CORNEAL CONTACT LENSES—Special Value in Severe Anisometropia in Children

Careful selection of patients and skillful fitting result in a high rate of success with corneal contact lenses—over 96 per cent in 339 patients treated in the present series. The lenses were especially valuable in anisometropia in children (11 cases). Children can be taught to care for contact lenses and insert and remove them for themselves.     

Soft contact lenses

A series of 55 patients were fitted with a new type of hydrophilic soft contact lens. These were found more comfortable than hard contact lenses and they had a protective and pain-relieving action in cases of chronic corneal disease. Vision was not as good as with hard contact lenses and a greater potential danger of infection was found. They are preferred by many patients despite the noticeable thick edge and the difficulty of obtaining an identical replacement.     

Quantification of protein deposits on silicone hydrogel materials using stable-isotopic labeling and multiple reaction monitoring

This study was designed to use multiple reaction monitoring (MRM) for accurate quantification of contact lens protein deposits. Worn lenses used with a multipurpose disinfecting solution were collected after wear. Individual contact lenses were extracted and then digested with trypsin. MRM in conjunction with stable-isotope-labeled peptide standards was used for protein quantification. The results show that lysozyme was the major protein detected from both lens types. The amount of protein extracted from contact lenses was affected by the lens material. Except for keratin-1 (0.83?±?0.61 vs 0.77?±?0.20, p?=?0.81) or proline rich protein-4 (0.11?±?0.04 vs 0.15?±?0.12, p?=?0.97), the amounts of lysozyme, lactoferrin, or lipocalin-1 extracted from balafilcon A lenses (12.9?±?9.01, 0.84?±?0.50 or 2.06?±?1.6, respectively) were significantly higher than that extracted from senofilcon A lenses (0.88?±?0.13, 0.50?±?0.10 or 0.27?±?0.23, respectively) (p?相似文献   

Effect of nutrient limitation on adhesion characteristics of Pseudomonas aeruginosa

Pseudomonas aeruginosa causes a variety of diseases in humans including lung and ocular infections. Infections of the cornea are usually associated with wearing contact lenses and can result in loss of vision. This study aimed to determine the effect of carbon or nitrogen limitation on the adhesion to contact lenses of a strain of Ps. aeruginosa isolated from contact lens-related corneal inflammation. Cells were grown in a continuous culture apparatus in varying levels of glucose or ammonia to effect nutrient limitation. Adhesion to contact lenses was measured as total counts and viable counts. The cell surface hydrophobicity and charge were measured using adhesion to surface-modified Sepharose. Changes in lipopolysaccharide were determined using 1D SDS-PAGE and changes in cell-surface proteins were measured using 2D gel electrophoresis. The more the cultures were nitrogen limited, the greater the increase in adhesion to unworn hydrogel contact lenses 0.3 x 10(3) - 2.2 x 10(3) cells/mm2 on Etafilon A lenses. Cells that were carbon limited showed a greater increase in adhesion to contact lenses when the lenses had been coated in artificial tears. It appeared that lipopolysaccharide may have been involved in the constitutive adhesion to unworn lenses that occurred during C-limitation, whereas changes in the outer membrane proteins contributed to the increased adhesion under nitrogen limitation, or the change in adhesion that occurred to carbon-limited cells using contact lenses coated in artificial tears. Nine cell-surface proteins appeared during nitrogen limitation with kDa/pI of 75/4.8, 4.9, 5.0; 62/5.6; 89/6.5; 38/6.4; 28/1.5; 18/6.4; 12/4.5. Any or all of these may have been involved in the increased adhesion and further experiments are underway to examine this possibility.     

Human IgA inhibits adherence of Acanthamoeba polyphaga to epithelial cells and contact lenses

Specific anti-Acanthamoeba IgA antibodies have been detected in the serum and tears of patients and healthy individuals. However, the role of human secretory IgA antibodies in inhibiting the adherence of Acanthamoeba had not been previously investigated. Therefore, the purpose of this study was to purify secretory IgA from human colostrum and analyze its effect on the adherence of Acanthamoeba trophozoites to contact lenses and Madin-Darby canine kidney (MDCK) cells. IgA antibodies to Acanthamoeba polyphaga in colostrum of healthy women as well as in saliva and serum of healthy subjects were analyzed by ELISA and Western blot analysis. In serum, saliva, and colostrum, we detected IgA antibodies that recognized several antigens of A. polyphaga. In addition, colostrum and IgA antibodies purified from it inhibited adherence of A. polyphaga trophozoites to contact lenses and MDCK cells. These results suggest that IgA antibodies may participate in the resistance to the amoebic infection, probably by inhibiting the adherence of the trophozoites to contact lenses and corneal epithelial cells.     

