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1.
Ophthalmic Physiol Opt ; 41(2): 393-400, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33295033

RESUMO

PURPOSE: Centre-distance multifocal contact lenses (MFCLs) for myopia control are thought to slow myopia progression by providing both clear foveal vision and myopic defocus. Characterising the power profile of lenses is important to understanding their possible effects on retinal defocus when worn. The power profiles of three commercially available MFCLs were determined. METHODS: Three centre-distance MFCL designs were studied: Biofinity Multifocal D +2.50 add (comfilcon A), Proclear Multifocal D +2.50 add (omafilcon A), and NaturalVue Multifocal (etafilcon A). Two lenses each in power from -1.00D to -6.00D in 1D steps were stored in ISO 18369-3:2017 standard phosphate buffered saline for 24 h. Optical power profiles were measured in a wet cell with the SHSOphthalmic profiler accounting for centre thickness and manufacturer-reported material refractive index. Sagittal power maps from the SHSOphthalmic were exported, and custom MATLAB code was used to generate power profiles by averaging along the vertical and horizontal meridians. One-way anova with Tukey's HSD post-hoc t-tests were used to analyse maximum add power by lens design. RESULTS: Plus power increased out from the lens centre for all three MFCLs. Power profiles of Biofinity D and Proclear D MFCLs show three distinct areas within the optic zone; the distance zone (from lens centre to about 1.6 mm radius), intermediate zone (about 1.6 mm radius to 2.1 mm) and near zone (about 2 mm radius to 4 mm). For NaturalVue MFCLs, plus power starts increasing almost immediately from the lens centre, reaching maximum measured mean plus power at a radius of 2.7 mm. From 2.7 mm to 3.0 mm, there was a decrease in plus power, which was then generally maintained out to the optic zone edge. Across all lens powers, maximum add power was highest with the NaturalVue MFCL (+3.32 ± 0.44D), then Proclear D (+1.84 ± 0.28D) and Biofinity D (+1.47 ± 0.34D) MFCLs (all p < 0.04). Add power peaked at different locations for different lens powers and designs. CONCLUSIONS: Power profiles of MFCLs vary based on lens design and power. These power profiles are consistent with reported myopic and hyperopic changes in peripheral refraction with MFCLs and provide some explanation for reported differences in peripheral refraction with these MFCLs. Further work is needed to determine whether these power profile differences influence myopia progression.


Assuntos
Acomodação Ocular/fisiologia , Lentes de Contato Hidrofílicas/normas , Hiperopia/terapia , Miopia/terapia , Refração Ocular/fisiologia , Acuidade Visual , Desenho de Equipamento , Humanos , Hiperopia/fisiopatologia , Miopia/fisiopatologia , Refratometria/métodos , Testes Visuais
2.
Optom Vis Sci ; 97(8): 544-548, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32769840

RESUMO

SIGNIFICANCE: Standardized guidelines that are clinically practical are needed to assist the prescriber in minimizing the risk of conveying infection through multiuse diagnostic contact lens use and reuse.Contact lens prescribers face the specter of transferring potential pathogens from one patient to another when reusing diagnostic (trial) contact lenses on multiple patients because infectious organisms have been recovered from worn contact lenses, although there is no evidence of transmission through this mechanism. These pathogens can be introduced into the system from one patient to another, or they may be introduced by clinician lens handling, storage, or both. These pathogens can cause acute or chronic systemic or ocular infection that can lead to significant morbidity (temporary or permanent) that includes vision loss.


Assuntos
Soluções para Lentes de Contato/uso terapêutico , Lentes de Contato Hidrofílicas/normas , Desinfecção/métodos , Contaminação de Equipamentos/prevenção & controle , Higiene/normas , Prescrições/normas , Manejo de Espécimes/métodos , Lentes de Contato Hidrofílicas/microbiologia , Transmissão de Doença Infecciosa/prevenção & controle , Infecções Oculares/prevenção & controle , Desinfecção das Mãos , Humanos , Procedimentos Ortoceratológicos
3.
Eye Contact Lens ; 44 Suppl 2: S233-S240, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29077584

