Dissertations / Theses on the topic 'Contact lenses'
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Kollbaum, Pete S. "Optical aberrations of contact lenses and eyes corrected with contact lenses." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3278221.
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Thesis (Ph.D.)--Indiana University, School of Optometry, 2007.Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5877. Adviser: Arthur Bradley. Title from dissertation home page (viewed May 9, 2008).
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Utkina, M. S. "Invention of contact lenses." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45609.
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Contact lenses is a great invention which is intended for people with a sight problem. They have changed the lives of millions of people around the world. It was estimated that 125 million people (2%) used contact lenses in 2004. A contact lens is a thin lens placed directly on the surface of the eye and it is considered a medical device and may be worn to correct vision or for cosmetic or therapeutic reasons. They might seem like a new, modern invention, but the idea has actually been around for hundreds of years. So, the history of contact lenses development is long and rich.
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Chernenko, S. O. "Virtual reality contact lenses." Thesis, Сумський державний університет, 2012. http://essuir.sumdu.edu.ua/handle/123456789/28515.
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Cardall, Martin. "Contact lenses and sport." Thesis, Aston University, 2008. http://publications.aston.ac.uk/14644/.
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Contact lenses seem to be the ideal method of vision correction for ametropic people who participate in sporting activities. This thesis sets out to evaluate the viewpoint of the optometric professional and that of the patient on the use of contact lenses in sport and to establish if education is needed within this area. It also aims to provide some scientific evidence on the effect of exercise on the physiology of the cornea with and without contact lenses. Silicone hydrogel contact lenses have previously been suggested to impede heat dissipation from the cornea compared to mid water hydrogels. This was further demonstrated with exercise. The physiological integrity of the cornea is dependant on the amount of oxygen available to its surfaces. Contact lenses can disrupt the diffusion of oxygen to the cornea. Previous methods of measuring the oxygen consumption of the cornea have been limited by their invasive nature and assessment of only a small surface area of the cornea. They are not suitable to measure corneal oxygen consumption during exercise with and without contact lenses. A new method needed to be established. This was achieved by designing a novel method by the use of an oxygen sensor inside an airtight goggle using dynamic quenching of luminescence method. This established a non-contact way of measuring the effect oxygen uptake with and without contact lenses in vivo, allowing the contact lens to be undisturbed in their natural environment. The new method differentiated between the closed-eye and the open-eye condition with a good within-visit repeatability. It also illustrated that the cornea utilises oxygen at a faster rate during controlled aerobic exercise at moderate intensity. New contact lenses are available specifically for sport, these claim to reduce glare and increase contrast for daylight outdoor sports. However, visual benefits of these types of contact lenses cannot be measured easily in an indoor clinical environment, such as the optometric practice. To demonstrate any potential benefits of these lenses emulation of them should be conducted outdoors.
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Lorentz, Holly. "Lipid Deposition on Hydrogel Contact Lenses." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2963.
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The primary objective of this study was to quantify and characterise lipid deposition on soft (hydrogel) contact lenses, particularly those containing siloxane components. Studies involving a variety of in vitro doping and in vivo worn contact lenses were undertaken, in which lipid deposition was analyzed by either TLC or HPLC. Specific experiments were completed to optimize a method to extract the lipid from the lens materials, to compare the total lipid deposition on nine different hydrogel lenses and to analyze the effect that lipid deposition had on wettability. A method for extracting lipid from contact lenses using 2:1 chloroform: methanol was developed. This study also showed that siloxane-containing contact lens materials differ in the degree to which they deposit lipid, which is dependent upon their chemical composition. Small differences in lipid deposition that occur due to using variations in cleaning regimens were not identifiable through TLC, and required more sophisticated analysis using HPLC. Contact lens material wettability was found to be influenced by in vitro lipid deposition. Specifically, conventional hydrogels and plasma surface-treated silicone-hydrogel materials experienced enhanced wettability with lipid deposition. Reverse-phase HPLC techniques were able to quantify lipid deposits with increased sensitivity and accuracy. From the HPLC studies it was found that contact lens material, concentration of the lipid doping solution, and the composition of the lipid doping solution in in vitro deposition studies influenced the ultimate amount and composition of lipid deposits. In vivo HPLC studies showed that the final lipid deposition pattern was influenced by the interaction between the composition of the tear film and the various silicone hydrogel contact lens materials. In conclusion, HPLC analysis methods were more sensitive and quantitative than TLC. Lipid deposition was ultimately influenced by the concentration and composition of the lipid in the tear film and the contact lens material. Contact lens wettability was influenced by the presence and deposition of lipid onto the contact lens surfaces. Finally, this reverse-phase HPLC lipid analysis protocol was not the most sensitive, robust, or accurate. In the future, other methods of analysis should be explored.
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McBriar, D. I. "The plasma treatment of contact lenses." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6292/.
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This thesis investigates the use of low temperature plasmas as a means of improving the surface properties of hard gas permeable contact lenses. It is important that the polymers used for this application should have good optical properties, should allow transport of oxygen to the cornea and be biocompatible, that is they should not stimulate an adverse response in the tissues which they contact. Whilst most patients have no problems with current materials there are a significant number who experience irritation of the eyes and abnormal build up of deposits on the lens surface. It has been found that mild oxygen plasma treatment of the contact lens can be helpful in alleviating these problems. In this volume the effects of such treatment are examined by x-ray photoelectron spectroscopy and alternative treatments proposed. It is found that the oxygen plasma treatment increases the wettability of the lens surface by the incorporation of oxygen in the polymer. This effect decays with time but is not wholly lost on prolonged storage. The mechanism of this decay appears to be a migration of oxidized material from the surface and is dependent on the storage conditions. During this decay an anomalous transient increase in hydrophilicity was encountered which can be associated with the temporary return of highly oxidized material to the surface. This effect is observed in other polymers and can be shown to be temperature dependent. The use of plasma polymerization as an alternative treatment was investigated and a number of materials produced with similar surface properties to the oxygen treated lens material. It was hoped that a coating would be generally applicable to a variety of lens materials.*Adsorption studies showed that the oxygen treated material has the property of reversibly adsorbing glycoproteins which may account for its performance in the eye. Some of the plasma polymer coatings gave a similar response.
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Ali, Maryam Byrne Mark E. "Therapeutic contact lenses for comfort molecules." Auburn, Ala., 2007. http://hdl.handle.net/10415/1334.
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Hager, Michele LynnManeca. "A Study of Contact Lens Comfort in Patients Wearing Comfilcon A Soft Contact Lenses Compared to Their Habitual Soft Contact Lenses." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243711014.
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Giner, Tort Anna. "Optical and visual characterization of multifocal contact lenses and multifocal intraocular lenses." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/663449.