Ultrasonic model and system for measurement of corneal biomechanical properties and validation on phantoms

Non-invasive measurement of biomechanical properties of corneas may provide important information for ocular disease management and therapeutic procedures. An ultrasonic non-destructive evaluation method with a wave propagation model was developed to determine corneal biomechanical properties in vivo. In this study, we tested the feasibility of the approach in differentiating the mechanical properties of soft contact lenses as corneal phantoms. Three material types of soft contact lenses (six samples in each group) were measured using a broadband ultrasound transducer. The ultrasonic reflections from the contact lenses were recorded by a 500MHz/8-bit digitizer, and displayed and processed by a PC. A reference signal was recorded to compute the normalized power spectra using Fast Fourier Transformation. An inverse algorithm based on least-squares minimization was used to reconstruct three parameters of the contact lenses: density, thickness, and elastic constants lambda+2micro. The thickness of each sample was verified using an electronic thickness gauge, and the averaged density for each type of lenses was verified using Archimedes' principle and manufacturer's report. Our results demonstrated that the ultrasonic system was able to differentiate the elastic properties of the three types of the soft contact lenses with statistical significance (P-value<0.001). The reconstructed thicknesses and densities agreed well with the independent measurements. Our studies on corneal phantoms indicated that the ultrasonic system was sensitive and accurate in measuring the material properties of cornea-like structures. It is important to optimize the system for in vivo measurements.     

Quantification of protein deposits on silicone hydrogel materials using stable-isotopic labeling and multiple reaction monitoring

This study was designed to use multiple reaction monitoring (MRM) for accurate quantification of contact lens protein deposits. Worn lenses used with a multipurpose disinfecting solution were collected after wear. Individual contact lenses were extracted and then digested with trypsin. MRM in conjunction with stable-isotope-labeled peptide standards was used for protein quantification. The results show that lysozyme was the major protein detected from both lens types. The amount of protein extracted from contact lenses was affected by the lens material. Except for keratin-1 (0.83 ± 0.61 vs 0.77 ± 0.20, p = 0.81) or proline rich protein-4 (0.11 ± 0.04 vs 0.15 ± 0.12, p = 0.97), the amounts of lysozyme, lactoferrin, or lipocalin-1 extracted from balafilcon A lenses (12.9 ± 9.01, 0.84 ± 0.50 or 2.06 ± 1.6, respectively) were significantly higher than that extracted from senofilcon A lenses (0.88 ± 0.13, 0.50 ± 0.10 or 0.27 ± 0.23, respectively) (p < 0.05). The amount of protein extracted from contact lenses was dependent on both the individual wearer and the contact lens material. This may have implications for the development of clinical responses during lens wear for different people and with different types of contact lenses. The use of MRM-MS is a powerful analytical tool for the quantification of specific proteins from single contact lenses after wear.     

Dynamics of tear fluid components transportation through contact lenses

The interference optical method has been applied to monitor the transportation of Na⁺ and Cl⁻ in solution through new and used contact lenses. The phenomenon of passive transportation (simple diffusion), induced by differences in osmotic pressure on both sides of the contact lenses has been discussed. Permeability coefficient of contact lenses of different optical power: −2.75 D and −3.75 D has been calculated.     

Colonization of hydrophilic contact lenses by yeast

The growth of six strains of yeast was analyzed in vitro in order to assess their capacity for colonizing (adhesion and invasion) hydrophilic contact lenses. Lenses with different water content were cultured in two culture media for 3, 7, 14, and 21 days. Only strain 93150 of Candida albicans could adhere to and invade the polymers. Specifically, fungal growth was observed in cultures with Sabourauds broth. The degree of yeast colonization of contact lenses was significantly related to the species, the strain, and the culture medium in which the yeast and lenses were cultured. The results here obtained were compared with those reported for the filamentous fungus Aspergillus niger 2700. For both microorganisms, the strain and the medium in which the lenses and microorganism were cultured influenced the colonization, but the percentage of colonized lenses, the degree of colonization, and the density and size of the internalized colonies were always noticeably lower for C. albicans 93150. Colonization by A. niger 2700 was also related to the type of material of the lenses and the incubation period. For both microorganisms, when the strain is right and the growth and development are correct, colonization of hydrophilic contact lenses occurs.     

