Optimization of goblet cell density quantification methods.

The purpose of this study was to develop a standardized, accurate and efficient method for estimating conjunctival goblet cell density (GCD) via optimizing sample storage conditions and quantification methods. Conjunctival impression cytology (CIC) membranes were collected from both eyes of 32 participants and were randomized to two storage durations (2-3 weeks, 6-7 weeks) and two storage container types (microcentrifuge tube, flat histology cassette). The CIC membranes were stained and subdivided into 25 areas (5 mm × 5 mm) for imaging and the GCs were counted under 200X magnification using three different methods: (1) full CIC membrane GC count of the 25 images with cell-counting software ("full"; reference method), (2) partial membrane GC count of 9 images with cell-counting software ("partial"), and (3) manual counting of the 25 images ("manual"). In all cases, GCD was determined by dividing the GC count by the counting area. The average time required for quantification was recorded to gauge efficiency. Results showed no significant difference in GC count between the two storage durations (p = 0.745) or storage container types (p = 0.552). The median (interquartile range (IQR)) time required to quantify a CIC membrane for the full, partial, and manual methods of GC counting, was 14.8(17.6), 4.6(5.2) and 5.0 (5.0) minutes, respectively. The agreement of GCD values between the full and manual methods (bias: 0.4, 95% LOA: [-4.6, 5.5]) was stronger than that comparing the full and partial methods (bias: 0.5, 95% LOA: [-18, 17]). All together, through systematic examination of key procedural variables, an optimized method for GCD quantification within 7 weeks of sample collection was outlined. Adaption of procedures described in this paper to facilitate accurate and efficient GCD quantification may serve as a valuable step in clinical trials investigating DED pathophysiology and/or novel DED treatment strategies.

Adhesion of Pseudomonas aeruginosa, Achromobacter xylosoxidans, Delftia acidovorans, Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution.

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.

Uptake and Release of Polyvinyl Alcohol from Hydrogel Daily Disposable Contact Lenses.

SIGNIFICANCE: Polyvinyl alcohol is a wetting agent that could reduce the symptoms of dry eye and contact lens discomfort. Currently, only one lens type, nelfilcon A (DAILIES AquaComfort Plus), releases polyvinyl alcohol. The concept of releasing this agent from contact lenses could be applied to other lens materials. PURPOSE: The purpose of this study was to measure the release of polyvinyl alcohol from commercially available hydrogel daily disposable contact lenses using refractive index and iodine-borate methods. METHODS: Etafilcon A, omafilcon A, and nelfilcon A were soaked in phosphate-buffered saline and 0.2% trifluoroacetic acid/acetonitile for 24 hours to remove residual blister pack components. The lenses were then incubated in a 10-mg/mL solution of polyvinyl alcohol for 24 hours. After the incubation period, the lenses were placed in 2 mL of phosphate-buffered saline. At specified time intervals, t = 0.5, 1, 2, 4, 8, 12, and 24 hours, the samples were evaluated using refractive index and an iodine-borate assay. Polyvinyl alcohol uptake was determined by extracting the lenses with methanol for 24 hours. RESULTS: There were no differences in the uptake of polyvinyl alcohol between lens types (P > .05). The release of this wetting agent for all lens types followed a burst-plateau profile after the first 30 minutes (P > .05). Nelfilcon A had a slightly higher release of polyvinyl alcohol (P < .05) than did etafilcon A but was similar to omafilcon A (P > .05). CONCLUSIONS: The results suggest that the contact lenses tested in this study have similar efficiency in delivering polyvinyl alcohol.

Efficacy of Contact Lens Care Solutions in Removing Cholesterol Deposits From Silicone Hydrogel Contact Lenses.