RESUMO

OBJECTIVES: The objective of this investigation was to evaluate the level of comfort and ocular dryness during wear with six daily disposable contact lenses (DDCL) and also determine the changes in contact lens equilibrium water content (EWC) resulting from their wear. METHODS: In this contralateral open trial, 27 subjects were randomly fitted with six DDCL (stenfilcon A, delefilcon A, nelfilcon A, narafilcon A, nesofilcon A, and omafilcon A). The evaluation of comfort and ocular dryness sensation was recorded by the participants at two moments of the day (11 AM and 5 PM) over a period of 10 days of contact lens wear. The assessment was made with the aid of visual analogue scales (0-10). The refractive index of 54 contact lenses was accessed by a single operator using a digital automated refractometer (CLR 12-70; Index Instruments). The EWC of the lenses was estimated based on its refractive index values. RESULTS: Comfort ratings were slightly higher for delefilcon A (9.56±0.67, P=0.01) and narafilcon A (9.40±0.93, P=0.01) and these lenses wearers also reported less ocular dryness. The results revealed a pronounced water content reduction for omafilcon A (P=0.002), narafilcon A (P=0.008), and nesofilcon A (P=0.003). CONCLUSION: Although changes in subjective responses and EWC were distinct among the materials analyzed, all the contact lenses performed well during the 10 days of wear.


Assuntos
Lentes de Contato Hidrofílicas , Síndromes do Olho Seco/prevenção & controle , Dor Ocular/diagnóstico , Adulto , Lentes de Contato Hidrofílicas/efeitos adversos , Lentes de Contato Hidrofílicas/normas , Equipamentos Descartáveis , Feminino , Humanos , Masculino , Satisfação do Paciente , Refratometria , Água/análise
4.
Eye Contact Lens ; 43(6): 340-345, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27243350

RESUMO

OBJECTIVE: To investigate if initial multifocal contact lens (MFCL) performance predicts short-term dispensing performance. METHODS: A retrospective analysis of 55 participants (Px) in a masked, crossover, clinical trial, using ACUVUE OASYS for Presbyopia and AIR OPTIX AQUA Multifocal. Subjective questionnaires were administered at the following instances: initial fitting, two take home questionnaires (THQ) completed between days 2 and 4 and at assessment, ≥5 days after fitting. Questionnaires included vision clarity and lack of ghosting at distance, intermediate and near at day/night time points rated on a 1 to 10 (1-step, 10 most favorable) rating scale. Vision stability, vision while driving, overall vision satisfaction, willingness to purchase and comfort, as well as acuity-based measures were also collected. RESULTS: There were no statistical differences in comfort and vision at all distances, in vision stability or driving at either time points between THQ and assessment (P>0.05). However, there was a statistical decline in subjective overall vision satisfaction and comfort between fitting and assessment visits (P<0.001). Willingness to purchase remained the same at fitting and assessment in 68% of Px, whereas only 4% of Px converted to a positive willingness to purchase at assessment. The majority of acuity-based measures remained constant between fitting and assessment visits. CONCLUSION: Initial performance at fitting was not able to predict short-term performance of MFCL. Subjective measures peaked at fitting and declined thereafter whereas acuity-based measures remained constant. Utility of subjective rating tools may aid practitioners to gauge success of MFCL.


Assuntos
Lentes de Contato Hidrofílicas , Presbiopia/reabilitação , Adulto , Lentes de Contato Hidrofílicas/normas , Estudos Cross-Over , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Aceitação pelo Paciente de Cuidados de Saúde , Satisfação do Paciente , Estudos Retrospectivos , Inquéritos e Questionários , Acuidade Visual
5.
Eye Contact Lens ; 42(5): 298-302, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26513721

RESUMO

PURPOSE: The diameters of soft contact lenses are conventionally measured at room temperature (RT), however, all soft lenses shrink when raised to eye temperature (ET). The purpose of this study was to evaluate RT to ET shrinkage in a representative sample of contemporary spherical soft contact lenses. METHODS: Twenty-four reusable and daily disposable lens types (10 hydrogel and 14 silicone hydrogel) in three powers were measured for total diameter at RT (20°C±1°C) and ET (34°C±1°C). Lens diameter measurements were undertaken after equilibration in ISO saline in a temperature controlled lens analyzer (Optimec Ltd, Malvern, UK). Theoretical changes in base curve radii were also calculated. RESULTS: All lens types reduced in diameter when raised to ET. The largest mean changes with silicone hydrogel and hydrogel lenses were with Avaria (Δ0.33 mm) and SofLens Daily Disposable (Δ0.69 mm), respectively. The smallest mean changes for silicone hydrogel and hydrogel lenses were with 1-DAY ACUVUE TruEye (Δ0.04 mm) and SofLens 38 (Δ0.11 mm), respectively. There was, however, a wide range in change between the different lenses tested. CONCLUSIONS: This study has identified the levels of shrinkage in current soft contact lenses. In many cases, these shrinkage levels can be expected to have significant effects on clinical performance.