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Vision is presented and universally accepted as the most precious of the human senses.lt is structured in three main parts: the optical system {eye), the photo-sensor {eye's retina), and the data processor (brain). If one of them is affected by any disease or dysfunction, vision will be terrible or even nonexistent One of the most common dysfunction is presbyopia.lt i s an age-related disorder that is undergone by all the population s ince their mid-late-40s and it is consists in the loss of the ability to focus near objects (accommodation). A huge number of possible corrections of it can be easily found. On one hand, there are temporary corrections ,as progressive spectacle tenses or multifocal contact tenses. On the other hand, permanent corrections as multifocal i ntraocular lenses, multifocal cornea! ablation, accommodating intraocular tenses, monovision systems, or scleral modifications are also applied to correct presbyopia. Another age-related dysfunction is cataract. Cataract is the opacification of the crystalline fens and decreases the quality of the visual function. Consequently, it is one of the leading visual impairments in adults over 60 years old, affecting the half of the adults aged between 75-85 years old. The only possible solution far cataract is the extraction of the opacified fibers of the crystalline lens and the replacement of them with an intraocular lens by surgery. Due to the fact that all the patients affected by an age-related cataract are also affected by presbyopia it is totally understandable that a number of patients choose mulltifocal introcular lens to substitute their crystalline tenses .This way, only one surgery is needed to salve both age-related dysfunctions. Usually, young presbyopes choose a temporary correction as a first option to correct presbyopia. Some presbyopia corrections are based on the simultaneous vision principie, as, far example, multifocal contact or intraocular lenses. The optical design of these kind of lenses is very complex. Consequently, It is characterization is also difficult When these lenses were launched into the market, it was only possible to characterize optical quality before the implantation or the adaptation of them (characterization in vitro) and the visual quality after the surgery or the clinical adaptation was performed (characterization) .M. present and thanks to the technological advances, different new commercial instruments that are to perform characterization in vivo of the visual quality before the implantation or the adaptation of simultaneous vis ion tenses. They are based on the simulation of the vision that these tenses give to the implanted eye. Some experimental prototypes and commercial aberrometers or double pass systems have used to perform an optical quality characterization in vivo, but some issues have been reported. Taking into account all this information, the main goal of this thesis is the design and the assembly of a new open-field double-pass system with asymmetric focus that is suitable to characterize invivo optical quality in patients implanted or adapted with multifocal intraocular or contact lenses. In order to achieve this aim, different studies and processes were carried out Review of presbyopia corrections and the characterization of them (Clinical study about objective over-refraction wearing multifocal contact lenses); Verification of the suitability of one commerciat simulator (Clinical study with the commercial simulator VirtlOL (10lens S.l.)); Design and assembly of the double-pass system with asymmetric focus (Opto-mechanical design/
Validation of all the elements included in the system/ Optical validation of the system); Programming of the softwares to manage the system; Validation of the new prototype (Two clinical studies characterizing eyes implanted with multifocal introcular tenses by using the new system were done).La visió és entesa i, universalment acceptada, com el sentit humà més valorat .Aquesta esta estructurada en tres parts principals: el sistema òptic (l'ull), el fot-sensor (la retina ocular) iel processador (el cervell). Si una d'aquestes parts es veu afectada per una disfunció o malaltia, la visió pot arribar a ser de molt baixa qualitat i, fins hi tot, inexistent Una de les disfuncions més comunes és la presbícia. La presbícia és una disfunció lligada a l'edat que pateix tota lla població a partir dels 40 anys, aproximadament. Consisteix en la pèrdua de la capacitat d'enfocar objectes propers (acomodació). Actualment, es troba un ampli nombre de possibles correccions. Per una banda, tenim les correccions temporals, com ulleres o lents de contacte progressives, i, per l'altre, correccions permanents, com lents intraoculars multifocals , ablacions corneals multifocals, lents intraoculars acomodatives, sistemes de monovisió, o modificacions esclerals, entre altres. Una altre disfunció associada a l'edat és la cataracta, la qual crea la opacificació del cristal·lí impedint una visió nítida. Conseqüentment, la cataracta és una de la deficiències visuals més estesa a partir dels 60 anys, afectant a la meitat de la població entre els 75 i els 85 anys . La única solució per eliminar les cataractes és eliminant les fibres opacificades i substituir-les per una lent intraocular quirúrgicament. Donat que tots els pacients amb cataractes són, a la vegada, prèsbites, està justificat que un nombre de pacients decideixi implantar-se lents intraoculars multifocals per substituir el seu cristal·lí. D'aquesta manera es solucionen dues degeneracions associades a l'edat en una sola cirurgia. Els joves prèsbites acostumen a optar per correccions prèsbites temporals, mentre que molts dels prèsbites amb cataractes opten per solucions permanents. Algunes de les correccions de la presbícia, com les lents de contacte o intraoculars multifocals , estan basades en el principi de visió simultània. Els dissenys òptics d'aquest tipus de lents són molt complexos, cosa que fa que la seva caracterització sigui molt complicada. Quan aquestes lents van aparèixer al mercat, només era possible caracteritzar-les òpticament abans de la seva implantació o adaptació de manera in vitro, i de caracteritzar-les visualment després de la seva adaptació o implantació de manera in vivo. Actualment, i gracies a tots els avenços tecnològics, diferents instruments clínics han estat desenvolupats per realitzar mesures de les qualitats visuals abans de la seva implantació. Tots ells, es basen en simular-li al pacient la visió que tindria després de ser implantat. Per un altre cantó, alguns prototips experimentals iaberrometres o sistemes de doble-pas comercials han estat utilitzats per dur a terme la caracterització de la qualitat in vim en pacients implantats o adaptats amb sistemes multifocals, pero diferents problemes han estat plantejats. Tenint en compte tota aquesta informació, el principal objectiu d'aquesta tesi ha estat la de dissenyar i muntar un nou sistema de doble-pas d'enfocament asimètric de camp obert que fos capaç de fer una caracterització de la qualitat òptica in vivo de pacients implantats o adaptats amb lents de contacte o intraoculars multifocals. I per arribar a aquest objectiu, s'han dut a terme els següents passos: Revisió de les correccions per a la presbícia i caracterització d'elles (Estudi clínic de la sobre-refracció objectiva de pacients adaptats amb lents de contacte multifocals); Validació de la capacitat de mesura d'un simulador comercial (Estudi clínic amb el simulador comercial VirtlOL (1OLens S.L); Disseny i muntatge del sistema de doble-pas amb enfocament asimètric (Disseny opto-mecànic/ Validació de tots els components del sistema/ Validació òptica del sistema); Programació dels programes informàtics que gestionen el sistema i processen
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Saunders, B. D. "The optical performance of bifocal contact lenses." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254463.
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Zollinger, Shannon Marie. "Interest and Success of Multifocal Contact Lenses." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306500257.
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Smith, Molly J. "Peripheral Refractive Error in Multifocal Contact Lenses." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460470062.
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Sariri-Khayatzadeh, Reyhaneh. "Tear protein interaction with hydrogel contact lenses." Thesis, Aston University, 1995. http://publications.aston.ac.uk/9747/.
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The design and synthesis of biomaterials covers a growing number of biomedical applications. The use of biomaterials in biological environment is associated with a number of problems, the most important of which is biocompatabUity. If the implanted biomaterial is not compatible with the environment, it will be rejected by the biological site. This may be manifested in many ways depending on the environment in which it is used. Adsorption of proteins takes place almost instantaneously when a biomaterial comes into contact with most biological fluids. The eye is a unique body site for the study of protein interactions with biomaterials, because of its ease of access and deceptive complexity of the tears. The use of contact lenses for either vision correction and cosmetic reasons or as a route for the controlled drug delivery, has significantly increased in recent years. It is relatively easy to introduce a contact lens Into the tear fluid and remove after a few minutes without surgery or trauma to the patient. A range of analytical techniques were used and developed to measure the proteins absorbed to some existing commercial contact lens materials and also to novel hydrogels synthesised within the research group. Analysis of the identity and quantity of proteins absorbed to biomaterials revealed the importance of many factors on the absorption process. The effect of biomaterial structure, protein nature in terms of size. shape and charge and pH of the environment on the absorption process were examined in order to determine the relative up-take of tear proteins. This study showed that both lysozyme and lactoferrin penetrate the lens matrix of ionic materials. Measurement of the mobility and activity of the protein deposited into the surface and within the matrix of ionic lens materials demonstrated that the mobility is pH dependent and, within the experimental errors, the biological activity of lysozyme remained unchanged after adsorption and desorption. The study on the effect of different monomers copolymerised with hydroxyethyl methacrylate (HEMA) on the protein up-take showed that monomers producing a positive charge on the copolymer can reduce the spoilation with lysozyme. The studies were extended to real cases in order to compare the patient dependent factors. The in-vivo studies showed that the spoilation is patient dependent as well as other factors. Studies on the extrinsic factors such as dye used in colour lenses showed that the addition of colourant affects protein absorption and, in one case, its effect is beneficial to the wearer as it reduces the quantity of the protein absorbed.
