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Soft Contact Lenses (soft + contact_lense)
Selected AbstractsEquivalences between refractive index and equilibrium water content of conventional and silicone hydrogel soft contact lenses from automated and manual refractometry,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007José M. González-Méijome Abstract Purpose The purpose of the present study was to develop mathematical relationships that allow obtaining equilibrium water content and refractive index of conventional and silicone hydrogel soft contact lenses from refractive index measures obtained with automated refractometry or equilibrium water content measures derived from manual refractometry, respectively. Methods Twelve HEMA-based hydrogels of different hydration and four siloxane-based polymers were assayed. A manual refractometer and a digital refractometer were used. Polynomial models obtained from the sucrose curves of equilibrium water content against refractive index and vice-versa were used either considering the whole range of sucrose concentrations (16,100% equilibrium water content) or a range confined to the equilibrium water content of current soft contact lenses (,20,80% equilibrium water content). Results Values of equilibrium water content measured with the Atago N-2E and those derived from the refractive index measurement with CLR 12,70 by the applications of sucrose-based models displayed a strong linear correlation (r2 = 0.978). The same correlations were obtained when the models are applied to obtain refractive index values from the Atago N-2E and compared with those (values) given by the CLR 12,70 (r2 = 0.978). No significantly different results are obtained between models derived from the whole range of the sucrose solution or the model limited to the normal range of soft contact lens hydration. Conclusions Present results will have implications for future experimental and clinical research regarding normal hydration and dehydration experiments with hydrogel polymers, and particularly in the field of contact lenses. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] Hydrogels: From soft contact lenses and implants to self-assembled nanomaterialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Jindrich Kopecek Abstract Hydrogels were the first biomaterials designed for clinical use. Their discovery and applications as soft contact lenses and implants are presented. This early hydrogel research served as a foundation for the expansion of biomedical polymers research into new directions: design of stimuli sensitive hydrogels that abruptly change their properties upon application of an external stimulus (pH, temperature, solvent, electrical field, biorecognition) and hydrogels as carriers for the delivery of drugs, peptides, and proteins. Finally, pathways to self-assembly of block and graft copolymers into hydrogels of precise 3D structures are introduced. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5929,5946, 2009 [source] Technical Note: Effect of contact lenses on measurement of the accommodation microfluctuationsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Mhairi Day Abstract Aim:, Dynamic measurement of accommodation in subjects with myopia usually involves recording through soft contact lenses (CLs) to correct the refractive error. Conversely, dynamic accommodation measurement in emmetropic control subjects is generally undertaken without any corrective lenses. The aim of this experiment was to determine whether CL correction affects the measurement of accommodation microfluctuations using infrared refractometry, and whether this needs to be considered in studies which attempt to compare accommodation responses between the two groups. Methods:, Ten young emmetropic subjects viewed a high contrast Maltese cross target monocularly using the right eye at a target vergence of 0 D. The subjects viewed the target under two conditions: with CL condition and without CL condition, where the subjects viewed the target with the eye only. Accommodation responses of the right eye were recorded continuously for 2 min at a sampling rate of 52 Hz using the Shin-Nippon SRW-5000 autorefractor. Results:, No significant difference (two-tailed paired t -test, t9 = ,1.499, p = 0.168) was found in mean accommodation response between the with CL (mean ± S.D. = ,0.02 ± 0.24 D) and without CL conditions (mean ± S.D. = +0.01 ± 0.25 D). No significant (two-tailed paired t -test, t9 = 0.151, p = 0.883) difference in the magnitude of the accommodation microfluctuations was found between the with CL (mean ± S.D. = 0.162 ± 0.04 D) and without CL condition (mean ± S.D. = 0.169 ± 0.04 D). Power spectrum analysis revealed no differences in the characteristics of the microfluctuations waveform between the two conditions. A control experiment carried out on a subgroup of five subjects using a negative (,3 D) CL demonstrated that there was no significant effect of the dioptric power of the CL on the magnitude of the accommodation microfluctuations (anova: F3,15 = 0.254, p = 0.782). Conclusion:, Thin soft CLs do not affect the magnitude or frequency characteristics of accommodation microfluctuations when measured using the Shin-Nippon SRW-5000. [source] New silicone hydrogels based on interpenetrating polymer networks comprising polysiloxane and