PURPOSE: To determine the efficacy of multipurpose solutions (MPSs) on the removal of cholesterol deposits from silicone hydrogel (SH) contact lens materials using an in vitro model. MATERIALS AND METHODS: Five SH lens materials: senofilcon A, comfilcon A, balafilcon A, lotrafilcon A, and lotrafilcon B were removed from the blister pack (n=4 for each lens type), incubated for 7 days at 37°C in an artificial tear solution containing C radiolabeled cholesterol. Thereafter, lenses were stored in a preserved saline solution control (Sensitive Eyes Saline Plus) or cleaned with 1 of the 5 MPSs incorporating different preservatives (POLYQUAD/ALDOX, polyquaternium-1/alexidine, polyquaternium-1/PHMB, and 2 based on PHMB alone) using a rub and rinse technique, according to the manufacturer's recommendations, and stored in the MPS for a minimum of 6 hr. Lenses were then extracted with 2:1 chloroform:methanol, analyzed in a beta counter, and µg/lens of cholesterol was determined. RESULTS: Balafilcon A and senofilcon A lens materials showed the highest amounts of accumulated cholesterol (0.93±0.02 µg/lens; 0.95±0.01 µg/lens, respectively), whereas lotrafilcon A and lotrafilcon B deposited the lowest amounts (0.37±0.03 µg/lens; 0.47±0.12 µg/lens, respectively). For all lens materials, the MPS preserved with POLYQUAD/ALDOX removed more deposited cholesterol than any other test solution; however, the amount of removed cholesterol contamination from the individual contact lenses was only statistically significant for balafilcon A and senofilcon A (P=0.006 and P=0.042, respectively). Sensitive eyes and the other evaluated MPSs showed no significant effect on cholesterol removal (P>0.05). CONCLUSION: Cholesterol-removal efficacy varies depending on the combination of lens material and solution. Only 1 MPS showed a statistically significant reduction of cholesterol deposit for only 2 of the 5 tested lens materials.

Depth Profile Assessment of the Early Phase Deposition of Lysozyme on Soft Contact Lens Materials Using a Novel In Vitro Eye Model.

OBJECTIVE: To characterize the location of fluorescently labeled lysozyme on commercial contact lenses (CLs) using an in vitro eye model that simulates tear volume, tear flow, air exposure, and mechanical wear. METHODS: One commercially available conventional hydrogel CL material (etafilcon A) and three silicone hydrogel CL materials (balafilcon A, lotrafilcon B, and senofilcon A) were evaluated in this study. The CLs were mounted on the in vitro eye model and exposed to artificial tear fluid containing fluorescein isothiocyanate (FITC)-labeled lysozyme for 2 and 10 hrs. After these short incubation periods, circular discs were punched from the CLs at the center and periphery and were prepared for confocal laser scanning microscopy (CLSM). The CLSM captured a series of consecutive images spaced 5 µm apart, and the resulting images were rendered into two dimensional cross-sectional views of the CL. The mean fluorescence at each 5 µm slice was used to generate a histogram depicting the penetration of FITC-lysozyme into CLs. RESULTS: For both incubation periods, the CLSM images and histogram of etafilcon A showed that FITC-lysozyme is more concentrated at the lens surface, with a moderate amount of deposition in the lens matrix. For balafilcon A, FITC-lysozyme was evenly distributed throughout the lens. For lotrafilcon B, there was a greater amount of FITC-lysozyme deposition on the surfaces of the lens versus the matrix. Senofilcon A had differential FITC-lysozyme distribution profiles depending on the location of the lens. At the lens periphery, FITC-lysozyme primarily deposited on the surface, whereas FITC-lysozyme was uniformly distributed at the center of the lens. CONCLUSIONS: With the use of a sophisticated in vitro eye model, the study revealed a complex deposition pattern of FITC-labeled lysozyme on various CL materials after short periods of exposure. An understanding of the early deposition pattern of lysozyme on different CL material may elucidate new insights into the processes behind CL discomfort.

Lipid Deposition on Contact Lenses when Using Contemporary Care Solutions.