Assuntos
Lentes de Contato Hidrofílicas , Temperatura , Temperatura Corporal , Lentes de Contato Hidrofílicas/normas , Equipamentos Descartáveis , Humanos , Hidrogéis , Teste de Materiais , Silicones
6.
Ophthalmic Physiol Opt ; 33(5): 581-91, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23510388

RESUMO

PURPOSE: To quantify the optical quality of various daily disposable contact lenses in vivo and to ascertain its variation in terms of wearing time by means of objective non-invasive determination of wavefront patterns. METHODS: The crx1 adaptive-optics system was used to measure the wavefront aberrations in 15 myopic eyes before and at 2-h intervals after contact lens fitting, over a 12-h wearing period. Seven types of contact lenses having different material, water content and lens design were evaluated in this study: Dailies Total1, Dailies AquaComfort Plus, Proclear 1 Day, 1-Day Acuvue TruEye, 1-Day Acuvue moist, SofLens daily disposable and Clariti 1-Day. The aberration data were analysed by fitting Zernike polynomials up to the 5th-order for 3 and 5-mm pupils. The optical quality under each condition and at each point in time was described by means of the Root-Mean-Square (RMS) value of wavefront aberration, Modulation Transfer Function (MTF), Point Spread Function and cut-off spatial frequency. RESULTS: A RMS increase was observed after contact lens fitting as well as over time, both for a 3-mm and a 5-mm pupil. Each type of lens induced a different amount of wavefront aberrations, which vary over time also in a different manner. Dailies Total1 showed the lowest RMS values both at baseline and at the end of the day. In addition, Dailies Total1 provided the best MTF out of all the contact lenses that were assessed. These observations were reflected in higher cut-off spatial frequencies and visual resolution both at baseline and after 12 h of wearing time. CONCLUSIONS: Aberrometry makes it possible to analyse accurately and in vivo the optical quality of contact lenses and to assess how lenses having different characteristics - such as material or water content - behave for different wearing times. These variations across contact lenses may result in differences in visual performance.


Assuntos
Lentes de Contato Hidrofílicas/normas , Miopia/reabilitação , Aberrometria/métodos , Adulto , Aberrações de Frente de Onda da Córnea/fisiopatologia , Equipamentos Descartáveis/normas , Feminino , Humanos , Masculino , Miopia/fisiopatologia , Óptica e Fotônica/métodos , Fatores de Tempo , Acuidade Visual/fisiologia , Adulto Jovem
7.
Eye Contact Lens ; 39(3): 254-62, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23584047

RESUMO

OBJECTIVES AND METHODS: Contact angle, as a representative measure of surface wettability, is often employed to interpret contact lens surface properties. The literature is often contradictory and can lead to confusion. This literature review is part of a series regarding the analysis of hydrogel contact lenses using contact angle techniques. Here we present an overview of contact angle terminology, methodology, and analysis. Having discussed this background material, subsequent parts of the series will discuss the analysis of contact lens contact angles and evaluate differences in published laboratory results. RESULTS: The concepts of contact angle, wettability and wetting are presented as an introduction. Contact angle hysteresis is outlined and highlights the advantages in using dynamic analytical techniques over static methods. The surface free energy of a material illustrates how contact angle analysis is capable of providing supplementary surface characterization. Although single values are able to distinguish individual material differences, surface free energy and dynamic methods provide an improved understanding of material behavior. The frequently used sessile drop, captive bubble, and Wilhelmy plate techniques are discussed. Their use as both dynamic and static methods, along with the advantages and disadvantages of each technique, is explained. CONCLUSIONS: No single contact angle technique fully characterizes the wettability of a material surface, and the application of complimenting methods allows increased characterization. At present, there is not an ISO standard method designed for soft materials. It is important that each contact angle technique has a standard protocol, as small protocol differences between laboratories often contribute to a variety of published data that are not easily comparable.