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Rubido, Jacinto S. "Ocular response to silicone-hydrogel contact lenses." Thesis, Aston University, 2004. http://publications.aston.ac.uk/14538/.
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The thesis investigates the ocular response to silicone-hydrogel (SiH) contact lens wear, a relatively new contact lens material that has a higher modulus of rigidity and different surface coating than used in conventional hydrogel materials. The properties of SiH materials differ significantly from conventional hydrogels and, using subjective and objective means of assessment, the thesis examines how these properties affect reflection and biometry, ocular physiology, tear film characteristics, symptomatology, adverse events and complications. A range of standard and newly designed investigative techniques were employed, and latter involving novel imaging techniques, for the objective assessment of physiological changes which occur with contact lens wear. The study is the first to combine these techniques with biochemical analyses of the tear film composition. Forty-seven subjects were fitted with SiH lenses and randomly allocated to one of the two materials currently on the market (Lotrafilcon A or Balafilcon A) on an either daily or continuous wear basis. An additional control group of 14 age-matched non-contact lens wearers were monitored over the same period. Measurements were taken before and 1, 3, 6, 12 and 18 months after initial fitting. The findings reported in this thesis will enable contact lens practitioners and manufacturers to understand further the optical, physiological and biochemical nature of the ocular response to SiH contact lenses and hence facilitate the development of this important generation of contact lens material.
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Zhao, Yibei. "Phospholipid Transport in Silicon Hydrogel Contact Lenses." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3083.
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Dry eye syndrome has been associated with the lack of phospholipids in the tear film, leading to disruption of the tear film and subsequent irritation. Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. This thesis examines the use of silicone hydrogel contact lenses as phospholipid delivery devices. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATFcontaining varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 hrs and is proportional to the amount of DMPC loaded. The ease of loading and the controllable release of DMPC from silicone hydrogels present the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears. To reduce manufacturing steps and concern for residual n-propanol in the lens, it is beneficial to incorporate the DMPC into the monomer formulation and then photopolymerize the lens. Results showed that using this process, DMPC can be placed in the lens and then eluted at faster rates than when it was loaded from n-propanol.
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Merchea, Mohinder Mohan. "Refractive error shift with continuous use (Rescu) lenses." Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054652868.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xv, 144 p.; also includes graphics (some col.) Includes bibliographical references (p. 129-144). Available online via OhioLINK's ETD Center
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Liman, Muhammad Mukhtar. "Diamond turning of contact lens polymers." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/19223.
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Contact lens production requires high accuracy and good surface integrity. Surface roughness is generally used to measure the index quality of a turning process. It has been an important response because it has direct influence toward the part performance and the production cost. Hence, choosing optimal cutting parameters will not only improve the quality measure but also the productivity. In this study, an ONSI-56 (Onsifocon A) contact lens buttons were used to investigate the triboelectric phenomena and the effects of turning parameters on surface finish of the lens materials. ONSI-56 specimens are machined by Precitech Nanoform Ultra-grind 250 precision machine and the roughness values of the diamond turned surfaces are measured by Taylor Hopson PGI Profilometer. Electrostatics values were measured using electrostatic voltmeter. An artificial neural network (ANN) and response surface (RS) model were developed to predict surface roughness and electrostatic discharge (ESD) on the turned ONSI-56. In the development of predictive models, turning parameters of cutting speed, feed rate and depth of cut were considered as model variables. The required data for predictive models were obtained by conducting a series of turning test and measuring the surface roughness and ESD data. Good agreement is observed between the predictive models results and the experimental measurements. The ANN and RSM models for ONSI-56 are compared with each other using mean absolute percentage error (MAPE) for accuracy and computational cost.
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Gill, Felicity Rosemary. "Turning the tide for gas permeable contact lenses." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54980/.
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Gas permeable (GP) lens materials and design technology have advanced in recent years and GP lenses are recognised as providing the wearer with a reduced risk of serious sight-threatening complications, better vision and better long-term comfort. Yet despite these advantages, GP lens prescribing in the UK remains in decline. This thesis investigates how the decline might be addressed by studying the influence of prescribing habits, fitting strategies and lens surface treatments. Initially a questionnaire was designed to investigate practitioner attitudes and behaviour toward GP lenses, and to ascertain whether eye care practitioner (ECP) reservations were responsible for prescribing decline. This survey found that, despite ECP awareness of the advantages of GP lenses, the challenges of reduced initial comfort and increased time required in fitting, results in significant negative practitioner attitudes. In an effort to address the reservations discovered, an investigation of topical anaesthetic (TA) instillation prior to GP fitting was performed in a large case-control study. The results demonstrated that this practice has no negative clinical impact on the ocular surface, marginally improves patient comfort at fitting, and significantly reduces patient anxiety prior to successive GP lens insertion. The remainder of this thesis presents the results from a longitudinal study where groups of neophyte and soft lens wearers were fitted with GP lenses for three months with and without plasma surface treatment (PST). Subjects were monitored and lenses harvested for surface analysis using atomic force microscopy. Examination of GP lenses demonstrated that PST produces smoother surface topographies, prior to and following wear, but this difference reduces after three months wear. Subjects previously wearing soft lenses report lower levels of comfort than neophytes, and PST does not seem to enhance the experience for either group in this cohort. In summary, this thesis presents important findings about the influence of initial comfort on patient anxiety and practitioner attitudes towards GP lens fitting, and gives important insights into the impact of plasma treatment on comfort and performance over the first three months of lens wear.
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Heideman, Kyle C. "Surface Metrology of Contact Lenses in Saline Solution." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/337379.
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Measurement of the quality and performance of soft contact lenses is not new and is continually evolving as manufacturing methods develop and more complicated contact lenses become available. Qualification of soft contact lenses has not been a simple task since they are fundamentally difficult to measure. The shape of the lens is extremely sensitive to how the lens is supported and the material properties can change quickly with time. These lenses have been measured in several different ways, the most successful being non-contact optical methods that measure the lens while it is immersed in saline solution. All of these tests measure the lens in transmission and do not directly measure the surface structure of the lens. The reason for this is that the Fresnel reflectivity of the surface of a contact lens in saline solution is about 0.07%. Surface measurements have been performed in air, but not in saline. The lens needs to be measured in solution so that it can maintain its true shape. An interferometer is proposed, constructed, verified, and demonstrated to measure the aspheric low reflectivity surfaces of a contact lens while they are immersed in saline solution. The problem is extremely difficult and requires delicate balance between stray light mitigation, color correction, and polarization management. The resulting system implements reverse raytracing algorithms to correct for retrace errors so that highly aspheric, toric, and distorted contact lens surfaces can be measured. The interferometer is capable of measuring both surfaces from the same side of the contact lens as well as the lens thickness. These measurements along with the index of refraction of the lens material are enough build a complete 3D model of the lens. A simulated transmission test of the 3D model has been shown to match the real transmission test of the same lens to within 32nm RMS or 1/20th of a wave at the test wavelength.