Corneal Cell Adhesion to Contact Lens Hydrogel Materials Enhanced via Tear Film Protein Deposition

Tear film protein deposition on contact lens hydrogels has been well characterized from the perspective of bacterial adhesion and viability. However, the effect of protein deposition on lens interactions with the corneal epithelium remains largely unexplored. The current study employs a live cell rheometer to quantify human corneal epithelial cell adhesion to soft contact lenses fouled with the tear film protein lysozyme. PureVision balafilcon A and AirOptix lotrafilcon B lenses were soaked for five days in either phosphate buffered saline (PBS), borate buffered saline (BBS), or Sensitive Eyes Plus Saline Solution (Sensitive Eyes), either pure or in the presence of lysozyme. Treated contact lenses were then contacted to a live monolayer of corneal epithelial cells for two hours, after which the contact lens was sheared laterally. The apparent cell monolayer relaxation modulus was then used to quantify the extent of cell adhesion to the contact lens surface. For both lens types, lysozyme increased corneal cell adhesion to the contact lens, with the apparent cell monolayer relaxation modulus increasing up to an order of magnitude in the presence of protein. The magnitude of this increase depended on the identity of the soaking solution: lenses soaked in borate-buffered solutions (BBS, Sensitive Eyes) exhibited a much greater increase in cell attachment upon protein addition than those soaked in PBS. Significantly, all measurements were conducted while subjecting the cells to moderate surface pressures and shear rates, similar to those experienced by corneal cells in vivo.     

Individual recognition and the dominance hierarchy in the domesticated pig. The role of sight

The role of sight in the dominance hierarchy of groups of eight pigs was studied by the induction of temporary blindness using opaque contact lenses or hoods which covered the face. The effect of blindness was examined in three social situations: (i) the simultaneous introduction of eight previously unacquainted, blinded pigs; (ii) groups of pigs with a known social order were blinded and (iii) a single pig within a group of known social order was blinded. The contact lenses had a minimal effect on the hierarchy formation whilst both the lenses and the hoods had no effect on the established groups. The hoods prevented hierarchy formation amongst the unacquainted pigs. It is suggested that sight alone is not necessary for hierarchy maintenance and that the hoods stopped the formation of a hierarchy by an effect other than the deprivation of sight, e.g. by covering pheromone producing areas.     

A glucose-sensing contact lens: from bench top to patient

In the past few years we have seen the development of several new technologies for the continuous and non-invasive monitoring of physiological glucose, such as the GlucoWatch, glucose-sensing skin patches and approaches based on a glucose-sensing tattoo. One approach that differs from current thinking is based on the determination and monitoring of tear glucose, which is well known to track blood glucose with an approximate 30 min lag time, using disposable and colorless contact lenses. These contact lenses can be worn by diabetics who can colorimetrically see changes in their contact lens color or other fluorescence-based properties, giving an indication of tear and blood glucose levels.     

Acanthamoeba adherence to contact lenses, removal by rinsing procedures, and survival to some ophthalmic products.

Unworn soft and rigid gas-permeable contact lenses were inoculated with an Acanthamoeba keratitis strain to study the protozoon's ability to adhere. Furthermore, the efficacy of the rinsing in saline on acanthamoeba removal was evaluated, as well as the amebicidal activity of five commercial cleaning/disinfecting products: hydrogen peroxide, chlorhexidine, polyaminopropyl biguanide-poloxamine, thimerosal-polyquaternium, and thimerosal-chlorhexidine. Microscopic count of cells showed that Acanthamoeba trophozoites and cysts adhered to all types of contact lenses. A significantly greater adherence of trophozoites than cysts was recorded. The rinsing in saline using a flow-method was significantly more effective than the immersion-method, particularly in removing trophozoites from rigid gas-permeable lenses. The cleaning/disinfecting solutions tested were ineffective in removing or in affecting the viability of all Acanthamoeba trophozoites or cysts in the 17 hours allotted for the experiment. The need for a better care in mechanical and physical hygiene procedures is stressed.     

Observation of soft contact lens disinfection with fluorescent metabolic stains

A rapid fluorescent staining method using a tetrazolium dye and propidium iodide for the in-use assessment of disinfection of Pseudomonas aeruginosa biofilms on soft contact lenses showed that 11 to 13% of cells on lenses remained actively respiring and recoverable by culture methods after 30 min of exposure to 3% hydrogen peroxide.     

Direct detection of proteins adsorbed on synthetic materials by matrix-assisted laser desorption ionization-mass spectrometry.

The irreversible accumulation of biological material on synthetic surfaces ("biofouling") adversely affects for instance contact lenses, implantable biomedical devices, biosensors, water purification, transport and storage systems, and marine structures. It is shown here that proteins adsorbed on contact lenses can be detected directly, rapidly, and conveniently, with high sensitivity, by matrix-assisted laser desorption ionization (MALDI)-mass spectrometry. This new approach allows detection of minor (and major) proteinaceous constituents of biofouled layers on samples retrieved from clinical usage and in vitro protein adsorption studies, at levels substantially below monolayer coverage. Identification of the detected biological molecules can be done by comparison of the detected mass peaks with known protein molecular masses or with spectra recorded of pure compounds or by separate biochemical assays. The MALDI mass spectra recorded on different contact lenses contain peaks assignable to lysozyme and a number of smaller proteins. Such sensitive characterization of the early stages of biofouling enhances the understanding of protein/materials interactions and assists in designing guided strategies toward control of biological adsorption processes.     