Assuntos
Lentes de Contato Hidrofílicas/normas , Hidrogéis/química , Molhabilidade , Humanos , Propriedades de Superfície
8.
Eye Contact Lens ; 39(1): 4-12, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23292050

RESUMO

Since the initial launch of silicone hydrogel lenses, there has been a considerable broadening in the range of available commercial material properties. The very mobile silicon-oxygen bonds convey distinctive surface and mechanical properties on silicone hydrogels, in which advantages of enhanced oxygen permeability, reduced protein deposition, and modest frictional interaction are balanced by increased lipid and elastic response. There are now some 15 silicone hydrogel material variants available to practitioners; arguably, the changes that have taken place have been strongly influenced by feedback based on clinical experience. Water content is one of the most influential properties, and the decade has seen a progressive rise from lotrafilcon-A (24%) to efrofilcon-A (74%). Moduli have decreased over the same period from 1.4 to 0.3 MPa, but not solely as a result of changes in water content. Surface properties do not correlate directly with water content, and ingenious approaches have been used to achieve desirable improvements (e.g., greater lubricity and lower contact angle hysteresis). This is demonstrated by comparing the hysteresis value of the earliest (lotrafilcon-A, >40°) and most recent (delefilcon-A, <10°) coated silicone hydrogels. Although wettability is important, it is not of itself a good predictor of ocular response because this involves a much wider range of physicochemical and biochemical factors. The interference of the lens with ocular dynamics is complex leading separately to tissue-material interactions involving anterior and posterior lens surfaces. The biochemical consequences of these interactions may hold the key to a greater understanding of ocular incompatibility and end of day discomfort.


Assuntos
Lentes de Contato Hidrofílicas/normas , Hidrogéis , Silicones , Córnea/metabolismo , Córnea/patologia , Humanos , Teste de Materiais/métodos , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
9.
Eye Contact Lens ; 39(1): 100-8, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23274760

RESUMO

One of the major breakthroughs in the development of silicone hydrogel contact lenses has related to the ability of manufacturers to overcome the surface hydrophobicity that occurred with silicone elastomer lenses. However, the wettability of silicone hydrogel lenses continues to be of interest as a potential link between in vivo lens performance and contact lens-related comfort. This article will review some of the knowledge we have gained in the area of contact lens wettability over the past decade and will discuss some of the challenges related to its measurement.


Assuntos
Lentes de Contato Hidrofílicas , Hidrogéis/química , Elastômeros de Silicone/química , Molhabilidade , Lentes de Contato Hidrofílicas/normas , Humanos , Propriedades de Superfície
10.
Eye Contact Lens ; 39(1): 13-9, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23271477

RESUMO

In response to patient demands for extended contact lens wearing times, the contact lens industry has developed novel silicone-hydrogel (SiHy) lens materials that combine the enhanced oxygen permeability of silicone polymers with the water-based comfort of conventional hydrogels. In the past 12 years since the successful launch of these SiHy lenses, much has been learned about their ability to provide the biocompatibility necessary to sustain ocular health and comfort. A review of the unique physiologic requirements for a successful extended wear lens and how the first and current SiHy lenses address them is provided.


Assuntos
Materiais Biocompatíveis , Lentes de Contato Hidrofílicas/normas , Hidrogéis , Desenho de Prótese/métodos , Silicones , Humanos , Teste de Materiais
11.
Eye Contact Lens ; 39(4): 290-4, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23771011

RESUMO

OBJECTIVE: To examine potential changes in comfort, ocular health, and vision between 2 weeks and 1 month for wearers of lotrafilcon B lenses. METHODS: Up to 120 current wearers of lotrafilcon B lenses were recruited to wear a new pair of lenses for 1 month, using their habitual lens care system. Subjective ratings, biomicroscopy scores, visual acuity, and lens assessments were recorded at 2 weeks and at 1 month. In addition, participants responded to 4 Likert-type statements regarding comfort and vision after the full month of wear. RESULTS: No significant differences were noted in biomicroscopy scores between 2 weeks and 1 month. Noninferiority from 2 weeks to 1 month was established for subjective ratings of visual clarity (P=0.003; n=112) and ocular redness (P<0.001; n=112); the other 7 subjective ratings (for comfort, dryness, etc.) decreased less than 1 unit on 10-point scales. Significant majorities of respondents (all P<0.001 vs. 50%) agreed or strongly agreed that the lenses provided excellent comfort (83.5% of respondents) and clear vision (83.5%) throughout the month and that comfort (71.5%) and vision (77.9%) were the same at the end of the month as at the beginning of the month. Two adverse events occurred during the trial. Both were asymptomatic and considered clinically insignificant. CONCLUSIONS: Significant majorities of patients agreed that the lenses provided consistent comfort and vision throughout the month. Most wearers of lotrafilcon B lenses did not perceive substantial deteriorations in comfort or vision over the recommended wearing interval. Outcomes support monthly replacement of these lenses.