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Tam, Ngai Keung. "Comfort and Compatibility of Silicone Hydrogel Contact Lenses." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4031.
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Silicone Hydrogel (SiHy) contact lenses are highly successful compared to previous soft lenses; they were developed to provide superior oxygen permeability. However, the hydrophobic natures of the silicone segments enhance lipid sorption which may diminish the lens surface wettability, clarity and comfort. While lens and lens care product are designed to remove lipid deposition, there is lack of experimental evidence to evaluate the actual performances with respect to lipid removal. An in vitro model using an artificial tear fluid containing radiolabeled lipids was employed in this thesis research to evaluate the efficacy of different multi-purpose lens care solutions in removing lipids from SiHy contact lenses. Additional rubbing with the lens care solution is often encouraged by professionals. Part of this research evaluated the effect of additional rubbing process on lipid removal. Overall, a multi-purpose solution (MPS) for lens care, Opti-Free PureMoist®, removed the most lipid deposition from lenses (senofilcon A, comfilcon A, and balafilcon A and one conventional hydrogel lens polymacon). The overall removal percentages were approximately 55% of DPPC and 28% of cholesterol from a conventional hydrogel. However, the MPSs did not remove lipids effectively from SiHy lenses. The highest percentages of removal were 3.08% of DPPC and 0.76% of cholesterol from SiHy lotrafilcon B lenses with Opti-Free PureMoist. The rubbing process increased the amount of removal in some MPSs, but the effects were small. The lack of removal of lipid suggests that the surfactants in the MPSs are not hydrophobic enough to remove lipids from SiHy lenses. Apparently a majority of deposited lipids absorbed into the lens matrix as rubbing did not enhance removal significantly. Future study on determining the concentration profile of lipid sorption throughout the lens thickness is encouraged. Another topic in this research thesis is the use of hydrogel lenses to deliver comfort agents or lubricating molecules from lenses. A screening study was performed in this research to select possible agents to be loaded into several SiHy macromer formulations. Experiments showed that comfort agents PNVP and Kollidon were the best candidates for such a procedure.
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Port, Michael John Anthony. "The application of ultrasound in contact lens metrology." Thesis, City University London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368028.
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Wolfe, Jessica Taylor. "Compliance and Education in Soft Contact Lens Wearers." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586539881925913.
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Korsan, Jenna M. "Soft Multifocal Contact Lenses for Myopia Control in Children." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429012620.
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Kapoor, Yash. "Controlled ophthalmic drug delivery by surfactant-laden contact lenses." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0022886.
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Gulsen, Derya. "Ophthalmic drug delivery through nanoparticle-laden soft contact lenses." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008247.
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Sawyer, Kevin Andrew. "Contact stresses and their optical effects in biconvex lenses." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187141.
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Stress analyses by the finite element and theory of elasticity methods are used to predict the stress fields and intensities in biconvex lenses subject to the contact forces of mounting. In particular, the effects of radial stress imposed by the cell and the contact stresses produced by retainer rings are investigated. Typical retainer ring geometries are utilized in the study. Stress distribution data are related to the stress birefringent characteristics of glass, and the effects of mounting forces on the performance of optical elements are predicted. Optical retardation due to stress birefringence as a function of lens radius is presented in graphical form. Results of the numerical analyses are verified by the photoelastic method. Effects on lenses using typical mounting methods are investigated and compared to the analytic predictions. Experimental results correlate well with the analytical predictions. Results of this research indicate that retainer ring mounts produce localized stress birefringence effects which occur only in the area of contact and that radial mounting produces a stress birefringence field which is evident throughout the entire clear aperture of the lens.
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Olufayo, Oluwole Ayodeji. "Ultra-high precision machining of contact lens polymers." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/3001.
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Contact lens manufacture requires a high level of accuracy and surface integrity in the range of a few nanometres. Amidst numerous optical manufacturing techniques, single-point diamond turning is widely employed in the making of contact lenses due to its capability of producing optical surfaces of complex shapes and nanometric accuracy. For process optimisation, it is ideal to assess the effects of various conditions and also establish their relationships with the surface finish. Presently, there is little information available on the performance of single point diamond turning when machining contact lens polymers. Therefore, the research work undertaken herewith is aimed at testing known facts in contact lens diamond turning and investigating the performance of ultra-high precision manufacturing of contact lens polymers. Experimental tests were conducted on Roflufocon E, which is a commercially available contact lens polymer and on Precitech Nanoform Ultra-grind 250 precision machining. Tests were performed at varying cutting feeds, speed and depth of cut. Initial experimental tests investigated the influence of process factors affecting surface finish in the UHPM of lenses. The acquired data were statistically analysed using Response Surface Method (RSM) to create a model of the process. Subsequently, a model which uses Runge-Kutta’s fourth order non-linear finite series scheme was developed and adapted to deduce the force occurring at the tool tip. These forces were also statistically analysed and modelled to also predict the effects process factors have on cutting force. Further experimental tests were aimed at establishing the presence of the triboelectric wear phenomena occurring during polymer machining and identifying the most influential process factors. Results indicate that feed rate is a significant factor in the generation of high optical surface quality. In addition, the depth of cut was identified as a significant factor in the generation of low surface roughness in lenses. The influence some of these process factors had was notably linked to triboelectric effects. This tribological effect was generated from the continuous rubbing action of magnetised chips on the cutting tool. This further stresses the presence of high static charging during cutting. Moderately humid cutting conditions presented an adequate means for static charge control and displayed improved surface finishes. In all experimental tests, the feed rate was identified as the most significant factor within the range of cutting parameters employed. Hence, the results validated the fact that feed rate had a high influence in polymer machining. The work also established the relationship on how surface roughness of an optical lens responded to monitoring signals and parameters such as force, feed, speed and depth of cut during machining and it generated models for prediction of surface finishes and appropriate selection of parameters. Furthermore, the study provides a molecular simulation analysis for validating observed conditions occurring at the nanometric scale in polymer machining. This is novel in molecular polymer modelling. The outcome of this research has contributed significantly to the body of knowledge and has provided basic information in the area of precision manufacturing of optical components of high surface integrity such as contact lenses. The application of the research findings presented here cuts across various fields such as medicine, semi-conductors, aerospace, defence, telecom, lasers, instrumentation and life sciences.
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Nichols, Jason J. "Evaporative tear film and contact lens factors associated with dry eye symptoms in contact lens wearers." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1085771728.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiii, 122 p.; also includes graphics Includes bibliographical references (p. 80-94). Available online via OhioLINK's ETD Center
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Rutschilling, Ryan R. "Evaluation of Wear Experience with Silicone Hydrogel Lenses in Current Silicone Hydrogel Planned Replacement Lens Wearers." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618559832574561.
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Sousa, Juliana Nunes. "Tradução e validação do questionário "Contact Lenses Dry Eye Questionnaire" (CLDEQ)." Master's thesis, Universidade da Beira Interior, 2012. http://hdl.handle.net/10400.6/1219.