SIGNIFICANCE: There remains only a small amount of data from human studies demonstrating the effect of contact lens/lens care solution combinations on the deposition of lipids. Therefore, information on the degree to which modern materials deposit lipids when used with contemporary care solutions would be valuable. PURPOSE: The present study aims to determine the effect of lens care system combinations on levels of total lipid, cholesterol, and cholesteryl esters extracted from three different contact lenses (CLs) when used with four contemporary care systems. METHODS: Experienced CL wearers were recruited to participate in this study. Combinations of three CLs (etafilcon A [ETA], galyfilcon A [GALY], and senofilcon A [SENO]) and four CL care solutions (Biotrue, ClearCare, OPTI-FREE PureMoist, and RevitaLens Ocutec) were investigated. A total of 791 CLs were analyzed. Subjects were randomized to one lens type and then used all four lens care solutions in random sequence for 10-14 days before the CLs were collected and analyzed for the amount of cholesterol, cholesteryl esters, and total lipids. RESULTS: The mean range of cholesterol recovered across the different care solutions was 0.34-2.77 µg/lens, 3.48-4.29 µg/lens, and 4.75-6.20 µg/lens for ETA, SENO, and GALY lenses, respectively. Use of OPTI-FREE PureMoist with ETA lenses led to a significantly greater amount of cholesterol being recovered when compared to the use of the other solutions with ETA lenses (P < .05). The mean range of cholesteryl esters recovered across different care solutions was 1.31-2.02 µg/lens, 6.43-7.19 µg/lens, and 7.96-10.13 µg/lens for ETA, SENO, and GALY lenses, respectively. There were no differences in the amount of cholesteryl esters and total lipids extracted for a given lens type when used with any of the four care solutions (P > .05). CONCLUSIONS: This study did not demonstrate conclusively that any of the solution/CL combinations were superior to any of the other combinations when the amounts of lipid deposition were compared among the tested lenses.

In Vitro Effect of Lysozyme on Albumin Deposition to Hydrogel Contact Lens Materials.

SIGNIFICANCE: Albumin deposition on contact lenses could be detrimental to contact lens (CL) wear because this may increase the risk of bacterial binding and reduce comfort. Lysozyme deposition on selected lens materials would reduce albumin deposition on lenses. PURPOSE: This study aims to determine if lysozyme deposition on CLs could act as a barrier against subsequent albumin adsorption, using an in vitro model. METHODS: Six hydrogel CL materials (etafilcon A, polymacon, nelfilcon A, omafilcon A, ocufilcon B, and nesofilcon A) were evaluated. Four CLs of each type were soaked in lysozyme solution for 16 hours at 37°C. Lysozyme-coated lenses were then placed in vials with 1.5 mL of artificial tear solution containing I-labeled albumin for 16 hours at 37°C with shaking. Four uncoated lenses of each type were used as controls. Lenses soaked in radiolabeled albumin were rinsed in a phosphate-buffered saline solution, and radioactive counts were measured directly on lenses using a gamma counter. Albumin uptake on lenses was measured using a calibration curve by plotting radioactive counts versus protein concentration. RESULTS: Results are reported as mean ± SD. Lysozyme-coated etafilcon A lenses exhibited lower levels of deposited albumin than uncoated etafilcon A lenses (58 ± 12 vs. 84 ± 5 ng/lens; P < .05). There were no differences in albumin adsorption between control (uncoated) and lysozyme-coated polymacon (105 ± 10 vs. 110 ± 34 ng/lens), nelfilcon A (51 ± 7 vs. 42 ± 20 ng/lens), omafilcon A (90 ± 20 vs. 80 ± 38 ng/lens), ocufilcon B (87 ± 20 vs. 115 ± 50 ng/lens), and nesofilcon A (170 ± 29 vs. 161 ± 10 ng/lens) lens materials (P > .05). Uncoated nesofilcon A lenses deposited the highest amount of albumin when compared with other uncoated lenses (P < .05). CONCLUSIONS: This study demonstrates that lysozyme deposited onto etafilcon A resists the deposition of albumin, which may potentially be beneficial to CL wearers.

In Vitro Cholesterol Deposition on Daily Disposable Contact Lens Materials.