Assuntos
Lentes de Contato Hidrofílicas , Hidrogéis , Erros de Refração/reabilitação , Silicones , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Lentes de Contato Hidrofílicas/efeitos adversos , Lentes de Contato Hidrofílicas/normas , Doenças da Córnea/etiologia , Edema/etiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Satisfação do Paciente , Estudos Prospectivos , Erros de Refração/fisiopatologia , Acuidade Visual/fisiologia , Adulto Jovem
12.
Optom Vis Sci ; 89(8): 1107-18, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22820470

RESUMO

PURPOSE: A physical model eye capable of carrying soft contact lenses (CLs) was used as a platform to evaluate optical performance of several commercial multifocals (MFCLs) with high- and low-add powers and a single-vision control. METHODS: Optical performance was evaluated at three pupil sizes, six target vergences, and five CL-correcting positions using a spatially filtered monochromatic (632.8 nm) light source. The various target vergences were achieved by using negative trial lenses. A photosensor in the retinal plane recorded the image point-spread that enabled the computation of visual Strehl ratios. The centration of CLs was monitored by an additional integrated en face camera. Hydration of the correcting lens was maintained using a humidity chamber and repeated instillations of rewetting saline drops. RESULTS: All the MFCLs reduced performance for distance but considerably improved performance along the range of distance to near target vergences, relative to the single-vision CL. Performance was dependent on add power, design, pupil, and centration of the correcting CLs. Proclear (D) design produced good performance for intermediate vision, whereas Proclear (N) design performed well at near vision (p < 0.05). AirOptix design exhibited good performance for distance and intermediate vision. PureVision design showed improved performance across the test vergences, but only for pupils ≥4 mm in diameter. Performance of Acuvue bifocal was comparable with other MFCLs, but only for pupils >4 mm in diameter. Acuvue Oasys bifocal produced performance comparable with single-vision CL for most vergences. CONCLUSIONS: Direct measurement of single-pass images at the retinal plane of a physical model eye used in conjunction with various MFCLs is demonstrated. This method may have utility in evaluating the relative effectiveness of commercial and prototype designs.


Assuntos
Lentes de Contato Hidrofílicas/normas , Refração Ocular/fisiologia , Erros de Refração/terapia , Desenho de Equipamento , Humanos , Erros de Refração/fisiopatologia , Reprodutibilidade dos Testes
13.
Optom Vis Sci ; 89(10): 1468-76, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22982767

RESUMO

PURPOSE: The purpose of this study is to demonstrate a novel method for measuring the modulus of contact lenses in their as-received, variable-thickness form and to determine whether modulus varies with location within commercial lenses and whether it is dependent on lens geometry and temperature. METHODS: The thickness profiles of lenses having powers from -8 diopters (D) to +4 D were measured using a Rehder electronic thickness gauge. Strip-shaped specimens having a width of 5.5 mm were then cut from the lenses. Graphite particles were sprinkled on the specimen surface so that its motions could be tracked using digital image-correlation techniques. The specimens were mounted in a BioTester test system using BioRakes (rather than clamps) and stretched uniaxially until all parts of the lens between the attachment points had elongated by at least 10%. This procedure allowed local modulus values to be determined at 110 locations over the surface of each lens and any property variations within the lenses to be characterized. Tests were performed at 5, 23, and 37°C. RESULTS: Material modulus was found to be essentially constant within any given lens and was independent of the optical power of the lens. Young's Modulus values ranged from 0.3 to 1.9 MPa, depending on the lens manufacturer and product, and some lens materials showed a decrease in modulus with temperature. For the materials tested, those with lower water content had a tendency to exhibit higher moduli. CONCLUSIONS: Testing of the kind reported here is important for assessing the efficacy of current and proposed contact lens materials and designs, especially if such designs make use of variable properties to enhance function or fit.