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A nível mundial estima-se que a incidência de olho seco em usuários de lentes de contacto tende a aumentar. Deste modo, com a ausência de questionários traduzidos para o idioma português, e com a fraca correlação entre sinais e sintomas de olho seco associado com uso de lentes de contacto relatadas na comunidade científica, decidiu-se traduzir e validar cultural e linguisticamente para o idioma Português o questionário Contact Lenses Dry Eye Questionnaire (CLDEQ), desenvolvido por Carolyn G. Begley da University of Indiana em 2000.
A metodologia adotada para a tradução e validação linguística do CLDEQ seguiu as normas estabelecidas pela Comunidade Internacional que engloba as seguintes fases: tradução do questionário para a língua portuguesa, síntese das traduções, retraduções da tradução obtida na primeira fase para a língua inglesa, análise pela comissão de apreciação, testar a versão pré-final e submissão da documentação à respetiva comissão de apreciação.
Após a tradução do questionário por um conjunto de tradutores, estas são posteriormente comparadas e condensadas de modo a obter apenas uma só tradução. O questionário resultante da fusão das traduções foi testado, em duas fases complementares entre si, com o objetivo de minimizar possíveis ambiguidades linguísticas e científicas. Deste modo, aplicou-se numa primeira fase uma versão preliminar do questionário, denominada pré-pré teste, a uma amostra de sete indivíduos e posteriormente, a uma amostra de trinta e dois indivíduos, uma versão ajustada da versão preliminar.
Os resultados obtidos permitem antever que a metodologia utilizada propiciou uma boa tradução do questionário de forma a facultar uma adequação cultural e linguística ajustada à população portuguesa, possibilitando a sua disponibilização a todos os profissionais na área da visão, de modo a poderem usufruir da sua aplicação na população com o objetivo de determinar a presença da condição de olho seco.
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Rogers, Ronan. "In vitro and ex vivo wettability of hydrogel contact lenses." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2974.
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The wettability of contact lenses has become an area of intense research, with the belief that the more "hydrophilic" or wettable the lens surface is, the more comfortable the lens may be, as the posterior surface of the eyelid will move more smoothly over it, hence increasing comfort. There are many ways to assess the wettability of a given material, namely sessile drop,1 captive bubble 2 or Wilhelmy plate. 3 This thesis used the sessile drop method to determine the surface wettability of various hydrogel contact lens materials, by measuring the advancing contact angle made between the lens surface and a pre-determined volume of HPLC-grade water. This was followed by measuring the surface wettability following periods in which the lens materials were soaked in various contact lens care regimens. Further studies determined wettability of lens materials after various periods of in-eye wear and finally a study was undertaken to evaluate if a novel biological technique could be used to differentiate proteins that deposit on hydrogel lens materials that may affect wettability and cause discomfort.
A variety of hydrogel lenses, taken directly from their packaging and after soaking in various care regimens, were analyzed to determine their sessile drop advancing contact angles, in vitro. These studies indicated that poly-2-hydroxyethylmethacrylate (pHEMA)-based lenses are inherently more wettable than silicone-based lenses, unless they have a surface treatment that completely covers the hydrophobic siloxane groups. Additionally, certain combinations of lens materials and care regimens produce inherently more wettable surfaces when measured in vitro.
Suitable methods to assess contact lens wettability ex vivo, or after subjects had worn lenses for set periods of time, were developed. It was determined that using latex gloves to remove lenses had no impact upon the lens surface wettability and that rinsing of the lens surface after removal from the eye was required to determine the wettability of the underlying polymer.
The final wettability studies involved an analysis of various lens materials from clinical studies conducted within the Centre for Contact Lens Research (CCLR). These studies investigated differences in wettability between silicone hydrogel lenses manufactured from differing polymers and variations in ex vivo wettability of several combinations of lens materials and solutions, worn for varying periods of time.
A novel method to investigate proteins extracted from lenses using 2D-Difference in Gel Electrophoresis (DIGE) found that this technique could be used to analyze proteins extracted from contact lenses. The data obtained showed that there was no difference between a group of subjects who were symptomatic of lens-induced dryness or a control group, and that care solutions had a minimal influence on the pattern of deposition seen.
The overall conclusion of these studies is that hydrogel lens wettability is affected by the polymer composition and that care regimen components can modify the surface wettability.
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Danboise, Brook Alicia. "Role of MAP Kinase in Fusarium Association With Contact Lenses." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/biology_diss/45.
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Fusarium solani is a soil-borne pathogen devastating agricultural crops throughout the world. While most pathogens are host specific, the fusaria are able to infect both plants and animals. In 2004, an outbreak of Fusarium occurred in association with contact lens wear. Several species of Fusarium were involved but F. solani and F. oxysporum were most prominent. In this work, we have identified a MAP kinase (MAPK), highly similar to fmk1 in F. oxysporum, belonging to the YERK1 subfamily of extracellular regulated kinases. Directed disruption of fmk1 in F. solani AFR4 (FSSC 1) affected several aspects of fungal growth and pathogenicity. Colonies of AFR4„½fmk1 displayed pigmented colony-like formation as opposed to the cottony-white diffuse growth observed with the wild-type strain. Mutants displayed changes in morphology and conidiation patterns with AFR4„½fmk1 mutants producing increased amounts of macroconidia vs. microconidia. AFR4„½fmk1 germ tube emergence was similar to that of wild-type AFR4 and wet weight growth was equivalent but germinules were not able to sense nutrient in chemotropic assays. The disruption of fmk1 increased spore surface hydrophobicity leading to a decrease in association with commercially available hydrogel contact lenses. FMK1 did not affect unworn lens penetration in phosphate buffered saline as both wild-type and mutant strains were able to penetrate commercially available silicone hydrogel contact lenses. AFR4 displayed increased penetration of silicone lenses and this is likely due to: increased spore/lens association, and the inability of AFR4„½fmk1 macroconidia to germinate in phosphate buffered saline. Diminished invasive growth was also noted with disruption of fmk1. Wild-type AFR4 was detected throughout the eye after conidial microinjection while AFR4„½fmk1 was limited to the vitreous fluid. The reduced invasive growth seen is attributed to the loss of chemotropism. The ability to sense and respond to the environment is essential for pathogenicity. MAPK has been deemed essential for plant pathogenicity and now, with its affect on chemotropism, appears to be necessary for animal pathogenicity. FMK1 plays a conserved role in the pathogenicity of Fusarium.
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Schafer, Jeffrey M. "A characterization of dryness symptoms with Silicone Hydrogel contact lenses." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407508203.
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Steele, Kelsy Robin. "Contact Lenses and Water Exposure: Current Practice Patterns and Perceptions." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523906059857207.
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Jones, Lyndon William James. "Ocular compatibility of hydrogel contact lenses : deposition and clinical performance." Thesis, Aston University, 1998. http://publications.aston.ac.uk/9635/.