poly(vinyl alcohol) networksPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2009V. N. Pavlyuchenko Abstract A method for the synthesis of a new silicone hydrogel as a biphase material for soft contact lenses is considered. The method is based on the synthesis of sequential interpenetrating polymer networks (IPN) and includes the following stages: (1) cross-linked silicone synthesis by the reaction of vinyl- and hydride-containing oligosiloxanes; (2) silicone network saturation with vinyl acetate and cross-linking monomer followed by UV-initiated polymerization to form an IPN comprising the silicone and cross-linked poly(vinyl acetate) (PVAc) network; (3) PVAc network alcoholysis with methanol to obtain silicone hydrogels comprising the silicone and cross-linked poly(vinyl alcohol) (PVAl). A study of hydrophilic, optical, mechanical, and structural features of the silicone hydrogels showed that optical transparency is achieved for materials with the highest density of silicone network cross-linking where the size of IPN structural units does not exceed 100,nm. The water content in hydrophilic networks of silicone hydrogel is found to be below the values typical of cross-linked PVAl, leading to non-additivity of IPN mechanical properties. Indeed, the elasticity moduli (E) of the hydrophilic and silicone networks are 0.4,0.7 and 0.7,1.8,MPa, respectively, whereas for some IPN this value reaches 3.0,MPa. The optimal parameters of synthesis providing the reduction of E to 0.8,1.6,MPa without deterioration of the required performance characteristics (optical transparency 90,92%, water content 20,39,wt%) are determined. Copyright © 2009 John Wiley & Sons, Ltd. [source] Contact lens induced keratitis associated with contact lens wearACTA OPHTHALMOLOGICA, Issue 5 2001Irene Dejaco-Ruhswurm ABSTRACT. Purpose: To evaluate clinical characteristics, risk factors, management and outcome of contact lens induced keratitis (CLIK) associated with contact lens wear. Methods: The study comprised all consecutive patients presenting with contact lens related presumed microbial keratitis during a 12-month period at our department. Detailed demographic data, type of contact lens, duration of lens wear, wearing schedule and lens hygiene were derived from a self-administered questionnaire. Severity of ulcer, corneal scrapings, treatment and final outcome were evaluated. Results: 27 patients with CLIK, some of which may have been sterile peripheral infiltrates, due to contact lens wear were detected. In the majority of the cases patients had used disposable soft contact lenses (89%) and most of them had a daily wearing schedule (78%). 51.8% patients cleaned their lenses regularly. 6 (22%) applied no disinfection since their lenses were disposable on removal. In 3 of our cases with CLIK, penetrating keratoplasty had to be performed. Conclusion: Disposable contact lenses seem to have been a predisposing factor for contact lens induced keratitis also when used on a daily wear schedule. Insufficient contact lens care products and/or manufacturing characteristics may be responsible for CLIK, which is also observed in otherwise compliant contact lens users. In 3 of our patients with CLIK keratoplasty became necessary, indicating that contact lens induced keratitis may result in severe corneal complications. [source] Bifocal soft contact lenses as a possible myopia control treatment: a case report involving identical twinsCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 4 2008Thomas A Aller OD Background:, Several studies have suggested that bifocal and progressive spectacles can reduce progression of myopia in esophoric children. This study compared myopic progression with bifocal (BSCL) and single vision soft contact lenses (SVSCL) in identical twins with near point esophoria. Methods:, Two 12-year-old myopic girls were randomly assigned to wear either BSCL or SVSCL for one year using a double-masked design. Both twins then wore BSCLs for another year. Ocular measurements included cycloplegic and manifest refractions, corneal curvature and axial length. Distance and near phorias were measured through distance corrections and near associated phorias, with both types of contact lenses. Results:, Through their SVSCLs, both children exhibited near associated esophorias, which were neutralised by the BSCLs. The child wearing SVSCLs over the first year showed significant myopic progression, increasing -1.19 D (binocular average), while the child wearing BSCLs showed no progression (+0.13 D). The latter child showed limited progression (-0.28 D) over the second year, while switching from SVSCLs to BSCLs arrested progression in the other child (+0.44 D after one year). Axial length data were consistent with the refractive findings; the child exhibiting more myopia at the end of the first 12 months of the study had longer eyes (by 0.64 mm) than her sister, although their corneas also had steepened more (by 0.44 D compared to 0.18 D). The children showed similar, small increases in eye size over the second year when both wore BSCLs (binocular averages: 0.05, 0.09 mm, respectively). Conclusion:, The apparent inhibitory effect of BSCLs on myopic progression reported in this twin study argues for further study of their efficacy as a control treatment for myopes with near esophoria. [source] | |||||||||||||