PURPOSE: The goal of this study was to analyze how various incubation times affect the uptake of cholesterol on silicone hydrogel (SH) and conventional hydrogel (CH) daily disposable (DD) contact lens materials using an in vitro radiochemical detection method. METHODS: Three SH (somofilcon A, delefilcon A, and narafilcon A) and four CH (etafilcon A, nesofilcon A, ocufilcon A, and nelfilcon A) contact lenses were incubated in an artificial tear solution that contained major tear film components and a portion of radioactive C-cholesterol. Lenses (N = 4) were incubated for four incubation times (2, 6, 12, or 16 h) to assess the effects on cholesterol deposition. Subsequent to the incubation, the lenses were extracted using 2:1 chloroform:methanol, and the extracts were analyzed in a beta counter and (in nanograms per lens) extrapolated from standard curves. RESULTS: In general, cholesterol deposited statistically significantly more on SH lenses than CHs (p ≤ 0.033), with the exception of somofilcon A and nesolfilcon A materials (p = 0.067). Within the SH materials, narafilcon A accumulated the largest quantity of cholesterol (p < 0.05) and somofilcon A the lowest (p < 0.05). The uptake of cholesterol ranged from 22.63 ± 2.98 ng/lens to 97.94 ± 4.18 ng/lens for all lens materials. The accumulation of cholesterol was shown to be continuous throughout the 16 h of incubation, without reaching a plateau (p < 0.001). CONCLUSIONS: For the periods that DD lens materials are worn, cholesterol deposits significantly more onto SH contact lenses than CHs. This could have implications for wearers who have higher levels of lipid in their tears that are fitted with SH DD materials.

The Use of Contact Lenses as Biosensors.

: The tear film is a complex multilayer film consisting of various proteins, enzymes, and lipids and can express a number of biomarkers in cases of disease. The development of a contact lens sensor presents a noninvasive alternative for the detection and management of various diseases. Recent work has resulted in the commercialization of a device to monitor intraocular pressure for up to 24 h, and there are extensive efforts underway to develop a contact lens sensor capable of continuous glucose tear film monitoring to manage diabetes. This clinical perspective will highlight the major developments within this field and list some of the major challenges that still need to be addressed.

Release of Fluconazole from Contact Lenses Using a Novel In Vitro Eye Model.

PURPOSE: Rapid drug release followed by a plateau phase is a common observation with drug delivery from contact lenses (CLs) when evaluated in a vial. The aim of this study was to compare the release of fluconazole from seven commercially available daily disposable CLs using a conventional vial-based method with a novel in vitro eye model. METHODS: An eye model was created using two 3-dimensional printed molds, which were filled with polydimethylsiloxane to obtain an inexpensive model that would mimic the eyeball and eyelid. The model was integrated with a microfluidic syringe pump, and the flow-through was collected in a 12-well microliter plate. Four commercial daily disposable conventional hydrogels (nelfilcon A, omafilcon A, etafilcon A, ocufilcon B) and three silicone hydrogels (somofilcon A, narafilcon A, delefilcon A) were evaluated. These CLs were incubated with fluconazole for 24 h. The drug release was measured in a vial containing 4.8 mL of phosphate-buffered saline and in the polydimethylsiloxane eye model with a 4.8-mL tear flow across 24 h. RESULTS: Overall, conventional hydrogel CLs had a higher uptake and release of fluconazole than silicone hydrogel CLs (p < 0.05). A higher drug release was observed in the vial condition compared with the eye model (p < 0.001). In the vial system, the drugs were rapidly released from the CL within the first 2 h, followed by a plateau phase. In contrast, drug release in the eye model under low tear volume was sustained and did not reach a plateau across 24 h (p < 0.05). CONCLUSIONS: Rapid drug release results from using a vial as the release system. Under low tear volume at physiological tear flow, commercial CLs can maintain a sustained drug release profile for up to 24 h. However, eyes with fungal keratitis may have increased tearing, which would significantly accelerate drug release.

Microbial Contamination of Contact Lens Storage Cases During Daily Wear Use.