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Currently over 50 million people worldwide wear contact lenses, of which over 75% wear hydrogel lenses. Significant deposition occurs in approximately 80% of hydrogel lenses and many contact lens wearers cease wearing lenses due to problems associated with deposition. The contact lens field is not alone in encountering complications associated with interactions between the body and artificial devices. The widespread use of man-made materials to replace structures in the body has emphasised the importance of studies that examine the interactions between implantation materials and body tissues. This project used carefully controlled, randomized clinical studies to study the interactive effects of contact lens materials, care systems, replacement periods and patient differences. Of principal interest was the influence of these factors on material deposition and their subsequent impact on subjective performance. A range of novel and established analytical techniques were used to examine hydrogel lenses following carefully controlled clinical studies in which clinical performance was meticulously monitored. These studies established the inter-relationship between clinical performance and deposition to be evaluated. This project showed that significant differences exist between individuals in their ability to deposit hydrogel lenses, with approximately 20% of subjects displaying significant deposition irrespective of the lens material. Additionally, materials traditionally categorised together show markedly different spoilation characteristics, which are wholly attributable to their detailed chemical structure. For the first time the in vivo deposition kinetics of both protein and lipid in charged and uncharged polymers was demonstrated. In addition the importance of care systems in the deposition process was shown, clearly demonstrating the significance of the quality rather than the quantity of deposition in influencing subjective performance.
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Jayakumar, Jaikishan Optometry & Vision Science Faculty of Science UNSW. "Age related variations in anterior ocular characteristics and response to short term contact lens wear." Awarded by:University of New South Wales. School of Optometry and Vision Science, 2005. http://handle.unsw.edu.au/1959.4/22443.
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The purpose of this thesis was to investigate age related variations in anterior ocular characteristics and their effect on the response to short-term (one-hour) open eye orthokeratology (OK) lens wear and overnight hydrogel lens wear. Sixty-three volunteer subjects were divided into three groups comprising children (Group I), young adults (Group II) and older adults (Group III). Anterior ocular characteristics that were measured included corneal topography with the Medmont corneal topographer, total, stromal and epithelial thickness with the Holden-Payor optical pachometer, microscopic cell characteristics with the confocal microscope, corneal aesthesiometry, corneal modulus of elasticity, and tear film, palpebral and eyelid characteristics. The older cornea was found to be more spherical in shape (asphericity Q = -0.24 ?? 0.07 in group III compared to -0.34 ?? 0.09 and -0.32 ?? 0.17 in groups I and II respectively) and showed a tendency from with-the-rule to against-the-rule astigmatism. Older subjects also had a decreased endothelial cell density (2596 ?? 111 cells/mm2 in group III compared to 2793 ?? 138 cells/mm2 in group II) and reduced eyelid tension compared to the younger groups. Children were found to have lower blink rates than adults. It was concluded that these changes might have a significant impact on contact lens wear. The responses to two contact lens based techniques, orthokeratology (OK) and hydrogel overnight wear (ON), were studied. Sixty subjects (20 per group) wore reverse-geometry lenses (BE, Ultravison Aust Pty Ltd) of Boston XO material in one eye under open eye conditions for one hour in one eye only. Changes in unaided visual acuity, corneal curvature, corneal thickness and confocal microscopic variables were measured after OK lens wear. All subject groups showed statistically significant improvements (p < 0.05) in unaided visual acuity, a trend for more positive (less prolate) corneal asphericity, increase in apical corneal radius and decrease in central total corneal thickness, after OK lens wear. When the groups were stratified, statistical significance was obtained between the older group and the other two younger groups for change in apical corneal radius (0.23 ?? 0.01 mm in group I, 0.15 ?? 0.01 mm for group II, 0.06 ?? 0.33 for group III). The change in asphericity also showed significant differences between the older age group (0.10 ?? 0.08 mm) and the young adult group (0.21 ?? 0.13). Central corneal thinning obtained after one hour of OK lens wear revealed significant differences between the older adult group (-1.9 ?? 3.2 ??m) and the other two groups (-5.0 ?? 5.9 ??m in group I, -5.0 ?? 2.0 ??m for group II). Sixty subjects wore hydrogel lenses (One-Day Acuvue, Johnson and Johnson Visioncare Pty Ltd) made of etafilcon A in one eye only overnight during sleep at their home. Changes in unaided visual acuity, corneal curvature, corneal thickness, confocal microscopic variables and slitlamp variables were measured after ON lens wear. All subjects showed significant thickening (p < 0.05) of the cornea with ON wear, more in the lens-wearing eye. This study reported that the edema response induced by Acuvue contact lenses is stromal in origin. The edema response of the older group (33.9 ?? 11.5 ??m) was lower than the other two groups as demonstrated by the difference in the change in central stromal thickness (49.3 ?? 20.3 ??m for group I and 51.0 ?? 20.0 ??m for group II). However, a statistically significant difference in the change in thickness was not reached either for the central total corneal thickness or for other topographic locations. Corneal and visual changes found in this study confirm previous reports of the effects of short term OK and hydrogel ON lens wear. Older lens wearers showed a reduced or delayed response to short-term lens wear. Studies investigating the effects of age with long lens-wearing durations are warranted to quantify these effects further.
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Castejón, Mochón José Francisco. "Estudio de las aberraciones oculares y su corrección mediante lentes de contacto hidrofílicas en ojos normales y muy aberrados." Doctoral thesis, Universidad de Murcia, 2006. http://hdl.handle.net/10803/10840.
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La aberración de onda ocular está estrechamente vinculada con la calidad visual y presenta valores característicos en cada ojo. Su medida y corrección tienen un gran interés tanto en el ámbito de ciencia básica como en la práctica clínica. En el presente trabajo se desarrolla un sistema experimental de medida del frente de onda ocular con gran rango dinámico basado en un sensor Shack-Hartmann. Con él se miden las aberraciones oculares monocromáticas en dos grupos de sujetos: uno de jóvenes con ojos sanos y otro de sujetos que han sido intervenidos de transplante de córnea (queratoplastia penetrante). Los resultados muestran que el valor RMS medio de las aberraciones de alto orden es 10 veces superior en estos últimos. Además se encontró una alta correlación entre las aberraciones corneales (obtenidas de la topografía corneal) y las aberraciones oculares del grupo con patología corneal.Se estudia, de forma simulada y real, la corrección de las aberraciones por medio de lentes de contacto hidrofílicas, diseñadas a partir del patrón de aberraciones de cada sujeto. El estudio se realiza para tres tipos de ojos: normales, con queratoconos y con transplante de córnea. Los resultados muestran que las principales limitaciones de este tipo de corrección se originan debido a la posición y orientación media de la lente de contacto en el ojo. Si tenemos en cuenta desplazamientos realistas de la lente de contacto encontramos que los sujetos normales presentan una pérdida de calidad óptica respecto de la corrección estándar (corrección esfero-cilíndrica). Sin embargo, existen casos patológicos en los que a pesar de las típicas rotaciones y traslaciones de las lentes de contacto, se podría disminuir el RMS de las aberraciones y aumentar la calidad visual, como se comprueba experimentalmente en los queratoconos.The ocular wave aberration is strongly related with the visual quality having specific values for each eye. Its measurement and correction is challenging for fundamental research as well as for clinical practice. In this work we develop an experimental apparatus to measure the ocular wavefront based on a Shack-Hartmann sensor with a high dynamic range. We use it for measuring monochromatic ocular aberration in two subject groups: a) normal young subjects (normal group hereafter) and b) penetrating queratoplasty eyes (pathologic group hereafter). The results show that mean RMS values of the high order aberrations in the pathologic group was ten times higher than that of the normal group. Further, there is a strong correlation between the corneal aberrations (obtained by corneal topography) and ocular aberrations in the pathological group. We study the aberration correction using soft contact lenses, custom designed from each subject aberrations, by mean of both experiments and theoretical predictions. The study is carried out for three types of eyes: normal, keratoconus and penetrating queratoplasty. Results show that the main factors limiting this correction method are owing to both the mean position and rotation of the contact lenses on eye. We found that the normal subjects show a loss of optical quality relative to standard correction (sphere and cylinder), caused by expected displacements of the lenses contacts. In spite of the rotations and translations expected of contact lenses, there are, however, pathologic cases in which it is possible to reduce the RMS and increase visual quality, such as it was experimentally demonstrated in the keratoconus eyes.
