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At least 235 records · Page 13Linked to original sources
PubMed1997

Potential sources of bacteria that are isolated from contact lenses during wear.

PURPOSE: The aim of this paper was to determine the possible contamination sources of contact lenses during wear. METHODS: Potential sources of the microbiota that colonized hydrogel contact lenses during wear were examined. The microorganisms that colonize contact lenses were grown, identified, and compared to those microorganisms that colonized the lower lid margins, upper bulbar conjunctiva, hands, and contact lens cases of contact lens wearers. In addition, the incidence of contamination of the domestic water supply in the Sydney area was obtained, and this was compared to the incidence of colonization of contact lenses by microorganisms in general and gram-negative bacteria in particular. RESULTS: There was a wide diversity of bacteria that were isolated from each site sampled. Coagulase-negative staphylococci and Propionibacterium spp. were the most common isolates from all ocular sites examined, and constituted the normal ocular microbiota. Other bacteria, including members of the families Enterobacteriaceae and Pseudomonadaceae, were isolated infrequently from all sites, but most frequently from contact lens cases. Statistical analysis revealed that there was a correlation between the isolation of bacteria from the contact lens and the lower lid margin (p < 0.001). Analysis of this correlation revealed that this was true for the normal microbiota. A correlation was also noted between the colonization of contact lenses by gram-negative bacteria and contamination of the domestic water supply. DISCUSSION: This study has demonstrated that the likely route for the normal ocular microbiota colonizing contact lenses is via the lid margins, whereas colonization by gram-negative bacteria, including potential agents of microbial keratitis, is likely to be from the domestic water supply.

Bacteria↗
PubMed1986

[Effect of contact lenses and visual acuity on the registration of saccadic eye movements using an infrared reflection method].

In order to examine the influence of contact lenses and visual acuity on recordings of saccadic eye movements with the infrared reflection method, horizontal 20 and 30 degrees saccades were recorded with and without contact lenses in 16 subjects (32 eyes) usually wearing contact lenses. As far as the main parameters of the saccades (accuracy, peak velocity and duration) were concerned, the reliability of the measurements (recognizable through the mean values) was not essentially influenced by the contact lenses. The precision of the measurements (recognizable through the standard deviation) was with the contact lenses significantly but, for clinical use, not essentially worse. The velocity waveforms of the saccades, however, were considerably changed by contact lenses in some cases. This is why examinations, in which saccadic velocity waveforms are used for diagnosis, should be performed without contact lenses. Visual acuity had no measurable influence on the main parameters of the saccades. However, considerably more corrective saccades were observed with contact lenses than without. There were reasons to believe that not the contact lenses themselves, but better visual acuity was responsible for the larger number of corrective saccades.

Adult↗
PubMed1976

Effect of the length of wear of contact lenses on corneal sensitivity.

Corneal touch thresholds (CTT) were determined once in the morning before inserting contact lenses then after 4, 8 and 12 h of continuous wear. Two groups of subjects participated in this study; 12 persons wearing hard contact lenses and 15 wearing soft contact lenses. All subjects were perfectly adapted to their contact lenses and had worn them for not less than three months. It was found that hard contact lenses caused a progressive diminution of corneal sensitivity. After 12 h corneal sensitivity was, on average, 110% lower (that is an increase of the threshold) than in the morning. Soft lenses also caused a progressive reduction of corneal sensitivity which after 12 h wear was, on average, 45% lower than in the morning, although there were marked differences. Moreover, 9 of the hard contact lens subjects had been tested a year earlier and it was found that their CTT after 8 h wear had slightly but not significantly diminished which indicated that these subjects had not adapted significantly to their lenses in one year.

Adaptation, Physiological↗
PubMed2002

Calibration error on the measurement of back vertex power for contact lenses with method using focimeter with manual focusing.

