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Contact Lens Materials (contact + lens_material)
Selected AbstractsSpoliation of a rigid gas permeable contact lens by sodium chloride: A free volume microprobe studyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009M. V. Deepa Urs Abstract The interaction of one of the major inorganic ions present in tears, viz., sodium chloride (NaCl), with a rigid gas permeable contact lens, poly(Fluorosilicone acrylate) (FP92) has been investigated using Positron Annihilation Lifetime Spectroscopy (PLS) and refrac-tive index measurement. We monitored the changes in its free volume size and number density in the presence of NaCl solute trans-ported through diffusion. Based on PLS results, we propose that the adhesion of sodium chloride salt to the fluorine and methacrylate sites of FP92 results in zones of excess salt concentration. The changes in refractive index of the contact lens material due to the salt adhesion, correlates well with the changes in free volume of the material. Presence of sodium chloride perturbs the free volume of the lens material and hence its polarizability (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chemistry and technology of 2-alkenyl azlactonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Steven M. Heilmann Abstract The chronology of 2-alkenyl azlactone research at 3M is discussed in terms of its origination; consideration of economics, overall safety, and opportunities for patent protection; elaboration of the chemistry; and, finally, applying lessons learned toward the development of commercial technologies. The chemistry is dominated by the presence of three electrophilic reaction centers and a readily polymerizable 2-alkenyl group. Technological development has been focused in four general areas: acrylamide monomers, acrylamide materials, azlactone materials, and polymer modification. Application areas disinclude lithographic printing plates, contact lens materials, adhesives, dispersants for printing inks, and supports for immobilizing enzymes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3655,3677, 2001 [source] Randomised controlled trial of the effects of two rigid gas permeable (RGP) contact lens materials and two surface cleaners on straylight valuesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2009Marten F. Fortuin Abstract Purpose:, In a double-masked randomized controlled crossover study we investigated both the retinal responses to straylight, and the effects of lens cleaners on straylight values, in two different RGP contact lens materials. Methods:, Thirty patients (20,59 years) wearing RGP lenses were refitted with new lenses made of Boston XO material in one eye and made of Comfort O2 (ONSI-56) material in the other eye. Reported wetting angles for the Boston XO material (103°) and for the ONSI-56 material (7.2°) were obtained by sessile drop measurements. After refitting, the study comprised three 5-week trial periods. In Period 1 half of the participants (Group A) wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye, and the other half (Group B) vice versa. In Period 2 Group A wore Comfort O2 (ONSI-56) lenses in their right eye and Boston XO lenses in their left, and Group B vice versa. All participants used Miraflow cleaner during periods 1 and 2. In Period 3, during which all participants used Boston cleaner, Group A wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye and Group B vice versa. Straylight data (log S) were obtained with and without contact lenses using the Oculus C-Quant straylight meter in all three periods. Central corneal thickness (CCT) was measured in the second and third periods. Results:, When not wearing lenses (n = 60 eyes) at the end of the second 5 week trial period straylight was measured twice with averages of 1.07 log S, and the corrected CCT measurements averaged 546 ,m. Straylight values with Comfort O2 (ONSI-56) reached 1.15 log S at the end of both the second (n = 25 eyes) and third periods (n = 23 eyes). Straylight values with Boston XO were 1.17 log S (n = 26 eyes) at the end of the second period, and 1.16 log S (n = 25 eyes) at the end of the third period. Conclusions:, Existing RGP lens wearers refitted with new lenses with different contact angles, made of Boston XO and Comfort O2 (ONSI-56) showed, over three 5 week periods, relatively small increases in straylight, which were functionally comparable, irrespective of the type of lens material or lens cleaner used. At every visit, straylight values and CCTs returned to baseline levels after RGP lens removal, confirming that the straylight fluctuations were mainly due to scattering from the RGP lenses; or tear film interaction; or a combination of both. [source] Contact lenses as a drug delivery device for epidermal growth factor in the treatment of ocular woundsCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 2 2010Clyde L Schultz PhD Background:, This work was conducted to investigate the uptake and release of epidermal growth factor (EGF) from hydrogel contact lenses and to determine whether the released protein would be therapeutically active in a rabbit corneal epithelial defect model of ocular trauma, prior to use in humans. Methods:, The uptake and release of EGF from hydrogel contact lens materials were determined by high-pressure liquid chromatography. Contact lenses composed of vasurfilcon A or lotrafilcon A (containing silicone) were incubated in a source solution containing 0.4 ppm EGF for seven hours. To determine the kinetics of drug uptake into the contact lens matrix, drug concentration in the source solution was measured at zero, one, 60, 240 and 420 minutes. To determine the kinetics of release, loaded contact lenses were immersed in a recipient solution of phosphate-buffered saline. Therapeutic activity in vivo was investigated by placing prepared lenses on the surface of abraded corneas of New Zealand White rabbits, with abraded corneas of contralateral eyes used as controls. Control eyes were treated with contact lenses placed in saline for injection. Wound closure was assessed hourly. Results:, Uptake and release of EGF were demonstrated for vasurfilcon A but not lotrafilcon A contact lens materials. The retention time of EGF released from vasurfilcon A contact lenses was similar to control EGF not exposed to contact lens polymers. The greatest adsorption of EGF into the lens material occurred within approximately 120 minutes, with a flattening of the rate of uptake thereafter. Abraded eyes in rabbits showed a significantly higher overall healing rate for EGF-treated contact lenses compared with control eyes (p < 0.0001). Conclusions:, EGF can be delivered from some but not all hydrogel materials. Lens materials composed of silicone may not be useful for delivering EGF to the eye. EGF-treated contact lenses may be a useful device to facilitate healing of ocular wounds. [source] | ||||||||||