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A brief history of contact lenses
?tefan ??lu,Mihai ??lu,Stefano Giovanzana,Rajiv D. Shah
Human & Veterinary Medicine , 2011,
Abstract: This paper presents a brief history of contact lenses in ophthalmology
Contact Lenses - A Review  [cached]
Dada V,Sharma Rajiv
Indian Journal of Ophthalmology , 1987,
Abstract: A review of recent literature on contact lenses shows increasingly more studies on soft contact lenses than PMMA hard lenses The articles on contact lens wear and ulcerative keratitis have highlighted the increased risk of microbial keratitis in contact lens wearers compared to the general population, higher virulence of pathogens isolated and special association of fungi with EWSCL This high risk is due to multiple factors, organism survival in moist lens cases and cleaning solutions, microtrauma to the corneal epithelium by repeated insertion and removal, corneal hypoxia and lens deposits in soft lenses Special problems of tonometry in eyes with bandage soft lenses and contact lens sterilization have been studied and useful suggestions have come forth from the authors
Refractive surgery or contact lenses – how and when to decide?
Xu K, Jhanji V
Clinical Optometry , 2011, DOI: http://dx.doi.org/10.2147/OPTO.S16200
Abstract: active surgery or contact lenses – how and when to decide? Review (7289) Total Article Views Authors: Xu K, Jhanji V Published Date November 2011 Volume 2011:3 Pages 63 - 72 DOI: http://dx.doi.org/10.2147/OPTO.S16200 Kunyong Xu1, Vishal Jhanji2 1Michael G DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada; 2Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Abstract: Correction of refractive errors can be achieved with spectacles, contact lenses, and refractive surgery. The past decade has seen a surge in the availability of alternatives for patients and surgeons in terms of both surgical and nonsurgical options for the management of refractive errors. Newer generation contact lenses provide enhanced safety and better handling, whereas modern-day refractive surgery presents a plethora of choices based on the clinical characteristics and requirements of patients. We have moved from an era of "one size fits all" to a purely customized way of treating patients with refractive errors. This review presents the background, advantages, and disadvantages of the two most commonly used options for correction of ametropia, ie, contact lenses and refractive surgery.
Modeling Galaxy Lenses  [PDF]
Roger Blandford,Gabriela Surpi,Tomislav Kundic
Physics , 2000,
Abstract: In order to use a gravitational lens to measure the Hubble constant accurately, it is necessary to derive a reliable model of the lens surface potential. If the analysis is restricted to the locations and magnifications of point images, the derived Hubble constant depends upon the class of mass models used to fit the data. However, when there is extended emission from an Einstein ring, it may be possible to derive a potential from the observed surface brightness in a model-independent manner. This procedure is illustrated with reference to B1608+656. The multi-band images are de-reddened, de-convolved and de-contaminated so that the luminous matter and the surface brightness contours in the Einstein ring are both faithfully mapped. This intensity distribution can then be used to reconstruct the potential. Progress in implementing this program is reported. The observed incidence of multiple-imaged galaxies on the Hubble Deep Fields is an order of magnitude smaller than naively predicted on the basis of radio lens surveys, like CLASS, but consistent with the rate computed using surface photometry of candidate lens galaxies assuming standard mass to light ratios. In order to resolve this paradox, it is suggested that most galaxy lenses are located in compact groups.
A Laboratory Assessment of Factors That Affect Bacterial Adhesion to Contact Lenses  [PDF]
Debarun Dutta,Mark DP Willcox
Biology , 2013, DOI: 10.3390/biology2041268
Abstract: Adhesion of pathogenic microbes, particularly bacteria, to contact lenses is implicated in contact lens related microbial adverse events. Various in vitro conditions such as type of bacteria, the size of initial inoculum, contact lens material, nutritional content of media, and incubation period can influence bacterial adhesion to contact lenses and the current study investigated the effect of these conditions on bacterial adhesion to contact lenses. There was no significant difference in numbers of bacteria that adhered to hydrogel etafilcon A or silicone hydrogel senofilcon A contact lenses. Pseudomonas aeruginosa adhered in higher numbers compared to Staphylococcus aureus. Within a genera/species, adhesion of different bacterial strains did not differ appreciably. The size of initial inoculum, nutritional content of media, and incubation period played significant roles in bacterial adhesion to lenses. A set of in vitro assay conditions to help standardize adhesion between studies have been recommended.
Innovations in gas permeable multifocal contact lenses
Edward S Bennett
Clinical Optometry , 2010, DOI: http://dx.doi.org/10.2147/OPTO.S7021
Abstract: novations in gas permeable multifocal contact lenses Review (8578) Total Article Views Authors: Edward S Bennett Published Date September 2010 Volume 2010:2 Pages 85 - 90 DOI: http://dx.doi.org/10.2147/OPTO.S7021 Edward S Bennett College of Optometry, University of Missouri-St. Louis, St. Louis, MO 63121, USA Abstract: A current area of great consumer interest, as well as potential for practice growth, pertains to the contact lens correction of presbyopia. In particular many recent innovations with gas permeable multifocal lens designs have resulted in them comparing favorably – and often superiorly – to both soft multifocal lenses and monovision lenses, notably in the area of quality of vision. Gas permeable (GP) back surface aspheric multifocal designs have become increasingly popular because newer designs often are able to incorporate higher add powers than their predecessors, often via the addition of add power to the front surface of the lens. In addition, several front surface lens designs have recently been introduced which have the benefits of minimizing any corneal topography changes as they are typically fit in alignment with the cornea, while also providing a higher add than can be provided on the back surface of the lens. Some high specific gravity materials have been introduced which potentially allow for thinner lenses which have less mass and may exhibit more consistent centration than aspheric multifocal designs in conventional materials. New segmented, translating designs are available with the ability to provide an intermediate correction while the introduction of a hybrid design provides the practitioner with a viable option when a GP lens results in either poor centration of excessive subjective awareness.
