Comparative study of silicone-hydrogel contact lenses surfaces before and after wear using atomic force microscopy

Purpose: The aim of this study was to analyze surface changes of three silicone-hydrogel contact lenses after daily wear. The lenses used in this study were balafilcon A, lotrafilcon B (both surface-treated), and galyfilcon A (non surface-treated). Methods: To understand how and where proteins, lipids, and other contaminants change contact lenses, surface roughness was assessed through Atomic Force Microscopy Tapping ModeTM. Roughness parameters were Mean Surface roughness (Ra), Mean-square-roughness (Rq), and Maximum roughness (Rmax). The surface topography of unworn and worn lenses was also mapped in great detail. Results: Contact lenses roughness parameters exhibited different values before and after wear and the surface appearance also changed. After wear, balafilcon A and galyfilcon A showed a significant increase on surface roughness parameters, being this increase more accentuated to galyfilcon A. In lotrafilcon B materials no significant changes were observed with wear. Conclusions: The present study suggests that surface treatment of silicone-hydrogel contact lenses can play a role in the prevention of a significant increase in roughness, and contribute to the better clinical tolerance of these lenses.University of PortoIBM

The effect of silicone-hydrogel and conventional hydrogel contact lenses wear on the tear film: a comparison between de lenses

Purpose: The aim of this study was to evaluate the effect of one conventional hydrogel and four silicone-hydrogel contact lenses of 6-months daily wear on the quantity and stability of the tear film. The tests were performed with a group of patients with no previous contact lenses experience before and after wear on 96 eyes. Methods: The contact lenses tested were: 19 Galyfilcon A (Acuvue® Advance™), 15 Balafilcon A (PureVision™), 20 Lotrafilcon A (Focus® Night & Day™), 14 Lotrafilcon B (O2Optix™) and 28 Etalfilcon A (Acuvue®). Each silicone-hydrogel contact lens was used for 1 month and the conventional hydrogel for 15 days. Every patient used a different lens in each eye. Tear film stability was monitored by tear Break-up-time (BUT) and Non Invasive Break Up Time (NiBUT) and tear volume was measured by the Total Tear Meniscus Height and the Red Phenol Test. Results: The following tables summarize the difference between the measurements obtained in the first and in the last day of wear of each contact lens brand and the results were analyzed comparing the conventional hydrogel and the siliconehydrogel contact lenses (Table 1, 2, and 3), the lenses belonging to the first generation of silicone-hydrogel contact lenses (table 4) and the lenses belonging to the second generation of silicone-hydrogel (Table 5). The significance (p value) of 0.05 is considered statistically significant. Conclusions: Although there are some differences between the lenses, there are no statistically significant differences between the lenses and measurements obtained before and after contact lenses wear on the tear film tests.Objectivo: Avaliar o efeito de 6 meses de uso diário de uma lente de contacto de hidrogel convencional e quatro lentes de contacto de silicone-hidrogel na qualidade e estabilidade do filme lacrimal. Os testes foram realizados num grupo de pacientes (96 olhos) sem experiência prévia de uso de lentes de contacto, antes e depois do período de uso das lentes. Material e Métodos: As lentes de contacto estudadas foram: 19 Galyfilcon A (Acuvue® Advance™), 15 Balafilcon A (PureVision™), 20 Lotrafilcon A (Focus® Night & Day™), 14 Lotrafilcon B (O2Optix™) e 28 Etalfilcon A (Acuvue®). Cada lente de silicone-hidrogel foi usada durante 1 mês e a lente de hidrogel convencional durante 15 dias. Todos os pacientes usaram uma lente diferente em cada olho. A estabilidade do filme lacrimal foi avaliada pelo teste de ruptura lacrimal (BUT) e pelo teste de ruptura lacrimal não invasivo (NIBUT). O volume lacrimal foi medido pala altura total do menisco lacrimal e pelo teste vermelho fenol (Red Phenol Test) Resultados: Nas tabelas seguintes apresenta-se a diferença entre as medidas obtidas no 1º e último dia de uso para cada marca de lente de contacto e os resultados foram analisados comparando a lente de contacto hidrogel convencional com as lentes de silicone-hidrogel (Tabela 1, 2 e 3), as lentes pertencentes à 1ª geração de lentes de silicone-hidrogel (Tabela 4) e as lentes que pertencem à 2ª geração das lentes de silicone-hidrogel (Tabela 5). O valor da significância (p) é considerada estatisticamente significativa quando ≤0.05. Conclusões: Embora existam algumas diferenças entre as lentes de contacto estudadas, não há diferenças estatisticamente significativas entre os valores obtidos nos testes de avaliação do filme lacrimal antes e depois do uso das lentes de contacto

Symptoms in a population of contact lens and noncontact lens wearers under different environmental conditions