PURPOSE: The International Standard ISO 9337-1, which sets forth the method for measuring back vertex power of contact lenses with manually focusing focimeters, specifies that test lenses conforming to ISO 9342 may be used to calibrate focimeters on its spectacle lens support, and correction values obtained in this way can be used directly in measuring contact lenses on its contact lens support. This study was conducted because of concern that the method mentioned in ISO 9337-1 is not good enough for the calibration of focimeters used to measure contact lenses. METHODS: To test the validity of this method, a research group from China National Institute of Metrology (NIM) studied it theoretically and carried out a series of comparison experiments, respectively, with the conventional test lenses conforming to ISO 9342 and test lenses made at NIM (with an expanded uncertainty of 0.025 D). RESULTS: The results show that the measurement error between the two calibration methods will exceed 0.50 D if the specification described in ISO 9337-1 is adopted. This error also exceeds allowable tolerances for focimeters and for contact lenses themselves. Experiments and theoretical calculations done by the NIM group show that these errors mainly come from spherical aberration. Vertex error induced by the lens support is not negligible. CONCLUSION: When focimeters are calibrated to find correction values with the method specified in ISO 9337-1, measurement error will not be eliminated if these correction values are used in measuring contact lenses, and the resulting deviation is too large to be ignored. Therefore, special test lenses should be used to calibrate focimeters to find correction values when these focimeters are used to measure back vertex power of contact lenses because contact lenses are a special product being used to correct human vision.

Calibration↗
PubMed1989

[Effect of welding arcs on the eyes of patients with contact lenses (literature study)].

Two accidents had been reported from abroad, within which contact lense users grew blind after staying quite near at electrical arcs. It is supposed that the contact lenses had been "welded" with the cornea by influence of the electromagnetic radiation. Removal of lenses shall have caused the cornea "ablation" and thus the subjects permanent blindness. Nilsson et al. (1, 2, 5) performed intensive animal tests which proved, that contact lenses get hot in special spectral ranges thus underlying a certain drying up. The "welding" between contact lenses and the cornea could not be confirmed by test animals, but partial glueing of contact lenses and cornea and surface lesions of the epithelium as well in some cases. Hüer and Conrads (3, 4) experimenting on enucleated pigs' eyes, reported on similar results.

Blindness↗
PubMedDate not supplied

Fungal growth on soft contact lenses: a SEM-study.

Three soft contact lenses of the HEMA type, discarded because of irritation of the cornea, were processed for and subsequently examined with the SEM, A large portion of the convex surface was covered with globular deposits of fungal spores. Cross-fractures of lenses showed penetration of the fungi into the matrix material of the lenses. The concave surface of the contact lenses showed at two points imprints of the epithelial cells of the cornea in the deposited material on that side of the lenses.

Contact Lenses, Hydrophilic↗
PubMed2006

Ultraviolet (UV) transmittance characteristics of daily disposable and silicone hydrogel contact lenses.

The ultraviolet (UV) transmittance spectra of daily wear hydrogel and disposable silicone hydrogel contact lenses were measured. Average transmittance percentages were calculated for each lens for the entire UV spectrum and individually for the UVC, UVB and UVA portions of the spectrum. The significance of the differences in transmittance spectra obtained for the lenses was analysed using a one-way ANOVA planned comparisons test (alpha=0.05). The transmittance data were then used to calculate a UV protection factor (PF) for each contact lens brand tested. The PFs for 1-DAY ACUVUE MOIST (6.22), ACUVUE ADVANCE (10.02) and ACUVUE OASYS (11.96) contact lenses show that these contact lenses have superior UV-blocking capabilities. The PFs for Focus DAILIES (1.79), SofLens 1-day disposables (1.72), NIGHT & DAY (1.84), O2 Optix (1.99) and Purevision (2.62) show that these contact lenses posses more modest UV-blocking characteristics. This paper reviews the importance of protection of the anterior ocular surface from UV damage and quantifies the protection afforded by selected commercially available disposable contact lenses.

Absorption↗
PubMedDate not supplied

Acanthamoeba and disinfection of soft contact lenses.

The association between acanthamoeba keratitis and the use of soft contact lenses is firmly established. Despite alerts and warnings, education of eye-care professionals and patients, and identification of risk factors that are associated with the use of soft contact lenses, acanthamoeba keratitis remains a threat. It is presumed that in some cases, the soft contact lens is the vector by which Acanthamoeba is introduced to the cornea. This presumption has spurred concern regarding the efficacy of systems used for the disinfection of soft contact lenses in killing the organism. Many questions have been raised regarding the proficiency of disinfection. These have stemmed from a poor understanding of the interactions among soft contact lenses, soft contact lens paraphernalia, and Acanthamoeba. Another issue to be addressed is the need for standardized testing of the efficacy of contact lens disinfection systems against Acanthamoeba. Only through a concerted and focused effort by eye-care and other concerned health care professionals can these questions be answered.

