvedin deionized (DI) water, and (2) natamycin encapsulated within Dexb-PLANPs in 9.1 % dimethylsulfoxide (DMSO)/DI water for 7 days(d) at 25±3 oC. The release of natamycin from these materials in 2mL of unpreserved saline solution, pH 7.4 at 32±2 oC was monitoredusing UV-Visible spectrophotometry at 304 nm over 7 d. The releasesolution was replenished every 24 hours (h).Results: The uptake of natamycin by all model lens materialsincreased between 1 and 7 d (p