Assuntos
Lentes de Contato Hidrofílicas/normas , Módulo de Elasticidade , Hidrogel de Polietilenoglicol-Dimetacrilato/normas , Teste de Materiais/métodos , Silicones/normas , Humanos , Temperatura
14.
Ophthalmic Physiol Opt ; 32(6): 527-34, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22978717

RESUMO

PURPOSE: Multifocal soft contact lenses have been used to decrease the progression of myopia, presumably by inducing relative peripheral myopia at the same time as the central image is focused on the fovea. The aim of this study was to investigate how the peripheral optical effect of commercially available multifocal soft contact lenses can be evaluated from objective wavefront measurements. METHODS: Two multifocal lenses with high and low add and one monofocal design were measured over the ±40° horizontal field, using a scanning Hartmann-Shack wavefront sensor on four subjects. The effect on the refractive shift, the peripheral image quality, and the depth of field of the lenses was evaluated using the area under the modulation transfer function as the image quality metric. RESULTS: The multifocal lenses with a centre distance design and 2 dioptres of add induced about 0.50 dioptre of relative peripheral myopia at 30° in the nasal visual field. For larger off-axis angles the border of the optical zone of the lenses severely degraded image quality. Moreover, these multifocal lenses also significantly reduced the image quality and increased the depth of field for angles as small as 10°-15°. CONCLUSIONS: The proposed methodology showed that the tested multifocal soft contact lenses gave a very small peripheral myopic shift in these four subjects and that they would need a larger optical zone and a more controlled depth of field to explain a possible treatment effect on myopia progression.


Assuntos
Lentes de Contato Hidrofílicas/normas , Miopia/fisiopatologia , Campos Visuais/fisiologia , Acomodação Ocular/fisiologia , Adulto , Humanos , Miopia/terapia , Pupila/fisiologia
15.
Ophthalmic Physiol Opt ; 32(6): 508-17, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22958210

RESUMO

PURPOSE: To compare the repeatability and validity of measurements of the back vertex power (BVP) of spherical soft contact lenses made in-air using the method specified in the International Standard (ISO 18369-3:2006) with the corresponding values when BVP was calculated from measurements made using a wet cell and focimeter method that is not approved by this Standard. METHODS: The BVP of 20 hydrogel and 20 silicone hydrogel lenses, with labelled powers ranging from +8.00 to -12.00 D, were measured with a focimeter by two operators on two occasions in-air in accordance with the relevant International Standard. Equivalent sets of measurements were made with the lenses immersed in-saline within a wet cell and their BVPs in-air were calculated. The validity of each method was assessed by comparing their results with an instrument that used the Hartmann method. RESULTS: The reliability results were generally a little better for the in-saline measurements than for the in-air measurements, although all reliability data demonstrated absolute values of mean errors (inter-operator and inter-session) that were <0.05 D for hydrogel lenses and <0.07 D for silicone hydrogel lenses. The in-air 95% confidence intervals were <0.45 D and <0.40 D for hydrogel and silicone hydrogel lenses, respectively and in-saline <0.39 and <0.31 D for hydrogel and silicone hydrogel lenses, respectively. The validity data revealed a relationship between measurement error and BVP for the in-air data (the focimeter overestimates the power of high plus and high minus lenses compared with the Hartmann instrument) and possibly a more complex relationship for the in-saline data. The 95% limits of agreement indicate better agreement for the in-saline validity data (-0.55 to +0.48 D for hydrogel lenses and -0.42 to +0.54 D for silicone hydrogel lenses) than those obtained in-air (-0.64 to +0.68 D for hydrogel lenses and -0.57 to +0.44 D for silicone hydrogel lenses). CONCLUSIONS: Using equipment readily available in a clinical setting, the wet cell method of measurement of the BVP of spherical soft contact lenses has been shown to provide results for reliability and validity that were at least as good as those obtained with the in-air method approved by the International Standard.