PURPOSE: To evaluate contact lens (CL) storage case contamination when used with four different CL care solutions during daily wear of three different CL materials. METHODS: A parallel, prospective, bilateral, randomized clinical trial (n = 38) was conducted. Subjects were randomly assigned to use one of three CL materials (etafilcon A, senofilcon A, or galyfilcon A) on a daily wear basis. Subsequently, each subject randomly used one of four different CL care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and CLEAR CARE) for 2 weeks, along with their respective storage cases. After every 2-week period, their storage cases were collected and the right and left wells of each storage case were randomized for two procedures: (1) microbial enumeration by swabbing the storage case surface and (2) evaluation of biofilm formation (multipurpose solution cases only) using a crystal violet staining assay. RESULTS: More than 80% of storage cases were contaminated when used in conjunction with the four CL care solutions, irrespective of the CL material worn. Storage cases maintained with CLEAR CARE (mean Log colony forming units (CFU)/well ± SD, 2.0 ± 1.0) revealed significantly (p < 0.001) greater levels of contamination, compared to those maintained with Biotrue (1.3 ± 0.8) and RevitaLens OcuTec (1.2 ± 0.8). Predominantly, storage cases were contaminated with Gram-positive bacteria (≥80%). There were significant differences (p = 0.013) for the levels of Gram-negative bacteria recovered from the storage cases maintained with different CL care solutions. Storage cases maintained with OPTI-FREE PureMoist (0.526 ± 0.629) showed significantly higher biofilm formation (p = 0.028) compared to those maintained with Biotrue (0.263 ± 0.197). CONCLUSIONS: Levels of contamination ranged from 0 to 6.4 Log CFU/storage case well, which varied significantly (p < 0.001) between different CL care solutions, and storage case contamination was not modulated by CL materials.

Impact of Lens Care Solutions on Protein Deposition on Soft Contact Lenses.

PURPOSE: To evaluate the effect of four contemporary lens care solutions on total protein, total lysozyme, and active lysozyme extracted from three contact lens materials. METHODS: Adapted contact lens wearers were recruited at three sites, and all subjects were randomly assigned to daily wear of either etafilcon A, galyfilcon A, or senofilcon A for 2 weeks. Four lens care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and ClearCare) were used by each subject in random order with a new pair of lenses after a washout period between solutions of at least 4 days. After 2 weeks of daily wear, contact lenses were collected for analysis. Proteins were extracted from a subset of contact lenses (n = 568) and total protein, total lysozyme, and lysozyme activity were quantified using a modified Bradford assay, an enzyme-linked immunosorbent assay, and a micrococcal assay, respectively. RESULTS: Higher levels of total protein were extracted from etafilcon A when used with Biotrue compared to other solutions (p = 0.0001). There were higher levels of total lysozyme extracted from galyfilcon A lenses when used with PureMoist than with Biotrue or ClearCare (p < 0.006). Higher total lysozyme was extracted from senofilcon A when used with RevitaLens OcuTec compared to Biotrue (p = 0.002). Lower lysozyme activity was recovered from senofilcon A lenses with RevitaLens OcuTec when compared to all other care solutions (all p < 0.004). When Biotrue, PureMoist, or RevitaLens OcuTec were used, higher total lysozyme was extracted from galyfilcon A compared to senofilcon A (p < 0.01). When RevitaLens OcuTec was used, higher levels of active lysozyme were extracted from galyfilcon A compared to senofilcon A (p = 0.02). CONCLUSIONS: The ability of lens care solutions to remove protein from lenses varies depending upon the care solution composition and also the polymeric make-up of the contact lens material.

Effects of Antifungal Soaked Silicone Hydrogel Contact Lenses on Candida albicans in an Agar Eye Model.