Arora A,Ali A,Khar RK,Zzaman MT
Electronic Journal of Biomedicine , 2009,
Abstract: In the tears lysozyme and albumin are also present besides other constituents. All these constituents form a biofilm on the hydrophilic contact lenses - minutes after the lens is placed in the eye. These deposits if not removed make the contact lens translucent and impair visual acuity. For the removal of deposit multipurpose solution is used.In the study, deposits of lysozyme and albumin were made on hydrophilic contact lenses deliberately. These deposits laden contact lenses were then treated with multipurpose solution for 12 hrs. The extent of removal of these deposits by the action of sodium citrate present in multipurpose solution was assessed by measuring albumin and lysozyme quantitatively by using standard analytical procedures.It was observed that 0.1% of sodium citrate could remove lysozyme and albumin efficiently. Albumin deposited more as compared to lysozyme and non ionic hydrophilic contact lenses are less prone to deposition than ionic. Any further increase in sodium citrate was not desirable.
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control  [PDF]
Frank Spors, Donald J. Egan, Jie Shen, Lance E. McNaughton, Stuart Mann, Neil M. Patel
Open Journal of Ophthalmology (OJOph) , 2012, DOI: 10.4236/ojoph.2012.23011
Abstract: Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statistical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods: The dominant eye of 40 participants (27 women, 13 men; mean age 27.3 ± 3.2 years; range 23 to 39 years) was fit with Proclear Multifocal center distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than –1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000 corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rectangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following evaluation of statistical significance and clinical relevance, results were compared to published data from successful Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for lenses of all reading additions. Lens groups with higher Add-powers demonstrated stronger changes with increased significance. Final RMS values relating to 2nd, 3rd and 4th Zernike Orders reached clinical significance with a wavefront error of 0.10 μm, the equivalent of 0.25D. Moreover, as Add-powers increased, 3rd and 4th order aberrations likewise showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained predominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher order wavefront aberrations in a manner dependent on their Add-power. In comparison to successful Orthokeratology outcomes, the amounts of resulting aberrations are notably different.
Novel Approaches in Formulation and Drug Delivery using Contact Lenses  [cached]
Kishan Singh, Anroop B Nair,Ashok Kumar,Rachna Kumria
Journal of Basic and Clinical Pharmacy , 2011,
Abstract: The success of ocular delivery relies on the potential to enhance the drug bioavailability by controlled and extended release of drug on the eye surface. Several new approaches have been attempted to augment the competence and diminish the intrinsic side effects of existing ocular drug delivery systems. In this contest, progress has been made to develop drug-eluting contact lens using different techniques, which have the potential to control and sustain the delivery of drug. Further, the availability of novel polymers have facilitated and promoted the utility of contact lenses in ocular drugdelivery. Several research groups have already explored the feasibility and potential of contact lens using conventional drugs for the treatment of periocular and intraocular diseases. Contact lenses formulated using modern technology exhibits high loading,controlled drug release, apposite thickness, water content, superior mechanical and optical properties as compared to commercial lenses. In general, this review discus various factors and approaches designed and explored for the successful delivery of ophthalmic drugs using contact lenses as drug delivery device.
Soft-contact-lenses-induced complications  [PDF]
Suvajac Gordana
Vojnosanitetski Pregled , 2008, DOI: 10.2298/vsp0801015s
Abstract: Background/Aim. Soft contact lenses occupy significant place in ophthalmology, both in the correction of refraction anomalies and in the treatment of many eye diseases. The number of patients that wear soft contact lenses for the purpose of correcting ametropia is constantly increasing. Due to the increasing number of wearers, the percentage of complications that can lead to serious eye damage and serious vision loss is also increasing. The aim of this study was to point out the most common complications related to soft contact lens use. Methods. In the period from 1995 2004 this prospective study included 510 patients wearing soft contact lenses for correcting ametropia. None of the patients wore contact lenses before and none suffered from any system or local diseases that could affected the development of eventual complications. The study took seven years with the patients who wore conventional lenses and three years with those who wore replacement contact lenses. All the necessary ophthalmologic examinations were done (visual acuity, refractokeratometry, the quantity of tear film, biomicroscopic examination of anterior eye segment). All the complications were filmed by video camera. Results. Of all the patients, 19 had blepharitis, 73 suffered from “dry eye”, 57 had conjunctival hyperemia, 12 had conjunctivitis, 34 had gigantopapillary conjunctivitis (GPC), 93 had punctiform epitheliopathy, 20 had corneal infiltration, one patient had keratitis, 91 had corneal vascularisation, and 95 patients had corneal deposits. Conclusion. Both the type and frequency of complications related to soft contact lens use in our group of patients, proved to be significant. Some of this complications (keratitis) can significantly damage vision and lead to loss of vision and sometimes can require operative treatment.
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