Acanthamoeba↗
PubMed1990

Adsorption and removal of protein bound to hydrogel contact lenses.

Tear film proteins are known to adsorb to new hydrogel contact lenses. Using a radioiodine tracing technique, proteins were shown to adsorb to contact lens surfaces. The quantity of protein adsorbed to the contact lenses within 2 to 4 h was 1 to 3 micrograms/lens. The degree of protein adsorption varied from lens-to-lens depending in part on the water content of the lens. High water content ionic lenses bound the most protein, whereas lower water content and nonionic lenses bound less protein. Enzyme cleaning of the protein-coated contact lenses removed about 75% of the adsorbed protein. When the enzyme-cleaned lenses were reincubated with protein, similar quantities were quickly readsorbed within a similar period of time. The rate of readsorption appeared to vary with the type of enzyme used to clean the lenses. Hydrogel lenses adsorb protein from the tear film rapidly and irreversibly. Cleaning the lenses has only a partial and temporary effect on the bound protein. The lens-bound proteins could become partly denatured during their binding to the lenses. These observations suggest a possible role for such proteins in ocular sensitivity to contact lenses.

Adsorption↗
PubMed1991

Adherence of Acanthamoeba castellanii to new daily wear, extended wear, and disposable soft contact lenses.

We studied the adherence of Acanthamoeba to three types of new, unworn soft contact lenses: daily wear; extended wear; and disposable contact lenses. We used a human corneal isolate of Acanthamoeba castellanii in commercially prepared saline. Unworn lenses were exposed to Acanthamoeba cysts or trophozoites with stirring. After exposure the numbers of Acanthamoeba adhering were determined by light microscopy and confirmed by scanning electron microscopy. In general, the adherence of Acanthamoeba cysts and trophozoites to disposable lenses was less than that to daily wear and extended wear lenses. However, any adherence of Acanthamoeba to soft contact lenses is a potential source of corneal infection.

Acanthamoeba↗
PubMed2003

Predicting and assessing visual performance with multizone bifocal contact lenses.

PURPOSE: To investigate how bifocal contact lenses, when combined with the aberrations of the eye, will affect visual performance. Also, to investigate the relationship between the patient's predicted and actual visual benefit with bifocal contact lenses. METHODS: The monochromatic aberrations of 16 subjects were measured and used to simulate visual quality with three bifocal contact lens designs. Actual and computed visual benefit was compared for an Acuvue bifocal contact lens in 5 of the 16 subjects. RESULTS: Subjects were predicted to have either a bifocal response or an increase in depth of focus for all lens designs. Our subjects were predicted to have a decrease in visual benefit for distance viewing and a gain in visual benefit at near compared with not wearing a contact lens. We found a statistically significant association between our subjects' predicted and actual visual benefit with the Acuvue Bifocal contact lens (r = 0.685, p = 0.008). CONCLUSIONS: Bifocal contact lens designs, when combined with the aberrations of the eye, will not always provide bifocal vision. Visual quality with a bifocal contact lens can be predicted based on a patient's ocular aberrations.

Adult↗
PubMed1989

[Contact lenses permeable to gas. Literature review].

Some medical-technical requirements concerning ophthalmic contact lenses were formulated. A whole series of scientific descriptions of contact lenses was analysed. A short characterization of lenses was given on the basis of PMMA (polymethacrylate of methyl), silicon rubber, poly-2-methacrylic cellulose and cellulose acetate-butyrate; the properties of contact lenses made of materials achieved through a modification of the above-mentioned ones as well as made of new materials were also examined. The problems of transmission of gases of contact lenses were described and the calculations necessary for a minimum of the gas transmittance were mentioned, starting from partial oxygen to the eye cornea. Some ways of solving the problems concerning the insertion of therapeutic substances into contact lenses are described together with prevention of the accumulation of lacrimation fluid protein on their surfaces.