None of the authors has a commercial or financial interest in the instruments or materials used in the study. The authors wish to thank the assistance of AP Almeida, AP Costa, A, Fernandes, A Teixeira, C Marques, C Pinho and J Matos for their assistance in data acquisition, and Dr. Ana Costa from the program of Support to the Edition of Scientific Papers at the University of Minho for help with English editing of the manuscript.PURPOSE: To investigate ocular symptoms related to dryness in an adult population of contact lens (CL) and non contact lens wearers (n-CL) using video display terminals (VDT) for different periods of time under different indoor conditions related to air conditioning (AC) and heating units (HU) exposure. METHODS: A questionnaire was distributed to 334 people within a university population of which 258 were part of the n-CL group and 76 of the CL wearers to assess symptoms of ocular discomfort potentially related to dryness. Only soft contact lens (SCL) wearers (n = 71) were included for further statistical analysis because of the reduced number of people wearing other lens types. A 2:1 match by gender group of 142 subjects in the n-CL group was used as a control sample. RESULTS: There was a marked difference between the prevalence of symptoms and the way they are reported by CL and n-CL wearers. Red eye, itching, and scratchiness are more common among CL wearers, but the difference is statistically significant only for scratchiness (p < 0.01, chi(2)). The vast majority of subjects who reported symptoms often and at the end of the day are significantly more prevalent among CL wearers (p < 0.01, chi(2)). Gender differences were also encountered. Female CL wearers reported more scratchiness than males in the n-CL wearing group (p = 0.029, chi(2)) and in the CL group (p < 0.008, chi(2)). Females wearing CL reported symptoms of red eye (p = 0.043, chi(2)) and scratchiness (p < 0.001, chi(2)) more significantly than those in the n-CL group. Within the CL group, the prevalence of symptoms occurring sometimes or often and at the end of the day was higher among females (p < 0.001, chi(2)). The use of VDT was associated with a higher level of scratchiness among CL wearers (p < 0.05, chi(2)). The number of hours working with VDTs seemed to be associated with an increase in the prevalence of burning sensation in the CL group (p < 0.01, chi(2)), whereas symptoms like red eye and scratchiness also increased significantly among n-CL wearers. Compared to n-CL wearers, all symptoms increase in CL wearers in environments with AC and HU, except excessive tearing. However, these differences are only statistically significant for scratchiness. CONCLUSIONS: Our results show that people who wear soft CL and work with VDTs for longer periods of time are more likely to develop symptoms like eye burning and scratchiness than n-CL wearers. This risk could be higher for women than men. Scratchiness and the appearance of symptoms near the end of the day are typically associated with ocular discomfort during CL wear in this sample, and clinicians should question their patients about these symptoms to anticipate serious discomfort.This study was partially supported by a grant from the Science and Technology Foundation (FCT) - Ministry of Science and Superior Education (MCES) under contract 8281/2002 from the European Social Funding granted to JMG-M

Alterações na transmitância UV-Visível induzidas pelo uso de lentes de contacto de silicone-hidrogel

Fundação para a Ciência e a Tecnologia (FCT) through Centro de Física da U

The influence of lens material and lens wear on the removal and viability of staphylococcus epidermidis

Purpose: The aim of this study was to evaluate the influence of lens material and lens wear on the removal capability of Staphylococcus epidermidis. Assessment of viability of remaining adhered bacteria was another goal of this work. Four silicone hydrogel materials (galyfilcon A, balafilcon A, lotrafilcon A, lotrafilcon B) and one conventional hydrogel material (etafilcon A) were assayed. Methods: Detachment studies on S. epidermidis were carried out in a parallel plate flow chamber. Contact lenses (CLs) were fitted to the bottom of the flow chamber and a bacterial suspension was perfused into the system, promoting bacterial adhesion. Afterwards, detachment was stimulated using a multipurpose solution (MPS, ReNu Multiplus®) and the percentage of removed bacteria estimated through microscopic observation and enumeration. Remaining adhered bacteria were stained with propidium iodide (PI) and enumerated in order to assess their viability. Additionally, the worn lenses were observed by confocal laser scanning microscopy (CLSM) to visualize bacterial distribution along the lens surfaces. Results: Bacterial removal was significant ( p < 0.05) for both unworn and worn galyfilcon A and etafilcon A. Galyfilcon A exhibited a detachment percentage of 59.1 and 63.5 while etafilcon A of 62.6 and 69.3, both for unworn and worn lenses, respectively. As far as bacterial viability is concerned, it was found that worn lenses exhibit a superior amount of non-viable bacteria than unworn CLs. Images obtained by CLSM revealed an irregular bacterial distribution for all lens materials. Conclusions: It appears that surface and/or bulk structure of the lens material affects removal of S. epidermidis while CL wear influences their viability.Fundação para a Ciência e a Tecnologia (FCT

The influence of surface treatment on hydrophobicity, protein adsorption and microbial colonisation of silicone hydrogel contact lenses

Purpose: To evaluate the influence of surface treatment of silicone-hydrogel CL on lens hydrophobicity, protein adsorption and microbial colonisation by studying several silicone hydrogel contact lenses (CL) with and without surface treatment. The lenses used in this study were Balafilcon A, Lotrafilcon A, Lotrafilcon B and Galyfilcon A. A conventional hydrogel CL (Etafilcon A) was also tested. Methods: Hydrophobicity was determined through contact angle measurement using the advancing type technique on air. The type and quantity of proteins adsorbed were assessed through SDS-PAGE and fluorescence spectroscopy, respectively. Microbial colonisation was studied by removing the microbes from the lenses through sonication, and counting the colony-forming units on agar plates. Results: Regarding hydrophobicity, both surface and non-surface-treated silicone hydrogel CL were found to be hydrophobic, and the conventional hydrogel CL was found to be hydrophilic. Concerning protein adsorption, different protein profiles were observed on the several lenses tested. Nevertheless, the presence of proteins with the same molecular weight as lysozyme and lactoferrin was common to all lenses, which is probably related to their abundance in tears. In terms of total protein adsorption, silicone hydrogel CL did not exhibit any differences between themselves. However, the conventional hydrogel Etafilcon A adsorbed a larger amount of proteins. Regarding microbial colonisation, Balafilcon A exhibited the greatest amount of colonising microbes, which can be due to its superior hydrophobicity and higher electron acceptor capacity. Conclusion: This study suggests that silicone hydrogel lenses adsorb a lower amount of proteins than the conventional hydrogel lenses and that this phenomenon is independent of the presence of surface treatment. Concerning microbial colonisation, the surface treated Balafilcon A, exhibited a greater propensity, a fact that may compromise the lens wearer’s ocular health.Fundação para a Ciência e a Tecnologia (FCT