PURPOSE: To evaluate the effects of two commercial silicone hydrogel contact lenses (CLs) soaked with natamycin (NA) or fluconazole (FL) on the growth of Candida albicans in an in vitro eye model. METHODS: Three-D printed molds were used as a cast for making eye-shaped models comprising potato dextrose agar. Senofilcon A (SA) and lotrafilcon B (LB) CLs were incubated with either 2 mL of NA or FL at a concentration of 1 mg/mL for 24 hr. To simulate a fungal infection, the eye models were coated with C. albicans. The drug-soaked lenses were placed on top of the eye models. Seven experimental conditions were examined: (1) NA-SA, (2) NA-LB, (3) FL-SA, (4) FL-LB, (5) SA, (6) LB, and (7) control-no lens. At specified time points (t=1, 8, 16, 24, 48 hr), the agar eyes from each experimental condition were removed from the incubator and photographed. The yeast cells from the 24 and 48 hr time point were also analyzed using light microscopy. RESULTS: At 24 and 48 hr, there was considerable growth observed for all conditions except for the NA-SA and NA-LB conditions. When observed under the microscope at 24 and 48 hr, the morphology of the yeast cells in the FL-SA and SA condition were similar to that of the control (oval shaped). There was limited hyphae growth observed for LB and significant visible hyphae growth for the NA-LB group. For NA-SA, NA-LB, and FL-LB groups, the cells were significantly smaller compared with the control. CONCLUSIONS: For NA-SA and NA-LB, there was limited growth of C. albicans observed on the eye models even after 48 hr. Under the microscope, the cell morphology differ noticeably between each testing condition, and is dependent on drug-lens combinations.

Efficacy of antimicrobials against biofilms of Achromobacter and Pseudomonas.

PURPOSE: Achromobacter xylosoxidans and Pseudomonas aeruginosa biofilms can develop in ophthalmic products and accessories such as contact lens cases, leading to the development of ocular infections. This study evaluated the efficacy of the antimicrobials polyaminopropyl biguanide (PAPB) and benzalkonium chloride (BAK) against A. xylosoxidans and P. aeruginosa biofilms. METHODS: Biofilms of A. xylosoxidans and P. aeruginosa used as a comparative control were formed by incubating the bacteria on contact lens cases and on coverslips in phosphate-buffered saline. The biofilms were then exposed to PAPB and BAK for 5 minutes and 4 hours. After exposure, alginate swabs were used to remove the biofilms from the lens cases and the bacteria were plated on tryptic soy agar for determination of survivors. Also, after exposure to these disinfectants, the A. xylosoxidans and P. aeruginosa biofilms were stained with SYTO 9 and propidium iodide. Using a confocal microscope with a 488-nm laser, the number of cells with damaged cell membranes was determined. RESULTS: After 5 minutes of exposure to BAK or PAPB, A. xylosoxidans biofilms were more resistant to the antimicrobial effects of these disinfectants than P. aeruginosa biofilms. After 4 hours, both organisms were reduced by more than 3 logs after exposure to either BAK or PAPB. Confocal microscopy studies revealed that BAK was more effective at damaging A. xylosoxidans and P. aeruginosa cell membranes than PAPB at the concentrations used in ophthalmic products. CONCLUSIONS: Biofilms of the emerging pathogen A. xylosoxidans were more resistant to the disinfectants PAPB and BAK than biofilms of P. aeruginosa. Because of the emergence of A. xylosoxidans and the demonstrated greater resistance to the common ophthalmic preservatives BAK and PAPB than the standard Gram-negative organism P. aeruginosa, A. xylosoxidans biofilms should be assessed in antimicrobial challenge tests to assure the safety of multiuse ophthalmic products.

Biological and Clinical Implications of Lysozyme Deposition on Soft Contact Lenses.

Within a few minutes of wear, contact lenses become rapidly coated with a variety of tear film components, including proteins, lipids, and mucins. Tears have a rich and complex composition, allowing a wide range of interactions and competitive processes, with the first event observed at the interface between a contact lens and tear fluid being protein adsorption. Protein adsorption on hydrogel contact lenses is a complex process involving a variety of factors relating to both the protein in question and the lens material. Among tear proteins, lysozyme is a major protein that has both antibacterial and anti-inflammatory functions. Contact lens materials that have high ionicity and high water content have an increased affinity to accumulate lysozyme during wear, when compared with other soft lens materials, notably silicone hydrogel lenses. This review provides an overview of tear film proteins, with a specific focus on lysozyme, and examines various factors that influence protein deposition on contact lenses. In addition, the impact of lysozyme deposition on various ocular physiological responses and bacterial adhesion to lenses and the interaction of lysozyme with other tear proteins are reviewed. This comprehensive review suggests that deposition of lysozyme on contact lens materials may provide a number of beneficial effects during contact lens wear.