Contact Lenses↗
PubMed2001

Adherence of Acanthamoeba to unworn conventional and disposable soft contact lenses.

PURPOSE: To compare the adherence of Acanthamoeba trophozoites and cysts to two types of unworn conventional and disposable contact lenses included in groups 1 and 4 of the Food and Drug Administration and to assess the adherence to the center and edge of the lenses. METHODS: We used 10 conventional and 10 disposable contact lenses belonging to groups 1 and 4 of the Food and Drug Administration. Each lens was divided into four segments. A human corneal isolate of Acanthamoeba suspended in saline (1x 105 amoebae/mL) was used. Lens segments were exposed to Acanthamoeba cysts and trophozoites for 2 hours. After removal, the count was made with an optical microscope at 100x magnification. Three fields at the center and three fields at the edge were read on each segment. RESULTS: Acanthamoeba adhered to both types of contact lenses, with a proportion of trophozoites to cysts between 6:4 and 7:3. There was a significantly higher adherence to disposable (8.14 +/- 3.57 organisms/mm(2)) than to conventional (4.94 +/- 2.33 organisms/mm(2)) (p < 0.0001) contact lenses. We also found that the greatest adherence was to the edge of the conventional (12.05 +/- 4.03 organisms/mm(2)) and disposable (26.10 +/- 7.84 organisms/mm(2) (p < 0.0001) contact lenses. CONCLUSIONS: This study shows that Acanthamoeba has varying adherence affinity for different new hydrogel contact lenses. The affinity for disposable lenses (etafilcon A) is significantly higher than that for conventional lenses (polymacon). This adherence is greater for ionic material and high water content. The use of low water content, nonionic contact lenses may reduce the adherence of Acanthamoeba. Finally, the edge may play an important role as an Acanthamoeba vector.

Acanthamoeba↗
PubMed1981

Fungal growth in aphakic soft contact lenses.

Fungal growth was detected in two aphakic hydrophilic contact lenses. Aspergillus species was cultured from the extended-wear contact lens and Dermatophilus congolensis was identified by specific antibody staining of the daily-wear contact lens. As in the 16 previously described cases of fungal contact lens growth, our patients had no evidence of ocular infection but did experience irritation which cleared up when contact lens wear was discontinued. Although only a small percentage of contact lenses are prescribed because of aphakia, these thicker contact lenses may be more susceptible to fungal growth and should be monitored carefully.

Actinomycetales↗
PubMed2004

The use of contact lenses to treat visually symptomatic congenital nystagmus.

It has been suggested that contact lens wear improves the visual function of patients with visual loss from congenital nystagmus. In this study, four patients with congenital nystagmus had two evaluations separated by at least one week (one with spectacles, one with contact lenses) including visual acuity, contrast sensitivity, oscillopsia scale, quality of life questionnaire (NEI VFQ-25), and eye movement recording with an infrared tracking system. All patients subjectively preferred contact lenses to spectacles. Their contrast sensitivity and VFQ-25 scores were improved with contact lenses compared with spectacles alone. Several parameters of nystagmus showed no change in two patients, worsening in one patient and improvement in one patient. This suggests that much of the clinical improvement observed in our patients may result from a better optical correction of their refractive error with contact lenses than with spectacles, rather than from a true damping effect of the nystagmus by contact lenses.

Adolescent↗
PubMed1998

Effect of topical anesthetic use on initial patient satisfaction and overall success with rigid gas permeable contact lenses.

