49 research outputs found
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 lens wear on refractive index of conventional hydrogel and silicone-hydrogel contact lenses: a comparative study
Purpose: The purpose of this work was to evaluate the ability of four silicone-hydrogel contact lenses (galyfilcon A, balafilcon A, lotrafilcon
A and lotrafilcon B) to retain their equilibrium water content before and after wear, through measurements of refractive index and compare
with that of a conventional disposable hydrogel contact lens (etafilcon A).
Methods: The refractive indices of 115 contact lenses were measured using an automated refractometer (CLR 12-70, Index Instruments,
Cambridge, U.K.) before and after a schedule of daily wear by 58 patients for 30 days in the case of silicone-hydrogel lenses and 15 days for
the conventional contact lenses.
Results: In the silicone-hydrogel contact lenses the changes on the refractive indices were not statistically significant, however after being
worn the refractive index of the conventional etalfilcon A hydrogel contact lens increased significantly ( p < 0.001).
Conclusion: The results presented here show that after being worn the silicone-hydrogel contact lens, show more capacity to retain or to reach
their initial equilibrium water content than conventional hydrogel contact lenses. This suggests that the silicone-hydrogel contact lenses are
less susceptible to spoilation over time maintaining its biocompatibility and contributing to the clinical success of lens performance.Vision and Johnson & Johnson.Bausch & Lom
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
perĂodo de uso das lentes.
Material e MĂ©todos: 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 mĂŞs 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 nĂŁo 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 1Âş e Ăşltimo 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
Correlation between tear osmolarity and tear meniscus
Purpose. To examine the relationship between tear meniscus height (TMH) and
subjective meniscus grading (subjective TM) with tear osmolarity.
Methods. Tear osmolarity measurements (using TearLab) and digital images of the
tear meniscus were obtained in 177 consecutive patients undergoing an eye
examination at our optometry clinic (Universidad de Santiago de Compostela, Spain)
who fulfilled the study's inclusion criteria. Participants were also administered the
McMonnies and Ocular Surface Disease Index (OSDI) questionnaires for the detection
of dry eye disease.
The lower tear meniscus was videotaped by a digital camera attached to a slit lamp in
its central portion without fluorescein instillation. After the study, a masked observer
extracted an image from each video, and measured the TMH using open source
software (NIH ImageJ). Subsequently, the masked observer subjectively graded the
appearance of each meniscus. For statistical analysis, subjects were stratified by age
and by dry eye symptoms as indicated by their scores in the two questionnaires.
Results. In the whole study population, a significant relationship was observed
between osmolarity and TMH (-0.41, p<0.001) and osmolarity and subjective TM (r =
0.35, p<0.001). A cluster analysis revealed similar correlations when subjects were
stratified by age or dry eye symptoms, these correlations being more pronounced in
older and more symptomatic individuals. Objective TMH measurements and subjective
meniscus quality were also correlated (r=-0.75, p<0.001).
Conclusions. Osmolarity and both objective TMH measurements and subjective
interpretation of the meniscus showed high correlation, especially in older symptomatic
subjects.Estudio patrocinado por el Ministerio de Educación y Ciencia y el Instituto de Salud Carlos III a través del proyecto PI10/01098.S
On the analysis of local and global features for hyperemia grading
In optometry, hyperemia is the accumulation of blood flow in the conjunctival tissue. Dry eye syndrome or allergic conjunctivitis are two of its main causes. Its main symptom is the presence of a red hue in the eye that optometrists evaluate according to a scale in a subjective manner. In this paper, we propose an automatic approach to the problem of hyperemia grading in the bulbar conjunctiva. We compute several image features on images of the patients' eyes, analyse the relations among them by using feature selection techniques and transform the feature vector of each image to the value in the adequate range by means of machine learning techniques. We analyse different areas of the conjunctiva to evaluate their importance for the diagnosis. Our results show that it is possible to mimic the experts' behaviour through the proposed approach.S
Alterações na transmitância UV-VisĂvel induzidas pelo uso de lentes de contacto de silicone-hidrogel
Fundação para a CiĂŞncia e a Tecnologia (FCT) through Centro de FĂsica da U
Meibomian gland loss area and its relationship with age and ocular surface disease index
Purpose: Meibography images bring information about the status and integrity of the meibomian glands (MG). This study aimed to correlate the meibomian gland loss area (MGLA) with age and dry eye symptomatology. Material and methods: A total of 110 subjects were recruited for the study. From the Meibography images obtained with the Topcon® CA-800 topographer, MGLA was calculated as the difference between the total area of the tarsus and the MG presence area measured by using the ImageJ software. Before the examination, all subjects completed an OSDI questionnaire. OSDI scores were grouped in 4 severity categories: normal (score ≤12), mild (score 12–22), moderate (score 22–32) and severe (score ≥32). Age was categorised into 3 subgroups: ≤25 years, from 25 to 45 years and ≥45 years. MGLA was also grouped in 4 categories of loss: ≤25 %, from 25 to 50%, from 50 to 75% and ≥75%. Results: Analysis was performed by dividing the sample into the 4 MGLA subgroups; these subgroups showed age differences (p=0.029; Kruskal-Wallis test) and differences in OSDI scores (p=0.001; Kruskal-Wallis test). The sample was divided into 3 age subgroups and differences were obtained in MGLA values among subgroups (p<0.001; Kruskal-Wallis test). Samples were divided in 4 OSDI subgroups and differences were obtained in MGLA values among subgroups (p=0.003; Kruskal-Wallis test). Positive correlation (Spearman Correlation) was obtained for both, MGLA vs. age (r=0.329, p<0.001) and MGLA vs. OSDI (r=0.380, p<0.001). Conclusion: In the present study MGLA showed a relationship with age and OSDI.S
Evaluation of the relationship between symptomatic assessment, corneal staining and tear meniscus by image analysis
Purpose: Vital staining is one of the most widely tests used to evaluate corneal damage. This study aimed to assess the relationship of corneal damage with tear meniscus height (TMH) and dry eye symptomatology. Material and methods: 530 subjects were recruited among patients of the Optometry Clinic (USC). Previously, all of them completed an OSDI questionnaire. Two videos of the ocular surface were recorded from each patient by a digital camera attached to a slit-lamp. Firstly, a video of the central tear meniscus under 40x with the Tearscope device illumination was recorded. From those videos, a masked observer extracted one image and TMH was measured by using the ImageJ software. Secondly, after fluorescein instillation, the corneal surface was recorded by another experienced masked observer, who assigned a category to the corneal damage based on the Oxford Scheme. The evaluation was stratified by corneal zones based on the CCLRU grading scales (central, superior, inferior, nasal and temporal). Results: When the sample was grouped by the corneal staining Oxford Grade, there was a statistical difference between groups in OSDI and TMH value (ANOVA: both p≤0.006). There was a difference in OSDI value when corneal damage was in nasal or inferior areas (t-test; both p≤0.015), and a difference in TMH value arose when damage was in the central, nasal or inferior areas (t-test; all p≤0.013). Conclusions: There is a relationship between corneal damage grade and corneal zones with dry eye symptomatology and tear film volume.This study was funded by the Spanish Ministry of Science and Education and the Institute of Health Carlos III (ISCIII)
through research project PI10/01098.S