Extraction versus in situ techniques for measuring surface-adsorbed lysozyme.

PURPOSE: To compare two techniques for measuring the activity of lysozyme deposited onto hydrogel contact lens and to image the binding of Micrococcus lysodeikticus to contact lenses. METHODS: Using a previously described protein extraction technique and a recently developed in situ technique, we measured the time-dependent activity of adsorbed lysozyme on six different contact lens materials during the first minute and up to 1 week of interaction with the material surface. Total activity of extracted lysozyme, total in situ activity, and the activity of the outer surface layer of sorbed lysozyme were determined using the two different techniques. Micrococcal cellular interaction with surface-adsorbed lysozyme was imaged using confocal microscopy. RESULTS: The differences between total extracted activities, total in situ activities, and surface activities were both measurable and material specific. In most cases, total extracted activity is greater than total in situ activity, which, in turn, is greater than surface activity. After 1 week, etafilcon A had the highest extracted activity at 137 µg/lens, followed by omafilcon A, balafilcon A, comfilcon A, senofilcon A, and lotrafilcon B at 27.4, 2.85, 2.02, 0.46, and 0.27 µg/lens, respectively. Micrococcal cell adhesion was greatest on contact lenses with high contact angles, such as balafilcon A, omafilcon A, and senofilcon A and lowest on contact lenses with low contact angles, such as etafilcon A, comfilcon A, and lotrafilcon B. Subsequent removal/prevention of adhered micrococcal cells was greatest on balafilcon A, which had the highest surface activity, and lowest on lotrafilcon B, which had the lowest surface activity. CONCLUSIONS: This study has measured and made direct comparisons between two established techniques for measuring the activity of adsorbed lysozyme. The extraction technique determines the activity of underlying layers of lysozyme or lysozyme within the matrix of the material. Conversely, the in situ technique allows conclusions to be drawn about only the biologically relevant lysozyme including the activity of just the outer surface of adsorbed lysozyme.

BCLA CLEAR Presbyopia: Management with contact lenses and spectacles.

This paper seeks to outline the history, market situation, clinical management and product performance related to the correction of presbyopia with both contact lenses and spectacles. The history of the development of various optical forms of presbyopic correction are reviewed, and an overview is presented of the current market status of contact lenses and spectacles. Clinical considerations in the fitting and aftercare of presbyopic contact lens and spectacle lens wearers are presented, with general recommendations for best practice. Current options for contact lens correction of presbyopia include soft simultaneous, rigid translating and rigid simultaneous designs, in addition to monovision. Spectacle options include single vision lenses, bifocal lenses and a range of progressive addition lenses. The comparative performance of both contact lens and spectacle lens options is presented. With a significant proportion of the global population now being presbyopic, this overview is particularly timely and is designed to act as a guide for researchers, industry and eyecare practitioners alike.

Evaluating the in vitro wettability and coefficient of friction of a novel and contemporary reusable silicone hydrogel contact lens materials using an in vitro blink model.