BACKGROUND: Rigid gas permeable (RGP) contact lenses have numerous benefits; however, RGP lens use is not increasing in the United States. An important factor for this trend has been initial comfort. Studies have demonstrated that how RGPs are presented to patients, in addition to lens design, can play an important role in the initial comfort process. Another important factor could be the use of a topical anesthetic during the fitting and dispensing visits. The purpose of this study was to use a multicenter format to determine if topical anesthetic use increased the likelihood of patient satisfaction and success. METHODS: A total of 80 subjects, with no previous rigid lens wear experience, was entered into this 1-month study, including 20 subjects from each of 4 institutions. Subjects were randomly divided into the following two groups: (A) anesthetic or (B) placebo, with the former group receiving one drop of a topical anesthetic before lens insertion at both the diagnostic fitting and dispensing visits, whereas the latter group received a placebo. Subjects completed a questionnaire on their perception of rigid lens wear both immediately before fitting and at the 1-month visit. After diagnostic fitting with rigid lenses, subjects completed an adaptation questionnaire after 15 min, 1 week, 2 weeks, and 1 month of lens wear. RESULTS: Seventy of the 80 subjects completed the study and, of the 10 subjects who discontinued, 8 were in the placebo group. In all categories evaluated, the anesthetic group experienced a more optimum adaptation experience at each visit vs. the placebo group. Specifically, overall comfort was rated significantly higher at both dispensing and 2 weeks. In addition, the anesthetic group exhibited significantly greater overall satisfaction with rigid lens wear at 2 and 4 weeks. Also, the anesthetic group perceived their adaptation, sensitivity, and adaptation time to be significantly better at the 1-month visit. There was no significant difference in corneal staining between these two groups at each visit, with the exception of a greater amount of staining in the central quadrant for the placebo group at the 1-month visit. CONCLUSIONS: The use of a topical anesthetic at the fitting and dispensing visits for first-time wearers of RGP lenses resulted in significantly fewer dropouts, improved initial comfort, an enhanced perception of the adaptation process, and greater overall satisfaction after 1 month of lens wear as compared to the use of a nonanesthetizing placebo at those visits. This result, in combination with both presenting RGP lenses in a nonthreatening manner and optimizing the lens design and fitting relationship, should result in a positive adaptation process and successful wear of RGP contact lenses.

Adaptation, Physiological↗
PubMedDate not supplied

Preventing complications in people who wear contact lenses.

The number of contact lens wearers has steadily increased over the past 10 years. Convenience, efficiency and availability of different types of lenses have made them popular. The rise in the use of contact lenses has increased the number of people at risk of contact lens-related complications. Studies have highlighted the consequences of poor contact lens care. Acanthamoeba keratitis is one of the most devastating complications of contact lens wear and can be avoided by adhering to the recommended contact lens regimen. This article reviews the literature on the complications of contact lens wear and stresses the need to educate the wearer. It examines the nurse's role in relation to health promotion and the basic principles for successful long-term contact lens wear. This information is relevant to all nurses caring for people with contact lenses and will be of particular interest to the nurse who wears contact lenses.

Contact Lenses↗
PubMed2002

Comparison of tear-film osmolarity in different types of contact lenses.

PURPOSE: To investigate the tear-film osmolarity of contact lens wearers for different types of contact lenses. METHODS: Fifty six eyes of 56 cases were evaluated in four different groups according to the type of contact lens worn, with 14 eyes in each group. Groups 1 and 2 consisted of subjects who wore frequent-replacement daily wear soft contact lenses; group 1 lenses had 55% water content, and lenses in group 2 had 38% water content. Groups 3 and 4 consisted of subjects who wore rigid gas-permeable contact lenses, with a Dk value of 90 in group 3 and a Dk value of 52 in group 4. Tear-film osmolarity values in milliosmole (mosm) units were determined by auto-osmometer (Orstat 6030, Daiichi Kagacu, Kyoto, Japan) before and after contact lens wear for each group, and the results were compared statistically by ANOVA test. RESULTS: Before the period of contact lens wear, the tear-film osmolarity values of group 1, 2, 3, and 4 were 283.61+/-12.83 mosm, 285.23+/-8.94 mosm, 285.57+/-11.39 mosm, and 280.15+/-12.07 mosm, respectively. After the period of contact lens wear, these values were measured at 312.15+/-16.03 mosm in group 1, 316.54+/-12.14 mosm in group 2, 313.14+/-9.66 mosm in group 3, and 316.38+/-11.60 mosm in group 4. Although the difference between the values before and after the period of contact lens wear was statistically significant for each group (F=291.45; P=0.0005), there was no statistically significant difference among the groups. CONCLUSIONS: When a contact lens is placed in the eye, the lens alters the normal structure of the tear film and affects its rate of evaporation; therefore tear-film osmolarity may increase. In our study, all contact lenses produced a similar effect on tear-film osmolarity.

Adolescent↗