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Guido, Christopher James. "Improvements to Whole Lens Reconstruction for Saline Submerged Soft Contact Lenses." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/612612.
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A method for measuring the thickness and surface profiles of soft contact lenses while submerged in a saline solution has been implemented utilizing a low coherence Twyman-Green Interferometer. Although the original measurements demonstrated that features on the contact lens surfaces could be accurately determined, it was believed that the layout of the system also induced surface profile distortions. A new opto-mechanical layout has been implemented which eliminates many of these low frequency distortions. Improvements to the original phase unwrapping algorithms have also been developed to overcome the low visibility output inherent to the measurement allowing for a more complete analysis of the two surfaces of a contact lens.
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Lin, Yu-Ju. "Validity and Repeatability of Pediatric Surveys for Spectacles and Contact Lenses." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243619071.
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Lewis, Kristen Oblad. "COMPARATIVE LIPIDOMICS OF HYDROGEL CONTACT LENSES IN-VITRO AND IN-VIVO." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243889772.
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Nixon, Alex D. "Visual Performance of Scleral and Soft Contact Lenses in Normal Eyes." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397498763.
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Chu, Byoung Sun. "The impact of presbyopic spectacles and contact lenses on driving performance." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/31885/1/Byoung_Chu_Thesis.pdf.
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Presbyopia affects individuals from the age of 45 years onwards, resulting in difficulty in accurately focusing on near objects. There are many optical corrections available including spectacles or contact lenses that are designed to enable presbyopes to see clearly at both far and near distances. However, presbyopic vision corrections also disturb aspects of visual function under certain circumstances. The impact of these changes on activities of daily living such as driving are, however, poorly understood. Therefore, the aim of this study was to determine which aspects of driving performance might be affected by wearing different types of presbyopic vision corrections. In order to achieve this aim, three experiments were undertaken. The first experiment involved administration of a questionnaire to compare the subjective driving difficulties experienced when wearing a range of common presbyopic contact lens and spectacle corrections. The questionnaire was developed and piloted, and included a series of items regarding difficulties experienced while driving under day and night-time conditions. Two hundred and fifty five presbyopic patients responded to the questionnaire and were categorised into five groups, including those wearing no vision correction for driving (n = 50), bifocal spectacles (BIF, n = 54), progressive addition lenses spectacles (PAL, n = 50), monovision (MV, n = 53) and multifocal contact lenses (MTF CL, n = 48). Overall, ratings of satisfaction during daytime driving were relatively high for all correction types. However, MV and MTF CL wearers were significantly less satisfied with aspects of their vision during night-time than daytime driving, particularly with regard to disturbances from glare and haloes. Progressive addition lens wearers noticed more distortion of peripheral vision, while BIF wearers reported more difficulties with tasks requiring changes in focus and those who wore no vision correction for driving reported problems with intermediate and near tasks. Overall, the mean level of satisfaction for daytime driving was quite high for all of the groups (over 80%), with the BIF wearers being the least satisfied with their vision for driving. Conversely, at night, MTF CL wearers expressed the least satisfaction. Research into eye and head movements has become increasingly of interest in driving research as it provides a means of understanding how the driver responds to visual stimuli in traffic. Previous studies have found that wearing PAL can affect eye and head movement performance resulting in slower eye movement velocities and longer times to stabilize the gaze for fixation. These changes in eye and head movement patterns may have implications for driving safety, given that the visual tasks for driving include a range of dynamic search tasks. Therefore, the second study was designed to investigate the influence of different presbyopic corrections on driving-related eye and head movements under standardized laboratory-based conditions. Twenty presbyopes (mean age: 56.1 ± 5.7 years) who had no experience of wearing presbyopic vision corrections, apart from single vision reading spectacles, were recruited. Each participant wore five different types of vision correction: single vision distance lenses (SV), PAL, BIF, MV and MTF CL. For each visual condition, participants were required to view videotape recordings of traffic scenes, track a reference vehicle and identify a series of peripherally presented targets while their eye and head movements were recorded using the faceLAB® eye and head tracking system. Digital numerical display panels were also included as near visual stimuli (simulating the visual displays of a vehicle speedometer and radio). The results demonstrated that the path length of eye movements while viewing and responding to driving-related traffic scenes was significantly longer when wearing BIF and PAL than MV and MTF CL. The path length of head movements was greater with SV, BIF and PAL than MV and MTF CL. Target recognition was less accurate when the near stimulus was located at eccentricities inferiorly and to the left, rather than directly below the primary position of gaze, regardless of vision correction type. The third experiment aimed to investigate the real world driving performance of presbyopes while wearing different vision corrections measured on a closed-road circuit at night-time. Eye movements were recorded using the ASL Mobile Eye, eye tracking system (as the faceLAB® system proved to be impractical for use outside of the laboratory). Eleven participants (mean age: 57.25 ± 5.78 years) were fitted with four types of prescribed vision corrections (SV, PAL, MV and MTF CL). The measures of driving performance on the closed-road circuit included distance to sign recognition, near target recognition, peripheral light-emitting-diode (LED) recognition, low contrast road hazards recognition and avoidance, recognition of all the road signs, time to complete the course, and driving behaviours such as braking, accelerating, and cornering. The results demonstrated that driving performance at night was most affected by MTF CL compared to PAL, resulting in shorter distances to read signs, slower driving speeds, and longer times spent fixating road signs. Monovision resulted in worse performance in the task of distance to read a signs compared to SV and PAL. The SV condition resulted in significantly more errors made in interpreting information from in-vehicle devices, despite spending longer time fixating on these devices. Progressive addition lenses were ranked as the most preferred vision correction, while MTF CL were the least preferred vision correction for night-time driving. This thesis addressed the research question of how presbyopic vision corrections affect driving performance and the results of the three experiments demonstrated that the different types of presbyopic vision corrections (e.g. BIF, PAL, MV and MTF CL) can affect driving performance in different ways. Distance-related driving tasks showed reduced performance with MV and MTF CL, while tasks which involved viewing in-vehicle devices were significantly hampered by wearing SV corrections. Wearing spectacles such as SV, BIF and PAL induced greater eye and head movements in the simulated driving condition, however this did not directly translate to impaired performance on the closed- road circuit tasks. These findings are important for understanding the influence of presbyopic vision corrections on vision under real world driving conditions. They will also assist the eye care practitioner to understand and convey to patients the potential driving difficulties associated with wearing certain types of presbyopic vision corrections and accordingly to support them in the process of matching patients to optical corrections which meet their visual needs.
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Fink, Barbara A. "Quantifying the effects of contact lens prescription parameters on human corneal oxygen uptake /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487331541709205.
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Radford, Cherry F. "The epidemiology of contact lens related disease in users of disposable lenses." Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283186.
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Woods, Russell Laurence. "The optical and visual performance of refractive and diffractive bifocal contact lenses." Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315696.
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Tegeler, Lisa Jan. "Mechanics and materials issues in processing and flexibility of soft contact lenses." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38071.
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Horne, Ryan Ruben. "Thermal and Convective Loading Methods for Releasing Hydrophobic Therapeutics from Contact Lenses." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6388.