Effect of Staphylococcus epidermidis on Hydrogel Contact Lens Retention on the Rabbit Eye

A slime-producing isolate of Staphylococcus epidermidis attached to FDA Group II hydrogel contact lenses persisted on rabbit eyes for up to 14 days, but except for minor redness of the eye no other effect was observed. Eye flora of eight representative New Zealand White rabbits included four different species of Staphylococcus including S. epidermidis and one species of Micrococcus, none of which produced overtly obvious biofilms. The slime-producing strain of S. epidermidis adhered more effectively to lenses than a non-slime-producing strain, and lenses challenged with the slime-producing strain remained on the rabbit eye for longer time periods than those with a non-slime-producing strain. Bacteria associated with the contact lens may affect the retention of the lens on the rabbit cornea during experimental studies.     

A biphasic model for micro-indentation of a hydrogel-based contact lens

The stiffness and hydraulic permeability of soft contact lenses may influence its clinical performance, e.g., on-eye movement, fitting, and wettability, and may be related to the occurrence of complications; e.g., lesions. It is therefore important to determine these properties in the design of comfortable contact lenses. Micro-indentation provides a nondestructive means of measuring mechanical properties of soft, hydrated contact lenses. However, certain geometrical and material considerations must be taken into account when analyzing output force-displacement (F-D) data. Rather than solely having a solid response, mechanical behavior of hydrogel contact lenses can be described as the coupled interaction between fluid transport through pores and solid matrix deformation. In addition, indentation of thin membranes ( approximately 100 microm) requires special consideration of boundary conditions at lens surfaces and at the indenter contact region. In this study, a biphasic finite element model was developed to simulate the micro-indentation of a hydrogel contact lens. The model accounts for a curved, thin hydrogel membrane supported on an impermeable mold. A time-varying boundary condition was implemented to model the contact interface between the impermeable spherical indenter and the lens. Parametric studies varying the indentation velocities and hydraulic permeability show F-D curves have a sensitive region outside of which the force response reaches asymptotic limits governed by either the solid matrix (slow indentation velocity, large permeability) or the fluid transport (high indentation velocity, low permeability). Using these results, biphasic properties (Young's modulus and hydraulic permeability) were estimated by fitting model results to F-D curves obtained at multiple indentation velocities (1.2 and 20 microm/s). Fitting to micro-indentation tests of Etafilcon A resulted in an estimated permeability range of 1.0 x 10(-15) to 5.0 x 10(-15) m(4)N s and Young's modulus range of 130 to 170 kPa.     

Acanthamoeba spp.: Efficacy of Bioclen FR One Step®, a povidone-iodine based system for the disinfection of contact lenses

Pathogenic strains of Acanthamoeba are causative agents of a serious sight-threatening infection of the eye known as Acanthamoeba keratitis. The prevalence of this infection has risen in the past 20 years, mainly due to the increase in number of contact lens wearers. Bioclen FR One Step® (Ophtecs Corporation) is the only available povidone-iodine based system for the disinfection of silicone hydrogel lenses and soft contact lenses on the market. Bioclen FR has been proven to be highly effective against bacteria and fungi that can cause problems for contact lens users. In this study, Bioclen FR One Step® was tested against three clinical Acanthamoeba isolates from contact lens cases. The results demonstrated that the tested Acanthamoeba clinical strains were sensitive to Bioclen FR One Step®.     

Hemagglutination (fimbriae) and hydrophobicity in adherence ofSerratia marcescens to urinary tract epithelium and contact lenses

The capacity of 59 isolates of Serratia marcescens, obtained from urinary tract infections, wounds, and contact lenses or their paraphernalia, to agglutinate erythrocytes from different animal species was tested. Three main patterns were found: mannose-sensitive agglutination of guinea-pig, fowl or horse erythrocyte; mannose-resistant agglutination of chicken or pigeon erythrocytes alone or in combination with mannose-sensitive agglutination; and no agglutination. Hemagglutination capacity was associated with isolates from urinary tract infection, but not with isolates associated with contact lenses. Adherence to human urinary tract epithelium did not correlate with the hemagglutination patterns nor with the origin of the isolates. Some strains of different hemagglutination pattern were selected for the study of hydrophobicity and adherence to contact lens polymers. Hydrophobicity, as determined by degree of partition in hexadecane and water (BATH-values), correlated neither with degree of adherence to contact lens polymers nor with the hemagglutination pattern. For a representative strain there was an excellent correlation (r2 = 0.98) between adherence and the water content (hydrophobicity) of the lens polymers. These results suggest that, as with tissues, other factors interact with hydrophobicity in causing adherence to plastics.