Assuntos
Lentes de Contato Hidrofílicas/normas , Refratometria , Acomodação Ocular , Ar , Humanos , Hidrogel de Polietilenoglicol-Dimetacrilato , Variações Dependentes do Observador , Refração Ocular , Reprodutibilidade dos Testes , Solução Salina Hipertônica , Silicones
16.
Eye Contact Lens ; 38(5): 313-8, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22890226

RESUMO

OBJECTIVES: To evaluate clinical performance of three lens types disposed of on a daily disposable (DD) basis. METHOD: A total of 120 participants were randomized into one of three lens types (etafilcon A, narafilcon A, and senofilcon A), all worn bilaterally on a DD regime. Participants were observed at baseline, 2-week, and 1- and 3-month visits where ocular physiology and lens performance variables were collected on a 0 to 4 grading scale in 0.1 increments. Subjective comfort and vision ratings were collected on a 1 to 100 rating scale and in the form of symptom severity. RESULTS: Forty participants wore each lens type with no differences in age or gender between groups (P>0.05). Etafilcon A exhibited more limbal redness compared with either of the other lens types (P<0.01). More superior corneal staining was noted with narafilcon A lenses compared with senofilcon A (P<0.01), and more superior conjunctival indentation was noted for narafilcon A compared with etafilcon A (P=0.001). No differences were found between lenses in the 1 to 100 rating scale (P>0.05). Narafilcon A showed more moderate to severe dryness symptoms and symptoms of blurred vision at lens wearing visits (P<0.05). One bilateral contact lens papillary conjunctivitis, one unilateral superior epithelial arcuate lesion, and one infiltrative keratitis were associated with narafilcon A only. Of the seven discontinuations, six were from the narafilcon A group. CONCLUSION: Different contact lens materials and designs, worn on the same DD modality, elicit different ocular and patient responses. Narafilcon A did not perform clinically as well as etafilcon A and senofilcon A worn on a DD modality.


Assuntos
Lentes de Contato Hidrofílicas/normas , Equipamentos Descartáveis , Miopia/reabilitação , Adulto , Lentes de Contato Hidrofílicas/efeitos adversos , Córnea/fisiologia , Feminino , Humanos , Modelos Logísticos , Masculino , Miopia/fisiopatologia , Satisfação do Paciente , Estudos Prospectivos , Índice de Gravidade de Doença , Visão Ocular/fisiologia
17.
Optom Vis Sci ; 88(10): 1196-205, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21873925

RESUMO

PURPOSE: Contact lenses (CLs) reduced the degree of hyperopic field curvature present in myopic eyes and rigid CLs reduced spherocylindrical image blur on the peripheral retina, but their effect on higher order aberrations and overall optical quality of the eye in the peripheral visual field is still unknown. The purpose of our study was to evaluate peripheral wavefront aberrations and image quality across the visual field before and after CL correction. METHODS: A commercial Hartmann-Shack aberrometer was used to measure ocular wavefront errors in 5° steps out to 30° of eccentricity along the horizontal meridian in uncorrected eyes and when the same eyes are corrected with soft or rigid CLs. Wavefront aberrations and image quality were determined for the full elliptical pupil encountered in off-axis measurements. RESULTS: Ocular higher order aberrations (HOA) increase away from fovea in the uncorrected eye. Third-order aberrations are larger and increase faster with eccentricity compared with the other HOA. CLs increase all HOA except third-order Zernike terms. Nevertheless, a net increase in image quality across the horizontal visual field for objects located at the foveal far point is achieved with rigid lenses, whereas soft CLs reduce image quality. CONCLUSIONS: Second-order aberrations limit image quality more than HOA in the periphery. Although second-order aberrations are reduced by CLs, the resulting gain in image quality is partially offset by increased amounts of HOA. To fully realize the benefits of correcting HOA in the peripheral field requires improved correction of second-order aberrations as well.


Assuntos
Astigmatismo/reabilitação , Lentes de Contato Hidrofílicas/normas , Campos Visuais , Adulto , Astigmatismo/fisiopatologia , Desenho de Equipamento , Feminino , Humanos , Masculino , Refração Ocular , Adulto Jovem
18.
Optom Vis Sci ; 88(10): E1188-95, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21804440