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This thesis investigates the feasibility of loading silicone hydrogel (SiHy) contact lenses with two different hydrophobic therapeutics, latanoprost and DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), for treatment of glaucoma and hyperemia respectively. The two methods of loading were 1) thermal loading in an aqueous medium and 2) convective loading in a solution of n-propanol. Dailies Total1® lenses prepared in this manner were tested for their loading and their release into artificial tears. Continuous release over 1-4 days at therapeutic levels is achievable from thermal loading of DMPC, convective loading of DMPC, and convective loading of latanoprost. The DMPC loading processes can be naturally integrated into standard manufacturing lines for Dailies Total1®. Both DMPC and latanoprost release at rates proportional to the amount loaded into a contact lens. Latanoprost loads into a contact lens strictly proportionally to the loading concentration and the time of loading. The convective loading step represents a significant improvement on both the time of loading (reduced from days to minutes) and the loading capacity of silicone hydrogel contact lenses. This thesis also compares the loading and release of latanoprost in the convective loading procedure using the SiHy contact lenses of Acuvue Advance® (Johnson & Johnson Vision Care, Jacksonville, FL) , Air Optix® (Alcon, Copenhagen, Denmark), Biofinity® (CooperVision), PureVision® (Bausch & Lomb), and Dailies Total1® (Alcon), and the polyHEMA lens, SofLens 38® (Bausch & Lomb), finding that silicone hydrogels load an order of magnitude more drug than the polyHEMA lens and release into artificial tears for an order of magnitude longer. Overall, these experiments provide a quantitative understanding of the dynamics of loading and release for both DMPC and latanoprost.
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Little, Simon A. "Determinants of postlens tear film morphology in hydrogel contact lens wear." Thesis, Queensland University of Technology, 1995. https://eprints.qut.edu.au/36723/1/36723_Digitised%20Thesis.pdf.
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The postlens tear film (PTF) in hydrogel lens wear has received relatively little attention in the literature. Early studies of the effects of hydrogel contact lens wear on corneal physiology indicated that there would be only a minimal increase in oxygen tension at the cornea with blink-induced postlens tear exchange. More recently, the potential importance of the PTF in lens movement and in flushing debris and necrotic cellular matter from beneath the lens has been contemplated. However, there have been few attempts to establish the roles or determinants of the PTF in hydrogel lens wear.
In early investigations with fluorexon, the PTF was considered to be constant after an initial period of lens settling. Studies of lens dehydration indicated that the PTF did not have an aqueous component since hydration gradients were not produced between the surfaces of the lens during wear. However, more recent studies have reported debris and particle movement in the PTF with some hydrogel lenses, indicating that a substantial aqueous component can be present. Furthermore, preliminary studies using a non-invasive biomicroscopic technique have suggested that the PTF can vary during lens wear.
In the biomicroscopic method of PTF examination, the specular reflection at the back surface of the lens is examined. Amorphous, coloured, mottled and striated PTF appearances have been observed. Non-amorphous PTF morphologies are thought to be produced by optical interference between the back surface of the lens and the ocular surface, ie within the full thickness of the PTF. However, the exact location of the reflecting interface at the ocular surface is uncertain. In addition, it is possible that the different patterns are produced by a postlens lipid layer, rather than being related to the total thickness of the PTF. Thus, unless these issues can be resolved, the biomicroscopic method can be used only for qualitative studies.
The work described herein better evaluates the diversity in the morphology of the PTF that is present in hydrogel lens wear. Furthermore, some possible determinants of PTF morphology in hydrogel lens wear are considered.
The first two studies in this thesis considered the population diversity and temporal variation of the PTF in hydro gel lens wear (chapters three and four). In both studies PTF appearance in specular reflection was categorised as amorphous, coloured, striated or dynamic (variable with blinking), where non-amorphous or patterned morphologies appeared to indicate progressive thinning of the PTF. The first study assessed PTF appearance and lens movement at routine aftercare visits. Patterned appearances were present in 25% of subjects and occurred approximately equally with each type of hydrogel lens that was being worn. Furthermore, patterned PTF appearances were found to be associated with reduced lens movement (Kruskal-Wallis ANOVA, p<0.001).
In the second study, the PTF and blink-induced movement were investigated when thin mid water content lenses were worn over six hours on each of two consecutive days. Patterned PTF appearances were observed in 53 % of subjects during the first 30 minutes of lens wear. Median lens movement was near zero initially and increased within the first hour to 0.34 mm and 0.30 mm on days one and two, respectively. Limited lens movement was related to apparent depletion of the PTF. In some subjects, lens movement and PTF morphology co-varied throughout the lens wearing periods. This relationship strongly indicates that changes in lens movement were accompanied by changes in the thickness or viscosity of the PTF. Since an increase in PTF viscosity would also require a reduction in the aqueous component, this finding provides additional evidence for the production of patterns in specular reflection by optical interference within the full thickness of the PTF.
Three further experiments investigated the determinants of PTF morphology. The effect of lens thickness on PTF morphology, and the role of the PTF in the mechanisms of inferior arcuate staining were investigated with ultrathin and standard thickness high water content hydrogel lenses. Lens dehydration, lens adherence and prelens tear film stability were also measured in order to evaluate their role in inferior arcuate staining. The ultrathin lenses were associated with a higher incidence of both staining and coloured PTF appearances, had greater front surface dehydration, and were more adherent to the eye. These findings indicate that the PTF has a role in the mechanism of inferior arcuate staining with ultrathin lenses. Lenses of greater thickness are associated with a lower incidence of inferior arcuate staining and appear to support a more substantial PTF.
The hypothesis that the PTF could be depleted by instillation of hypotonic saline was investigated in the next experiment. With instillation of the hypotonic solutions the appearance of the PTF in specular reflection changed to a faint coloured or coloured pattern in the majority of subjects. The faint coloured and coloured patterns were associated with lens binding. However, there were no significant changes in measured lens parameters. These findings indicate that lens binding and the development of coloured patterns in specular reflection were due to osmotic depletion of the aqueous component of the PTF.
The hypothesis that increased lens dehydration due to evaporation at the lens front surface may cause PTF depletion was tested in the final experiment. Ambient air flow was associated with an increase in the incidence of PTF patterns. Hydration gradients between the surfaces of the lenses suggested a flow of water from the PTF to the lens front surface during wear. Since patterned PTF appearances are associated with limited lens movement, these findings suggest that environmental factors, such as ambient air flow, may account for some of the variation in the amount of lens movement that can be observed during wear.
This series of studies has shown that PTF morphology can vary throughout a period of wear of currently available hydrogel contact lenses. Several determinants of PTF morphology have been identified; lens wearing time, lens thickness, ambient air flow and solution hypotonicity. In addition several consequences of PTF depletion have been identified; lens movement variation, lens binding, increased lens dehydration and inferior arcuate staining.
This work provides an improved understanding of the PTF in hydrogel lens wear. Since many of the determinants of PTF morphology identified herein are related to the flow of water through the contact lens, future work should assess the hypothesis that lens water transmissibility is a fundamental determinant of PTF morphology. Other future work should evaluate the relationship between PTF thickness and the efficiency of tear exchange and postlens debris expulsion. Ideally, this would be done once a method for the direct measurement of PTF thickness had been developed.
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Miller, Karina Y. "Contact Lens, Academics and Self-Perception Study: Follow-up Results." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586881377813119.
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Greiner, Katie Lynn. "Quality of Life of Pediatric Bifocal Soft Contact Lens Wearers." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243463393.
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