PURPOSE: To evaluate the in vitro wettability and coefficient of friction of a novel amphiphilic polymeric surfactant (APS), poly(oxyethylene)-co-poly(oxybutylene) (PEO-PBO) releasing silicone hydrogel (SiHy) contact lens material (serafilcon A), compared to other reusable SiHy lens materials. METHODS: The release of fluorescently-labelled nitrobenzoxadiazole (NBD)-PEO-PBO was evaluated from serafilcon A over 7 days in a vial. The wettability and coefficient of friction of serafilcon A and three contemporary SiHy contact lens materials (senofilcon A; samfilcon A; comfilcon A) were evaluated using an in vitro blink model over their recommended wearing period; t = 0, 1, 7, 14 days for all lens types and t = 30 days for samfilcon A and comfilcon A (n = 4). Sessile drop contact angles were determined and in vitro non-invasive keratographic break-up time (NIKBUT) measurements were assessed on a blink model via the OCULUS Keratograph 5 M. The coefficient of friction was measured using a nano tribometer. RESULTS: The relative fluorescence of NBD-PEO-PBO decreased in serafilcon A by approximately 18 % after 7 days. The amount of NBD-PEO-PBO released on day 7 was 50 % less than the amount released on day 1 (6.5±1.0 vs 3.4±0.5 µg/lens). The reduction in PEO-PBO in the lens also coincided with an increase in contact angles for serafilcon A after 7 days (p < 0.05), although there were no changes in NIKBUT or coefficient of friction (p > 0.05). The other contact lens materials had stable contact angles and NIKBUT over their recommended wearing period (p > 0.05), with the exception of samfilcon A, which had an increase in contact angle after 14 days as compared to t = 0 (p < 0.05). Senofilcon A and samfilcon A also showed an increase in coefficient of friction at 14 and 30 days, respectively, compared to their blister pack values (p < 0.05). CONCLUSION: The results indicate that serafilcon A gradually depletes its reserve of PEO-PBO over 1 week, but this decrease did not significantly change the lens performance in vitro during this time frame.

Physical entrapment of hyaluronic acid during synthesis results in extended release from model hydrogel and silicone hydrogel contact lens materials.

OBJECTIVES: This study was designed to assess the duration of hyaluronic acid (HA) release from model contact lens materials when HA was physically incorporated into the hydrogel during synthesis and to assess the effects of the HA release on lysozyme sorption. METHODS: Model conventional and silicone hydrogel contact lens materials containing HA of various molecular weights as a releasable wetting agent were prepared. The HA was released into phosphate-buffered saline and MilliQ water, and the release was monitored using ultraviolet spectroscopy. Hyaluronic acid release was quantified by enzyme-linked immunosorbent assay. The effect of the releasable HA on lysozyme sorption to the materials was also analyzed using 125-I-labeled protein. RESULTS: Hyaluronic acid loaded into the materials using this method could be released from conventional hydrogel materials for 21 days; the model silicone hydrogels showed release of more than 7 weeks. With one exception, the releasable HA decreased lysozyme sorption. CONCLUSIONS: Hyaluronic acid physically incorporated into contact lens materials during synthesis may therefore be released for extended periods of time of up to 7 weeks. Hyaluronic acid release leads to decreased protein adsorption in general. This method has potential for modification of conventional and silicone hydrogel lenses with releasable HA as a wetting agent.

In vitro uptake and release of natamycin from conventional and silicone hydrogel contact lens materials.

OBJECTIVES: To investigate the uptake and release of the antifungal ocular drug, natamycin from commercially available conventional hydrogel (CH) and silicone hydrogel (SH) contact lens (CL) materials and to evaluate the effectiveness of this delivery method. METHODS: Five commercial SH CLs (balafilcon A, comfilcon A, galyfilcon A, senofilcon A, and lotrafilcon B) and four CH CLs (etafilcon A, omafilcon A, polymacon, vifilcon A) were examined in this study. These lenses were incubated with natamycin solubilized in dimethyl sulfoxide, and the release of the drug from these lenses, in Unisol 4 pH 7.4 at 32±1°C, was determined using UV-visible spectrophotometry at 305 nm over 24 hours. RESULTS: There was a significant uptake of natamycin between 0 hour and 24 hours (P<0.05) for all CL materials. However, there was no significant difference between any of the lens materials, regardless of their composition (P>0.05). There was a significant difference in release between all the SH materials (P<0.05) and CH materials (P<0.05). All CL materials showed a significant increase in the release of natamycin until 1 hour (P<0.05), which was followed by a plateau (P>0.05). Overall, the release of natamycin was higher in CH than SH lenses (P<0.001). CONCLUSIONS: All CLs released clinically relevant concentrations of natamycin within 30 minutes, but this release reached a plateau after approximately 1 hour. Further CL material development will be necessary to produce a slow and sustained drug releasing device for the delivery of natamycin.