RESUMO

PURPOSE: To develop novel methodology to assess two in vivo wettability parameters, contact angle and index of liquid spreading (ILS), for hydrogel contact lenses and to provide a comprehensive investigation of the measurement errors (repeatability) associated with these two parameters. METHODS: A Novel On-eye Wettability Analyzer (NOWA) was constructed which delivered a drop of 0.4% sodium hyaluronate mixed with sodium fluorescein directly on to a lens surface in vivo while a two-camera digital system recorded both the resultant contact angle and liquid spreading. Ten subjects each wore a different etafilcon A lens (-0.50 DS) in the right eye for 30 min before measurement on three separate occasions. For contact angles, the coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intrasubject COR, and intersubject COR) was determined. For ILS, the COR associated with two measurement conditions (intrasubject COR and intersubject COR) was also determined. RESULTS: The in vivo contact angle for the etafilcon A lens was 19.8° ± 2.9° (mean ± standard deviation). COR values for contact angle were 3.2°, 5.2°, and 8.0° for image analysis, intrasubject measures, and intersubject measures, respectively. The mean ± standard deviation ILS was 2.0 ± 0.3 mm, and COR values were 0.4 and 0.8 mm for intrasubject and intersubject measures, respectively. CONCLUSIONS: This research demonstrates that it is possible to obtain hydrogel lens contact angles in vivo and to provide a new wettability parameter (ILS) with the NOWA instrumentation. The COR values obtained were considered to be acceptable. Intersubject COR values were greater than intrasubject COR values for both contact angle and ILS; this is likely to be due to greater variability of tear film characteristics between subjects than within an individual. The use of this novel methodology and its associated clinical parameters across a wider range of lens types in various clinical situations warrants further investigation.


Assuntos
Lentes de Contato Hidrofílicas/normas , Olho/química , Teste de Materiais/instrumentação , Molhabilidade , Desenho de Equipamento , Humanos , Reprodutibilidade dos Testes , Propriedades de Superfície , Tensão Superficial
19.
Eye Contact Lens ; 37(6): 337-41, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21904209

RESUMO

PURPOSE: To examine the relative changes in diameter and modulus of soft contact lenses when the temperature is raised from room temperature (RT) to eye temperature (ET). METHODS: Thirteen lens types including 9 silicone hydrogel lenses were measured for diameter and elastic modulus at RT (20 ± 1°C) and ET (34 ± 1°C). Lens diameter measurements were undertaken after equilibration in ISO saline in a temperature-controlled lens analyzer (Optimec, Ltd, Malvern, United Kingdom). Measurements of flexural modulus of elasticity were made using an Instron 3343 tensiometer (Instron, Norwood, MA) with the samples suspended in a temperature-controlled saline bath. RESULTS: All lens types reduced in diameter when raised to ET. The largest mean changes with silicone hydrogel and conventional hydrogel lenses were with Biofinity (Δ0.35 mm) and Acuvue 2 (Δ0.28 mm), respectively. All the silicone hydrogels showed a statistically significant reduction in modulus when raised to ET ranging from Δ0.06 MPa with comfilcon A to Δ0.78 MPa with balafilcon A. All the conventional hydrogels showed relatively small changes (<0.05 MPa) in modulus. Two of the four conventional hydrogels showed a statistically significant change in modulus (etafilcon A and ocufilcon A), but these were small and believed to be clinically insignificant. CONCLUSIONS: This study has highlighted some clinically relevant changes in soft contact lens modulus and diameter when raised from RT to ET. It has also shown the importance of standardizing modulus measurement technique.


Assuntos
Lentes de Contato Hidrofílicas , Módulo de Elasticidade , Temperatura , Temperatura Corporal , Lentes de Contato Hidrofílicas/normas , Olho , Hidrogéis/normas
20.
Clin Lab Sci ; 24(4): 202-7, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22288216

RESUMO

This is a case study of a 23 year old male diagnosed with Acanthamoeba keratitis. Initial misdiagnosis and inappropriate treatment lead to increased severity of the infection requiring surgical intervention. This case illustrates the complexity of Acanthamoeba keratitis infection, highlighting the diagnostic challenges which often begin with misdiagnosis and treatment, the role of the laboratory in providing confirmatory testing, and the relevance of patient knowledge related to contact lens wear and care.


Assuntos
Ceratite por Acanthamoeba/diagnóstico , Ceratite por Acanthamoeba/etiologia , Lentes de Contato Hidrofílicas/parasitologia , Córnea/parasitologia , Soluções para Lentes de Contato/normas , Lentes de Contato Hidrofílicas/normas , Diagnóstico Diferencial , Humanos , Masculino , Adulto Jovem
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